Liposomal irinotecan (HR070803) in combination with 5-fluorouracil and leucovorin in patients with advanced solid tumors: a phase 1b dose-escalation and expansion study

This phase 1b study aimed to evaluate the dose-limiting toxicity (DLT), maximum tolerated dose (MTD), pharmacokinetics, and preliminary efficacy of HR070803, a novel nanoliposomal formulation of irinotecan, in combination with 5-fluorouracil and leucovorin in patients with pretreated advanced solid tumors. This study consisted of dose-escalation and expansion stages. Dose escalation was performed with a traditional 3 + 3 design; patients received intravenous infusion of HR070803 from 60 to 80 mg/m 2 , followed by leucovorin (200 mg/m 2 ) and 5-fluorouracil (2000 mg/m 2 ) every 2 weeks. In the expansion stage, patients received treatments at selected tolerable dose. Fifteen patients received treatments at 60 mg/m 2 ( n = 12) and 80 mg/m 2 ( n = 3). DLTs occurred in 2 patients at 80 mg/m 2 (grade 2 neutropenia that resulted in a dose delay of ≥ 7 days, n = 1; grade 3 febrile neutropenia, n = 1). The MTD was determined to be 60 mg/m 2 . The most frequent HR070803related adverse events included anorexia, leukopenia, neutropenia, nausea, fatigue, and diarrhea. SN-38, the active metabolite of irinotecan, exhibited lower maximum plasma concentrations and a prolonged terminal half-life when irinotecan was administered via nanoliposome compared to conventional injection. Overall, 4 patients achieved a partial response (confirmed, n = 2), and 9 had stable disease. The MTD of HR070803 was 60 mg/m 2 when infused with 5-fluorouracil and leucovorin. Nanoliposomal encapsulation modified the pharmacokinetics of irinotecan and SN-38. HR070803 with 5-fluorouracil and leucovorin demonstrated a manageable safety profile and promising antitumor efficacy in advanced solid tumors. Trial registration Clinicaltrials.gov, NCT05086848. Retrospectively registered on Oct. 12, 2021.