Background. Nevirapine (NVP) resistance emerges in up to 70% of women exposed to single-dose (sd) NVP for prevention of mother-to-child transmission of human immunodeficiency virus (HIV).
Methods. HIV-infected pregnant women were randomized to receive sdNVP and either zidovudine/lamivudine (3TC), tenofovir/emtricitabine (FTC), or lopinavir/ritonavir for either 7 or 21 days. The primary endpoint was the emergence of new NVP resistance mutations as detected by standard population genotype at 2 and 6 weeks after treatment. Low-frequency NVP- or 3TC/FTC-resistant mutants at codons 103, 181, and 184 were sought using allele-specific polymerase chain reaction (ASP).
Results. Among 484 women randomized, 422 (87%) received study treatment. Four hundred twelve (98%) women had primary endpoint results available; of these, 5 (1.2%) had new NVP resistance detected by population genotype: 4 of 215 in the 7-day arms (1.9%; K103N in 4 women with Y181C, Y188C, or G190A in 3 of 4) and 1 of 197 (0.5%; V108I) in the 21-day arms (P = .37). Among women with ASP results, new NVP resistance mutations emerged significantly more often in the 7-day arms (13/74 [18%]) than in the 21-day arms (3/66 [5%], P = .019). 3TC/FTC-resistant mutants (M184V/I) emerged infrequently (7/134 [5%]), and their occurrence did not differ by arm.
Conclusions. Three short-term antiretroviral strategies, begun simultaneously with the administration of sdNVP, resulted in a low rate (1.2%) of new NVP-resistance mutations when assessed at 2 and 6 weeks following completion of study treatment by standard genotype. ASP revealed that 21-day regimens were significantly better than 7-day regimens at preventing the emergence of minor NVP resistance variants.
Clinical Trials Registration. NCT00099632.