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This paper presents a retrospective review of 6 cases of severe neutropenia attributed to suramin, the response to granulocyte-colony stimulating factor (G-CSF) and the possible mechanism. Plasma suramin concentrations, G-CSF, platelet-derived growth factor-AB (PDGF-AB) and fibroblast growth factor basic (FGF basic) levels were measured and correlated with neutropenic course. The time course of neutropenia was unpredictable and occurred both during and following discontinuation of suramin. Neutropenia rapidly resolved with G-CSF. Neither the measured growth factor levels nor plasma suramin concentrations correlated with neutropenia. We conclude that neutropenia secondary to suramin is unpredictable and responds to G-CSF administration permitting further suramin therapy. The mechanism remains unknown.

10 patients with ovarian cancer, whose disease had progressed while receiving platinum-based therapy, were entered onto a phase II clinical trial of the antiproliferative agent suramin. Suramin was administered in a fashion that is associated with durable objective disease response in patients with hormonally resistant metastatic prostate cancer. No individual had an objective response to therapy in this study, but 3 of 9 evaluable patients (33%) experienced disease stabilisation and subjective clinical improvement for periods ranging from 2 to 5 months. Disease stabilisation was associated with prolonged periods of comparatively high plasma levels of drug, which appeared to be determined primarily by reduced drug clearance. We conclude that suramin has potential activity in platinum-resistant ovarian cancer, and we have initiated a second clinical trial using pharmacological information derived from this study.