Disclosed are a novel crystalline form of 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl- 3,5-dihydro-4H-pyridazino[4,5--]indole-l-acetamide, processes ofpreparing said crystalline form of 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-o]indole-l- acetamide, compositions comprising saidform in admixture with one or more pharmaceutically acceptable excipients, anduses for the same.