A lyophilized pharmaceutical composition

A lyophilized pharmaceutical composition comprising lurbinectedin, wherein the composition is prepared by a process comprising:

• (a) dissolving a crystalline form of lurbinectedin in an aqueous solution having a pH less than 3.5 to provide a first solution;
• (b) providing a second solution comprising a bullring agent and an organic buffer in an aqueous solution at a pH of 5.6 or less;
• (c) combining the first and second solutions to provide a third solution;
• and
• (d) freeze-drying the third solution to provide the lyophilized pharmaceutical composition comprising lurbinectedin, and
• wherein the crystalline form of lurbinectedin of step (a) exhibits an X-ray powder diffraction pattern using Cu-Kα1 radiation comprising three or more peaks at 2-theta angles selected from 6.2±0.2°, 7.6±0.2°, 9.0±0.2°, 10.9±0.2°, 14.9±0.2°, and 15.3±0.2°.