Xencor presents initial data for XmAb819

On Friday, the company announced: “Xencor (XNCR), a clinical-stage biopharmaceutical company developing engineered antibodies for the treatment of cancer and autoimmune diseases, today announced initial results from the ongoing Phase 1 dose-escalation study of XmAb819, a ENPP3 x CD3 T-cell engaging bispecific antibody, in patients with advanced clear cell renal cell carcinoma (ccRCC). The results were presented in a poster at the AACR-NCI-EORTC Conference on Molecular Targets and Cancer Therapeutics in Boston, Massachusetts. The Phase 1 clinical trial is a multicenter, open-label, dose-escalation and dose-expansion study designed to evaluate XmAb819 as monotherapy in patients with advanced ccRCC. As of the September 19, 2025 data cut-off, 69 patients received XmAb819 across 10 intravenous dose cohorts and 5 subcutaneous dose cohorts. Patients received a median of 4 prior lines of therapy (range 1-8). All patients received prior anti-PD1 therapy and prior VEGF-TKI therapy, and 36% of patients were previously treated with a HIF2alpha inhibitor. Efficacy was assessed by investigators using RECIST v1.1. XmAb819 demonstrated evidence of anti-tumor activity and an acceptable safety profile that was generally well tolerated across dose levels. Of the 20 efficacy-evaluable patients treated at the dose levels that were preclinically predicted to be within the target dose range, 25% achieved a partial response as best response (n=5, 4 confirmed PRs and 1 unconfirmed PR), with a 70% disease control rate (DCR, 14/20). All five responders remain on treatment, and 50% (10/20) of all efficacy-evaluable patients within the target dose range remain on treatment. For one patient with a first-scan assessment of progressive disease, a subsequent 47% reduction in target lesions was reported, and the patient remains on-treatment as of the data cut-off (treatment week 30). All 6 patients within the target dose range with greater than 30% reduction in lesion size remain on treatment as of the data cut-off.”