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Stribild Advantages vs Atripla in Blacks Through Trial Week 144
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ICAAC 2014. September 5-9, 2014. Washington, DC
Full poster report - ICAAC: Long-Term Efficacy and Safety of E/C/F/TDF (STB) versus EFV/FTC/TDF (ATR) in HIV-1-Infected Treatment Naïve Black and Non-Black Subjects - (09/08/14)
Mark Mascolini
Previously untreated black study participants randomized to Stribild versus Atripla in phase 3 study 102 had a trend toward better virologic response after 144 weeks [1]. Side effect frequencies and lab abnormalities were generally similar in the two treatment arms or favored Stribild over Atripla.
Study 102 found Stribild (single-tablet elvitegravir/cobicistat plus tenofovir/emtricitabine) noninferior to Atripla (single-tablet efavirenz plus tenofovir/emtricitabine) as a first-line regimen after 48 and 96 weeks [2]. At week 96 virologic success rates were 84% were Stribild and 82% with Atripla. Respective success rates at week 144 were 80% and 75%. Because the HIV epidemic in the United States disproportionately affects blacks, researchers conducted this post hoc analysis of response rates in black versus nonblack trial participants at week 144 [1]. In the United States Stribild is indicated for antiretroviral-naive adults.
Among the 348 participants randomized to Stribild and the 352 randomized to Atripla, 106 (30%) and 91 (26%) were black. Among black participants, the Stribild and Atripla groups were similar in average age (35 and 36), proportion of men (77% and 80%), median pretreatment viral load (4.72 and 4.73 log), average pretreatment CD4 count (384 and 363), and history of injecting drugs (2% and 6%).
Among nonblack study participants, antiretroviral adherence measured by pill count through 144 weeks was at least 90% in 94% of both treatment arms. Among black participants, at least 90% adherence at 144 weeks was significantly more likely with Stribild than with Atripla (89% versus 76%, P = 0.023). Although the investigators did not say so, better adherence to Stribild than Atripla among blacks may reflect a better side effect profile with Stribild in blacks, detailed below.
Virologic success (defined as a viral load below 50 copies by FDA snapshot analysis) in blacks at week 144 stood at 78% in the Stribild arm and 66% in the Atripla arm. The 12.4% difference between arms (95% confidence interval -0.1% to 25%) approached statistical significance (P = 0.052). Among nonblack participants, week-144 response rates were similar with Stribild and Atripla (81% and 79%). Among blacks week-144 virologic failure rates were 12% with Stribild and 15% with Atripla.
Serious adverse event rates in blacks at 144 weeks were similar with Stribild and Atripla (19% and 18%). But grade 2 to 4 adverse event rates in blacks were lower with Stribild (13% versus 35%), as were rates of adverse events leading to treatment discontinuation (2% versus 11%, P = 0.014). No blacks stopped either regimen because of kidney problems through week 144.
Among blacks the most frequent adverse events with Stribild and Atripla were abnormal dreams (13% versus 22%) diarrhea (7% versus 10%), dizziness (4% versus 19%, P < 0.001), fatigue (2% versus 9%, P < 0.05), headache (6% and 6%), insomnia (1% versus 8%, P < 0.05), nausea (16% and 12%), rash (0 and 3%), and somnolence (4% versus 11%)
Median 144-week change in serum creatinine among blacks measured +0.13 mg/dL with Stribild and 0.00 mg/dL with Atripla (P < 0.001). (All study participants had an initial estimated glomerular filtration rate at or above 70 mL/min.)
Median lipid changes with Stribild versus Atripla at week 144 in blacks were statistically similar at 15 versus 21 mg/dL for total cholesterol, 8 versus 9 mg/dL for high-density lipoprotein cholesterol, 14 versus 16 mg/dL for low-density lipoprotein cholesterol, and 1 versus 0 mg/dL for triglycerides.
The researchers concluded that Stribild is "an efficacious, durable, well-tolerated, and safe treatment regimen for HIV-1-infected, treatment-naive, black patients."
References
1. Hardy D, Gathe J, Workowski K, et al. Long-term efficacy and safety of single-tablet regimen EVG/COBI/FTC/TDF (STB) compared to EFV/FTC/TDF (ATR) in HIV-1-infected treatment naive, blacks subjects. ICAAC 2014. September 5-9, 2014. Washington, DC. Abstract H-1001.
2. Zolopa A, Sax PE, DeJesus E, et al. A randomized double-blind comparison of coformulated elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate versus efavirenz/emtricitabine/tenofovir disoproxil fumarate for initial treatment of HIV-1 infection: analysis of week 96 results. J Acquir Immune Defic Syndr. 2013;63:96-100. http://www.ncbi.nlm.nih.gov/pubmed/23392460
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