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Promising Results for New HIV Attachment Inhibitor Drug Fostemsavir

March 10, 2015

At the 2015 Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle, 48-week results were presented from a phase 2b study of the new attachment inhibitor fostemsavir (BMS-663068). This drug is unique as it targets the surface protein gp120 on the virus which prevents attachment to the CD4 receptor ... something that no other approved HIV drug has done before. Results showed good control of HIV levels and tolerable side effects.

A total of 254 people were assigned to one of four groups with different doses of fostemsavir: 400mg (2x/day), 600mg (1x), 800mg (2x) and 1,200mg (1x). A fifth group took boosted atazanavir (Reyataz). Everyone also took tenofovir TDF (Viread) with raltegravir (Isentress). All had viral loads above 1,000 copies (43% with viral loads >100,000) before starting. Median CD4 count was 230, although 39% started with less than 200 CD4s.

The participants were treatment experienced with many having already had one or more regimens fail. However, they were all still sensitive to all of the study drugs as confirmed by resistance testing. Median age was 39, 60% were men and 30% were white.

Viral loads <50 copies were similar among the 5 groups and reached undetectable levels in 82%, 61%, 69%, 68% and 71% in those on doses of 400, 600, 800 and 1,200mg fostemsavir and atazanavir regimens. CD4 count increases of 140-200 cells were also similar across the five groups. None of these were statistically significant differences.

No serious side effects were reported with fostemsavir, and no one stopped the study because of side effects. No significant abnormalities with blood work were also reported. Fostemsavir has now moved into a Phase III study.

In a presentation from a second study of 42 people, fostemsavir was combined with darunavir (Prezista), ritonavir (Norvir) and etravirine (Intelence) to tease out possible drug interactions. Those results showed that fostemsavir appears to be well tolerated without significant drug interactions.


M Thompson, et al. "Attachment Inhibitor Prodrug BMS-663068 in ARV-Experienced Subjects: Week 48 Analysis". 2015 CROI, Seattle, WA.

IS Landry, et al. "HIV-1 Attachment Inhibitor Prodrug BMS-663068: Interactions with DRV/r and/or ETR". 2015 CROI, Seattle, WA.

This article was provided by Project Inform. It is a part of the publication The 22nd Conference on Retroviruses and Opportunistic Infections (CROI 2015). Visit Project Inform's website to find out more about their activities, publications and services.

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