Effect of 1,3,3,5,5-pentaziridino-1-thia-2,4,6-triaza-3,5-diphosphorine-1-oxide, a new antitumor agent with inorganic ring, on various experimental tumors.

1,3,3,5,5-Pentaziridino-1-thia-2,4,6-triaza-3,5-diphosphorine-1-oxide (SOAz), a new antitumor agent, was evaluated for antitumor activity against various mouse- and rat-tumor systems. The optimal treatment regimens of SOAz (i.p.) gave 262% and 134% increase in life span (ILS) in mice with P388 leukemia and L1210 leukemia implanted intraperitoneally, respectively, and 239% ILS in rats with Yoshida sarcoma of which 86% survived for 60 d after intraperitoneal tumor implantation. The compound showed a definite activity against Lewis lung carcinoma implanted intravenously. The compound also exhibited 80-100% inhibition of tumor local growth in all of four experimental tumor systems used in the present study. In contrast to cyclophosphamide, SOAz was active against B16 melanoma and Meth A, and demonstrated high activity against a subline of L1210 leukemia resistant to cyclophosphamide.