Suramin for germ cell tumors. In vitro growth inhibition and results of a phase II trial.
Academic Article
Overview
abstract
BACKGROUND: Several studies have indicated a role for specific growth factors in the differentiation or deregulated growth of germ cell cancers. One proposed mechanism of antitumor activity for suramin is the inhibition of these tumor-derived growth factors. METHODS: Based on these data, the effects of suramin were studied on the growth of a monolayer culture of two human teratocarcinoma cell lines, NT2/D1 and N2102ep. These represented one cell line that was sensitive (NT2/D1) and one that was resistant (N2102ep) to the differentiation agent retinoic acid. These studies were followed by a Phase II trial of suramin in patients with germ cell tumors. Patients were treated with a continuous infusion of suramin. Dosing was determined by a nomogram based on weekly serum concentrations. RESULTS: Suramin inhibited the growth of both cell types in a dose-dependent fashion at a concentration attainable in patient plasma. This provided the rationale for a clinical trial of suramin in patients with cisplatin-refractory germ cell tumors. Fourteen patients were treated, and no complete or partial responses were observed. One patient achieved a prolonged decline in serum alpha-fetoprotein level without change in the size of a bidimensionally measurable retroperitoneal mass for more than 11 months. CONCLUSIONS: Despite the results of the in vitro studies, a Phase II trial failed to demonstrate significant antitumor activity for suramin in patients with cisplatin-refractory germ cell tumors. Although the dosing of suramin by the nomogram was not associated with neurotoxicity, the time needed to achieve therapeutic levels was lengthy, and the levels, once achieved, were of short duration. Thus, an alternative means of administration, i.e., by intermittent bolus administration, is being investigated in trials for patients with prostatic carcinoma. The lack of definitive efficacy for suramin in this trial has led the authors to consider other agents in Phase II trials for cisplatin-refractory germ cell tumor.
