ViiV Healthcare, majority-owned by GlaxoSmithKline PLC with Pfizer Inc. and Shionogi & Co. Ltd. as shareholders, started a phase 3 study of cabotegravir, its injectable treatment for the prevention of HIV.

The study will compare the injection given every two months against the daily oral pre-exposure prophylaxis with Gilead Sciences Inc.'s Truvada. It is being conducted through a public-private collaboration of ViiV Healthcare, the HIV Prevention Trials Network, the U.S. National Institute of Allergy and Infectious Disease and Gilead Sciences.

The first phase 3 study will enroll about 4,500 men and transgender women at more than 40 sites in North and South America, Asia and Africa. A second phase 3 study for the prevention of HIV infection in young women is expected to start in 2017.