Objectives: Cobicistat (COBI) enhances atazanavir (ATV) pharmacokinetic parameters
similarly to ritonavir (RTV) in both healthy volunteers and HIV-infected adults. Primary efficacy
and safety outcomes of this Phase 3, international, randomized, double-blind, double-dummy, active-
controlled trial in HIV-1-infected treatment-naïve adults (GS-US-216-0114/NCT01108510)
demonstrated that ATV+COBI was non-inferior to ATV+RTV, each in combination with emtricitabine/
tenofovir disoproxil fumarate (FTC/TDF), at Weeks 48 and 144, with high rates of virologic
success for both regimens (85.2% and 87.4%, respectively, at Week 48; and 72.1% and 74.1% at
Week 144), and with comparable safety and tolerability. Here, we describe virologic response and
treatment discontinuation by a wider range of subgroups than previously presented.
Methods: Subgroup analyses by baseline CD4 count (≤200, 201-350, >350 cells/mm3), baseline
HIV-1 RNA level (≤100,000, >100,000 copies/mL), race, sex, and age (<40, ≥40 years) evaluated
ATV+COBI versus ATV+RTV univariate odds ratios (ORs) for virologic success (viral load <50
copies/mL, intention-to-treat US Food and Drug Administration Snapshot algorithm) and discontinuation
due to adverse events (AEs) at Weeks 48 and 144. Of 692 patients randomized, 344 received
ATV+COBI and 348 ATV+RTV.
Results: ATV+COBI versus ATV+RTV ORs for virologic success did not significantly differ by
regimen overall at Weeks 48 and 144 (OR 0.90; 95% confidence interval [CI]: 0.64, 1.26) or within
subgroups, except in females, for whom ATV+COBI was favored at Week 144 (OR 2.36; 95% CI:
1.02, 5.47). However, there were more discontinuations due to withdrawal of consent and pregnancies
in females receiving ATV+RTV versus ATV+COBI. ORs for discontinuation due to AEs did
not significantly differ by regimen overall at Weeks 48 and 144 (OR 0.98; 95% CI: 0.61, 1.58) or
Conclusion: These findings indicate that both ATV+COBI and ATV+RTV, each with FTC/TDF, are effective
and well-tolerated treatment options across a wide demographic range of HIV-infected patients.