Comparable efficacy and pregnancy outcomes with boosted atazanavir and lopinavir at standard doses

1 October 2013. Related: Conference reports, Antiretrovirals, Pregnancy, IAS 7th Kuala Lumpur 2013.

Polly Clayden, HIV i-Base

Retrospective data collected from nine London centres and presented at IAS 2013 suggests atazanavir/ritonavir (ATV/r) and lopinavir/ritonavir (LPV/r) at standard doses are comparable in efficacy and pregnancy outcomes.

In the UK and Ireland uptake of ART is high and rates of vertical transmission are low. HIV positive pregnant women frequently use protease inhibitors (PIs) despite concerns about pre-term delivery (for which data are conflicting) and altered pharmacokinetics.

The two PIs most commonly prescribed in this situation are ATV/r and LPV/r. Melissa Perry showed findings from a case note review conducted between September 2007 and August 2012 to look at which, if either, is preferred for pregnant women.

The investigators compared infant outcomes: pre-term delivery, transmission, birth weight, need for phototherapy and birth defects. Tolerability and virological response were compared in the women.

The analysis included 493 pregnancies. Women were a median age of 33 years, 81% were black African, 97% acquired HIV through heterosexual exposure, only 0.6% from injection drug use, 4% were coinfected with hepatitis B and 1% hepatitis C.

ATV/r use increased and LPV/r use decreased over the study period; overall 187 women received ATV/r and 306 LPV/r. Tenofovir/FTC was the most common RTI backbone for women receiving ATV/r (70%) and AZT/3TC for those receiving LPV/r (62%) – again reflecting changes in standard of care. The majority – 88% and 92% for ATV/r and LPV/r respectively – received the standard PI dose.

There were similar proportions of pre-term (< 37 weeks) deliveries in both treatment groups: 13% with ATV/r (n=19) vs 14% with LPV/r (n=40). Background population rate is 8% in UK and Ireland. There were also no differences in outcomes between women who conceived on antiretroviral treatment compared to those who received it post conception (See Table1).

There were two transmissions: ATV/r 1 (0.7%) vs LPVr 1 (0.4%), giving an overall rate of 0.5%.

The percentage of infants requiring phototherapy was low: ATV/r 2 (2%) vs LPV/r 2 (1%) and not seen more frequently in the ATV/r group (but very small numbers to make any comparison).

Birth defects were consistent with that reported to the Antiretroviral Pregnancy Register and occurred in 3 (3%) and 2 (2%) of infants exposed to ATV/r and LPV/r respectively at conception.

Low birth weight (<2500 g) occurred in 15% of infants in both treatment groups.

Two (2%) and 5 (5%) women receiving ATV/r pre- and post conception discontinued their PI due to tolerability, compared to 5 (6%) and 24 (11%) respectively for those receiving LPV/r. Although none of the comparisons were significant, Dr Perry pointed out that 55% of the 11% discontinuations in the post-conception LPV/r group were related to nausea and vomiting.

Women started ATV/r and LPV/r at a median of 20 and 22 weeks gestation. The majority of women had undetectable viral load (<50 copies/mL) at delivery: ATV/r 85% vs LPV/r 81%, p=0.61. Median time to undetectable: ATV/r 56 days vs LPV/r 43 days, p=0.52. This was despite the majority of women who received ATV/r receiving it at the standard dose with concomitant tenofovir.

This is the first study comparing pregnancy outcomes between these two PIs. Although it is limited as it is small and retrospective the findings are encouraging. Both regimens were successful in preventing vertical transmission. There were no differences in rates of pre-term delivery, outcomes, tolerability or virological suppression.

The pre-term delivery rate reported in this study is comparable to some studies and more favourable than others.

Comment

As the numbers of women in this analysis were small, the difference in side effects between LPV/r and ATV/r was not significant but the increase in discontinuations among women receiving LPV/r due to nausea and vomiting is worth emphasis and likely to become so with a larger sample size.

As with non-pregnant adults the use of LPV/r is declining and ATV/r increasing over time. It is reassuring that – despite the majority of women who received ATV/r receiving it at the standard dose with concomitant tenofovir – there was good viral suppression and a low transmission rate as with the women in the US cohort with increased doses of PIs described above.

Reference:

Perry M et al. Lopinavir and atazanavir in pregnancy: comparable infant outcomes, virological efficacy and preterm delivery rates. 7th IAS Conference on HIV Pathogenesis Treatment and Prevention, 30 June – 3 July 2013, Kuala Lumpur, Malaysia. Oral Abstract TUAC0101.