First-in-human phase I study of the microtubule inhibitor plocabulin in patients with advanced solid tumors.

Background Plocabulin (PM060184) is a novel marine-derived microtubule inhibitor that acts as an antitumor agent. This first-in-human study evaluated dose-limiting toxicities (DLT) to define the maximum tolerated dose (MTD) and phase II recommended dose (RD) of plocabulin given as a 10-min infusion on Day (D) 1, D8 and D15 every four weeks. Patients and methods Forty-four patients with advanced solid tumors received plocabulin following an accelerated titration design. Results Plocabulin was escalated from 1.3 mg/m2 to 14.5 mg/m2, which was defined as the MTD. No RD was confirmed, because frequent dose delays and omissions resulted in low relative dose intensity (66%) at the 12.0 mg/m2 expansion cohort. The main DLT was grade 3 peripheral sensory neuropathy (PSN); other DLTs were grade 4 tumor lysis syndrome, grade 4 cardiac failure and grade 3 myalgia. Toxicities were mainly mild to moderate, and included abdominal pain, myalgia, fatigue, nausea, and vomiting. Myelosuppression was transient and manageable. Plocabulin had a half-life of ~4 h and a wide diffusion to peripheral tissues. Antitumor response was observed in cervix carcinoma and heavily pretreated metastatic non-small cell lung cancer patients, and disease stabilization (≥3 months) in patients with colorectal, thymic, gastrointestinal stromal and breast tumors, among others. The clinical benefit rate was 33%. Conclusion The main DLT of plocabulin was PSN, as anticipated for a tubulin-binding agent. Since encouraging antitumor activity was observed, efforts to improve toxicity and to find the RD were planned in other trials evaluating D1&D8 and D1-D3 plus D15-D17 schedules.

Phase I study of lurbinectedin, a synthetic tetrahydroisoquinoline that inhibits activated transcription, induces DNA single- and double-strand breaks, on a weekly × 2 every-3-week schedule.

Background Lurbinectedin administered as a 1-h intravenous infusion every 3 weeks induces neutropenia, with the nadir usually occurring during the second week. This phase I study evaluated an alternative lurbinectedin dosing schedule consisting of a 1-h infusion on days 1 and 8 every 3 weeks. Patients and methods Twenty-one patients with advanced cancer received lurbinectedin using a standard cohort dose escalation design. Results Three dose levels of 3, 4, and 5 mg of lurbinectedin were explored. The recommended phase II dose was 5 mg, with 3 of 13 patients having dose-limiting toxicity (DLT), although grade 4 neutropenia occurred in 50% of patients. Other frequent toxicities were mild to moderate nausea and vomiting, fatigue, decreased appetite, stomatitis and asymptomatic creatinine and transaminase increases. No objective responses occurred, but prolonged stable disease was observed in 7 patients, including 3 with soft tissue sarcoma. Conclusion The recommended phase II dose of lurbinectedin is 5 mg, administered as a 1-h infusion on days 1 and 8 every 3 weeks. These data support further testing of this dose and schedule, particularly in soft tissue sarcoma.