The US Food and Drug Administration (FDA) has put a clinical hold on all the ongoing clinical trials of Gilead Sciences’ injectable lenacapavir in borosilicate vials for HIV treatment and prevention or pre-exposure prophylaxis (PrEP).

The pause is due to growing concerns regarding the compatibility of lenacapavir solution offered in borosilicate vials, which might result in the creation of sub-visible glass particles in the drug solution.

An experimental compound, lenacapavir is a long-acting inhibitor of HIV-1 capsid.

The mechanism of action of the therapy is different from presently approved classes of antiviral agents and hinders HIV-1 at various stages of its lifecycle.

It is currently not approved by any regulatory agency for any kind of usage.

With clinical hold in place, selection and enrolment of trial subjects and the dosing with injectable lenacapavir will be stopped in all trials using such formulation.

All additional trial activities, such as subject monitoring and dosing in comparator group, will advance as per the relevant trial protocol.

Furthermore, Gilead noted that the subject dosing with oral formulations of lenacapavir will progress without changes.

The trials which are placed on hold include Phase III GS-US-412-5624, Phase III GS-US-528-9023, Phase II/III GS-US-200-4625, Phase II GS-US-200-4334, Phase I GS-US-200-5710, Phase I GS-US-200-5709, Phase I GS-US-528-5744, Phase I GS-US-200-5717, Phase I GS-US-200-4540 and Phase Ib GS-US-536-5816.

Gilead Sciences chief medical officer Merdad Parsey said: “We are committed to working diligently with FDA to resolve this glass vial compatibility quality issue and resume injectable lenacapavir dosing in the affected studies in a timely fashion.”

In March this year, the company reported data from the Phase II/III CAPELLA trial where lenacapavir maintained increased rates of virologic suppression in heavily treatment-experienced people with multi-drug resistant HIV-1.