The hydrochloride salt form of afeletecan, a water-soluble camptothecin derivative conjugated to a carbohydrate moiety exhibiting antineoplastic activity. Afeletecan stabilizes the topoisomerase I-DNA covalent complex and forms an enzyme-drug-DNA ternary complex. As a consequence of the formation of this complex, both the initial cleavage reaction and religation steps are inhibited and subsequent collision of the replication fork with the cleaved strand of DNA results in inhibition of DNA replication, double strand DNA breakage and triggering of apoptosis. The peptide carbohydrate moiety of this agent stabilizes the lactone form of camptothecin in blood.