FOSTER CITY, Calif. An investigational treatment for HIV by Gilead Sciences that combines four drugs in one tablet works as well as a drug already on the market, Gilead said Monday.

Gilead announced the results of a mid-stage clinical trial of its single-tablet Quad anti-retroviral drug, which combines its drug Truvada (emtricitabine and tenofovir disoproxil fumarate) with elvitegravir and cobicistat. The company said that after 48 weeks, the drug showed activity similar to that of Atripla (efavirenz, emtricitabine and tenofovir disoproxil fumarate), which Gilead markets under a partnership with Bristol-Myers Squibb.

At the 48th week, 90% of patients in the Quad arm achieved viral loads of less than 50 copies per milliliter, compared with 83% of those taking Atripla. Results of the study were to be presented Monday at the 50th annual Interscience Conference on Antimicrobial Agents and Chemotherapy in Boston.