Key Findings
Xencor presented updated Phase 1 data for XmAb819, a potential first-in-class ENPP3 x CD3 bispecific T-cell engager, at the ESMO Congress 2026. The company identified 400 mcg/kg as the proposed intravenous RP3D based on a confirmed objective response rate (cORR) of 45.5%, an unconfirmed objective response rate (uORR) of 55%, and a 6-month PFS Kaplan-Meier estimate of 82%.
Technical Details
The Phase 1 study enrolled 119 patients with advanced ccRCC across 11 IV target dose levels, utilizing a weekly priming regimen followed by a maintenance dose. Expansion cohorts (n=68) evaluated three dose levels: 100 mcg/kg, 200 mcg/kg, and 400 mcg/kg. The patient population was heavily pre-treated, with a median of three prior lines of therapy; 94% were intermediate- to poor-risk per the IMDC model. All patients had prior exposure to at least one PD-(L)1 inhibitor and one VEGFR TKI, with 63% having received two or more VEGFR TKIs and 34% having received at least one HIF2α inhibitor.
Of the 25 patients with confirmed responses per RECIST v1.1, one achieved a complete response and 24 achieved partial responses. As of the September 1, 2026 data-cut, 19 responses remained ongoing with a median treatment time of 7 months.
Safety data showed a 5.9% treatment discontinuation rate due to treatment-emergent adverse events (TEAEs). Grade 3 or higher related TEAEs occurred in 72.1% of patients, most commonly liver enzyme elevations (AST increased: 35.3%; ALT increased: 33.8%), rash (22.1%), hypotension (7.4%), and cytokine release syndrome (5.9%).
Background & Context
XmAb819 is an engineered XmAb 2+1 bispecific antibody designed to selectively target malignant cells in solid tumors. It offers a distinct mechanism of action compared to current ccRCC treatments, which primarily rely on checkpoint inhibitors and VEGF-axis targeted therapies.
Significance & Outlook
Xencor intends to initiate a registration-enabling study by the end of 2027. This includes a global randomized study comparing XmAb819 monotherapy against tivozanib in ccRCC patients who have progressed after PD-(L)1 and VEGFR TKI therapy. The company maintains a cash runway into 2029 to support clinical development in oncology and autoimmune diseases.
Source: https://finance.yahoo.com/healthcare/articles/xencor-presents-phase-1-dose-083500804.html
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