A phase II study of ispinesib (SB-715992) in patients with metastatic or recurrent malignant melanoma: a National Cancer Institute of Canada Clinical Trials Group trial

To assess the response rate and toxicity of the kinesin spindle protein (KSP) inhibitor, ispinesib, in malignant melanoma. Seventeen patients were enrolled from April to November 2005. Ispinesib was administered as a 1-hour infusion at a dose of 18 mg/m² once every 3 weeks until disease progression. No objective responses were seen. Six patients (35%) had a best response of stable disease for a median duration of 2.8 months. Disease progression was documented in 9 (53%) after 1 or 2 cycles. Eighty-eight percent of patients received ≥90% of planned dose intensity. Grade 3 non-hematologic toxicities included dizziness (1) and blurred vision (1). There was one episode of febrile neutropenia, but no grade 3 or 4 biochemical adverse events. Pharmacokinetics was consistent with prior studies. KSP immunoreactivity was seen in 14 of 16 available archival tissue samples (88%). Ispinesib can be safely administered using the dose and schedule employed, with mild hematologic and non-hematologic toxicity. No objective responses were observed, and further development of single-agent ispinesib in malignant melanoma is not recommended. Although KSP expression appears to be common in melanoma, KSP may not be a suitable target for its treatment.