Safety and Pharmacokinetics of Dolutegravir in Pregnant HIV Mothers and Their Neonates: A Pilot Study

Antiretroviral therapy (ART) in pregnancy is able to effectively reduce mother-to-child transmission (MTCT) of HIV. If untreated, the risk of transmission is around 25% (greater with high viral loads) but ART administered optimally during pregnancy may reduce this risk to 1-2%. In order to successfully prevent infection, ART should be started in the first or second trimester, and should reduce maternal plasma viral load to undetectable levels. Unfortunately throughout low-middle income countries, MTCT rates are unacceptably high with an estimated 430 000 newborn children infected annually. The main causes for this are undiagnosed or late diagnosis of maternal infection, suboptimal adherence to therapy and drug resistance, particularly in mothers who have previously received single dose nevirapine.

In sub-Saharan Africa (SSA), women frequently engage with health services late in pregnancy, and new HIV diagnoses in the third trimester (≥28 weeks of pregnancy) are not uncommon. Risk of MTCT is high, especially as NNRTI-based therapy takes a median of 2 months to significantly reduce the HIV viral load, making it unlikely that commencement of these drugs in late pregnancy will offer protection of the infant from intrapartum transmission.

Vertical transmission of HIV remains a significant challenge in developing countries and antiretroviral prophylaxis for PMTCT is an important tool towards elimination of paediatric infections. Between 2009 and 2010, coverage of antiretroviral prophylaxis for prevention of mother to child transmission was 42% and an estimated 1.48 million infants were born to women living with HIV (WHO 2010). Global efforts are geared towards improving access to antiretrovirals for PMTCT by simplifying antiretroviral treatment protocols while ensuring optimal outcomes for HIV-infected women and their children (WHO 2010; WHO 2012).

Under consolidated antiretroviral guidelines issued by the WHO in 2013, efavirenz-based ART is now recommended the preferred NNRTI option for HIV-1 infected patients, including among women of childbearing age and pregnant women (WHO 2013). In 2012, Uganda adopted the Option B+ strategy for PMTCT of HIV. Under this strategy, lifelong ART is offered to all pregnant ART naïve women irrespective of CD4 count with efavirenz-based ART as the preferred treatment option. However, the effectiveness of this regimen could be compromised in the event of large populations of women who may have been either exposed to single dose nevirapine in the past or among women with transmitted NNRTI resistance.

The justification for studying DTG in pregnancy includes:

1. Likely widespread availability of generic DTG in the coming years. The manufacturer has indicated its willingness to make DTG available in low income countries, and is currently engaging with generic manufacturers. Estimates from the Clinton Foundation suggest that generic manufacture of DTG will make this drug affordable either as an alternative first line, or else second line agent (Hill 2013). Clinical guidelines from the US and Europe currently rank INSTIs such as raltegravir and elvitegravir alongside NNRTIs as preferred first line agents. INSTIs may replace NNRTIs in first line regimens due to their good safety and toxicity profile, lower propensity for drug interactions, and superior efficacy. Large phase III RCTs comparing raltegravir (Rockstroh, Dejesus et al. 2013), elvitegravir (Sax, DeJesus et al. 2012) and dolutegravir (van Lunzen, Maggiolo et al. 2012) against efavirenz-based therapy have shown superior virological outcome at 48 weeks, faster time to undetectable viral load, lower incidence of adverse events, and fewer treatment discontinuations, and these findings have recently been confirmed in a meta-analysis (Messiaen, Wensing et al. 2013).
2. Low risk for serious drug-drug interactions. The potential for drug-drug interactions is significantly less for INSTIs compared with other antiretrovirals (relative risk compared with raltegravir: boosted protease inhibitors [RR = 4.96], non-nucleoside reverse transcriptase inhibitors [RR = 2.48](Patel, Abdelsayed et al. 2011). These are particularly important considerations for low/middle income country settings where adults with newly diagnosed HIV infection often present with tuberculosis, or during antenatal screening in late pregnancy. Here DTG may carry significant advantages over NNRTIs, and other INSTIs. In the absence of alternatives to rifampicin-based TB therapy, DTG and raltegravir exposures are only moderately reduced (Dooley, Sayre et al. 2013), compared to larger (50-90%) reductions in concentrations of boosted PIs, nevirapine and elvitegravir. Dolutegravir is metabolized by glucuronidation (UGT1A1) with some contribution from CYP3A.
3. Rapid viral load drop potentially beneficial in late diagnosis during pregnancy. In Sub-Saharan Africa, pregnant mothers tend to engage with health services later in pregnancy compared with Europe, and new HIV diagnoses resulting from universal testing at ≥28w gestation are frequent. DTG results in a very rapid reduction in viral load; median time to undetectable viral load in the SINGLE study was 28 days vs. 84 days with Atripla (P<0.0001) (Walmsley, Antela et al. 2012). Use of DTG may lower risk of mother-to-child transmission of HIV in late presenters. Although meta-analysis shows no increase in birth defects with maternal efavirenz (Ford, Mofenson et al. 2010), there has been recent suspicion of neurological toxicity in a large French registry (Sibiude, Madelbrot et al. 2013) and neurodevelopmental delay in a South African cohort (Westreich, Rubel et al. 2010)
4. Proven efficacy in patients with established drug resistance to other antiretrovirals. In most resource-poor settings, options for anti-retroviral therapy are limited (2011), and the emergence of HIV drug resistance gives cause for concern (Hedt, Wadonda-Kabondo et al. 2008; WHO 2012). In a cross-sectional study conducted among HIV-1 antiretroviral naïve patients in five African countries, the highest prevalence of transmitted resistance was observed in Kampala, Uganda 12.3% (22 of 179; 7.5-17.1) (Hamers, Wallis et al. 2011). In Malawi, the prevalence of primary drug resistance in new infections was 6.1% which is comparable with figures of ~3% for South Africa (Manasa, Katzenstein et al. 2012), and 5.7% for Zambia (Hamers, Siwale et al. 2010), with over half of all mutations conferring resistance to non-nucleoside reverse transcriptases (NNRTI) (Wadonda-Kabondo, Banda et al. 2012). Studies across Africa have shown that treatment response to NNRTIs in mothers and children exposed to nevirapine (particularly single dose) during pregnancy is blunted (Musiime, Ssali et al. 2009). In this context, a novel class of ARV which is safe, affordable and effective is an urgent need
5. Safety profile in pregnancy. DTG is classified as FDA pregnancy Category B. There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, and dolutegravir was shown to cross the placenta in animal studies, the manufacturer recommends that this drug should be used during pregnancy only if clearly needed (ViiV 2013).
6. Necessity of investigating DTG PK in pregnant women. Alongside the clinical and humanitarian imperative to provide effective treatment for preventing HIV transmission in pregnant mothers with NNRTI-resistant HIV, there is an equally important ethical imperative to establish the safety, efficacy and pharmacokinetics of DTG in pregnant mothers and their breastfed infants in SSA, especially given the implementation of WHO Option B+, and the potential for widespread use of DTG in the forseeable future. Previous experience suggests it is universally the case that pregnant women in SSA receive new antiretrovirals (ARV) ahead of any proper evaluation, and clinical studies (if undertaken at all) occur at a much later stage after many mothers and infants have been exposed.
7. Importance of undertaking the study in SSA. Any pivotal study if undertaken in developed countries would have limited generalizability to an African setting because i) ARVs tend to be initiated later in gestation in newly presenting pregnant women, ii) the standard of care across SSA is likely to be an efavirenz or nevirapine-based regimen iii) infant breastfeeding is recommended in the presence of ARVs ii) host factors such as BMI, ethnicity etc may impact on pharmacokinetics (PK) of ARVs.
8. Continued administration of DTG for 2 weeks post-partum (whilst breastfeeding) to characterize PK in non-pregnant state. Under standard of care, the infant will receive 6 weeks of nevirapine syrup, and would be exposed to the NNRTI/NRTI/NRTI combination received by the mother under standard of care. In this study, infants will be exposed DTG via the breastmilk for a 2 week period following birth. We believe this risk to be acceptable given the potential benefits. Furthermore, the risk is unlikely to exceed any potential risk of in utero exposure to DTG. Drug-drug interactions between directly administered NVP and DTG ingested via the breastmilk are unlikely to have clinical significance, although we will study this. The potential risks of breastfeeding are fewer than those of giving formula feeding during the two week period that mothers continue to receive DTG postpartum. Replacement of breast feeding with formula feeding during the first two weeks post-partum would be unethical due to the loss of the immune benefits of colostrum to the neonate, risks intrinsic to formula feeding in low resource settings and increased risk of HIV transmission if mixed feeding occurs (Teasdale et al, 2011) The potential risks of low-level ARV causing drug-resistance in the infant should the PMTCT fail exist for the standard of care NNRTIs and NRTIs; it is not anticipated that DTG will carry a greater risk but nevertheless this is best monitored within a clinical trial setting before widespread uptake without monitoring.

Study Design Open label randomized trial of DTG in late pregnancy. HIV+ pregnant women (untreated at ≥28w gestation will be randomized 1:1 to receive a DTG-based regimen compared with standard of care (regimen not containing INSTI).