Gilead and Merck/MSD to collaborate on long-acting HIV combination of lenacapavir and islatravir

Simon Collins, HIV i-Base

On 15 March 2021, in a joint press release, two leading research-based pharmaceutical companies – Merck/MSD and Gilead – announced they would be collaborating on long-acting HIV combinations. [1]

Each company has extremely promising compounds in development that need to be used in combination with similar long-acting drugs. Working in partnership should lead to much faster development than each company waiting to develop combinations independently.

From Merck/MSD, this includes islatravir, a highly potent NRTTI with the potential for daily, weekly and monthly oral formulations in phase 3 studies and an annual implant in phase 2.

From Gilead, this includes a long-acting capsid inhibitor being dosed as an infusion every six months that recently presented phase 2 results.

Both companies with be involved in development sharing costs and potential income 60:40 (Gilead:Merck/MSD). Gilead will lead in the US with Merck/MSD leading in the EU and rest of the world. Each company will have options to use other selected HIV drugs being developed by the partner company.

Both compounds are also being studied independently for use as PrEP, where the need to use combinations are currently not thought to be needed.


This is good news. Collaborating to use the most promising compounds from each company always seemed a more effective and faster way to develop new treatment options.

It also probably makes good commercial sense compared to the time needed for each company to develop a combination independently.


  1. Joint press release. Gilead and Merck announce agreement to jointly develop and commercialize long-acting, investigational treatment combinations of lenacapavir and islatravir in HIV. (15 March 2021). (Gilead) (Merck).

This report was first posted on 15 March 2021.

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