Regional fibrosis after intraperitoneal administration of mafosfamide.

Mafosfamide is a cyclophosphamide analog which, unlike cyclophosphamide, does not require enzymatic activation and does not cause urinary tract toxicity. Administration of mafosfamide intraperitoneally, but not intravenously, causes a delayed, dose-dependent fibrotic peritoneal reaction associated with an increased incidence of delayed mortality. This phenomenon might complicate interpretation of in vivo laboratory studies of activity and toxicity in which the intraperitoneal route of administration is utilized. Further, this toxic effect presents a problem for the clinical development of this agent for regional therapies such as intraperitoneal installation.