Following promising data on two long-acting HIV medicines presented at the Conference on Retroviruses and Opportunistic Infections (CROI) 2021, Gilead Sciences and Merck announced Monday that they would collaborate to develop the drugs as a single long-acting combination.

The medicines, lenacapavir and islatravir showed promising activity in small, short-term studies. Lenacapavir, from Gilead, is an experimental HIV capsid inhibitor being developed as a twice-yearly injection. It has shown good activity in HIV long-term survivors with multidrug-resistant virus. Merck’s islatravir is an investigational nucleoside reverse transcriptase translocation inhibitor that, early studies show, could be administered as a monthly pill for treatment or a yearly implant for HIV prevention. Gilead and Merck are testing both drugs for prevention and treatment of HIV.

The announcement Monday promises a collaboration between the HIV giants to develop not just an lenacapavir/islatravir long-acting regimen for people living with HIV but also allows Gilead to develop combination oral treatments with Merck’s oral integrase inhibitors. The companies will start testing the lenacapavir/islatravir combination together as oral and injectable formulations beginning in the second half of 2021.

Neither medicine is currently available in the United States, so results from these studies are still far off.

“Merck and Gilead seek to build on their legacies of transforming HIV care by focusing on long-acting therapies, which may represent a meaningful innovation in HIV drug development,” the press release reads.

“Our work in HIV over the past decades has been shaped by listening to people living with HIV and the physicians who treat them,” Gilead CEO Daniel O’Day said in the press release. “Now we are taking the same approach with long-acting therapies, combining the most advanced science from both companies to accelerate progress.”

The announcement thrilled Melanie Thompson, MD, of the AIDS Research Consortium of Atlanta who, during the conference, said the separate presentations on the two drugs excited her but was concerned that the two companies wouldn’t work together to develop them as a single treatment.

On Monday, she said the deal hearkens back to the intercompany collaboration that enabled the development of combination treatment in the 1990s.

“I will happily eat my words,” she said of her earlier suspicion that the companies might not work together. “This does fall into the game-changer category in my book. Now I hope they will find a way to lower the prices on all of these drugs! Breaking down proprietary boundaries can only benefit people living with HIV,” she told POZ.

Click here to read the press release.