Anhydrate-free polymorphically pure micronized crystalline brexpiprazole di-hydrate for use in intramuscular injectable sustained release formulations

A process for preparing a batch of brexpiprazole dihydrate comprising less than 5% w/w of brexpiprazole anhydrate in relation to the total amount of brexpiprazole, which is suitable for pharmaceutical purposes, wherein the process comprises the steps of:

• a. providing a batch of brexpiprazole dihydrate by
• (i) providing brexpiprazole dihydrate in the form of crystalline material having a particle size distribution characterized by a d50 of at least 10 μm,
• (ii) adding brexpiprazole dihydrate to an aqueous medium to form a suspension, and
• (iii) subjecting the aqueous suspension of brexpiprazole dihydrate to a size reduction means to obtain brexpiprazole dihydrate in the form of crystalline material having a particle size distribution characterized by a d50 of at most 10 μm;
• b. taking a batch sample and subjecting same to PXRD analysis;
• and
• c. obtaining the batch as a pharmaceutical suitable batch, if reflections at 2-Theta angles of 10.0°+/−0.2° and 17.4°+/−0.2° are absent in the PXRD pattern.