Antineoplastic activity of ASTA Z 7557 (NSC-345842, INN mafosfamide) on transplantable murine tumors.

The antitumor activity of ASTA Z 7557, a stabilized primary metabolite of cyclophosphamide, was evaluated in comparison with cyclophosphamide (CP) against different rodent tumor systems. At equimolar doses, which corresponded in mg/kg to the optimal doses of each compound, Z 7557 showed a higher therapeutic activity than CP when both drugs were administered intraperitoneally (ip) during 5 consecutive days. The drug remained active against a P388 subline totally resistant to CP, but to a much lesser extent. The ip-implanted B16 melanoma was highly sensitive to 100 and 50 mg/kg administered during 9 consecutive days: an increase in lifespan (ILS) of 244% was produced and 5 mice out of 10 were cured. This treatment administered against Lewis lung carcinoma (LL) transplanted intravenously (iv) induced an ILS of 179% and 3 mice out of 10 survived on day 60. This effect was slightly inferior to that produced by 50 mg/kg of CP, but is balanced by the number of long-term survivors recorded after administration of low doses of Z 7557. When mice bearing the subcutaneously (sc) implanted colon 38 (C38) tumor were treated with 200 mg/kg on days 2 and 9, the tumor growth was inhibited by 83% in comparison to the control mice. The wide range of activity of Z 7557, its stability and its different chemical reactivity as compared to CP appear to justify interest in this activated oxazaphosphorine.