Ifinatamab deruxtecan shows antitumor activity in advanced treatment-refractory solid tumors in phase 1/2 trial

BACKGROUND: Ifinatamab deruxtecan is a novel B7-H3-directed antibody-drug conjugate that leverages the clinically validated deruxtecan technology. We report dose-escalation results from a trial of ifinatamab deruxtecan in patients with solid tumours. METHODS: In this two-part, multicentre, open-label, first-in-human, phase 1/2 study of ifinatamab deruxtecan conducted at clinics in ten hospitals and cancer centres in the USA and Japan, we recruited patients aged 18 years or older who had advanced treatment-refractory solid tumours (small-cell lung cancer, oesophageal squamous cell carcinoma, castration-resistant prostate cancer, squamous non-small-cell lung cancer, head and neck squamous cell carcinoma, bladder cancer, sarcoma, endometrial cancer, melanoma, or breast cancer), and Eastern Cooperative Oncology Group performance status of 0 or 1. Patients received ifinatamab deruxtecan at doses of 0·8-16·0 mg/kg intravenously every 3 weeks. The primary outcome of dose escalation was the safety profile, which was evaluated in patients who received one or more dose of ifinatamab deruxtecan. Antitumour activity (per Response Evaluation Criteria in Solid Tumours version 1.1; secondary outcome) was evaluated in patients receiving ifinatamab deruxtecan at doses of 4·8 mg/kg or higher. The data cutoff was Jan 31, 2023. This trial is registered with ClinicalTrials.gov (NCT04145622) and is ongoing. FINDINGS: Between Oct 25, 2019, and July 13, 2022, 97 patients were enrolled and treated. 77 (79%) patients were male and 20 (21%) were female, 56 (58%) patients were White, and 31 (32%) were Asian. Three patients (3%) had dose-limiting toxicities; however, on the basis of protocol-defined criteria, the maximum tolerated dose was not reached. The most common grade 3 or worse treatment-emergent adverse events (TEAEs) were anaemia (17 [18%] patients), neutropenia (four [4%]), lymphocyte count decreased (three [3%]), and neutrophil count decreased (three [3%]). Serious TEAEs occurred in 31 (32%) patients. TEAEs associated with death were reported in five patients (5%; pneumonia, pneumonia aspiration, COVID-19 pneumonia, interstitial lung disease, and one death of undesignated cause); death due to interstitial lung disease was considered related to study medication by the investigator. After a median follow-up of 8·6 months (IQR 4·1-12·9), the confirmed objective response rate across tumour types was 34% (95% CI 23-47; 24 of 70 evaluable patients). INTERPRETATION: The maximum tolerated dose was not reached with ifinatamab deruxtecan; however, one death due to treatment-related interstitial lung disease highlights the importance of prompt evaluation and careful management of patients who develop interstitial lung disease. Promising antitumour activity was observed across various solid tumours. These findings support further evaluation of ifinatamab deruxtecan in randomised controlled trials. FUNDING: Funding for this study was provided by Daiichi Sankyo Company (Daiichi Sankyo) and Merck Sharp & Dohme, a subsidiary of Merck, Rahway, NJ, USA.