The present invention relates to a premix comprising vemurafenib, in particular vemurafenib hydrochloride, and hydroxypropyl methyl cellulose acetate succinate, which is herein referred to as HPMC-AS in a specific weight ratio and to oral dosage forms comprising said premix. Further, the invention relates to a process for producing said premix comprising vemurafenib hydrochloride and HPMC-AS and to the corresponding process of producing an oral dosage form containing the premix of the invention.
