Xencor Selects 400 mcg/kg Phase 3 Dose for XmAb819 After Kidney Cancer Trial Shows 45.5% Response Rate

Xencor reported Phase 1 expansion-cohort data for XmAb819, its ENPP3 x CD3 T-cell engaging bispecific antibody, at the ESMO Congress 2026, selecting 400 mcg/kg as the proposed Phase 3 dose for advanced clear cell renal cell carcinoma. The data showed a 45.5% confirmed objective response rate, a 55% unconfirmed ORR, and an estimated 82% six-month progression-free survival rate in patients with the disease.

Xencor plans to seek FDA discussions in the first half of 2027 regarding accelerated approval and a tivozanib-controlled pivotal trial, with the Phase 3 study itself expected to begin in 2027. An analyst highlighted the drug's profile at ESMO as unprecedented in colorectal cancer as well, underscoring a potentially broad indication set for the molecule.

Shares of Xencor surged more than 36% in premarket trading on October 26 following the data release, reflecting strong investor enthusiasm for a drug now positioned as the company's key late-stage opportunity.