Gilead Sciences has presented impressive mid-stage data on its new four-drug HIV therapy which the company hopes will grab huge market share.

The company has announced Phase II results at the Conference on Retroviruses and Opportunistic Infections in San Francisco showing that Quad, a single pill containing Gilead’s investigational drugs elvitegravir and cobicistat with Truvada (emtricitabine and tenofovir), exhibited antiretroviral activity comparable to that of Atripla, which combines Truvada with Bristol-Myers Squibb’s Sustiva (efavirenz). The data showed that after 24 weeks, the proportion of patients who achieved HIV RNA (viral load) less than 50 copies/mL was 90% in the Quad arm and 83% in Atripla patients and discontinuation rates due to adverse events were comparable among both groups.

Norbert Bischofberger, Gilead's chief scientific officer, said ”we are excited about these results and look forward to working with the US Food and Drug Administration to finalise the Phase III clinical programme for the Quad and cobicistat”. His enthusiasm was shared by Calvin Cohen, principal investigator and director of research at the Community Research Initiative of New England.

He said that “simplified treatment regimens of co-formulated, fixed-dose medicines have become the standard of care in HIV therapy because they can help patients adhere to dosing schedules”. He added that “these positive efficacy and safety results indicate that the Quad has the potential to become an important new treatment option”.

In the fourth quarter, sales of Truvada were up 19% to $670.7 million, and were surpassed for the first time by Atripla, which leapt 50% to $697.8 million. Gilead and some analysts believe Quad could achieve similar blockbuster status.