Antiviral therapy 2016 12 06() doi 10.3851/IMP3112
Fostemsavir is a prodrug of temsavir, an attachment inhibitor that binds directly to HIV-1 gp120, blocking initial viral attachment and entry into host CD4 cells. Efficacy, safety, and dose-response data of fostemsavir in treatment-experienced, HIV-1-infected subjects, through Week 48, are reported.
AI438011 is an ongoing Phase IIb, randomized, active-controlled trial (NCT01384734). Subjects were randomized 1:1:1:1:1 into five arms: fostemsavir (400 mg twice daily [BID], 800 mg BID, 600 mg once daily [QD], or 1200 mg QD), and a reference arm (ritonavir-boosted atazanavir [ATV/r] 300/100 mg QD), each with a backbone of raltegravir 400 mg BID + tenofovir disoproxil fumarate 300 mg QD.
In total, 251 subjects were treated. Through Week 48, the proportion of fostemsavir subjects with HIV-1 RNA <50 copies/mL was 61-82% and 77-95% (modified intent-to-treat (mITT) and observed analysis, respectively); 71% and 88% for ATV/r subjects (mITT and observed). Observed virologic response rates were 74-100% versus 96% (fostemsavir versus ATV/r) in subjects with baseline viral load <100,000 copies/mL and 60-91% versus 71% when baseline viral load was ≥100,000 copies/mL. Across fostemsavir arms, median CD4+ count increases from baseline were 145-186 cells/µL and 142 cells/µL for the ATV/r arm. Fostemsavir doses were generally well tolerated and no fostemsavir-related adverse events led to discontinuation. CONCLUSIONS
Through Week 48, fostemsavir continued to be well tolerated and showed similar efficacy to ATV/r. These results support the ongoing Phase III trial in heavily treatment-experienced adults with limited therapeutic options (≤2 classes of active antiretrovirals remaining).