1-Amino-substituted 4-methyl-5H-pyrido[4,3-b]indoles (gamma-carbolines) as tricyclic analogues of ellipticines: a new class of antineoplastic agents.

A series of 1-amino-substituted 4-methyl-5H-pyrido[4,3-b]indoles that are structurally related to ellipticines by deletion of a ring have been synthesized in order to evaluate their DNA affinity, their in vitro cytotoxicity on L1210 cultured cells, and their in vivo antitumor activity. Among 24 derivatives that have been prepared and studied for the structure-activity relationship in this new class of antineoplastic agents, those that have a NH(CH2)3N(R)2 side chain (R = CH3 or C2H5) at their 1-position, a 4-methyl group, and an 8-OH substituent, either with a 5-NH or with a 5-NCH3 group, show the most potent cytotoxicities on L1210 cultured cells and in vivo antitumor properties in P388 and L1210 leukemia systems. In vivo antineoplastic activity of the most potent products was confirmed in P388 and L1210 leukemia systems. In vivo antineoplastic activity of the most potent products was confirmed on other mouse experimental tumors from the standard NCI screening:B16 melanoma and C38 adenocarcinoma.