Ifinatamab deruxtecan

Small cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor. Although patient survival has been significantly improved by immune checkpoint inhibitors combined with chemotherapy, three major unmet needs remain in SCLC management. First, while prophylactic cranial irradiation (PCI) can reduce the risk of brain metastases, its neurotoxicity limits its use, particularly in elderly patients or those with neurological deficits. Whole-brain radiotherapy (WBRT) remains the primary approach for brain metastases, and hippocampal-avoidance WBRT (HA-WBRT) combined with neuroprotective agents can significantly reduce cognitive risks. Stereotactic radiosurgery (SRS) has shown survival benefits and less cognitive damage for patients with up to 10 brain metastatic lesions. Emerging therapies, such as antibody-drug conjugates targeting B7-H3/DLL3 (I-Dxd, ZL-1310) and bispecific antibody tarlatamab, have demonstrated intracranial response rates of 62.5%-71%. Regardless of whether the brain metastases had previously undergone radiation therapy, the novel drugs showed consistent activity, indicating promising improvements in the prognosis of brain metastases. Second, the rapid progression and severe treatment-related toxicity of SCLC greatly affect patients' physical and mental well-being. Therefore, quality of life (QoL) should be prioritised. Strategies to improve QoL include early palliative care, proactive symptom management, application of HA-WBRT or SRS to preserve neurocognitive function, and novel agents such as tarlatamab to alleviate symptoms including cough and dyspnoea. Third, real-world evidence (RWE), which complements clinical trial data by reflecting treatment efficacy and safety in routine clinical practice, is gaining increasing recognition but faces challenges due to data heterogeneity, bias, and lack of methodological standardization. Future directions involve developing new drugs with high blood-brain barrier penetration, such as radioligand therapy, conducting prospective studies to optimize HA and SRS applications, establishing high-quality RWE databases to support personalized treatments, exploring molecular subtypes (SCLC-A/N/P/I) and leveraging AI technologies to advance precision radiotherapy. SCLC management needs to be patient-centered, integrating precise treatment of brain metastases, QoL improvement, and the application of RWE to achieve a balance between survival benefits and QoL.

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.

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.

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).

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 for this study was provided by Daiichi Sankyo Company (Daiichi Sankyo) and Merck Sharp & Dohme, a subsidiary of Merck, Rahway, NJ, USA.