Phase I trial of Perrimustine, a new cysteamine (2-chloroethyl) nitrosourea: an intrapatient escalation scheme

The recently synthesized nitrosourea, N-[N'-chloro-2-ethyl-N'-nitrosocarbamoyl]-S-methyl cysteamine sulfoxide (Perrimustine), is water soluble and has a high alkylating activity, similar to that of the widely used nitrsoureas BCNU and CCNU, and a low carbamoylating activity. Preclinical studies with a broad spectrum of murine tumors indicate that this new compound may be clinically useful. The maximally efficient dose range (MEDR) in L1210 bearing mice was 45 mg/m2 (subcurative dose) to 67 mg/m2 (subtoxic dose). The present phase I trial used an intrapatient escalation schedule, so that each patient entering the study received a potentially active dose. The first dose injected was 1:100 of the MEDR suboptimal dose to check for anaphylactic sensitivity. Patients were then given increasing doses at increasing time intervals until toxicity was observed. The highest dose was given on day 150-230. The main toxic effect was myelosuppression [five out of the 24 patients evaluated: one grade 4 thrombocytopenia, two grade 3 thrombocytopenia; anemia and leucopenia were milder (grade 1 to 2 on OMS scale)]. Of the 19 patients evaluated for clinical response, one showed response after the 45 mg/m2 dose (disappearance of the cerebral metastasis with persistence of hepatic localizations in a patient with melanoma) and the disease was stabilized in two cases (a pleural mesothelioma and a renal carcinoma with lung metastases) after 26 and 37 weeks, with total cumulative doses per m2 of 232 and 196 mg, respectively.