Waitt C, Orrell C, Walimbwa S, et al. - Given a lack of knowledge on dolutegravir (DTG) use in pregnancy limits the global transition to its use in WHO-preferred regimens for HIV treatment, researchers examined how drug concentrations (pharmacokinetics, PK), including in breastmilk, influences viral suppression when initiated in the third trimester (T3). In DolPHIN-1, they randomized HIV-infected treatment-naïve pregnant women (28–36 weeks of gestation, age 26 (19–42), weight 67kg (45–119), all Black African) in Uganda and South Africa to dolutegravir (DTG) or efavirenz (EFV)-containing anti-retroviral therapy until 2 weeks postpartum and followed them until 6 months postpartum. In the third trimester, low plasma DTG exposures were observed, however with transfer across the placenta and through breastfeeding. Likely due to slower metabolic clearance, persistence was observed in infants. HIV RNA suppression < 50 copies/mL was twice as fast with DTG vs EFV. This indicates the potential of DTG in reducing the risk of vertical transmission in mothers who are initiated on treatment late in pregnancy.