Crystallized form of lurbinectedin and method of making the same

A crystalline form of lurbinectedin of formula (I):

• characterized by 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°.