Persistent nevirapine resistance following mother to child transmission interventions

29 July 2004. Related: Conference reports, Pregnancy, Drug resistance, Intl Drug Resistance Workshop 13 Tenerife 2004.

Polly Clayden, HIV i-Base

Three studies presented at this meeting evaluated resistance in women having received single dose nevirapine to reduce mother to child transmission.

Patterns of selection and “fading” of Y181C and K103N in women with subtype A vs D

A resistance substudy of the HIVNET 012 trial from Susan Eshleman and colleagues examined the impact of subtype A vs D on the selection and “fading” of nevirapine associated mutations K103N and Y181C in a group of women following a single dose of nevirapine to reduce mother to child transmission. [1]

Genotypes were obtained at 7 days and 6-8 weeks and paired data were available for 159 women. Of this group 83 women had subtype A and 57 subtype D.

The investigators found a significantly higher overall rate of resistance (ie any nevirapine mutation) at 6-8 weeks than at 7 days, 47/140 (34%) and 31/140 (22%) respectively, in women with either A or D subtypes (p=0.013; OR 1,916; 95% CI: 1.287, 2.854). There was a higher rate of accumulation of mutations for subtype D vs A (OR 2.519; 95% CI: 1.136, 5.587).

The K103N mutation was detected at a higher rate in the 6-8 week samples: 41/140 (29%), than the 7 day samples: 18/140 (13%), (p=0.0001; OR 2.926; 95% CI: 1.287, 2,854) across both subtypes. Again the investigators noted a higher rate of accumulation for subtype D vs A although this was not statistically significant.

Conversely the detection rate for the Y181C mutation was higher at 7 days than at 6-8 weeks overall, 26/140 (19%) and 15/140 (11%) respectively (p=0.0145; OR 0.509; 95% CI: 0.297, 0.872. The investigators added: “Furthermore Y181 faded quickly in subtype A with little or no fading in subtype D.”

These findings demonstrate HIV-1 subtype to influence patterns of emergence and “fading” (from detection) for the K103N and Y181C mutations The investigators also looked at G190A but the number of mutations detected were too small for meaningful statistical analysis (they also noted other nevirapine mutations eg V106 and Y 188C in a small number of women). They report that for all three mutations, the results suggest that nevirapine mutations are better tolerated in subtype D than subtype A viruses and conclude that these findings suggest that HIV-1 subtype should be considered in the design and interpretation of studies to determine whether single dose nevirapine compromises subsequent NNRTI containing treatment.

Surveillance of nevirapine resistance in Kwazulu-Natal, South Africa

The startling scale of 75% nevirapine resistance at two weeks following single dose nevirapine, reported in women with subtype C at this meeting last year provoked much speculation around the longer term consequences of selecting nevirapine resistant virus [2]. Will NNRTI containing drug programmes be effective if women have access to treatment for their own HIV?

In their surveillance report Gordon and colleagues write: “It is essential that the rate and pattern of drug resistance development is closely monitored. This is especially true for South Africa, in the light of the initiation of its national antiretroviral programme [3].” They examined nevirapine resistance patterns in 30 mother and infant pairs (including one set of twins) with HIV-1 subtype C who had participated in a single dose (to mother and infant respectively) mother to child transmission (MTCT) programme at a clinic in Hlabisa, South Africa.

At six weeks following the nevirapine prophylaxis, 12/30 (40%) of women and 40% of infants had detectable resistance. The K103N mutation was the most common mutation in 10/12 (83%) of the mothers. Other mutations reported in the mothers included: Y181C in 3/12 (25%), Y188C in 3/12 (25%), V106M in 2/12 (17%) and G190A in 1/12 (8%) Two or more mutations were found in 4/12 (33.3%) mothers.

Of the group of infants, the Y181N was the most common mutation and was present in 11/12 (92%) of the children (including one of the twins). Additionally 2/12 infants (17%) had the K103N and another 1/12 (8%) had a subtype C associated V106M mutation.

The investigators also reported that the K103N mutation resulted in the loss of a protein kinase phosphorylation site at codons 102 to 105 in reverse transcriptase. This was replaced with myristoylation site at codons 99 to 104 and a glycosylation site at 103 to 106. All infants with nevirapine resistance lacked a tyrosine kinase phosphorylation site at codons 174 to 181.

The investigators concluded: “Given the high rate of resistance in mothers and infants after single dose nevirapine, the search for safer regimens to prevent MTCT should be intensified.”

Persistence of nevirapine resistance: the Ditrame Plus study

A resistance substudy of the Ditrame Plus trial – in which women received single dose nevirapine in addition to short course zidovudine to reduce MTCT and the infants short course zidovudine and single dose nevirapine syrups – evaluated nevirapine resistance at four weeks post partum. [4, 5]

Baseline and four week samples were available for 63 women, of this group 21 had infected and 42 uninfected infants. Samples from the 26 infected children were also evaluated (21 children whose mothers had and 5 children whose mothers had not received nevirapine, but who had received the infant dose.

The investigators reported 21/63 (33.3%) of women having developed nevirapine resistance at week four, with the K103N being the most common mutation. They also reported the mothers with infected and uninfected infants developed resistance at the same rate (33.3%), 7/21 and 14/42 respectively. No zidovudine resistance was detected in this group. Additionally DNA-PBMC nevirapine mutations were detectable in 15/20 (75%) of women for whom DNA samples were available at week four.

Analysis of nevirapine plasma concentrations revealed wide inter patient variability with a median concentration of 648 (range 417-954) ng/ml. Resistance was significantly associated with a higher plasma concentration of nevirapine and among women who received two doses of nevirapine 3/4 (75%) acquired resistance.

The investigators described predictive factors for nevirapine resistance for the mothers as: median viral load 4.93 log10 copies/ml (nevirapine resistance) vs 4.54 log10 copies/ml (no nevirapine resistance) (95% CI: 3.11[1.04-9.29], p=0.020); median nevirapine plasma concentration 851 (633 – 1063) ng/ml (nevirapine resistance) vs 598 (315-885) ng/ml, p=0.014 and CD4 <350 cells/mm3 81% nevirapine resistance vs 19% >350 cells/mm3, p=0.06. Multivariate analysis revealed two factors to be independently predictive of development of resistance: viral load OR 95% CI: 4 (1.13 – 14.09) p=0.12 and plasma concentration 2 days post partum OR 95% CI: 1.05-1.50, p=0.31.

Additionally 6/26 (23%) of the infected infants developed nevirapine resistance detectable in plasma and DNA-PBMC at four weeks post partum, and follow up samples in two children – one at 3 and one at 12 months old – detected archive mutations in the DNA-PBMC.

Summarising their findings the investigators note that the association between high level nevirapine plasma concentrations suggests, “That a high level of nevirapine concentration induced a prolonged viral replication under suboptimal drug selective pressure which promote the emergence of resistant strains.” Concerning the infants they write: “Recent studies have reported a negative impact of nevirapine resistance on a subsequent treatment including nevirapine; our results raise anxiety for those very young children presenting with resistant viruses.”

Comment

More bad news for highly active drugs with long half-lives, given as monotherapy (or effectively as monotherapy). Although nevirapine resistant variants “faded” from detection in women in HIVNET 012 by 12-24 months using population sequencing methods, resistant variants will surely still persist as minority variants and rapidly return when drug pressure is reintroduced. “Fading” is an inconguous term in a room of viroloists that have warned of the risks from archived resistance for many years now.

Jourdain et al showed dramatically reduced response in women receiving NNRTI containing regimens following acquisition of nevirapine resistance after receiving single dose nevirapine to reduce MTCT (at six months 75% unexposed, 53% of exposed but with no detectable mutations and 34% of exposed with detectable resistance were below 50 copies) [6]. Additionally when Mellors et al evaluated the role of minor NNTRI mutations, failure to achieve viral suppression was associated with previous NNRTI experience and NNRTI mutations at baseline [7,8]. However, genotyping failed to detect NNRTI mutations in 50/216 (23%) baseline samples in the NNRTI experienced patients, yet this group performed no better than those with detectable NNRTI resistance, and much worse that the NNRTI-naïve group who similarly showed no mutations.

Furthermore, as in the Thai study, adding nevirapine to background zidovudine is not associated with significantly less nevirapine resistance. The early emergence of the Y181C in the Uganda study (HIVNET 012) may help to explain the different rates of NNRTI mutations in mothers compared to infants, as previously reported and as seen in Kantor’s study. The more rapid “fading” of the Y181C would seem to suggest that this mutation is “less fit” relative to both K103N and wild-type virus at least in sub-type A virus.

Better news is that no resistance was reported for zidovudine as prescribed in the DITRAME study and this should equate with less of an impact on future therapy.

These data, and emerging pharmocogenomic data, highlight the need for more thorough investigation of antiretrovirals, new and old, and their resistance patterns, paying attention to clade, gender, age and ethnicity.

References:

1. Eshleman SH, Wang L, Guay LA et al. Distinct patterns of selection and fading of K103N and Y181C are seen in women with subtype A vs D HIV-1 after single dose nevirapine: HIVNET 012. XIII Intl Drug Resistance Workshop, Tenerife 8-12 June 2004. Abstract 50. Antiviral Therapy 2004; 9:S59.
2. Kantor R, Lee E, Johnston E et al. Rapid flux in non-nucleoside reverse transcriptase inhibitor resistance mutations among subtype C HIV-infected women after single dose nevirapine. XIII Intl Drug Resistance Workshop, Tenerife 8-12 June 2004. Abstract 78. Antiviral Therapy 2004; 9:S89.
3. Gordon M, Graham N, Bland R et al. Surveillance of resistance in KZN South Africa, including mother-infant pairs six weeks after single dose nevirapine. XIII Intl Drug Resistance Workshop, Tenerife 8-12 June 2004. Abstract 71. Antiviral Therapy 2004; 9:S80.
4. Dabis F, Ekouevi DK, Rouet F et al. Effectiveness of a short course of zidovudine and lamivudine and peripartum nevirapine to prevent HIV-1 mother-to-child transmission. The ANRS 1201 DITRAME Plus trial, Abidjan, Cote d’Ivoire. 2nd IAS Conference. France. 8-12 July 2003. Abstract 219.
5. Chaix ML, Ekouevi DK, Peytavin G et al. Persistence of nevirapine resistant virus and pharmacokinetic analysis in women who received intrapartum NVP associated to a short course zidovudine (ZDV) to prevent perinantal HIV-1 transmission: the Ditrame Plus ANNRS 1201/02 Study, Abidjan, Cote d’Ivoire. XIII International HIV Resistance Workshop 8-12 June 2004, Tenerife. Abstract 160. Antiviral Therapy 2004; 9:S176.
6. 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. XIII International HIV Resistance Workshop 8-12 June 2004, Tenerife. Abstract 41LB.
7. Mellors J, Palmer S, Nissley D et al. Low frequency NNRTI-resistant variants contribute to failure of efavirenz-containing regimens. 11th CROI 2004, Abstract 39.