Phase I study of the novel distamycin derivative tallimustine (FCE 24517)

Abstract

Background: Tallimustine, a benzoyl nitrogen mustard derivative of the antiviral agent distamycin A, is a new alkylat-ing agent which binds to A-T rich regions of DNA in the minor groove producing highly sequence-specific alkylations. Its main preclinical features are a significant antitumour activity in animal models and a lack of cross-resistance in vitro and in vivo with L-PAM. Myelotoxicity was dose-limiting in animals, with a more than 100-fold difference in bone marrow sensitivity between mice and dogs. Patients and methods: Forty adult patients (pts) with solid malignancies were entered in the study. The drug was administered as an IV bolus every 4 weeks. CBC was repeated twice a week and serial assessments of renal function were performed in the week following the first cycle. From the starting dose of 50 μg/m2, corresponding to 1/3 of the highest non-toxic dose (HNTD) in dogs, there were increases through 10 dose levels, with reliance only on the features of the myelotoxicity observed. Results: The main toxic effect was neutropenia which was dose-limiting, selective and short-lasting. Only previously-untreated pts received doses of 750 μg/m2 or more, withgrade 4 neutropenia occurring in ≥75% of the cycles. The maximally tolerable dose (MTD) was defined as 1250 μg/m2, with 3 of 3 pts developing febrile neutropenia requiring IV antibiotics. A platelet count of < 100 × 103/μl was observed in only one pt. Bone marrow aspiration performed in selected pts on days 8 and 15 confirmed a highly selective impairment by tallimustine of the myeloid lineage, with rapid recovery of the proliferative compartment.Pharmacokinetic studies performed at 1000 μg/m2 and 1250 μg/m2 showed a rapid fall of the plasma levels within the first 2 hours with drug concentrations between 100 ng/ml and 400 ng/ml within the first hour. A partial response of 4 months' duration was reported in one previously-untreated pt with cutaneous recurrences of malignant mesothelioma. Conclusions: The report of some antitumour efficacy, the high selectivity of neutropenia, the lack of significant non-hematological toxic effects and the occurrence of detectable but still low plasma drug concentrations suggest that further clinical evaluation of higher doses of tallimustine in combination with colony-stimulating factors would be justified. © 1994 Kluwer Academic Publishers.