A phase 1b, open-label, dose-escalation trial of the delta-like ligand 3 (dll3)/cd3 igg-like t cell engager, bi 764532, in patients with dll3-positive glioma

Abstract BACKGROUND Patients with progressive diffuse gliomas have limited treatment options. DLL3, a Notch ligand, is expressed on most diffuse gliomas. BI 764532, a humanized IgG-like T cell engager, binds selectively to DLL3-positive cells and promotes T cell-mediated cytotoxicity. Preclinical data showed activity of BI 764532 against intracranial tumors. In an ongoing first-in-human trial in patients with DLL3-positive small-cell lung carcinoma and other neuroendocrine carcinomas (NECs) including extrapulmonary NECs and large-cell NECs of the lung (NCT04429087), BI 764532 exhibited promising efficacy and manageable tolerability. Here we describe a planned Phase Ib dose-escalation/expansion trial of BI 764532 monotherapy in patients with DLL3-positive refractory/relapsed diffuse glioma. METHODS The dose-escalation part will include ~12–20 patients (≥3 patients per dose level) from 12 sites across Europe/USA. Dose escalation will be guided by Bayesian logistic regression model with overdose control. BI 764532 will be administered intravenously. Treatment will continue until disease progression, undue toxicity, informed consent withdrawn, or other reasons requiring treatment discontinuation. Once a recommended dose for expansion is established, ~15 patients from Europe will be treated in a dose-expansion phase. Key inclusion criteria: ≥18 years old; histologically confirmed primary progressive diffuse glioma who have failed on standard-of-care therapies; DLL3-positivity by IHC on archived tumor tissue by central pathology review. Key exclusion criteria: extracranial metastatic or leptomeningeal disease; previous treatment with DLL3-targeting therapies; prior treatment with bevacizumab/other anti-VEGF/anti-angiogenic treatment ≤6 months prior to first administration of BI 764532; persistent toxicity from previous treatments that has not resolved to ≤CTCAE Grade 1; diagnosis of immunodeficiency, or intake of immunosuppressive therapy ≤7 days prior to first administration of BI 764532. Primary endpoints: dose-limiting toxicities (DLTs) during the maximum tolerated dose evaluation period (escalation phase); DLTs during the entire treatment period (expansion phase). Other objectives include pharmacokinetics, pharmacodynamics, preliminary efficacy and evaluation of DLL3 as a potential biomarker.