A process of making crystalline polymorph of 7-ethyl-10-hydroxycamptothecin exhibiting an X-ray diffraction pattern having peaks at 10.9±0.2, 13.2±0.2, 23.9±0.2, and 26.1±0.2 2-theta degree is disclose, wherein the process comprises:(1) dissolving crude 7-ethyl-10-hydroxycamptothecin with a solvent selected from the group consisting of acetic acid, dimethyl sulfoxide, N,N-dimethylacetamide and mixtures thereof to form a solution (wherein the dissolving is preferably carried out at a temperature of at least 80 deg. Celsius) (2) forming crystals of 7-ethyl-10-hydroxycamptothecin by adding an antisolvent selected from the group consisting of 1,2-dichloroethane, acetone, ethyl acetate, ethanol, and mixtures thereof to the solution of step (1) to obtain a slurry (wherein the step (2) is preferably conducted at a temperature of 0-30 deg. Celsius) and(3) filtering the slurry of step (2) to obtain the crystalline solid 7-ethyl-10-hydroxycamptothecin.
