Xencor Announces Phase 1 Study Results For XmAb819 Antibody Accepted For Proffered Paper Oral Presentation At European Society of Medical Oncology October 23-27

Details of the Proffered Paper Oral Presentation

• Title: Phase 1 results of XmAb819, a novel ENPP3 x CD3 bispecific, in advanced clear cell renal cell carcinoma (ccRCC)
• Presenter: Sumanta Pal, M.D., FASCO, Professor and Vice Chair of Academic Affairs, City of Hope Comprehensive Cancer Center

ESMO has indicated that the abstract will be available on its website at 3:05 p.m. PDT on Sunday, October 18.

XmAb819 Evaluation Across ENPP3+ Tumors

XmAb819 is being evaluated for the treatment of patients with ENPP3+ tumors in a Phase 1 clinical study (Clinicaltrials.gov Identifier: NCT05433142). Initial results from dose-escalation in advanced ccRCC were presented during the AACR-NCI-EORTC Conference in October 2025. Currently:

• Expansion cohorts are evaluating intravenous doses to support selection of a dose for the planned Phase 3 pivotal study for patients with advanced ccRCC,
• Dose escalation of subcutaneous administration in advanced ccRCC is ongoing,
• A sub-study for patients with ENPP3+ advanced colorectal cancer, non-small cell lung cancer and papillary renal cell carcinoma opened to enrollment in the second quarter of 2026, and
• A sub-study for patients with intermediate- or poor-risk advanced ccRCC who have progressed after nivolumab in combination with ipilimumab as a first-line treatment (IO doublet therapy) is planned to open to enrollment in the third quarter of 2026.

About XmAb819

XmAb819 is a first-in-class, tumor-targeted, T-cell engaging XmAb® 2+1 bispecific antibody in development for patients with clear cell renal cell carcinoma (ccRCC) and other tumors with high ENPP3 expression, including colorectal cancer, non-small cell lung cancer and papillary renal cell carcinoma. XmAb819 engages the immune system and activates T cells for highly potent and targeted lysis of tumor cells expressing ENPP3. ENPP3 is a differentially expressed target, with high-level expression in renal cell carcinoma (RCC) and low-level expression on normal tissues. With two tumor-antigen binding domains and one T-cell binding domain, Xencor’s XmAb® 2+1 format enables antibodies to bind more avidly and selectively kill tumor cells with higher antigen density, potentially sparing normal cells.