Key Highlights

  • Xencor, Inc. (NASDAQ:XNCR) rose 27.09% to USD 32.00 in early trading on Monday, October 26, 2026, after XmAb819 data were presented at the ESMO Congress 2026 in Madrid and released on Sunday, October 25, 2026.
  • At the proposed 400 mcg/kg dose, XmAb819 produced a 45.5% confirmed objective response rate in kidney cancer, with an 82% six-month progression-free estimate, in a very small cohort of 11 patients.
  • The 68-patient expansion cohort showed grade 3 or higher related adverse events in 72.1% of patients, and 5.9% discontinued treatment because of related events.
  • Xencor selected 400 mcg/kg as the proposed Phase 3 dose, plans to discuss accelerated approval with the FDA in the first half of 2027 and projects cash into 2029.

Xencor (NASDAQ:XNCR): data that cleared a high bar

Xencor, Inc. (NASDAQ:XNCR) rose 27.09% to USD 32.00 in early trading on Monday, October 26, 2026, from an implied prior close of about USD 25.18 and a market value of about USD 1.87 billion before the move. The catalyst is a company release at 4:35 a.m. ET on Sunday, October 25, 2026, presenting Phase 1 dose-selection data for XmAb819, a bispecific antibody that targets ENPP3 on kidney cancer cells and CD3 on T cells, in clear cell renal cell carcinoma. In 68 expansion patients with a September 1, 2026 data cut, confirmed objective response rates were 30% at 100 mcg/kg, 44% at 200 mcg/kg and 45.5% at 400 mcg/kg.

How the Data Support a Phase 3 Plan

The 400 mcg/kg cohort holds 11 patients, with five confirmed partial responses and one unconfirmed response, which makes the 45.5% response rate encouraging but statistically fragile. Disease control rates were 87%, 64% and 82% across the three doses, and median progression-free survival was not reached, with an 82% six-month estimate at the top dose. Xencor (NASDAQ:XNCR) selected 400 mcg/kg intravenously as the proposed Phase 3 dose and expects at least 20 efficacy-evaluable patients at that dose by the first half of 2027. It plans a global randomised trial against tivozanib, an approved kidney cancer drug, in patients previously treated with checkpoint and VEGFR inhibitors, and aims to start a registration-enabling study by the end of 2027.

Risks and What to Watch

The main risks are safety and sample size. Grade 3 or higher treatment-related events occurred in 72.1% of expansion patients, and a cohort of 11 can change materially as more patients are added. The accelerated approval path depends on FDA agreement in the first half of 2027, and the global Phase 3 study against tivozanib will take years and capital, although Xencor projects cash into 2029. After a 27.09% rise, valuation also leaves less room for disappointment, since the company is unprofitable. Investors should watch for the larger 400 mcg/kg dataset by the first half of 2027, the FDA discussion and the Federal Reserve decision on Wednesday, October 28, 2026.

Where Things Stand

The answer is that Xencor, Inc. (NASDAQ:XNCR) rose 27.09% to USD 32.00 because XmAb819 delivered a 45.5% confirmed response rate at the chosen dose, which supports a Phase 3 design and a path towards accelerated approval, although the cohort is small and adverse events are frequent. Cash is projected into 2029, which covers the planned programme. The next catalysts are the 20-patient efficacy readout and FDA discussion in the first half of 2027, the registration-enabling study by the end of 2027 and the Federal Reserve decision on Wednesday, October 28, 2026. Clinical results are uncertain, and this is not investment advice.