Phase II trial of karenitecin in patients with malignant melanoma: Clinical and translational study

Purpose: A phase II trial of the novel camptothecin karenitecin (BNP1350) was conducted to determine its efficacy and tolerability in patients with metastatic melanoma. Patients were biopsied to determine topoisomerase expression at baseline and response to therapy. Patients and Methods: Eligible patients had metastatic melanoma with up to three prior chemotherapy and/or any number of immunotherapy regimens. Treatment consisted of an i.v. infusion of 1 mg/m² karenitecin daily for 5 days with cycles repeated every 3 weeks. Fine-needle aspiration biopsies were done before treatment and on day 3 to determine topoisomerase expression from patients' tumors. Results: Forty-three patients were evaluable for response and toxicity. Most patients (72%) had stage M1C disease and were previously exposed to chemotherapy (56%). The investigational agent was well tolerated with limited gastrointestinal side effects or fatigue. The major toxicity seen was reversible noncumulative myelosuppression. One patient had a complete response after 11 months of therapy. No partial responses were seen, but 33% of the patients had disease stabilization lasting ≥3 months. Topoisomerase I, IIα, and IIβ expression and localization were determined in a subset of patients. Topoisomerase I expression was highest, followed by topoisomerase IIβ and topoisomerase IIα. Conclusion: Karenitecin was a well-tolerated investigational agent in this phase II study; side effects were generally mild and mostly hematologic. Karenitecin has significant activity in metastatic melanoma. Melanoma metastases express high levels of topoisomerase I. We did not observe any compensatory increase in topoisomerase II upon treatment with karenitecin.