The present invention relates to acid addition salts of the integrase strand transfer inhibitor bictegravir with acids selected from the group consisting of hydrochloric acid and 1,5 naphthalenedisulfonic acid and crystalline forms thereof. Furthermore, the invention relates to processes for the preparation of the salts and their respective crystalline forms and to a pharmaceutical composition comprising one or more of them, preferably in a predetermined and/or effective amount, at least one pharmaceutically acceptable excipient and optionally one ore more additional antiviral agent(s). The pharmaceutical composition of the present invention can be used as a medicament, in particular for the treatment and/or prophylaxis of HIV-1 infections.
