Reports from the conference

Abstracts from this meeting are posted to the conference website, and many pdf for poster presentations are already online:

http://www.retroconference.org/2005

A once-daily dosing schedule for HIV-positive children may offer an advantage to families and healthcare workers in terms of convenience and adherence. The currently approved paediatric dose of lopinavir/ritonavir (LPV/r, Kaletra) is 230/57.5 mg/m2 taken twice daily with food. Gwenda Verweel and colleagues evaluated the pharmacokinetics, tolerability, and efficacy of once-daily dosing of LPV/r in children.

In this study children on stable treatment with a viral load < 50 copies/mL for at least 6 months received LPV/r 460/115 mg/m2 once daily with AZT and 3TC. LPV/r was taken with food in the morning. Intensive pharmacokinetic studies were performed after observed drug intake during steady state at two weeks. Target for Cmin was 1.0mg/L. After this period the time of dosing could be changed to the evening meal.

Single sample plasma levels were collected at day 28 and months 2, 3, and 6. Clinical assessment included plasma RNA levels, lymphocyte counts, biochemistry, haematology, and side effects monitoring.

Six-month follow up results were available for 14 children (7 boys and 7 girls) with a median age of 4.5 (range 3.3 to 9.5) years. The dose of LPV/r 460/115 mg/m2 once daily, resulted in comparable LPV plasma levels to those in adults after an 800/200 mg once-daily regimen.

The authors report that: 3/14 children had a C trough that was considered to be too low (< 1.0 mg/L) and a dose increase was necessary; 11 children took LPV/r with their evening meal; and 44% (17 of 39) of the LPV/r plasma levels were higher than their corresponding values on day 14. 2/3 children taking LPV/r with breakfast had lower plasma levels than those on day 14.

All 14 children had viral load < 50 copies/mL after 6 months of treatment. CD4 cell counts did not change significantly during the study.

This once-daily regimen of LPV/r was generally well tolerated. Of the 14 children, 6 experienced mild gastrointestinal side effects but all were resolved after 2 months. Cholesterol and triglyceride levels were stable during 6 months of follow-up.

The authors concluded that LPV/r 460/115 mg/m2 once daily led to LPV plasma levels comparable to adult data. In 3 of 14 children dose increase to 600mg/m2 or 798mg/m2 was necessary because of low Cmin (24hr). Intake with a large meal (like dinner) is important to obtain adequate plasma levels when LPV/r is dosed once daily in children. They also noted that because of interpatient variability in plasma levels, TDM might be useful to guide the correct dose for children.

Lopinavir/ritonavir is increasingly recommended for treating young infants but in the absence of published data. Ellen Chadwick and colleagues from the PACTG 1030 study group evaluated dose requirements for babies <6 months that provide systemic exposure similar to that which has been shown to be safe and effective in older children and adults.

Results were available for 12 infants (5 boys, 7 girls) and stratified by age: 14days to 6 weeks and 6 weeks to 6 months. A dose of 300 mg/m2 lopinavir/ 75mg/m2 ritonavir was studied in combination with two nucleosides.

Intensive PK studies were performed at two weeks with a dose adjustment if LPV/r 12-hour post-dose concentration (C12) was < 1 mg/L; C12 was measured every 12 weeks and intensive pharmacokinetic studies were repeated if there was dose adjustment at one year of age.

The study defined virologic success as viral load < 400 copies/mL at week 16; failure as never achieving < 400 copies/mL and late suppressors as achieving < 400 copies/mL after week 16. CD4 percentage was measured every 12 weeks.

Median follow-up at analysis was 50 weeks (range 19 to 112 weeks). At entry, median age was 9.4 weeks (range 3.6 to 25.7 weeks), log10 HIV-1 RNA 5.6 (3.77 to 6.88) and CD4 percentage 37% (19 to 59%). Six of the 12 infants (50%) had virologic success, 2 (17%) virologic failure, and 4 (34%) were defined as late suppressors (< 400 copies/mL at week 32 to 48). The authors noted that poorer adherence contributed to poorer response.

In 6 infants studied through week 36, CD4 percentage showed a median increase of 8% (–9 to +20%) from baseline.

One infant required dose adjustment. Infants with virologic success vs virologic failure/late suppressors were significantly younger (median 5.6 vs 15.9 weeks, p = 0.004).

The authors found that the dose of 300 mg/m2 LPV/r twice daily was well tolerated in young infants and produced encouraging results in those infants adherent to therapy. At week 2 lower plasma concentrations were reported than found in adults despite a surface area adjusted dose approximately 35% higher than recommended for adults.

To better define age-related differences in pharmacokinetics and response to LPV/r, this group will study a second cohort of 12 infants.

Jennifer Kiser and colleagues reported findings from PACTG 1020, a prospective phase I/II open-label area-under the concentration time curve (AUC)-controlled study to determine the safety, pharmacokinetics, and optimal dose of once-daily atazanavir (ATV) powder and capsules with and without ritonavir (RTV) in HIV-positive children in combination with two nucleosides.

ART-naïve and -experienced children with viral load > 5000 copies/mL and ATV phenotypic susceptibility (< 10-fold wild type IC50) were eligible for this study.

There are 8 study groups in PACTG 1020: groups 1 to 4 evaluating unboosted and in groups 5 to 8 boosted ATV. This poster reported preliminary PK data from 23 children in groups 5-8 receive RTV boosted ATV at a dose of 310mg/m².

Intensive PK studies were performed on day 7 and at week 56, plus 14 days after dose adjustment. A new ATV dose is calculated for children with: an AUC <30µg*hr/mL or AUC >90µg*hr/mL, increases of 25% in weight.

The authors reported week 1 pharmacokinetic results for 23 children ages 0.3-19.6 years. Overall median AUC and oral clearance (CL/F) were 60.8µg*hr/mL and 4.7L/hr/m² respectively.

In the youngest group (group 5, median age 1.0 [range 0.3-1.3] years, n = 6), median AUC and oral clearance (CL/F) were 53.6 (range 7.3-110) mcg•hr/mL and 8.1 (range 2.5-36) L/hr/m² in children receiving powder at a dose of 125 (range 50-150)mg /298 (range182-367)mg/m².

In older children receiving powder (group 6, median age 4.1 [range 2.6-12] years, n = 7), the median AUC and CL/F were 50.3 mcg•hr/mL and 6.2 L/hr/m² at a dose of 200 (range 150-500) mg/312 (range 268-327) mg/m². Older children receiving capsules (group 7, median age 10.5 [range 8.7-11.5], n=5) the median AUC and CL/F were 73.8 (range 60-134.2) mcg•hr/mL and 4.2 (range 2.2-4.7) L/hr/m² at a dose of 400 (range 300-500) mg/286 (range 274-349) mg/m².

In the oldest group of children receiving capsules (group 8, median age 17.7 [range 13.1-19.6], n=5) the median AUC and CL/F were 62.4 (range 51.5-84.7) mcg•hr/mL and 4.5 (range 3.4-6.0) L/hr/m2 at a dose of 500 (range 400-600) mg/286 (range 281-311) mg/m².

The authors concluded: “The median ATV AUC and CL/F in adults receiving ATV/RTV 300/100mg once daily are 53.8 µg•hr/mL and 3.2 L/hr/m² respectively. Thus ATV CL/F is age-dependent and faster in children than in adults, as seen with other protease inhibitors.

“As expected, the addition of RTV decreases the clearance and increases the AUC of ATV in children.”

These data are preliminary and the optimal dose of ATV/RTV has not yet been established. The authors added: “Further evaluations are underway in P1020 to establish the optimal dose of ATV/RTV in subjects 91 days to 21 years in the United States and South Africa.”

In this study, 27 HIV-positive children (age range 5.0 to 17.5 years) with viral load < 50 copies/mL for the last 48 weeks, on HAART containing lamivudine (3TC) + d4T+ 1 PI were randomised either to switch d4T to TDF and PI to EFV at baseline (n = 14; group A) or at week 24 (n = 13; group B).

All children maintained 3TC and were followed with clinical assessment, viral load, CD4 count, fasting metabolic, and renal parameters for 48 weeks.

The authors reported from baseline to week 24 and at week 48, both groups had unchanged CD4 count 884, 759, 848 vs 809, 795, 754 cells/mm3; HIV RNA < 50 copies/mL; unchanged and normal levels of serum creatinine, phosphate, calculated creatinine clearance; absence of proteinuria and glycosuria.

The children in Group A, from baseline to week 24, showed a significant decrease on total cholesterol (–20%, p< 0.03), triglycerides (–35%, p< 0.05) and total cholesterol/HDL ratio from 3.5 to 3.0, p< 0.006); and at week 48, the authors reported stable cholesterol levels and a further decrease of triglycerides and HDL cholesterol. Children in this group with elevated (> 95th percentile for age and sex) cholesterol and triglyceride levels showed a marked decrease of both over the study period (from 43 to 0% and from 36 to 7%, respectively).

In Group B, from baseline to week 24, the children showed unchanged cholesterol, triglycerides, HDL cholesterol and percentage of HIV with elevated cholesterol and triglyceride levels; at week 48, the authors reported a significant decrease of cholesterol (–14%; p < 0.03), triglycerides (–41%; p < 0.05), and HDL cholesterol (from 3.9 to 3.2; p < 0.006). The children with elevated cholesterol and triglyceride levels showed marked reduction of both after the initiation of the new regimen (from 46 to 8% and from 54 to 0%, respectively).

No adverse events were reported throughout this study.

The authors concluded: “The replacement of PI by EFV and d4T by TDF in HIV-infected children who had been receiving a HAART regimen containing 3TC+d4T+PI who had long lasting viral suppression provides continued virological suppression, stable CD4 response.

References:

1. Verweel G, van der Lee M, Burger D et al. 6-Month follow-up of once-daily lopinavir/ritonavir in HIV-1-infected children. 12th CROI Boston 2005 Abstract 769.
2. Chadwick EG, Rodman J, Palumbo P et al. A prospective evaluation of pharmacologic, virologic, and immunologic parameters of lopinavir/ritonavir for HIV-1-infected infants < 6 months of age. 12th CROI, Boston 2005. Abstract 766.
3. Kiser J, Rutstein R, Aldrovandi G et al. Pharmacokinetics of atazanavir/ritonavir in HIV-infected infants, children, and adolescents: PACTG 1020A. 12th CROI, Boston 2005. Abstract 767.
4. Viganò A, V Giacomet V, Beretta S et al. Switching stavudine to tenofovir and protease inhibitor to efavirenz results in a favourable clinical outcome in HIV-infected children. 12th CROI, Boston 2005. Abstract 770.

As is customary for this scientific meeting, Retrovirus this year provided an opportunity for important research.

Abstracts from this meeting are posted to the conference website, and many pdf for poster presentations are also already online:

http://www.retroconference.org

There was a wealth of exciting data on new compounds with an indication to work against currently resistant HIV, and important overviews that this year are available as online webcasts, with slides.

http://www.retroconference.org/2005/Pages/webcasts.htm

Particularly recommended presentations include:

February 23, 2005

Plenary: Nevirapine and PMTCT

• Controversies in the use of nevirapine for the prevention of mother-to-child transmission – James McIntyre

Symposium: Chemokine Receptor Blockade: Bench to Bedside

• Preclinical development of chemokine receptor inhibitors – Donald E Mosier
• Clinical activity and efficacy trials of chemokine receptor inhibitors – Daniel Kuritzkes

Symposium: Heart and HAART

• Cardiovascular risk prediction in the general population – Jorge Plutzky
• Cardiovascular outcomes in HIV infection – Jens D Lundgren
• Managing cardiovascular risk and lipid disorders – Esteban Martinez

February 24, 2005

Plenary: Lipodystrophy

• Fitting the pieces of the puzzle – Peter Reiss

Symposium: Critical Paediatric Issues in Developing Countries

• Safer breastfeeding for babies born to HIV-positive mothers: part of the answer to a dilemma – Jean Humphrey
• Is early diagnosis of HIV infection feasible in resource-limited settings? – Christine Rouzioux
• Paediatric antiretroviral therapy: challenges and triumphs – Diana Gibb

Special Symposium: Transmitted HIV-1 Drug Resistance and Rapid Disease Progression

• Introductory remarks and summary of case report of recent infection by a multi-drug resistant, dual-tropic HIV-1 in association with rapid progression to AIDS – David Ho
• Variations in the natural history of HIV infection in the NIAID Multicenter AIDS Cohort Study (MACS) and the Women’s Interagency HIV Study (WIHS) – Stephen Gange
• Variations in the natural history of HIV seroconverters in US military cohorts – Matthew Dolan
• Transmission of drug resistant HIV: frequency, transmissibility, and fitness – Andrew Leigh Brown
• Public health aspects of the NYC case – Harold Jaffe

With over 900 studies and presentations we are only able to include a few reports in this issue of HTB. Further reports will follow in the next issue.

The conference is the focus of many online web reports which are also recommended.

Amongst the most useful include:

National AIDS Treatment Advocacy Project – NATAP.

http://www.natap.org

The Body

http://www.thebody.org

HIV and Hepatitis.com

http://www.hivandhepatitis.com

Medscape

http://www.medscape.com

Clinical Care Options

http://www.clinicaloptions.com

Reports in this issue include:

• Developments in nevirapine use in MTCT reduction

• Mashi study – late breakers on breastfeeding

• Maternal health and infant mortality

• Paediatric care in lower income settings

• Tenofovir not linked to bone toxicity in children followed for one year

• Gut memory CD4 T cells implicated in a central role for HIV disease pathology: dramatic impact prior to seroconversion

• Case of multi-drug resistant (MDR) rapid progressor

• Case report of antibody reversion and negative viral load four-years after treatment discontinuation

• 24-week efficacy of TMC114 in PI-experienced patients

• Maturation inhibitor shows anti-HIV activity in single dose pilot study

• New antiretrovirals at 12th CROI

• Absolute risk is modest, but cumulative cardiovascular risk of HAART over five years is similar to ‘ever smoked’: new data on gender and age

• Omega-3 supplement effective to reduce triglycerides

• Entecavir is effective against 3TC-resistant hepatitis B

• Switch to tenofovir from AZT or d4T improves fat loss and improves lipid parameters compared to abacavir

• Continued use of a thymidine analogue may limit benefit from rosiglitazone when used to treat lipoatrophy

• Tenofovir is non-inferior to adefovir for the treatment of hepatitis B in HBV-HIV co-infected patients

A “roller coaster” was James McIntyre’s description of recent events surrounding controversies associated with nevirapine (or how “Concerns about Good Clinical Practice escalated to crimes against humanity”) in his Wednesday plenary at this conference [1]. And Bob Huff had described, “…a tsunami propagating across oceans, political shockwaves reverberated across continents” in the December edition of GMHC’s Treatment Issues [2]. Conspiracies, whistleblowing and dangerous politics to one side, this conference showed some interesting new scientific reports concerning the use of nevirapine to reduce mother to child transmission (MTCT).

Increased levels of resistance detected with real time PCR assay

Several studies presented similar findings related to concerns about resistance with single dose nevirapine exposure.

Three oral presentations in the resistance session, inconveniently scheduled at the same time as DITRAME Plus and other MTCT presentations, reported greater frequency of nevirapine mutations than are detected with standard genotyping. All three studies used real time PCR to analyse samples from South African women with subtype C HIV who had received single dose nevirapine at the onset of labour.

Conventional genotype assays are unable to reliably detect variants that comprise less than 20% of the sample virus population. Jeffrey Johnson’s group used a real-time PCR assay with a detection limit of 0.2% K103N in a background of wild type virus (a sensitivity 100-times greater than conventional sequencing) [3].

The study analysed matched samples from 50 women pre- and post- nevirapine exposure (at 6-36 weeks post partum). Using conventional genotyping, no women had detectable K103N mutation prior to receiving nevirapine and 10/50 women had detectable K103N in the post partum samples.

Results from real-time analysis also found all pre-treatment samples to have undetectable K103N and found the mutation present in all 10 samples (100%) that had detectable K103N by conventional sequencing. Additionally, the more sensitive assay found 16/40 (40%) specimens, in which no mutation was detected by standard genotype, to have detectable K103N.

Clonal sequence analysis confirmed the resistance mutation in five samples and provided K103N-positive virus frequencies of 1.1 of 11.1% of the sample virus populations.

A more complex analysis presented by Sarah Palmer revealed similar results [4]. This study used standard genotyping compared to an allele-specific RT-PCR assay for K103N and Y181C to test longitudinal samples from 17 women. Both NNRTI- associated mutations were detected as follows:

The median frequency of mutations was 3% (range 1 to 63%).

Using these findings the investigators estimated that, among their cohort, up to 69% of women could have mutations at 4 months, 32% at 5-9 months and 22% out to one year from receiving single dose nevirapine.

In a third presentation Shayne Loubser presented real-time PCR and standard genotyping results results for RNA samples at 6 weeks post-partum [5]. This study found the K103N mutation in 16 of 18 (89%) samples using real-time PCR and in 9 of 18 (50%) by conventional population sequencing. The investigators reported that generally only samples with ≥ 32% K103N by real-time PCR were detected by sequencing.

Additionally, a longitudinal analysis of samples from 16 women was performed to monitor the levels of K103N in RNA over time. At 12 months the K103N was still detectable at low levels in 4 of 16 (25%) RNA samples and in none of 15 DNA samples tested.

However, the authors noted: “We found no evidence for archiving of K103N mutations in DNA at 1 year post-single-dose NVP”.

Finally, a poster from Susan Eshleman and colleagues used a sensitive point-mutation assay to look at whether K103N could persist at low levels in women and infants for a year or more after exposure to single dose nevirapine [6].

The level of K103N-containing variants was quantified using a sensitive resistance assay, LigAmp, which has a lower limit of detection of 0.08%.

The authors reported that at 6 to 8 weeks after receiving nevirapine, K103N was detected by standard genotyping in 8 of 9 women for which samples were available and 2 of 5 infants, and was detected by LigAmp at a level above 0.1% in 8 of 9 women and 4 of 5 infants.

At 12 to 24 months, the K103N mutation was not detected by standard genotyping in any of the samples, but was detected by LigAmp above pre-nevirapine levels in 3 to 9 women (at 0.8%, 1.3%, and 3.5%) and 1 to 5 infants (at 1.5%).

The findings from these studies suggest that only a minority of women do not develop nevirapine resistance mutations after single dose exposure, that conventional sequencing substantially underestimates the emergence of resistance, and that resistance continues long after conventional genotyping suggests it “fades”. There was inconclusive discussion around whether or not resistance is archived in DNA even when it is fading in plasma, but it was uncontroversial was that these results stress the importance of assessing the clinical implications of resistant variants.

Subtype comparison

A poster from Susan Eshleman’s group reported results from a study comparing the rate of nevirapine resistance in Malawian women with subtype C (from the NVAZ study) to Ugandan women subtypes A and B (from the HIVNET 012 study), 6 to 8 weeks after single-dose NVP exposure [7].

The authors reported a significantly higher rate of resistance among women with subtype C, 45/65 (69%), than either subtype A, 28/144 (19%, p<0.001) or D, 35/97 (36%, p<0.001). Additionally the number of women with two or more nevirapine mutations was higher among the women with subtype C, 29/65 (45%) than with subtype A, 12/144 (8%, p<0.001) or subtype D, 16/97 (17%, p<0.001).

In a multivariate analysis they found viral load and subtype to be independent predictors of nevirapine resistance: C vs.A OR =8.84 (95% CI: 4.33-18.04); C vs D OR=3.44 (95% CI: 1.67-7.07) and log 10 viral load at delivery OR=2.27/log 10 RNA copies/ml (95% CI: 1.55-3.32). Maternal age, parity and time from nevirapine dosing to 6-8 week visit were not. The investigators also observed similar associations between these factors and the detection of two or more nevirapine mutations.

Although related findings have been reported previously this is the first study to make a direct comparison across the subtypes.

DITRAME Plus

In an oral presentation, Francois Dabis reported results from the ANRS DITRAME Plus 1.1 study. This study evaluated the frequency of resistance mutations following a short course (from 32 weeks) of AZT/3TC, plus single dose nevirapine to reduce mother to child transmission, ending with three days of AZT/3TC post partum [8]. This was an in an open label study conducted in Abidjan Cote D’Ivoire.

Data were available for 329 women for which the 6 week transmission rate was 4.7% (n=16, 95% CI 2.4 – 7.0). The median baseline CD4 cell count was 293 cells/mm3 for transmitting mothers and 416 cells/mm3 for non-transmitters and the median viral load was 5.16 and 4.45 log10 copies/mL, respectively.

Of this group the overall frequency of nevirapine associated resistance mutations was 1.14% (CI: 0.03 to 6.17%) and 8.33% (CI 3.66 to 15.76%) for 3TC.

Findings from this study are consistent with interim results from the TOPS study presented by James McIntyre in Bangkok. The TOPS study showed that adding AZT/3TC to cover the nevirapine “tail” significantly reduced nevirapine resistance (9.3 vs 50%). Further analysis of 226 mothers from TOPS, where early results are expected to hold out, will be available mid-2005 [9].

Following this presentation Charles Gilks from the WHO commented that they would be convening a small expert group to consider these findings with respect to the WHO guidelines “very soon”.

Impact on second pregnancy

There has been widespread concern that resistance following the use of single dose nevirapine for MTCT reduction will impact on its efficacy in second and subsequent pregnancies.

Neil Martinson presented data from a case controlled pilot study across 13 sites in Soweto comparing women using nevirapine for the first and second time in pregnancy [10]. Baseline results were available for 106 women who had received nevirapine for the second time and compared in a 2:1 comparison to a control group of 212 women who had received nevirapine for the first time. Six week resistance data were available for 77 exposed and 140 naïve at baseline women.

Transmission rates to infants determined by DNA-PCR, for whom results were available, were 5/132 (3.8%) in the control group and 8/75 (10.7%) in the second pregnancy group. Resistance was detected in 54% of the control group and 45% of the second pregnancy group of women by standard genotyping. There were a greater number of women with two or more nevirapine associated mutations in the control group (47% vs 23%, 2 mutations and 34% vs 17%, 3 or more mutations) but these women appeared to have more advanced HIV that the authors suggested could explain this.

The differences in transmission rates were reported as not statistically significant and the investigators concluded that previous nevirapine exposure had no effect.

The conclusion that the second pregnancy was not compromised by previous use of nevirapine raised much debate. A speaker from the floor questioned how the investigators could conclude that there was “no effect” (of previous dose) when, although not statistically significant, the results showed such a strong trend (RR = 2.3).

Further analysis of these results is ongoing and urgently needed.

Reducing resistance risk and using HAART in pregnancy

Discussions continue around the best strategies to reduce the risk of resistance.

A report from the “Mashi” study (see below) suggests that adding single dose nevirapine to maternal AZT prophylaxis offers no added benefit in transmission reduction. This contrasts with results from both DITRAME and PHPT-2 which both reported a substantial reduction in transmission with this strategy (although similar nevirapine resistance rates to single dose alone) [11, 12, 13].

There were also encouraging results from groups that follow the strategy that James McIntyre called “Treat them all”.

Women in the PMTCT-Plus programme receive triple therapy if they are eligible for HAART (WHO stage 4, WHO stage 2 or 3 with CD4 count < 350/mm3, CD4 count < 200/mm3). A poster from Besigin Tonwe-Gold’s group in Abidjan reported no transmissions, four weeks after birth, among the women receiving HAART [14].

Similar findings (approx 4% transmission rate at 1 month) were reported in an oral presentation from Leonardo Palombi from the DREAM programme in Mozambique in which 778 women had received generic HAART (nevirapine/3TC/d4T) for more than two weeks in the last stage of pregnancy [15]. Additionally, the authors reported low levels of resistance among the women (3/20) for whom genotype results were available.

Palombi noted that with the women who did not require treatment for their own HIV for whom treatment was stopped (originally after one month changing to 6 months over the course of the study), they had originally stopped the nevirapine 6 days earlier than the nucleosides but this had changed to 15 days.

A poster authored by Lyn Zijenah and colleagues reported 16 week data from 51 women receiving a generic nevirapine containing combination of AZT/3TC (Duovir) and nevirapine (Nevimune), both manufactured by Cipla. The study compared virologic response between women who had previously received single dose nevirapine (n=21) or short course AZT (n=30) to reduce mother to child transmission [16]. This Zimbabwean study also reported results for 33 men receiving the same treatment.

At week 16, the investigators reported a median increase in CD4 count from 135 cells/mm³ (IQR: 65-143) to 253 cells/mm³ (IQR: 155-302) among the women in the group. Of the women for whom viral load results were available the number with detectable virus < 500 copies/mL, was 4/30 exposed to short course zidovudine and 1/13 exposed to single dose nevirapine.

The investigators report despite “growing concern about the impact of maternal prophylaxis on subsequent treatment”, in this early analysis of women with subtype C HIV, previously exposed to single dose nevirapine they were no more likely than those receiving AZT short course to have an impaired treatment response to nevirapine containing HAART.

It is difficult though to reach any conclusion from this early analysis from a small study that contrasts with previous findings from Jourdain et al (showing an impaired response amongst previously nevirapine exposed women to subsequent nevirapine containing HAART) at six months [17]. There is a need for longer follow up.

Adverse events

There are concerns over treatment in pregnancy particularly for women with >250 cells/mm³ because of hepatoxicity risk in this group.

A poster from Timothy Thomas’s group described adverse events attributed to nevirapine among women from the Kisumu Breastfeeding Study [18].

This is an open label trial to evaluate safety, tolerability, adherence and efficacy of using AZT, 3TC and nevirapine from week 34 in pregnancy and for the first six months of breastfeeding.

The authors report a similar percentage of serious hepatic or cutaneous adverse events among women receiving nevirapine in other studies: 19/241 (7.9%) total serious adverse events 11/241 (4.6%) grade 3 or 4 serious adverse events. The authors note, however: “while other reports indicate increased risk for women with CD4 counts > 250 cells/mm³, this is not seen among pregnant HIV+ women in Kisumu to date. The data underscore need for close monitoring of women on NVP-HAART.”

In an oral presentation from the Thai Red Cross 2.1% pregnant women receiving the same combination as in the Kisumu Study were reported to have experienced grade 3 to 4 serious adverse events and this report observed > 400 CD4 cells/mm³ (p=0.018) to have increased risk [19].

It is unclear whether guidelines from FDA and Boehringer Ingleheim – the originator manufacturer of nevirapine – will be as relevant in African and other low and middle income settings.

COMMENT

As the details regarding the safety of continuous nevirapine therapy initiated in pregnancy, and the frequency and impact of mutations associated with nevirapine resistance following single dose (SD) nevirapine are gradually studied and refined and whatever the concerns regarding the adherence to GCP in HIVNET 012, it is imperative that key findings are not obscured.

First, there is little concern, despite the above, that the results of HIVNET 012 are likely to be substantially inaccurate. Second, the efficacy of SD nevirapine in reducing HIV mother to child transmission has been independently shown in the Thai PMCT-2 study where the addition of SD nevirapine to third trimester zidovudine further reduced transmission from 6% to 2%. Third, SD nevirapine has an excellent safety record in mothers and infants.

Then, in terms of the real time PCR sensitive assays to detect NVP resistance, while real time PCR detected resistance in 40-88% of women who did not have resistance detected with standard genotype at 6 weeks to 12 months post-exposure, in longitudinal studies, the frequency of detection declines over time and levels of resistance detected at 12 months were low (in the study with largest numbers it was 0.8-1.5% of quasispecies).  So resistance may persist longer but still declines over time and is low level after a year.  The lack of archiving in DNA at one year post exposure was very interesting.  The data is unclear on clinical implications of this resistance as detected by sensitive assays ie what level of resistance is associated with potential lower virologic response.

And fourth, mutations, “fading” or otherwise, are of great importance if they adversely impact on future therapy but are less relevant if NNRTI containing combination therapy, or indeed any form of HAART, is inaccessible, as is currently the case for the majority of HIV-infected persons. James Mcintyre’s talk included the “reality check” that – depending on whose data we believe only about 5% or less of HIV infected pregnant women even receive SD nevirapine.

Some have suggested that the most important data from this year’s CROI for HIV infected pregnant women globally are those from Soweto looking at HIV transmission in subsequent pregnancies when SD nevirapine was administered in both pregnancies. The finding that the transmission rate rose from 3.8% in the first pregnancy to 10.7% in the second pregnancy gives cause for concern despite the lack of statistical significance (p= 0.096 – Chi2 with Yates correction). However factors other than previous nevirapine exposure, such as the longer duration of HIV infection by the time of the second pregnancy, need to be excluded and it was noted that the 3.8% transmission rate in the first pregnancy was very low.

Where HAART for maternal health is, or is likely to become, widely available, the use of SD nevirapine alone or added to a background of short course zidovudine monotherapy to prevent MTCT no longer seems tenable. Strategies to protect the NNRTI class, particularly given the current higher cost of protease inhibitors in resource-poor settings, are urgently required.

At present the co-administration of other antiretroviral therapy to cover part or all of the period of actual nevirapine exposure seems the most likely approach, but data from the Mashi study suggest that early nevirapine administration to the neonate may have equal efficacy to maternal dose. If validated this would clearly avoid the risk of nevirapine resistance developing in the mother.

Adding SD Nevirapine to third trimester dual NRTI therapy with combivir may reduce the risk of NNRTI resistance (but at the cost of resistance to 3TC as seen in DITRAME Plus 1.1). The DITRAME study is interesting but the issue of whether the 3 day “tail” was associated with this – although mirrored in the earlier TOPS findings from McIntyre et al – or whether having low viral replication at the time of delivery was associated with low rate of resistance is unclear.  Additionally, the data from DREAM conflicted – these women received HAART during pregnancy and 6 days (now increased to 15 days) of AZT/3TC “tail” coverage and they saw 15% resistance.  As NVP levels persist for up to 21 days or longer the dramatic effect of short term “tail” of 3 days provoked comment. Besides more results from TOPS, other studies are ongoing looking at different regimens for different time periods (7 vs 28 days) that should provide more definitive data.

Interestingly, the frequency of the M184V mutation in the DITRAME study (8.3%) was considerably less than that seen in the French cohort (40%) when 3TC was added at 32 weeks to ZDV monotherapy.

Finally, concerning nevirapine containing HAART in pregnancy, none of the studies at this year’s CROI (nor at Glasgow November 2004) indicate a higher risk of toxicity in pregnant women than expected. However, a number of studies have now suggested that the 250 cells/mm3 cut off may not apply in pregnancy or as findings from Thomas et al suggest may be different in different settings. Most would agree that close monitoring is important.

References:
1. McIntyre J. Controversies in the use of nevirapine for the prevention of mother-to-child transmission. Wednesday Plenary 12th CROI, Boston, 2005.
2. Huff B. Single Dose Theory. GMHC treatment issues. Vol 18, No 11/12, p 1.
3. Johnson J, Li JF, Morris L et al. Resistance emerges in the majority of women provided intrapartum single-dose nevirapine. 12th CROI, Boston, 2005. Abstract 100.
4. Palmer S, Boltz V, Maldarelli F et al. Persistence of NNRTI-r resistant variants after single-dose nevirapine in HIV-1 subtype-C-infected women. 12th CROI, Boston, 2005. Abstract 101.
5. Loubser S, Balfe P, Sherman G, et al. Sensitive real-time PCR quantification of 103N resistance mutants following single-dose treatment with nevirapine. 12th CROI, Boston, 2005. Abstract 102.
6. Eshleman S, Nissley D, Claasen C et al. Sensitive drug resistance assays reveal long-term persistence of HIV-1 variants with the K103N nevirapine-resistance mutation in some women and infants after single-dose NVP: HIVNET 012. 12th CROI, Abstract 800.
7. Eshleman S, Hoover D, Chen S et al. Comparison of nevirapine resistance in women with subtype C compared with subtypes A and D after single-dose NVP. 12th CROI, Boston, 2005. Abstract 799.
8. Chaix ML, Dabis F, Ekouevi D et al. Addition of 3 days of ZDV+3TC postpartum to a short course of ZDV+3TC and single-dose NVP provides low rate of NVP resistance mutations and high efficacy in preventing peri-partum HIV-1 transmission: ANRS DITRAME Plus, Abidjan, Côte d’Ivoire. 12th CROI, Boston, 2005. Abstract 72LB.
9. McIntyre J, Martinson N, Boltz V et al. Addition of short course Combivir (CBV) to single dose Viramune (sdNVP) for prevention of mother-to-child transmission of HIV-1 can significantly decrease the subsequent development of maternal NNRTI-resistant virus. XV Intl AIDS Conference, 11-16 July 2004, Bangkok. LbOrB09.
10. Martinson N, L Pumla, Morris L et al. Effectiveness of single-dose nevirapine in a second pregnancy. 12th CROI, Abstract 103.
11. Shapiro R, Thior I, Gilbert P et al. Maternal single-dose nevirapine may not be needed to reduce mother-to-child HIV transmission in the setting of maternal and infant zidovudine and infant single-dose nevirapine: results of a randomised clinical trial in Botswana. 12th CROI, Boston, 2005. Abstract 74LB.
12. Lallemant M, Jourdain G, Le Coeur S et al. A randomised, double-blind trial assessing the efficacy of single-dose perinatal nevirapine added to a standard zidovudine regimen for the prevention of mother-to-child transmission of HIV-1 in Thailand. 11th CROI 2004. Abstract 40LB.
13. Dabis F, Ekouevi DK, Bequet L et al. A short course of zidovudine and peripartum nevirapine is highly efficacious in preventing mother-to-child transmission of HIV-1: the ARNS 1201 DITRAME Plus study. 10th CROI 2003. Abstract 854.
14. Tonwe-Gold B, Ekouevi D, Rouet F et al. Highly active antiretroviral therapy for the prevention of perinatal HIV transmission in Africa: Mother-To-Child HIV Transmission Plus, Abidjan, Côte d’Ivoire, 2003-2004. 12th CROI 2005. Abstract 785.
15. Palombi L, Germano P, Liotta G et al. HAART in pregnancy: safety, effectiveness, and protection from viral resistance: results from the DREAM cohort. 12th CROI, Boston, 2005. Abstract 67.
16. Zijenah L, Kadzirange G, Rusakaniko R et al. Community-based generic antiretroviral therapy following single-dose nevirapine or short-course AZT in Zimbabwe. 12th CROI, Abstract 632.
17. Jourdain G, Ngo-Giang-Huong N,Tungyai P et al. Exposure to intrapartum single-dose nevirapine and subsequent maternal six-month response to NNRTI-based regimens. 11th CROI 2004. Abstract 41LB.
18. Thomas T, Amornkul P, Mwidau J et al. Preliminary findings: incidence of serious adverse events attributed to nevirapine among women enrolled in an ongoing trial using HAART to prevent mother-to-child HIV transmission. 12th CROI, Boston, 2005. Abstract 809.
19. Phanuphak N, Apornpong T, Intarasuk S et al. Toxicities from nevirapine in HIV-infected males and females, including pregnant females with various CD4 cell counts. 12th CROI, Abstract 21.

There were two late breaker presentations from the “Mashi’ (milk) study. This was a complicated analysis looking at MTCT rates in the setting of different maternal and infant interventions before, during and after delivery.

Mashi is a randomised, partially double blinded 2×2 factorial clinical trial conducted at four sites in Botswana. The study endpoints and questions were: whether addition of single dose maternal and infant nevirapine added to maternal and infant AZT course reduce transmission rate and whether maternal dose added benefit at one month; whether HIV transmission rates differed in breastfed of formula fed infants receiving AZT prophylaxis at 7 months and whether transmission and mortality differed in breastfed (BF) and formula fed (FF) infants receiving prophylaxis at 18 months.

All pregnant women received short course AZT prophylaxis from 34 weeks gestation, and all infants received 1 month of AZT. Mother-infant pairs were randomised to receive blinded maternal and infant single dose nevirapine (N/N) or maternal and infant placebo (P/P). Infants were then randomised by feeding strategy: FF vs BF and AZT for 6 months.

Seventeen months into the study, following the Thailand PHPT-2 results the study was revised [3]. The revised protocol discontinued the infant placebo so that N/N was compared with maternal placebo and infant nevirapine (P/N).

Additionally HAART became available to women with AIDS in the revised study (71 women at the time of delivery, 40 in N/N and 31 in N/P groups). The original study was designed to assess superiority of N/N over P/P, and the revised study to assess equivalence of P/N to N/N.

Maternal dose nevirapine vs no maternal dose

Analysis was performed on 1179 live infants in both study periods (485 and 694 in the original and revised studies respectively). The authors report 56 (4.7%) were HIV infected by 1 month of which 41 (73%) were HIV infected at birth across all groups. In the original study, 13/243 (5.3%) of infants in the N/N group were HIV infected at 1 month, compared to 15/242 (6.2%) in the P/P group (p = 0.7, 95% CI –5.2% to 3.5%). (There were 2 [2.8%] transmissions among the women receiving HAART).

Further analysis revealed that there was an interaction with the feeding strategy component of the study and showed a modest difference in formula fed (FF) infants between P/P and N/N 4/121 (3.3%) vs 0/124 (0%) (p=0.05) at 1 month. However in the breastfeeding (BF) arm there was no effect 2/121 (1.7%) vs 2/119 (1.7%).

In the revised study, 15/345 (4.3%) in the N/N group were HIV infected at 1 month, compared with 13/349 (3.7%) in the P/N group (p = 0.7, 95% CI –2.4% to 3.8%), meeting study criteria for equivalence. Analysis by feeding strategy showed no significant difference with or without maternal nevirapine.

Resistance occurred in 69/157 (44%) women receiving single dose nevirapine for whom data were available.

Feeding strategy

There were 591 infants in the FF and 588 in the BF and AZT arms. The investigators reported very high levels of adherence to FF (91% never breastfed) among the women assigned to the FF arm but only 18% exclusive breastfeeding (and 86% AZT adherence) in the BF and AZT arm. The median duration of breastfeeding was 5.8 months.

At 7 months transmission rates were significantly lower in the FF arm 5.6% vs 9.1% (95% CI 0.4 to 6.5%, p = 0.04). Infant mortality rate was greater in the FF arm than the BF and AZT arm (9.3% vs 4.9%, p=0.004).

The investigators also noted that overall infant adverse event rates at 7 months were similar in both arms, except for higher mortality in the FF arm (7.6% vs 3.7%, p = 0.003); 9.2% in the BF and AZT arm stopped AZT for toxicity.

However by 18 months follow up there was no difference in HIV-free survival between the two arms, FF: 33 infected, 46 deaths; BF and AZT: 54 infected, 34 deaths (p=0.41). HIV infection was higher in the BF and AZT arm: 9.2% vs 5.6% but the FF arm showed a higher mortality rate 5.8% vs 7.8%.

At 12 months maternal mortality was similar in both arms: 13/602 (2.2%) and 14/598 (2.3%) in the FF and BF and AZT arms respectively.

This is the first study to compare two different types of intervention to prevent postnatal HIV transmission. The BF and AZT arm had higher HIV infection and lower mortality rates than the FF arm by 7 months and comparable HIV-free survival rates by 18 months.

This presentation (at 4%) was one of three in this session (DITRAME Plus and DREAM) that boasted: “The lowest mother to child transmission rates reported in Africa”.

COMMENT

It is interesting that the rate of late postnatal transmission in this study – that is transmission occurring in infants who were uninfected at one month of age but infected by seven months – in the breastfed infants who received the 6 months of AZT was 4.5%.

In the Coutsoudis et al meta-analysis of over 4,000 breastfeeding mother-infant pairs the estimated rate of late postnatal transmission in infants who were not receiving any ARV prophylaxis was 4.2% at age 6 months and with their estimate of 0.89% per month of breastfeeding, for 6 months of breastfeeding, would be about 5% at age 7 months.  So not much different than with no infant prophylaxis at all.

Neither analysis takes into account the effect of maternal HAART nested in the study and it would also be interesting to see resistance data for the infected infants.

References:
1. Shapiro R, Thior I, Gilbert P et al. Maternal single-dose nevirapine may not be needed to reduce mother-to-child HIV transmission in the setting of maternal and infant zidovudine and infant single-dose nevirapine: results of a randomised clinical trial in Botswana. 12th CROI, Boston, 2005. Abstract 74LB.
2. Thior I, Lockman S, Smeaton L et al. Breast-feeding with 6 months of infant zidovudine prophylaxis vs formula-feeding for reducing postnatal HIV transmission and infant mortality: a randomised trial in Southern Africa. 12th CROI, Boston, 2005. Abstract 75LB.

A poster authored by Louise Kuhn and colleagues evaluated the effect of maternal HIV status on a group of uninfected infants born to HIV positive mothers in Lusaka, Zambia [1].

Due to MTCT programmes this group is increasing and although they are not infected themselves, mortality and morbidity among exposed, uninfected children is substantial in sub Saharan Africa.

The study asked the question: “Does HIV disease progression and immune dysfunction among HIV positive mothers increase the mortality and morbidity of their uninfected infants?”

The authors reported that among this group of 620 breast fed infants, at <4 months mortality was significantly associated with low maternal CD4 count <350 cells/mm3, (HR = 2.87, 95% CI 1.03 to 8.03) even after adjusting for maternal death (HR = 6.84, 95% CI 2.65 to17.70) and low birth weight (HR 2.43, 95% CI 1.05 to 5.65).

They write: “Uninfected infants born to immunosuppressed HIV-positive mothers appear to be at increased risk of mortality. This increase is not explained by the risks associated with separation because of maternal death or hospitalisation nor does it result from lower birth weight.”

They offer various possible explanations: diminished care giving capacity of an ill mother; the effect of interuterine viral exposure; the effect of maternal immunosuppression on the developing foetal immune system; maternal depression and nutritional deficiencies in breast milk

They raise the concern that infants born to HIV positive mothers are overlooked as a high risk population that may not benefit from treatment programmes. And conclude: “Better understanding of these processes are needed to identify interventions to address the needs of the hidden population of children affected by HIV.”

A poster from Glenda Gray’s group also included some maternal health data in an analysis that looked at the incidence of hospital admissions and deaths in both HIV-infected and uninfected infants, and factors that were associated with infant morbidity and mortality.

They found that maternal disease progression appears to negatively affect child survival in both negative and positive infants, in multivariate analysis maternal CD4 <200 cells/mm³ was a significant risk factor for infant mortality and morbidity (OR=1.5, 95% CI 1.1 to 2.5]. In their conclusion they state: “…child survival will improve by preventing maternal HIV infection and treating HIV infected mothers”.

COMMENT

More strong arguments for taking care of maternal health.

References
1. Kuhn L, Kasonde P, Kankasa C et al. Not infected but still affected: prognosis of uninfected infants born to HIV+ mothers in Zambia. 12th CROI, Boston, 2005. Abstract 805.
2. Gray G, Niekerk R, Urban M et al. Death and hospital admissions in infants born to HIV-infected women. 12th CROI, Abstract 803.

Resistance in infected infants exposed to maternal or infant MTCT strategies

Two studies looked at resistance in infected infants exposed to maternal or infant MTCT strategies.

Marina Giuliano presented data from an analysis of samples from infected infants and transmitting mothers in the SIMBA study.

In SIMBA, 404 infants of HIV infected women (in Uganda and Rwanda), who had received AZT and ddI from 36 weeks gestation until 1 week post-partum, were randomised to receive daily prophylaxis of 3TC or nevirapine for the duration of breastfeeding (as long as 6 months) or until HIV infection was confirmed. The study achieved a very low breastfeeding transmission rate among the infants (1% in the first six months of life).

Thirty children were HIV infected, 7% in week 0-4 and 1% between 4 weeks and 6 months.

Of the 26 children for which data were available, 13 had received prophylaxis with nevirapine and 13 with 3TC. 20 were diagnosed with HIV infection at birth; 3 by week 3; and 1 at week 6.

12/13 (92%) of samples from the infants who had received nevirapine prophylaxis, had detectable nevirapine associated mutations (9 – Y181C, 3 – G190A, 2 – K103N, 1 – Y188H, 1 – V106A); 3 infants had multiple mutations.

These were compared to the maternal samples and none of these mutations were present in the maternal virus. At 6 to 9 months follow up, in the 9 available infant samples; the nevirapine-associated mutations were still present.

The M184V mutation was detected in 9/13 (69%) samples from infants who had received 3TC prophylaxis. The mutation was no longer detectable -“faded” – at 3 to 6 months in the majority of infants (it only remained detectable in 2).

The presentation provoked discussion about using both nevirapine and 3TC as prophylaxis in this way due to the low genetic barrier of both drugs. Dr Giuliano explained that both drugs were available as syrups.

The authors concluded: “Post-partum prophylaxis with nevirapine or lamivudine leads almost invariably to the selection of resistance mutations in the children who are diagnosed with the infection while receiving these drugs; this should be considered when choosing the antiretroviral regimen for these children. The presence of resistance-associated mutations in untreated women in Africa needs to be evaluated in a larger sample.”

Note: All 15 children who were HIV-positive and alive in June 2003 from the SIMBA study started a combination of antiretroviral therapy with either AZT/3TC/Kaletra or AZT/NVP/Kaletra within SIMBA Plus [2].

Infant nevirapine resistance at 6 weeks

A poster from Nicole Ngo-Giang-Huong and colleagues showed an analysis of nevirapine resistance patterns exposed to maternal or infant dose of nevirapine and maternal or infant AZT.

Two groups of infants were evaluated. The first included 33 infants born to mothers enrolled in PHPT-2 trial, in which mothers received AZT from 28 weeks gestation and single dose nevirapine and infants were randomised to receive nevirapine or placebo. Of this group, 30 infants received 7 days of AZT and 3 infants received 6 weeks of AZT post partum.

The second group included 20 children born to mothers who received AZT for < 2 weeks and single dose nevirapine. All children received a single dose nevirapine and AZT for 6 weeks.

Standard genotype was performed at 6 weeks in infant samples. The prevalence of nevirapine-associated mutations was analysed according to the duration of infant and maternal AZT prophylaxis. Results were available for 50/53 (94%) of infant samples. The authors reported that all viruses were the circulating recombinant form CRF01_AE.

Nevirapine associated mutations were detectable in 4/50 (8%) of available samples. The mutations detected were: K103N alone or associated with the G190A in 3 children and Y181C in 1 child. Of the 4 nevirapine mutations detected, 3/29 occurred in infants who received 7 days of AZT, and 1/21 occurred in an infant who received 6 weeks of AZT prophylaxis.

The authors concluded: “The incidence of NVP-resistance mutations in perinatally HIV-infected children exposed to perinatal NVP plus ZDV is lower than what has been described in others studies after exposure to NVP only.” They add: “Our data do not show a difference in the prevalence of NVP-resistance mutations according to the duration of infant or maternal ZDV prophylaxis. The pattern of NVP mutations observed could be associated with the CRF01_AE subtype as well as ZDV prophylaxis.”

Successful Thai paediatric HAART programme

In an oral presentation Thanayawee Puthanakit presented 72 week data from a paediatric study – part of the national treatment programme – to assess the effectiveness of NNRTI containing regimens in children, conducted at four government hospitals in Thailand.

From August 2002 to July 2003, 107 treatment naïve children between 2 and 15 years with advanced HIV: CD4 <15% (median 3%), were enrolled. Non-paediatric fixed dose combination of nevirapine, 3TC and d4T (GPOvir) or efavirenz plus 3TC and d4T were used, manufactured by the Thai generic company GPO. Dosages were calculated based upon the children’s body weight. Pills were divided into quarters or halves if necessary.

The primary endpoint of the study was the percentage of children with HIV RNA < 50 copies/ml at 72 weeks. Secondary endpoints were the change in percentage of CD4 and the incidence of resistance mutation virus.

The authors reported a high adherence rate, >95% of prescribed dose at every visit in 86% of children; 64% of the nevirapine group and 91% of the efavirenz group achieved HIV RNA < 50 copies/ml and a CD4 increase to a median 21% at 72 weeks.

The most common resistance mutation pattern was that which conferred resistance to both 3TC and NNRTI.

The authors concluded: “The use of generic fixed-dose formulations and non-paediatric formulations are feasible and effective in resource-limited settings.”

Dr Puthanakit also noted that one bottle of 60 tablets of adult GPOvir contains the equivalent doses of 41 bottles of paediatric formulations.

Stability of paediatric formulations at varying temperatures

Choices of antiretrovirals for paediatric use are particularly scant. Kaletra capsules and ddI and d4T oral solutions are sometimes recommended and prescribed in lower income settings.

Refrigerated storage is recommended for these formulations (2-8 degrees C or up to 25 degrees C for Kaletra) but many countries lack refrigeration and have climates where temperatures reach more than 40 degrees C. Data are lacking on the stability of these formulations at higher temperatures.

A poster from Shahin Lockman evaluated the stability of these antiretroviral formulations after storage under experimental conditions for as long as 11 weeks at temperatures up to 55 degrees C.

Stability was assayed with reversed phase high performance liquid chromatography (HPLC) with UV detection.

The investigators found paediatric oral solutions of ddI were stable at temperatures as high as 35°C for 8 weeks; d4T oral solutions, however, showed significant loss of stability after 4 weeks at 25 degrees C, and the majority of drug was lost after even after one week at 35 degrees C. The lopinavir component of Kaletra is stable at temperatures as high as 45 degrees C for 11 weeks, and the ritonavir component is stable at temperatures as high as 35 degrees C for 11 weeks.

COMMENT

Of the WHO 2004 estimated 4.9 million people currently living with HIV, 700,000 are estimated to be children. The 3×5 target for people on antiretrovirals includes 10-15% children, although there is not much data it is estimated that 10,000 to 14,000 children are currently receiving treatment.

Treating children with HIV can be complicated and treating children with HIV in lower income settings can be more complicated still, as Di Gibb reminded us in an excellent overview at this CROI entitled “Antiviral therapy for children: challenges and triumphs”, and these studies also illustrate some of the hurdles (and successes).

Dr Gibb asked: “What are the implications for first line strategies for children exposed to antiretrovirals through maternal or infant MTCT prophylaxis? A mother may not even know she’s received nevirapine. What should children receive? There has been lots of talk at this conference and it is clearly of concern. South Africa is so concerned that their paediatric guidelines recommend starting with LPV/r in children under 3 years”. She explained that the PACTG 1060 trial will look at d4T/3TC/NVP vs d4T/3TC/LPV/r in infants with prior exposure to nevirapine with CD<20%. These data are urgently needed.

In terms of the infant resistance data from Thailand, it is unclear if this is low because of the AZT or if it is low because this is a subtype E virus  (or recombinant E), which have much lower rates of resistance than do C or D (C highest, D next, A next, E/B may be lower than A or similar).  So we cannot directly compare these rates to those reported from Africa, where different subtypes predominate.  But they do seem lower than most reports.

The results from the Thai paediatric treatment programme are impressive and raise issues around dosing, formulations and PK. As in this study, cut up adult fixed dose combination tablets are being used in for treating children by some groups. As Dr Gibb noted, liquid formulations present major problems in terms of volume, storage and transport. And as Dr Puthanakit also pointed out, they are 3 to 10 times more expensive than equal adult dose. Additionally as the stability study shows there are problems with d4T at higher temperatures.

Urgently needed are PK data for cut up tablets for children across different age bands and nutritional status.

Dr Gibb emphasised that the “way forward” is FDCs specifically for children and showed the CIPLA “Pedimune” currently in development. These FDCs will be in more than one size: “Junior” – d4T 12mg/ 3TC 60mg/ nevirapine 100mg and “Baby” – d4T 6mg/3TC 30mg/NVP 50mg, giving infants an accurate dose of nevirapine (they are underdosed with cut up adult tablets). The tablets will also be scored for more accurate cutting and doses will be calculated in 5 kilo bands.

Additionally, GPO is working on a paediatric formulation of GPOvir, interestingly with slightly less d4T and slightly more 3TC as are other Indian generic manufacturers.

She also included a wish list of other co-formulated scored pills for children.

Finally she emphasised that despite the sobering comments in the recent WHO report, “…children have been tragically neglected in efforts to accelerate access to ARVs…despite proof to the contrary, policy-makers and caregivers are often unconvinced that ARV therapy works for children…” ARV treatment works in children.

References:
1. Marina Giuliano, C Galluzzo, E Germinario et al. Selection of resistance mutations in children receiving prophylaxis with lamivudine or nevirapine for the prevention of postnatal transmission of HIV. 12th CROI, Boston, 2005. Abstract 99.
2. SIMBA and SIMBA Plus and http://www.iatec.com
3. Ngo-Giang-Huong N, Jourdain G, Tungyai P et al. Infant zidovudine prophylaxis and emergence of nevirapine resistance at 6 weeks in perinatally HIV-infected infants exposed to intra-partum or newborn nevirapine. 12th CROI, Boston, 2005. Abstract 802.
4. Puthanakit T, Oberdorfer A, Akarathum N et al. Effectiveness of NNRTI-based HAART in ART-naive HIV-infected children participating in Thailand’s National Access Programme: 72-week Result. 12th CROI, Boston, 2005. Abstract 50.
5. Lockman S, Ndase P, Holland D et al. Stability of didanosine and stavudine paediatric oral solutions and Kaletra capsules at temperatures from 4°C to 55°C. 12th CROI, Boston, 2005. Abstract 668.

A prospective, longitudinal, 48 month study by Italian researchers concludes that in HIV infected children, a 12 month treatment with tenofovir (TDF) was not associated with an impairment on bone mineral accrual.

Vania Giacomet and colleagues in Milan, designed their study after decreased bone porosity and osteomalacia were described in infant macaques exposed to tenofovir (TDF, Viread). Few human data were available.

13 HIV-positive children (aged ranged from 6.4 to 17.3 years) on HAART containing 3TC (lamivudine, Epivir), d4T (stavudine, Zerit) and a protease inhibitor (PI) with a mean exposure of 69 months, were switched to a regimen of 3TC, TDF and efavirenz (EFV, Sustiva).

Bone mineral density (BMD) and content (BMC) were monitored 12 months prior to the switch (T-12), at the time of the switch (T0) and 12 months after the switch (T+12). A group of 166 healthy volunteers aged from 5.7 to 19.9 years acted as a control group. Expected changes in bone mineral measurements were calculated from the control group data and were then compared to those observed in the HIV-positive children.

During both the year prior to the switch and the year using tenofovir the annual increase in spine BMC and BMD seen in the HIV-positive children was similar to those expected in the control children, regardless of the antiretroviral regimen. In the year prior to the switch the increase in total body BMC and BMD in 3TC/d4T/PI-treated children was higher than those expected in the control group.

In the following year, the increase of total body BMC and BMD in children treated with 3TC/TDF/EFV was similar to those expected in the control children. The annual changes on lumbar spine BMC and BMD, on total body BMC were similar between 3TC/d4T/PI and 3TC/TDF/EFV-treated children, while the annual change on total body BMD was higher in the 3TC/d4T/PI-treated children.

Ref: Giacomet V, Mora S, Cafarelli L et al. A 12-month treatment with tenofovir does not result in bone mineral loss in HIV-infected children. 12th CROI, Boston, 2005. Abstract 51a.

Daniel Douek of The Vaccine Research Centre, NIAID, NIH, Bethesda, MD, USA proposed a model of HIV pathogenesis in which the loss of CD4 T cells is a result of an early massive infection and deletion of memory CD4 T cells, followed by exhaustion of the CD4 T cell pool as a result of chronic immune activation.

Douek showed that during the first 17 days of SIV infection in rhesus macaques the loss of CD4 T cells in the blood was relatively minor, as it was in mesenteric and inguinal lymph nodes. However, in the jejunum of the gut, mucosal T cells were reduced by 80% during this short period. Because most memory T cells reside in the gut, rather than the blood or lymph nodes and both HIV and SIV infect memory cells with a CCR5+ phenotype, Douek looked more specifically at changes in memory T cells. Interestingly, memory T cells were reduced by 80% in the blood, lymph nodes and the mucosa of the gut within the first 17 days of SIV infection.

Douek then presented data from a patient who had very early HIV infection (before seroconversion), compared to an uninfected control, showing a very large expansion of CCR5+ CD8 T cells in the blood and lymph nodes. This is consistent with other viral infections such as EBV and CMV. This expansion does not occur for CD4 T cells. The percentage of cells expressing CCR5 is shown below in table 1.

Table 1: Percentage of cells expressing CCR5

However, a complete loss of CCR5+ CD4 memory T cells was observed in the gut of this patient*. Further more Douek showed photographic images taken by colonoscopy from these two individuals, revealing a marked reduction in the lymphoid tissue of the terminal illium in this patient. Biopsies of the mucosa revealed total loss of CD4 T cells from their Peyer’s patches. Going back to the macaque/SIV model Douek and colleagues quantified the infected fraction of memory CD4 T cells in each of these compartments by single cell qPCR for SIV gag. In the blood 30% of CD4 T cells were found to be infected, in the lymph nodes around 50% were infected and 60% were infected in the gut mucosa. Therefore the rate of infection of memory CD4 T cells in acute infection is more than 100-fold higher than in chronic infection.

Douek’s new hypothesis of HIV pathology proposes that the majority of memory CD4 T cells are lost during acute infection, and that the loss of these cells can be solely ascribed to the consequences of viral infection. Taking this as the initial insult to the CD4 T cell pool, the ensuing immune activation that characterises chronic infection leads to a persistent drive of CD4 T cells through successive rounds of activation and death, gradually draining the memory CD4 T cell compartment in an effort to maintain homeostasis.

Douek points to the example of chemotherapy in bone marrow transplantation, in which CD4 T cell reconstitution is limited and dependant both on age and intact lymph node architecture, unlike CD8 T cell reconstitution, which is mainly driven by peripheral expansion. In response to the direct infection-associated and activation-associated depletion in CD4 T cell numbers, the body tries to reconstitute them by producing more. However in HIV/SIV infection the local lymph node microenvironments and thymic out-put are significantly damaged.

With the accumulation of “effector-type” T cells in the lymph nodes they begin to resemble sites of peripheral inflammation, rather than sites of normal T cell homeostasis. The lymph node architecture is destroyed, as these sites become fibrosed, where normal tissue is replaced by collagen. Douek’s own data here shows a strong correlation between the percentage of “effector-type” CD4 or CD8 T cells in the lymph node and the percentage of collagen per mm2 of tissue (p values not shown). Futhermore, Douek positively correlates the percentage of collagen deposition per mm2 of lymph node tissue with a poor CD4 T cell count increase following initiation of anti-retroviral therapy, regardless of baseline CD4 T cell count.

Therefore, Douek hypothesises that CD4 T cell reconstitution is vulnerable because of the suppression of thymic out-put and destruction of local lymph node architecture, whereas the CD8 T cell reconstitution is not as it more independent of these sites. Douek claims that this explains why CD4 T cell numbers diminish as a result of viral infection and deletion during acute infection in the first instance and in the second instance by the homeostatic strain placed on them by immune activation during chronic infection.

COMMENT

This presentation points in the direction of an interesting story involving lymphoid tissue in the gut. However, the observational data involving endoscopy, biopsy and CCR5 are based on a single patient, and although the SIV model supports this theory, there was little statistical analysis included in the presentation and no p-values shown relating to collagen in lymph tissue and CD4 count. Longitudinal data on this individual patient would help.

Although research in primary infection involving endoscopy is hard to reproduce due to practical and ethical concerns, it was not clear whether these early changes were expected to reverse during chronic infection.

Ref: Douek D. Making Sense of HIV Disease Pathogenesis. 12th CROI 2005. Oral abstract 127.

One individual case study, partly presented before the conference, generated a lot of activity at the meeting for several reasons.

Part of the controversy related to this case having been presented in a New York City Department of Health press conference two weeks prior to this strictly embargoed meeting, dominating media attention. It was then admitted as a late poster [1] and allotted an additional four-speaker oral symposium that was added to the programme for Thursday evening and which has been added to the webcast presentations. [2]

This was a man from New York in his late 40’s who had been infected within the last 4-20 months (previous antibody test was negative in May 2003, clinical history suggested infection within last 6 months). He was symptomatic with weight loss, fatigue and had a sustained CD4 count of 80 cells/mm³.

This patient had a approximate 60%/40% mixture of R5 and R5/X4 dual tropic virus, associated with later stage disease. Additionally, he had Multi-Drug Resistance at baseline* including resistance to RTIs, PIs and nevirapine. The replicative capacity of this MDR resistant virus had similar in vitro fitness to wild-type HIV.

The context of the original press conference also focused on the co-factors of recreational use of crystal methamphetamine and history of multiple sex partners over the previous year. Many advocates saw as this as generating unhelpful media attention that targeted gay men in an alarmist way, with little supporting data, and without mentioning the context of reduced funding for public health programmes.

Cases of transmission of MDR virus have been reported for many years, without evidence of a widespread ‘superbug’ that the press reports then focused on. Although generally transmitted virus doesn’t have reduced fitness when this is a patients reference strain, this was not made clear in the original presentations.

It seems more likely that this individual is one of the unlucky rapid progressors. MACS and WIHS cohort data show approximately 1% people progress to CD4 < 200 cells/mm³ within 1 year and modeled that 0.1% progress within 6 months. In the US Military Cohort 15/2700 seroconvertors progressed to AIDS at one year.

Prevention issues are certainly important, though this was barely addressed in the presentations. There are around 40,000 new diagnoses in the US annually, and a separate poster estimated that there are over 120-150,000 HIV-positive individuals live in New York. [3]

This scale of treatment access in the US was also highlighted in an oral presentation from showing that less than 50% of people in the US who could clinically benefit form treatment actually receive it. [4]

This case study was published just after the conference, together with and editorial in the 19 March issue of The Lancet. [5]

* Mutations shown by genotyping: NRTI: M41L/A, D67D/N, V118I, M184V/I, L210L/G/M/R/V/W, T215C/Y, K219E; NNRTI: K101E, Y181I; Protease: L10I, L33F, E34Q, M46I, I54M, L63P, A71V, G73S, V77I, I84V, L89V, L90M.

References
1. Markowitz M, Mohri H, Ho D et al – A case of recent infection with a multi-drug-resistant and dual-tropic HIV-1 in association with rapid progression to AIDS. 12th CROI, Boston, 2005, Poster 973b. (Abstract not online).
2. Special Symposium: Transmitted HIV-1 Drug Resistance and Rapid Disease Progression. Webcast Thursday 24 February. 12th CROI, Boston, 2005,
3. Torian LV, Bennani Y, Frieden T – What is the True Prevalence of HIV in New York City?: Estimating the Number of Undiagnosed and Unreported Persons Living with HIV and AIDS in 2002. 12th CROI, Boston, 2005, Poster 970.
4. Teshale E, Kamimoto L, Harris N et al. Estimated Number of HIV-infected Persons Eligible for and Receiving HIV Antiretroviral Therapy, 2003—United States. 12th CROI, Boston 2005. Abstract 167.
5. Fast-track article and editorial in The Lancet, 19 March 2005; 365: 1031-38

In contrast to the extensive publicity given to the New York case study above, amongst the basic science posters at the meeting was a report of a patient with documented HIV infection, who has apparently cleared HIV.

Diagnosis was confirmed by antibody test (Elisa and Western Blot) and viral load at two labs both at diagnosis in 1995 and subsequently on frozen samples. Viral load was 4,000 copies/mL at diagnosis and rose to 29,000 and 24,000 copies/mL two years later prior to starting HAART. CD4+ T-cell count was 856 cells/mm³.

The patient used HAART for three years, achieving undetectable viral load within four months although CD4 count didn’t increase. He tested negative for antibody when being screened for a study. On stopping treatment, viral load was found to be negative and both viral load and antibody have remained negative for four years since discontinuing treatment.

Further results and tests on stored samples will hopefully be presented at future meetings, although natural scepticism about these results will mean that they need to be thoroughly verified.

COMMENT

The most likely explanation for these results would appear to be failure of the assays used to test for HIV antibodies. However the possibility must be considered that sero-reversion has taken place. It would be highly recommendable that these results should be validated by other labs.

The main problem here is that there is no clinical indication to re-test HIV positive patients for p24 antibodies following diagnosis, so we have no idea if there is an actual phenomena here that has until now been missed. Whatever the case, sero-reversion should not be taken to be equivocal with viral eradication.

One possible explanation for a reduction in HIV p24 IgG to undetectable levels, might be persistent suppression of virus by HAART, resulting in loss of viral antigen which may support long-term memory B cell production of antibodies. However there is still much debate about the means by which memory B cells maintain their levels and whether or not any level of persistent antigen is required for this.

That considered, there is an abundance of evidence that B cells do not behave normally in HIV-infection and so premature loss of HIV-specific memory B cells may be a real phenomena in some long-term HAART treated patients that requires further investigation, and that may have important implications (re blood donation, other screening etc). Speculatively, such a phenomena might be more expected in patients receiving HAART who have very limited viral reservoirs due to early treatment, as in this reported patient.

Ref: Levy I, Rahav G, Bakhanashwili1 M et al. Negative HIV antibody test and negative viral RNA in a patient with documented HIV infection. 12th CROI, Boston, 2005. Abstract 310.

An interim 24-week analysis of data from 497 patients in a multinational study of the new protease inhibitor TMC114 with ritonavir, demonstrated exciting efficacy in three-class-experienced patients with limited treatment options and was presented as an oral late-breaker session.

Four different dosing regimens were generally safe and well tolerated and the researchers concluded by recommending a dose of 600/100mg twice a day for further clinical development in treatment experienced patients because on a series of measures that dose was as potent or more potent than others and produced comparable or fewer side effects.

TMC114 had previously shown potent activity in protease inhibitor (PI) resistant patients in a 14-day trial. The new study looked at its effect in people who had experienced at least 3 classes of antiretrovirals with prior use of at least 1 PI, had at least one primary PI mutation, and viral load >1,000 copies/mL.

Patients were randomised to receive optimal background therapy (OBR, at least 2 NRTIs with or without T-20) and one of 4 doses of TMC114/r (400/100mg once a day, 800/100mg once a day, 400/100mg BD or 600/100mg BD) or chosen PI (CPI).

Baseline median CD4 count and viral load were 141 cells/mm3 and 4.6 log10 copies/mL respectively.

Interim week 24 interim results (intent to treat) are shown in the table below. The TMC-144/r dose 600/100mg twice-daily dosing produced a greater mean change in viral load, a greater percentage of subjects with 1log or more reduction, a marginally greater percentage with fewer than 400 copies/mL, and a greater percentage with fewer that 50 copies/mL than any other group, while at the same time having the same or only a slightly higher percentage of subjects with grade 3 and 4 adverse events and a lower or comparable percentage of severe adverse events.

Mean change in CD4 was +75 cells/mm³ for TMC114/r 600/100 twice-daily vs +15 cells/mm³ for CPI. See Table 1 below.

Table 1: 24-week interim results of TMC114 vs comparitor PI

Ref: Katlama C, Berger D, Bellos N et al. Efficacy of TMC114/r in 3-class experienced patients with limited treatment options: 24-week planned interim analysis of 2 96-week multinational dose-finding trials. 12th CROI, Boston, 2005. Abstract 164LB.

A phase I trial of PA-457, the first of a new class of antiviral drugs, demonstrated that single, oral doses show dose-related antiviral activity, and were safe and well tolerated. PA-457 retained activity in two patients with extensive resistance mutations.

PA-457 is the first of a new class of drugs called maturation inhibitors, which block the conversion of the HIV-1 capsid precursor CA-SP1 (p25) to mature capsid protein (p24) resulting in the release of non-infectious virus particles. It has been shown to potently inhibit the HIV-1 replication, including strains resistant to currently prescribed drugs and is highly active in the SCID mouse model.

This American-German, double-blind, placebo-controlled study assessed the antiviral response and pharmacokinetics of PA-457 following a single, oral dose. 24 HIV-positive patients with CD4 counts >200 cells/mm³ and plasma viral load of 5,000 to 250,000 copies/mL were divided into 4 groups of 6 people and each group was given a different single, oral dose: placebo, or 75mg, 150mg, or 250mg of PA-457.

Data from 16 patients (4 in each group) were available for report at CROI. All doses were safe and well tolerated with no drug related adverse events. There were reductions in mean viral load in all three groups compared to the placebo group which was sustained for more than 10 days in the higher dose groups.

Median maximum viral load reduction for each treatment group showed a dose-dependent relationship of –0.17 log, –0.27 log, –0.45 log and –0.51 log in the placebo, 75mg, 150mg and 250mg groups respectively (p < 0.05).

Preexisting mutations in one patient with 210W, 103N, 181C, 77I, and 90M in the 250mg group produced a –0.73 log reduction. Another subject with 184V, 103N, 10I, and 77I in the 150mg group had a –0.53 log reduction.

Ref: Martin D, Jacobson J, Schurmann D et al. PA-457, the first-in-class maturation inhibitor, exhibits antiviral activity following a single oral dose in HIV-1-infected patients. 12th CROI, Boston, 2005. Abstract 159.

“…… the future is rosy and now what we must deal with is developing effective therapies for hepatitis C…”

When Richard Haubrich presented the exciting data on the use of TMC114, the new protease inhibitor from Tibotec, as a late breaker on Friday, I realised that a mere 12 years has passed since I had sat in the World Aids Conference in Berlin in 1993 with the distinct feeling that nothing was going to halt the onslaught of disease that was then engulfing my patients. Now my thoughts are like those of Dame Maggie Smith in ‘The Prime of Miss Jean Brodie’ who proclaims “give me a girl and she’s mine for life”. The vast majority of those with HIV can look forward to a long and relatively healthy life with an improving selection of agents, not necessarily needed to improve virologic control but altered to ameliorate toxicity and tolerability concerns.

The biggest challenges to long-lived survival with HIV are access to therapy, co-infection with hepatitis and long-term adherence; the latter often compounded by mental health and substance abuse issues. Notwithstanding the rather dubious presentation of a “new” phenomenon of rapid progression with multi-drug resistant virus from the New York crew [1], something that has clearly been seen in various units around the world (and reported more sensibly in the scientific press), the spectre of “super-HIV bugs” appears a relatively uncommon occurrence. More importantly, at the moment, seems the inexorable rise of sexually transmitted Hepatitis C, this co-infection being the contender for greatest increase in HIV-disease related mortality, and the emergence of lymphogranuloma venerum [2] and multi-drug resistant Staphylococcus aureus (MRSA) [3] infections, markers of sexual health risk taking, by some gay men.

So what did the 12th Conference on Retroviruses and Opportunistic Infections have to offer in the way of new antiretrovirals. There were novel mechanisms of action such as maturation inhibitors and a nucleotide competitive reverse transcriptase inhibitor entry and overall around 20 agents were discussed that were not already licensed for use. The drugs on offer at this meeting are noted below with links to their abstract presentation at the conference in the Table below.

Table 1: New agents presented at 12th CROI

Many of these compounds look to have significant advantages over the drugs that we currently use and some hold out significant promise for those who have exhausted their therapeutic options.

To examine the new agents in the order in which they attempt to prevent the virus from entering, integrating and disrupting the lifecycle of the cell we come first to the entry inhibitors and receptor blockers. On Wednesday at a session on chemokine receptor blockade, Stephen Harrison from Harvard took on explaining the intricacies of the structural biology of the HIV envelope that must interact with the cell surface to enable viral RNA entry. He explained that “little is known about the trimeric organisation” of this structure in the pre-cleaved state when gp-41 is still bound together with gp-120. Much more is understood about the process with which fusion occurs involving the 6-helix bundle which unzips, a process blocked by the first agent licensed in this extra cellular mechanism, enfuvirtide or T-20. It is the conformational changes that occur as the virus approaches the cell, is modified from a liganded to an unliganded form and performs a docking maneouver that allows for the action of these new drugs. Much of the work requires the elucidation of the crystal structure of the molecule in various states and at the present can only be imputed from the action of blocking agents.

Lin and co-workers showed data on BMS-488043 a small molecule which attaches to gp-120, causing a conformation change which disrupts the linkage to the CD4 receptor [4]. Resistance to this agent has been mapped to a deep pocket in the inner domain of the protein.

Moving on from the structural complexity of this extra-cellular dance Donald Mosiers, from the Scripps Institute in La Jolla, examined the pre-clinical development of chemokine receptor inhibitors. He first noted that at least CCR5 offers an ideal target against HIV since it is well conserved, necessary for transmission and has evidence that reduced activity is protective against HIV infection and progression (delta-CCR5 homo- and heterozygotes respectively). He then broke the potential drugs into three groups:

1. Large molecules: e.g. PRO 140 (Progenics),
2. Intermediate size molecules: such as modified native ligands (Met-RANTES, AOP-RANTES, NNY-RANTES, etc) which render CCR5 inaccessible,
3. Small molecules: against CXCR4 (AMD3100) or CCR5 (TAK-652, UK-427,857, SCH-C/D, CMPD167, GW873140, UCB35625 etc) which interpolate into the membrane binding domain.

However, many of these agents show a wide range of sensitivities against HIV-1 isolates of up to 2 log¹⁰ that will cause challenges in their development. We may for the first time be presented with therapies with widely differing levels of activity within individuals. With CCR5 coding region variability and CCR5 promoter polymorphisms amongst the reasons for variable response we may find these inhibitors effective at distinct stages of HIV disease. Host genetics may also have a marked influence, something that is just being recognized for other agents we have used for many years such as nevirapine [5]. On the positive side it seems that many mutations are required to block R5 or X4 virus and escape from co-receptor blocking by receptor switching may be rare. In addition, work in both SCHID-HU mice and primates, suggest that these may be fruitful agents in the search for safe effective microbicides.

Dan Kuritzkes of Harvard Medical School then walked us through the clinical activity and early efficacy studies of the drugs which had reached clinical studies. He first noted that the development of the only CXCR4 blocking agent, AMD3100, had recently been stopped and that it was not clear whether blocking this co-receptor was safe, since in mice total blockade appears lethal. Moving on he presented potted histories of the three agents furthest along in development.

Schering-D (417690) has a molecular weight of 650, making it relatively small, and therefore hopefully easy and cheap to make; has a long half-life, is boosted by ritonavir, and has synergy with existing compounds. Data was presented at last years meeting of a 1.5log drop in HIV RNA after 10 days of monotherapy, with emergence of one mixed population (R5/X4) individual who reverted to R5 virus by day 14. This drug has just started large scale efficacy studies.

UK 427,857 from Pfizer has finally been named as Maraviroc and has been dosed in around 400 individuals to up to 900mg, although above 600mg some postural hypotension occurs which may limit further dose escalation. Drug levels are reduced by 50% when food is co-administered and there are interactions with several other antiretrovirals induced by CYP3A4 interactions. A novel probe study was presented by Muirhead and co-workers [6] that showed efavirenz to result in 50% reduction in Maraviroc levels whilst a doubling of drug exposure occurred when it was added to Kaletra-containing regimens. Nevirapine, meanwhile, showed a marginal increase in Cmax but no effect on AUC12H. These data underline the potential dosing challenges as we move this group of drugs into the marketplace.

Once again, at 10 days around 1.5log drops are seen in HIV RNA. Within the first studies one patient switched receptor usage from R5 to X4 virus with unclear reasons or implications. Kuritzkes noted that “the current sensitivity of tropism assays could be called into question…” and that the use or these agents could result in emergence of pre-existing minority variants due to selective pressure against R5 virus.

Finally it appears that subtly changing the structure of a series of CCR5 antagonists allows resistance to UK427,857 to be overcome which is comforting and suggests that class resistance does not result for resistance to this agent [7].

GW873140, from GSK was the third R5 blocker discussed in this talk. This compound, a spirodiketopiperazine, which has been given to around 40 patients at doses of 200-600mg and has a similar viral load log drop to the other molecules mentioned above. It also appears synergistic with other R5 and X4 blockers in vitro [8]. Once again a dual tropic patient was unmasked by the addition of this agent with X4 emerging at day 10.

A study by GSK [9] showed that after drug withdrawal significant (>50%) receptor occupancy occurs for at least 5 days, a dose dependent effect which appears to be true of the other drugs which bodes well for those patients with adherence issues.

In contrast with Maraviroc this agent does not affect lopinavir/ritonavir levels but the latter causes a 7-fold increase in GW8731140 levels [10]. These pharmacokinetic data suggest that the interaction between CCR5 antagonists and other antiretrovirals is going to be a challenge for clinical practice in the coming years and will further enhance the importance of therapeutic drug monitoring.

Two other molecules had data presented on them at the meeting, TAK-652 from Takeda and CMPD167 from Merck. TAK-652 is the third offering from this Japanese group replacing the original lead compound TAK-779 and the follow-up one, TAK-220. This version has an IC50 of 1nm and levels achieved after a single dose of 8.8nm suggesting that once daily dosing will be possible as well as an impressive range of activity against resistant isolates as well as synergy or additive effects with other antiretrovirals [11,12].

Finally, the role of CCR5 blockers in prevention was assessed in a primate model, by Veazey and co-workers, using CMPD 167. Intravaginal CMPD 167 mixed with hydroxyl methyl cellulose was administered followed by a challenge with SIV. Four out of 5 treated animals were not infected compared to the control group where all 6 acquired infection [13], opening the way to further work in this area.

Finally, Chris Petropoulos from Virologic gave an overview of the multi-factorial process of viral entry, each step of which has a particular pathway to drug resistance. Both competitive (T20 binding) and non-competitive resistance (utilization of inhibitor-receptor complex) occur as well as potentially receptor switch or escape (which may be CCR5 independent). Probably these assays will differ quite markedly from each other.

Once again the Dream works team from Tibotec, ably supported by the master Rudi Pauwels, now relocated to St-Lègier in Switzerland, came up with something new, a group of drugs called nucleotide-competing reverse transcriptase inhibitors (NcRTIs). The work was presented by Dirk Jochmans and focused on compound X which through a series of elegant experiments appears to differ structurally from the NRTI’s and functionally from the NNRTI’s, i.e. it binds the active site of RT to block DNA polymerisation and nucleotide binding [14]. When questioned Jochmans suggested that this agent was a part of a lead optimisation programme; that it works only on lentiviruses and that studies on resistance and mitochondrial DNA were ongoing.

Several new non-nucleoside reverse transcriptase inhibitors were showcases at the meeting with the most exciting data being for TMC278, a diarylpyrimidine or DAPY compound. It is an extremely potent agent, EC50 of 0.5nm for wild type virus and appears to work against multiple NNRTI resistant mutants up to as many as 8 mutations, with a half-life of 38 hours and potentially active metabolites [15].

Clinical data was presented by Frank Goebel from Berlin [16] which comprised a 7-day randomised, double blind, dose ranging monotherapy study, followed by roll-over to standard antiretroviral therapy; TMC278-C201. The study was conducted in subjects with T4 levels from 75-500 and viral loads >5,000copies/mL

There were 9 sites in 3 countries and 47 male subjects were randomised to 25mg, 50mg, 100mg and 150mg daily for 7 days. Viral load median fall was 1.2log with no real difference across doses suggesting that much lower doses may be just as efficient.

No resistance developed and there were no pharmacokinetic or pharmacodynamic relationships seen. No significant adverse events were reported and a phase III study is due to start soon, when questioned the speaker confirmed that TMC125 and TMC 278 will both continue in development for the foreseeable future.

Boehringer-Ingelheim showed data on their new NNRTI, BILR 355BS, a novel 8-substituted dipyridodiazepinone, for the first time [17, 18]. The agent has good activity against wild type and resistant HIV but with a half-life of 2.5 hours it requires ritonavir boosting (100mg once daily) to achieve a half life of 16-17 hours. This may be the limiting factor in the suitability of this particular molecule to be developed.

Finally, two dioxolane thymine nucleosides with activity against this target were presented. One, the thymidine DOT showed efficacy in vitro against many of the nucleoside resistant mutations, [19], but until further studies are undertaken it is unclear whether this agent suffers from the same toxicity profile as other thymidine analogues. The original compound DAPD (amdoxovir) was evaluated in a double blind, placebo controlled, clinical study where the agent or placebo was added to optimised background which contained enfuvirtide in all patients [20]. The study halted recruitment when the development of amdoxovir was called into question. Although the drug appeared safe there was no appreciable difference between it and placebo but the study design was flawed and unlikely to produce meaningful results. The further progress of this agent is unclear at the moment.

In a session on New Targets, Michael Parniak from the University of Pittsburgh gave an elegant lecture on the potential for RNAaseH to be a suitable therapeutic target. This an endonuclease which selectively degrades the RNA strand of the double stranded RNA/DNA duplex and is both absolutely essential and specific since the cellular version resides in an alternate cellular compartment. Even so there are few inhibitors in development or even described although the N-acyl hydrazone compounds are now under evaluation in the laboratory.

Daniel Himmel from Rutgers University presented data on one of the first putative RNAaseH inhibitors [21], although, as he showed elegantly with X-ray crystallography, the active binding site for KMMP05 is in the palm of the P66 subunit between the primer grip and the polymerase binding site. It may be that this molecule works by deflecting the trajectory of the nucleic acid or through altered enzyme processivity. One question was asked concerning the potential for mutations within the NNRTI binding site at positions 188 or 108 to adversely affect these molecules; only time will tell.

Integrase inhibitors

The next target that came under scrutiny was integrase and an overview of the area was provided by the doyen of this target, Daria Hazuda from Merck Research Laboratories. Whilst providing a resume of the various types of integrase inhibitors she concentrated on the group which had moved the most, the strand-transfer agents of which several companies including GSK, Japan Tobacco, Gilead, Pfizer and BMS have potential molecules under development. At least one, L870810, has shown antiviral activity. This molecule was shown to be reduced in efficacy by mutations at positions 72, 121, 125 and 151 changes occurring within a deep binding trench [22]. Some evidence exists of low cross-resistance between agents with only the N155S causing reduced sensitivity across both the diketo acids and the naphthyridine carboxamides.

Susan Little presented the only hard data at the meeting on this group of drugs which consisted of double blind placebo controlled study of L870810 (4 drug:1 placebo) as 10 days of monotherapy in 30 naïve or experienced (but off-drug) subjects (Protocol 004) [23]. Dosing was 200mg (7 subjects) or 400mg (17 subjects) twice daily versus placebo (6 subjects) and the baseline T4 count was around 460 and viral load of 4.6log.

In the higher dose group median viral load decline was 1.7log [6/16 <400copies/mL; T4 rise +89 cells (+30-+148)] and in the lower dosage arm a 1.73 log drop was seen [VL<400 1/5 subjects; T4 +73 (-107 - +253)]. Rebound occurred at varying rates over the next 24 days. This drug has been put of hold due to non-human toxicity concerns.

The other integrase inhibitor to have data shown came from BioAlliance Pharma, Paris, France [24]. The styrylquinolones act at pre-integration step of the viral life-cycle and as such are distinct from the strand transfer inhibitors. FZ41 appears to be both synergistic, in vitro, with the latter group of integrase inhibitors as well as a range of reverse transcriptase inhibitors and this makes it a particularly attractive proposition to develop.

Protease inhibitors

What is really required to improve protease inhibitors are agents that do not require pharmacokinetic boosting with ritonavir to achieve suitable serum levels to inhibit the prevalent viral strains and agents that do not affect lipid metabolism or affect insulin sensitivity. All of the currently licensed product appear to have lesser or greater effects on these parameters and it is this associated toxicity that most impacts on the likelihood of a patient staying on the drugs long-term. There was little at the meeting to suggest that the newer agents in current clinical development are going to be much better than what we have in these respects; however they do seem to be much more potent. The nearest agent to licensing, which is freely available across many developed countries is tipranavir from Boehringer-Ingelheim.

Twenty four week data was shown in two large studies of tipranavir against a comparator PI, RESIST-1 and -2 [25]. These were phase 3, multi-centre, randomised, open-label studies of standard of care containing either tipranavir 500mg boosted with ritonavir 200mg twice daily or a comparator ritonavir boosted protease inhibitor. 1483 patients were randomised and 1159 were available for analysis at week 24. By this point viral load was less than 400copies/mL in 34% in tipranavir/r-treated individuals compared to 18% in the control arm and T4 cell rise was 31 and 6 respectively. Treatment response at 24 weeks in subjects using T20 was 58% (tipranavir/r group) compared to 26% (Comparator PI/r group).

There was heavy exposure to antiretrovirals in each arm with a median exposure to PI’s of 4 although over 45% had had greater than 5. At week 24 the combined analyses showed that 41% of the tipranavir/r achieved a treatment response versus 19% of the comparator PI/r arm (P<0.0001).

Jonathan Schapiro presented the relationship between outcome and baseline resistance analysed in a number of ways [26]. By whichever way the resistance at baseline was characterized; all mutations, primary PI mutations, tipranavir composite score, there was a significantly better outcome for tipranavir treated subjects.

However the presence of greater than three key mutations at 33, 82, 84, 90 resulted in a short lived viral load decline which had trended back to approximately 0.5log below baseline by week 24. Clearly this drug, like all other new agents, does significantly better when combined with other effective antiretrovirals and if the patient has not received T-20 (enfuvirtide) then it would be criminal to use one without the other, especially since the pharmacokinetic interactions of tipranavir with other PIs makes their combination unfeasible.

Albert Wu from Johns Hopkins n Baltimore resented a poster on the effect of tipranavir in the RESIST studies on Health Related Quality of Life (HRQOL) which showed that there was a significant improvement in general health and mental health scores in the tipranavir arms compared to the comparator and significant rises (P<0.05) for all dimensions of the HIV-MOS tool from baseline [27]

Probably the most interesting data of the conference for those who treat late stage HIV disease was the protease inhibitor for Tibotec, TMC114. This has been evaluated in a two large multi-centre, international studies (TMC 114-C213/C202) in highly experienced, triple class experienced patients [28].

Patient disposition showed the study was mainly conducted in Caucasian males who had been heavily pre-treated with an extensive antiretroviral exposure (median 11 drugs, 17% prior exposure to T-20 (12% in the control group) and 8% had used tipranavir. Each group had a median of 18 PI mutations of which 8 were known resistance mutations and 3 were primary PI-resistance mutations. Twenty nine percent of the comparator arms used double boosted PIs but less than 20% of subjects had any available PI to which they retained sensitivity on an phenotypic assay.

Planned interim analysis at week 24 showed significant reduction in viral load in the TMC114 arms compared to the control arm and some dose relationship with best results at the 600mg twice daily dose level.

Two percent of TMC114 patients discontinued for virological failure versus 43% in the control group and the median T4 rise was 75 cells at the highest TMC dose compared to 15 cells in the control arm. A sustained mean VL reduction of 1.85log compared to 0.27 log and the proportion of subjects with >1log reduction in viral burden was 72% versus 16%. Importantly over the study no significant changes were seen in markers of liver function or in lipid markers.

Several other early studies of novel proteases were also showcased. GSK has a drug 640385 which need to be given with ritonavir boosting and was tested in a repeat dose blinded placebo controlled study at doses of 100mg and 250mg once daily, 50mg, 150mg and 300mg twice daily always accompanied with 100mg doses of ritonavir [29]. A further arm with 800mg of 640385 twice daily without ritonavir was also included but the latter showed AUC values of less than a fifth of the boosted regimens which all fared much better and achieved levels well above the value of 28ng/mL, calculated to be necessary to suppress PI-resistant isolates. Further studies are about to commence in PI-experienced patients.

AG-001859, a new PI from Pfizer, with reasonable data from in vitro studies against resistant isolates [30] as have NCI in conjunction with Japanese group, UIC-02031 [31]. This is a non-peptidic PI that incorporates cyclopentanyltetrahydrofuran and has potent activity against a wide range of multi-drug resistant HIV isolates. Both of these agents have a long way to go before reaching the clinical setting.

PA-457 is the first molecule of a new and exciting class of compounds, called maturation inhibitors, which interfere with the creation of new virions prior to them budding from the surface of the infected cell. It prevents the conversion of the HIV-1 capsid precursor, CA-SP1 (p25) to mature capsid proteins (p24) resulting in defective core condensation and release of non-infectious viral particles. David Martin from Panacos Pharmaceuticals showed data from a double blind, placebo controlled single dose study which evaluated doses of 75mg, 150mg and 250mg and placebo in 4 groups of 6 patients who were antiretroviral naïve or off therapy for at least four weeks; two subjects had extensive antiretroviral drug resistance mutations [32]. The drug had been shown to be well tolerated in healthy volunteers, [33], with along half-life and in this study of HIV-infected individuals; no treatment emergent side effects were noted. Viral load decline was significantly reduced (P<0.05) in a dose-dependent manner with median reduction at the highest dose of 0.51log and a greatest decline of 0.73log. Return to baseline viral RNA levels was inhibited for at least 20 days in the 250mg dose arm. Further studies are underway.

All in all, this was a fantastic show from this meeting, with lots of candidate agents being evaluated for treatment. Many of the therapies are being evaluated as single agents being given as add on or replacements compared to the best option, both being used with an optimized background regimen derived form clinical history, resistance test results and physician experience; the latter being clearly of great importance in terms of outcome. The use of single new drugs in someone with multi-resistant virus should be discouraged and trial design should reflect the new paradigm that there is a high likelihood of failure in this situation and combinations of agents to which the virus will sensitive provides the best hope for suppression.

In conclusion, the future is rosy and now what we must deal with is developing effective therapies for hepatitis C, where the story is much less favourable, and for late HIV diagnosis, which remains a socio-political issue.

Source: NATAP.org

References

All references refer to the Programme and Abstracts of the 12th Conference on Retroviruses and Opportunistic Infections, 22-25 February 2005, Boston USA. Available at:

http://www.retroconference.org/Search_Abstract_2005/AbstractSearch.aspX

1. Markowitz M, Mohri H, Ho D et al – A case of recent infection with a multi-drug-resistant and dual-tropic HIV-1 in association with rapid progression to AIDS. 12th CROI, Boston, 2005, Poster 973b.
2. Spaargaren J, Coutinho R, Fennema H et al. A new lymphogranuloma venereum strain of chlamydia trachomatisIdentified in HIV-+ men having sex in Amsterdam. 12th CROI, Boston, 2005. Abstract 896.
3. Rieg G, Daar E, Wit M et al. Community-aquired methicillin-resistant staphylococcus aureus colonization among HIV-infected men who have sex with men: a point prevalence survey. 12th CROI, Boston, 2005. Abstract 877.
4. Lin P, Ho H, Fan L et al. Inhibition mechanism of small-molecule HIV-1 attachment inhibitors. 12th CROI, Boston, 2005. Abstract 544.
5. Owen A, Almond L, Hartkoorn R et al. Relevance of drug transporters and drug metabolism enzymes to nevirapine: superimposition of host genotype. 12th CROI, Boston, 2005. Abstract 650.
6. Muirhead G, Pozniak A, Gazzard B et al. A novel probe drug interaction study to investigate the effect of selected ARV combinations on the pharmacokinetics of a single oral dose of UK-427,857 in HIV+ve subjects. 12th CROI, Boston, 2005. Abstract 663.
7. Westby M, Smith-Burchnell C, Hamilton D et al. Structurally-related HIV co-receptor antagonists bind to similar regions of CCR5 but have differential activities against UK-427,857-resistant primary isolates. 12th CROI, Boston, 2005. Abstract 96.
8. Nakata H, Koh Y, Maeda K, Takaoka Y et al. Greater synergistic anti-HIV effects upon combinations of a CCR5 inhibitor AK602/ONO4128/GW873140 with CXCR4 inhibitors than with other anti-HIV drugs. 12th CROI, Boston, 2005. Abstract 543.
9. Sparks S, Adkison K, Shachoy-Clark A et al. Prolonged duration of CCR5 occupancy by 873140 in HIV-negative and HIV-positive subjects. 12th CROI, Boston, 2005. Abstract 77.
10. Adkison K, Shachoy-Clark A, Fang L et al. The pharmacokinetic Iiteraction between the CCR5 antagonist 873140 and lopinavir/ritonavir in healthy subjects. 12th CROI, Boston, 2005. Abstract 664.
11. Baba M, Kanzaki N, Miyake H et al. TAK-652, a novel small molecule CCR5 antagonist with potent anti-HIV-1 activity. 12th CROI, Boston, 2005. Abstract 541.
12. Tremblay C, Giguel F, Chou T. TAK-652, a novel small molecule inhibitor of CCR5 has favorable anti-HIV interactions with other antiretrovirals in vitro. 12th CROI, Boston, 2005. Abstract 542.
13. Veazey Ronald, Klasse P, Dufour J et al. Vaginal application of a small molecule CCR5 inhibitor protects macaques against vaginal SHIV 162P transmission. 12th CROI, Boston, 2005. Abstract 128.
14. Jochmans D, Kesteleyn B, Marchand B et al. Identification and biochemical characterisation of a new class of HIV inhibitors: nucleotide-competing reverse transcriptase inhibitors. 12th CROI, Boston, 2005. Abstract 156.
15. de Béthune M-P, Andries K, Azijn H et al. TMC278, a new potent NNRTI, with an increased barrier to resistance and good pharmacokinetic profile. 12th CROI, Boston, 2005. Abstract 556.
16. Goebel F, Yakovlev A, Pozniak A, TMC278: potent anti-HIV activity in antiretroviral therapy-naïve patients. 12th CROI, Boston, 2005. Abstract 160.
17. Yoakim C, Bonneau P, Déziel R et al. Novel 8-substituted dipyridodiazepinone inhibitors with broad-spectrum of activity against NNRTI-resistant HIV-1. 12th CROI, Boston, 2005. Abstract 557.
18. Bonneau P, Robinson P, Duan J et al. Antiviral characterisation and human experience with BILR 355 BS, a novel next-generation non-nucleoside reverse transcriptase inhibitor with a broad anti HIV-1 profile. 12th CROI, Boston, 2005. Abstract 558.
19. Chu C, Yadav V, Rapp K et al. Dioxolane thymine nucleoside is active against a variety of NRTI-resistant mutants. 12th CROI, Boston, 2005. Abstract 554.
20. Gripshover B, Santana J, Ribaudo H et al. A randomised, placebo-controlled trial of amdoxovir vs placebo with enfuvirtide plus optimised background therapy for HIV-infected subjects failing current therapy (AACTG 5118). 12th CROI, Boston, 2005. Abstract 553.
21. Himmel D, Sarafianos S, Clark A et al. Crystal structure of a complex of HIV-1 reverse transcriptase with an RNase H inhibitor bound at a novel site on the enzyme. 12th CROI, Boston, 2005. Abstract 157.
22. Fransen S, Gupta1 S, Paxinos E et al. Integrase inhibitor susceptibility can be measured using recombinant viruses that express patient virus integrase alone, or in combination with protease and reverse transcriptase. 12th CROI, Boston, 2005. Abstract 725.
23. Little S, Drusano G, Schooley R et al. Antiretroviral effect of L-000870810, a novel HIV-1 integrase inhibitor, in HIV-1-infected patients. 12th CROI, Boston, 2005. Abstract 161.
24. Leh H, Thomas C, Zouhiri F et al. Styrylquinolines derivatives targeting HIV integrase are in vitro synergic with reverse transcriptase inhibitors and diketo acids. 12th CROI, Boston, 2005. Abstract 547.
25. Cooper D, Hicks C, Cahn P et al. 24-week RESIST study analyses: the efficacy of tipranavir/ritonavir is superior to lopinavir/ritonavir, and the TPV/r treatment response is enhanced by inclusion of genotypically active antiretrovirals in the optimised background regimen. 12th CROI, Boston, 2005. Abstract 560.
26. Schapiro J, Cahn , Trottier B et al. Effect of baseline genotype on response to tipranavir/ritonavir (TPV/r) compared with standard-of-care comparator (CPI/r) in treatment-experienced patients: the phase 3 RESIST-1 and -2 trials. 12th CROI, Boston, 2005. Abstract 104.
27 Wu A, Huang I, Lobo F et al. Health-related quality of life with tipranavir in combination with an optimised background regimen in 2 randomised clinical trials. 12th CROI, Boston, 2005. Abstract 617.
28. Katlama C, Berger D, Bellos N et al. Efficacy of TMC114/r in 3-class experienced patients with limited treatment options: 24-week planned interim analysis of 2 96-week multinational dose-finding trials. 12th CROI, Boston, 2005. Abstract 164LB.
29. Ford S, Reddy S, Anderson M et al. 640385, a novel HIV-1 protease inhibitor: safety and pharmacokinetics following repeat administration with and without ritonavir in healthy subjects. 12th CROI, Boston, 2005. Abstract 563.
30. Hammond J, Jackson L, Graham J et al. In vitro selection and characterisation of HIV with reduced sensitivity to AG-001859. 12th CROI, Boston, 2005. Abstract 561.
31. Koh Y, Nakata H, Ogata-Aoki H et al. UIC-02031: a novel nonpeptidic protease inhibitor containing a stereochemically defined fused cyclopentanyltetrahydrofuran potent against multi-PI-resistant HIV-1 in vitro. 12th CROI, Boston, 2005. Abstract 562.
32. Martin D, Jacobson J, Schurmann D et al. PA-457, the first-in-class maturation inhibitor, exhibits antiviral activity following a single oral dose in HIV-1-infected patients. 12th CROI, Boston, 2005. Abstract 159.
33. Martin D, Ballow C, Doto J et al. The safety, tolerability, and pharmacokinetics of multiple oral doses of PA-457, the first-in-class HIV maturation inhibitor, in healthy volunteers. 12th CROI, Boston, 2005. Abstract 551.

The D:A:D study is the largest and longest running prospective cohort study assessing the relationship between HAART and cardiovascular disease. This is a multinational study including over 23,000 patients enrolled in national cohorts from Europe, Australia and the US.

Data presented in an oral presentation from the latest analysis of this important dataset, which now includes over 76,000 patient years with median exposure to HAART of 4.5 years, continued to show that NNRTI- or PI-including combination therapy is an independent risk factor for cardiovascular disease.

By 2004, 277 patients experienced a first myocardial infarction (MI). The incidence of MI/1000 patient years increased from 1.39 in treatment naïve patient, to 2.53 in those exposed for < 1 year, to 6.07 in those exposed for ≥ 6 years (RR compared to no exposure:  4.38 [95% CI 2.39 to 8.04], p = 0.0001). After adjustment for other potential risk factors, there was a 1.17-fold [95%CI, 1.11 to 1.24] increased risk of MI per additional year of combined ART exposure.

After six years there are now sufficient events in the database to look at role of age and gender. Although the rate of myocardial infarction was higher in men than women (2.04 [1.30 to 3.21]), the RR associated with HAART was similar in men (1.14 [1.06 to 1.24]) and women (1.38 [1.07 to 1.76], p value for interaction 0.51). The relationship was similar in younger and older patients (men > 45 and women > 55 years; p value for interaction 0.41).

Including time-updated levels of serum total cholesterol in the same model, reduced the association of additional year of combined ART with myocardial infarction to 1.10 [1.01 to 1.19]. Adjustment for lipid-lowering medication did not further affect the association between HAART exposure and MI. Lipodystrophy was not associated with the risk of MI (RR 0.99 [0.75 to 1.30]).

The presentation concluded that while the overall absolute risk of myocardial infarction remains modest, the risk continues to increase with longer exposure to HAART and that these relative increases in risk appears similar in men and women, and in older and younger subjects.

COMMENT

The conclusion from this study is right to stress that the absolute risk for cardiovascular disease in many patients is low. Although accounting for lipid abnormalities explains much of the risk it does not explain it all. Also, if choice of HAART contributes to elevated lipids then the rationale for adjusting this out of the calculation may not help when considering implications for patients for whom HAART raises their lipids.

In an excellent symposium on CVD that included reference to D:A:D and other studies the cumulative risk was also pointed out to have a similar impact as ‘ever-smoked’ and that the management of individual patients should include evaluation for CVD risk prior to starting or changing HAART, and probably annually thereafter. [2, 3] On-line risk calculators provide a free and instant tool for assessing this with a patient, although a previous D:A:D analysis indicates that Framingham-based risk equations slightly underestimate risk for an HIV-positive population.

Best advice to patients remains lifestyle changes that significantly reduce risk, such as smoking cessation. However the same symposium included a long presentation and discussion on the target lipid concentrations. Recent studies in the general population have shown that reducing cholesterol levels provide a continuous range of benefit that is not just related to highest baseline levels. On a population basis, this has resulted in US guidelines reducing the target goals further and linking different goals to different individual 10-year risks.

Non-HDL NCEP targets in the US (possibly a more appropriate measure for HIV-positive patients who often have elevated triglyercides) for patients with >20% 10-year risk, <20% 10-year risk or 1-2 risk factors are now <3.36, <4.14 and <4.91 mmol/l respectively. LDL targets for the same risk groups are <2.59, <3.36 and <4.14 mmol/l respectively.

References
1. El-Sadr W, Reiss P, De Wit S et al on behalf of the D:A:D Study Group. Relationship between prolonged exposure to combination ART and myocardial infarction: effect of sex, age, and lipid changes. 12th CROI, Boston, 2005. Oral Abstract 42.
2. Lundgren JD – Cardiovascular outcomes in HIV infection. Symposium: Heart and HAART. 12th CROI, Boston, 2005.
3. Martinez E – Managing cardiovascular risk and lipid disorders. Symposium: Heart and HAART. 12th CROI, Boston, 2005.

In an oral presentation at the conference, a double blind, randomised trial carried out by French researchers with 122 subjects over 16 weeks showed the efficacy of using Omega-3 polyunsaturated fatty acids to treat hypertriglyceridaemia in patients receiving HAART.

Sixty HIV-positive patients received Maxepa capsules containing 1g fish oil (2 capsules, 3 times a day, 18% EPA, 12% DHA) and 62-patients received placebo (1g paraffin oil capsules), all of whom were receiving HAART and had high triglycerides greater than 2 g/L after four weeks of appropriate dietary advice. Patients were given 8 weeks of treatment or placebo, followed by 8 weeks of open label treatment.

The median change in triglycerides at week 8 was –25.5% in those receiving treatment compared to +1% in those on placebo. At the same point the mean triglycerides were 3.4 +/-1.8 g/L in those on treatment, and 4.8 +/- 3.1 g/L in the placebo group (whose only intervention had been dietary advice). Triglycerides were normalised in 22.4% of those receiving Maxepa, but in only 6.5% of those on placebo.

During the open label period triglyceride reductions were maintained in those who had originally received Maxepa, and decreased by 21.2% in patients who had previously been given placebo.

The researchers report that safety was good with no statistically significant differences being observed in the occurrence of adverse events between the two groups.

Patients with baseline triglycerides >10g/L were not randomised and received open label Maxepa. The mean decrease in triglycerides in this group was –35.6%.

Hypertriglyceridaemia is a common blood lipid change seen in people on antiretroviral therapy and its increasing incidence is thought to be associated with high cardiovascular risk.

The researchers concluded that the study demonstrated the efficacy of Omega-3 supplement to decrease triglycerides in ART-treated HIV-infected patients with baseline elevated triglycerides; and represented a potential option for first line therapy for ART-associated hypertriglyceridaemia because of its efficacy, good tolerance, and absence of drug interactions.

COMMENT

This study looked at the use of 6 capsules of Maxepa per day (2 capsules 3 times a day), but some doctors recommend 5 capsules twice a day. However, many UK clinics prefer to use Omacor 1g capsules which contain 46% EPA and 38% DHA and require just 2 capsules twice a day. Both are available in the UK.

Ref: De Truchis P, Kirstetter M, Perier A et al. Treatment of hypertriglyceridemia in HIV-infected patients under HAART, by (n-3)polyunsaturated fatty acids: a double-blind randomised prospective trial in 122 patients. 12th CROI, 2005. Abstract 39.

OMACOR home page .
http://www.omacor.co.uk

An international, phase II study of the anti-hepatitis B drug Entecavir (ETV) showed that in HIV-HBV coinfected patients with 3TC-resistant HBV, adding ETV therapy reduced HBV DNA and normalised ALT within 24 weeks, with tolerability comparable to placebo. No interaction with HIV infection or HAART was reported.

ETV-038 is an ongoing, double blind, comparative trial with 68 coinfected participants who had HBV viraemia while being treated with 3TC. The study included sites in Brazil, UK, USA, Argentina and Spain. Most (88%) had HBV with at least one 3TC-resistant mutation. Patients were randomised to receive ETV 1mg (n=51) or placebo (n=17) once-daily for 24 weeks followed by open label ETV for all participants for another 24 weeks. All patients continued taking 3TC.

The mean baseline HBV viral load was 9.13 log10 copies/mL. The mean reduction in HBV DNA at 24 weeks was greater in the ETV group than in the placebo group (-3.66 vs +0.11log10 copies/mL, p<0.0001), with 84% vs 0% achieving either <400 copies/mL or a >/= 2 log10 reduction from baseline (p<0.0001). After 24 weeks, ALT had normalised in 49% in the ETV group compared to 0% in the placebo group (p=0.05).

Frequency of adverse events was comparable between the two groups after a mean follow-up of more than 40 weeks. There were no significant changes in HIV viraemia or in CD4 count in either group.

COMMENT

On March 11, the FDA Antiviral Drug Advisory Committee voted to approve entecavir for first- and second-line therapy based on studies in HBV monoinfected patients. They also recommended comparative studies be conducted between entecavir and adefovir and tenofovir.

ETV was equivalent (non-inferior) to lamivudine for the secondary histologic endpoint of improvement in Ishak fibrosis score in the nucleoside-naïve studies but was superior in the lamivudine-refractory patient population.

Entecavir does not interact with HIV antiretrovirals in vitro.

There was discussion at the FDA public hearing about paediatric use. BMS applied for approval of pills & oral solution. There is no paediatric PK and safety data, and this is the population that would use the oral solution.

Ref: Pessoa W, Gazzard B, Huang A et al. Entecavir in HIV/HBV-co-infected patients: safety and efficacy in a phase II study (ETV-038). 12th CROI, Boston, 2005. Abstract 123.

One of the most publicised UK studies at the conference included an oral presentation of the RAVE Study. This is a switch study comparing differences in fat recovery and lipid parameter when using tenofovir or abacavir in patients with lipoatrophy who are changing from AZT or d4T. Results presented by Graeme Moyle from the Chelsea and Westminster Hospital showed that tenofovir was associated with fewer treatment discontinuations and greater improvements in lipid parameters.

Previous switch studies have shown that removing AZT or d4T from regimens can lead to an improvement in some lipoatrophy symptoms, and prospective data have suggested that neither abacavir nor tenofovir DF (TDF) is associated with lipoatrophy.

This was a randomised, open-label 48-week study using abacavir 300mg twice daily vs. TDF 300mg once daily in adults on HAART with moderate to severe lipoatrophy who had viral loads <50 copies/mL and who were naïve to the replacement drugs. Limb fat was measured by DEXA for primary endpoint and CT for secondary endpoint.

They randomised 71 adults receiving d4T and 34 receiving AZT to receive abacavir (n=53) or TDF (n=52).

Limb fat mass was similar in both groups at baseline, and there was a significant increase in both groups at 48 weeks (+0.5 kg vs +0.3 kg) with no difference between the two groups (p = 0.36). Similar changes in visceral fat and subcutaneous abdominal fat were observed by DEXA and CT scan. Virological suppression and CD4 impact were also similar in both groups.

Differences between the two arms in the ITT analysis was driven by six discontinuations in the abacavir arm, including 3 with hypersensitivity reactions, compared to just one in the TDF arm.

Mean changes (SD) in total cholesterol, LDL and triglycerides were –0.31 (1.15), –0.10 (0.93), and –0.46 (1.83) mmol/L with abacavir and –0.46 (1.11), –0.25 (0.72), and –0.49 (1.87) mmol/L with TDF. The changes in these parameters over 48 weeks showed TDF was associated with significantly greater lipid improvements (p=0.01, 0.05 and 0.01 respectively).

Ref: Moyle G, Sabin C, Cartledge J et al. A 48-week, randomised, open-label comparative study of tenofovir DF vs abacavir as substitutes for a thymidine analogue in persons with lipoatrophy and sustained virological suppression on HAART. 12th CROI, Boston, 2005. Abstract 44LB.

Previous articles in HTB have tracked the rationale for potential benefit of rosiglitazone (RSG), a PPARg agonist and transcription regulator, to reverse lipoatrophy, together with reports from several studies that found conflicting clinical results, but generally found no benefit.

HIV-positive patients with lipoatrophy have decreased PPAR-g and rosiglitazone has increased limb fat in HIV-negative adults with Type-2 Diabetes Mellitis (who also have reduces PPAR-g). A report from last years Lipodystrophy Workshop highlighted a study from Patrick Mallon showing that thymidine analogues could work downstream of any beneficial effect, negating any potential benefit. [1]

Dr Mallon brought new data to the Retrovirus meeting that analysed responses to rosiglitazone by continued use of background thymidine analogue that appears to confirm this finding clinicallly.

Mallon reported on 44 men (4mg RSG BID n = 21; placebo n = 23) to a sub-study of the 48 week ROSEY rosiglitazone study. 21 were receiving the thymidine analogues (tNRTI) zidovudine (AZT) (n = 3) or stavudine (d4T) (n = 18) at baseline. Changes in mitochondrial RNA (mRNA) in fat biopsies and lipid metabolism genes were analysed at 0, 2 and 48 weeks.

At week 2, only those randomized to RSG in the no-tNRTI group experienced a significant rise in PPAR-g expression (p = 0.046). Similar significant increases in PPAR-g co-activator 1 (PGC-1) expression were also observed in the RSG no-tNRTI group. At week 48, PPAR-g expression was significantly higher only in the no-tNRTI group, regardless of randomised treatment allocation (p = 0.04), with RSG having no effect in the tNRTI group.

However, no significant correlations were observed between changes in PPAR-g or PGC-1 expression and change in limb fat.

COMMENT

Although it is disappointing that no clinical benefit could be seen even when increased levels of PPAR-g were achieved without the use of thymidine analogues, this may be a reason to look again at this class of drugs, perhaps using pioglitazone, which does not increase cholesterol or triglycerides.

References

1. Nucleosides reduce PPAR-gamma: a role for rosiglitazone without thymidine analogues. Report form 6th Lipodystrophy Workshop. HIV Treatment Bulletin, December2004/January 2005.

2. Mallon P, Sedwell R, Rogers G et al. The effect of rosiglitazone on PPARg expression in human adipose tissue Is limited by continued exposure to thymidine NRTI. 12th CROI, Boston, 2005. Abstract 41.

Marion Peters and colleagues presented 48-week results from a randomised, double blind, placebo controlled trial study comparing tenofovir disoproxil fumarate (TDF) to adefovir dipivoxil (ADV) in coinfected patients. The non-inferiority design indeed showed that TDF was not inferior to ADV for the treatment of hepatitis B virus (HBV).

ADV 10mg is active against both wild type and lamivudine-resistant HBV and is licensed to treat HBV. TDF 300mg is licensed to treat HIV and has in vitro activity against both wild type and lamivudine-resistant HBV but this has not been studied in randomised, controlled trials. The aim of ACTG A5127 was to assess TDF 300mg daily compared to ADV 10mg daily using time weighted average change from baseline in serum HBV DNA up to week 48. Non-inferiority was defined as a tolerance of –1log10 copies/mL. The research was also designed to compare the clinical responses of the two drugs, and to evaluate safety and tolerability.

The subjects were coinfected patients on stable HAART with serum HBV DNA >100,000 copies/mL and plasma HIV-1 RNA < 10,000 copies/mL within 12 weeks prior to study entry.

52 subjects received either ADV with TDF placebo, or TDF with ADV placebo, for up to 96 weeks. The study closed early based on the results of a prespecified interim review.

At baseline, 75% of subjects had HIV RNA <50 copies/mL and 98% had compensated liver disease; median serum HBV DNA was 8.71 and 9.36 log10 copies/mL in the ADV and TDF arms respectively. Median duration of follow-up was 75 weeks. Mean log10 time-weighted average change from baseline to week 48 was–3.21 and –4.44 log in the adefovir and tenofovir arms respectively. The 99.9% lower bound on this reduction was –0.05 logs, which confirmed the non-inferiority of TDF.

However these results certainly appeared to show a trend for greater potency with tenofovir, and this point was raised by several questions from the audience. Gilead Sciences are the manufacturer of both these drugs.

In multi-covariate analysis, treatment arm (p = 0.017), baseline serum HBV DNA (p = 0.0001), and alkaline phosphatase (p = 0.033) were associated with time-weighted average change from baseline to week 48.

Laboratory abnormalities were noted in 18 subjects in each arm; 11 subjects (5 ADV, 6 TDF) experienced serum ALT flares between 3.0 and 15.9 times baseline. ALT flares did not lead to decompensation in these compensated subjects. Four subjects on each arm prematurely discontinued drug including 2 deaths.

Ref: Peters M, Anderson J, Lynch P et al. Tenofovir disoproxil fumarate is not inferior to adefovir dipivoxil for the treatment of hepatitis B virus in subjects who are co-infected with HIV: Results of ACTG A5127. 12th CROI, Boston, 2005. Abstract 124.