Coadministration increased temsavir AUC, Cmax and Ctau by 45%, 53% and 44%, respectively. There was no change in ritonavir concentration. No dose adjustment of either medicinal product is necessary.

Based on drug interaction study results, ritonavir can be coadministered with fostemsavir without a dose adjustment. Coadministration of ritonavir (100 mg once daily) and fostemsavir (600 mg twice daily) increased temsavir Cmax, AUC and Cmin by 53%, 45% and 44% (n=18).

The pharmacokinetics of temsavir, the active moiety of fostemsavir, were determined in HIV-negative subjects following administration of fostemsavir (600 mg twice daily) and ritonavir (100 mg once daily) alone and in combination. Temsavir Cmax, AUC and C12 increased by 53%, 45% and 44%. These moderate increases in temsavir exposure were not associated with any additional safety signals and dose adjustment of fostemsavir is not required when coadministered with ritonavir.