Shares in Gilead Sciences dropped this week after the firm revealed its first bid to develop a new triple therapy pill to combat HIV had failed. The company will now reformulate the drug, which combines Truvada (emtricitabine and tenofovir disoproxil fumarate) with Bristol-Myers Squibb’s Sustiva (efavirenz), and says it still hopes to file for approval of the once-daily medication by the end of the year.

The first formulation failed because Sustiva, when given as part of a combined pill, did not achieve the same medication level in the blood compared to a dose of B-MS’ drug given alone.

Gilead and B-MS hooked up last year to develop a once-daily, fixed dose combination of three anti-HIV drugs – two Gilead drugs, Viread (tenofovir) and Emtriva (emtricitabine), and B-MS’ Sustiva (efavirenz) [[18/05/04e]]. The companies are also exploring a co-packaged version that would include the three products as an interim step until a fixed-dose combination product could be made available.