The FDA has put a clinical hold on Gilead Sciences’ injectable HIV drug lenacapavir because of the risk of glass particles from the vials getting into the medication.

Gilead said the agency took this step because of “emerging concerns” about the compatibility of vials made of borosilicate glass with lenacapavir solution, which could potentially lead to the formation of subvisible glass particles in the solution of lenacapavir.

The hold affects a slew of ongoing early-, mid- and late-stage trials evaluating the long-acting HIV-1 capsid inhibitor. These include a phase 3 trial assessing lenacapavir for preventing HIV in cisgender men, transgender women, transgender men and gender nonbinary people 16 years and up who have sex with biological males and are at risk of HIV infection.

Other trials put on ice include another phase 3 trial evaluating lenacapavir plus standard of care treatment, emtricitabine/tenofovir alafenamide, for preventing HIV in adolescent girls and young women at risk of HIV infection and a phase 2/3 study investigating Gilead’s drug for individuals pre-treated for HIV infection who have developed multidrug resistance.