The present invention relates to chlorin e4 sodium and a process for its preparation. Chlorin e4 sodium is suitable for use in photodynamic therapy, cytoluminescent therapy and photodynamic diagnosis, for example for treating or detecting a tumour. The present invention also relates to a pharmaceutical composition comprising chlorin e4 sodium, to the use of chlorin e4 sodium in the manufacture of a phototherapeutic or photodiagnostic agent, and to a method of photodynamic therapy, cytoluminescent therapy or photodynamic diagnosis, for example for treating or detecting a tumour.
