Tibotec Pharmaceuticals and Gilead Sciences have agreed to develop a new once-daily combination antiretroviral pill that combines the protease inhibitor Prezista with the investigational booster cobicistat.

In addition, the companies are currently in negotiations to develop a second pill combining Prezista, cobicistat, Emtriva, and an investigational new form of Viread called GS 7340.

“We are excited to be able to study and develop Prezista with an alternative boosting agent in a combination product which has the potential to reduce the number of tablets patients take,” said Dr. Johan Van Hoof, area head of Global Therapeutics for Infectious Diseases and Vaccines at Janssen Pharmaceutica (Tibotec’s parent company), in a press release.

Prezista (darunavir) is currently listed as a preferred protease inhibitor for first-line antiretroviral regimens for people with HIV. Cobicistat is under development by Gilead as a boosting agent similar to Norvir (ritonavir) and is in Phase 3 clinical trials. Gilead expects to file a New Drug Application for cobicistat with the U.S. Food and Drug Administration (FDA) in mid-2012.

The new combination pill would be the second once-daily protease inhibitor pill that combines an antiretroviral with a boosting agent; the other is Abbott Laboratories’ Kaletra (lopinavir/ritonavir). All other protease inhibitors must currently be taken with Norvir as a separate pill.

According to the agreement, the Prezista plus cobicistat combination will be developed and marketed by Tibotec, which is also responsible for filing a New Drug Application for the pill.

The companies stated that the agreement to develop a Prezista plus cobicistat combination pill is contingent on signing a second agreement to create a once-daily combination of Prezista, cobicistat, Emtriva (emtricitabine), and GS 7340. GS 7340, which is still in Phase 1 clinical trials, is a new formulation of Viread (tenofovir) that is expected to be safer and more effective than the current version.

If the agreement is signed, Gilead will be responsible for developing and marketing the second combination pill.

Tibotec and Gilead are also in the process of developing a once-daily combination pill that contains Truvada (tenofovir/emtricitabine) plus Edurant (rilpivirine), Tibotec’s new non-nucleoside reverse transcriptase inhibitor. Edurant was approved by the FDA in May (see related AIDS Beacon news). Tibotec expects the new combination pill to be available in the third quarter of this year.

For more information, please see the press releases from Gilead and Tibotec (pdf).