Phase I results on the efficacy, safety and pharmacokinetics of lurbinectedin and irinotecan in advanced solid tumors.

Lurbinectedin and irinotecan showed synergistic antitumor activity when combined in preclinical studies, and have non-completely overlapping toxicity profiles. A two-stage phase I/II trial was designed to evaluate the combination. The first (dose escalation) stage of the trial assessed two schedules, lurbinectedin on Day (D)1 plus irinotecan on D1,D8 or D1 every three weeks in 83 patients with relapsed advanced solid tumors. Two recommended doses (RDs) were defined for lurbinectedin on D1 plus irinotecan on D1,D8: lurbinectedin 2.0 mg/m² plus irinotecan 75 mg/m², and lurbinectedin 3.0 mg/m² plus irinotecan 40 mg/m², both with primary growth factor prophylaxis. No RD was defined for lurbinectedin on D1 plus irinotecan on D1. Lurbinectedin on D1 plus irinotecan on D1,D8 q3wk showed a manageable safety profile at the RDs, with most common toxicities being myelosuppression, fatigue and gastrointestinal disorders. No toxic deaths occurred. Thirteen confirmed partial responses and 24 disease stabilizations ≥ 4 months were found at all dose levels, including the RDs. Compared to other tumor types, antitumor activity was higher in small cell lung cancer (SCLC), soft tissue sarcoma (synovial), endometrial carcinoma, glioblastoma and pancreatic adenocarcinoma. No major pharmacokinetic interaction was found between lurbinectedin and irinotecan. The second (expansion) stage of the trial is evaluating the RD of lurbinectedin 2.0 mg/m² plus irinotecan 75 mg/m² with primary growth factor prophylaxis in selected advanced solid tumors. An ongoing phase III trial is also evaluating the combination in second-line SCLC after prior platinum-containing chemotherapy. Trial registration number: NCT02611024 (Nov 20, 2015).