The present invention relates to a co-crystal of roxadustat with L-proline and to a process for its preparation. Furthermore, the invention relates to a pharmaceutical composition comprising said roxadustat L-proline co-crystal, at least one pharmaceutically acceptable excipient and optionally at least one photostabilizing agent. The pharmaceutical composition of the present invention can be used as a medicament, in particular for the treatment and/or prevention of anemia in patients with end-stage renal disease (ESRD) and/or chronic kidney disease (CKD).
