At the ESMO Congress 2026, Xencor Inc. (NASDAQ:XNCR) shared updated results from the Phase 1 study of XmAb819 for advanced clear cell renal cell carcinoma (ccRCC).
Robust Response Rates Across Expansion Cohorts
The Phase 1 trial evaluated 119 participants across 11 intravenous dose cohorts.
Within the 68-patient expansion group, confirmed objective response rates climbed alongside dose increases, rising from 30% at 100 mcg/kg to 45.5% at 400 mcg/kg.
Across these expansion groups, 25 patients achieved confirmed responses, including one complete response and 24 partial responses, with 19 responses remaining ongoing at the September data cut.
Favorable Safety And Maturing Efficacy
Patients tolerated XmAb819 well throughout the expansion cohorts, recording a low 5.9% treatment discontinuation rate linked to adverse events.
Subsequent October follow-up data revealed that patients receiving the 400 mcg/kg target dose achieved an unconfirmed overall response rate of 55% and an 82% progression-free survival rate at six months.
Moreover, the study cohort has not yet reached the median progression-free survival estimate.
Late-Stage Clinical Plans And Regulatory Strategy
Xencor designated the 400 mcg/kg dose as its proposed intravenous dose for late-stage testing and outlined registration-enabling plans for late 2027.
The biopharmaceutical company expects data from at least 20 evaluable patients at this dose level during early 2027 to solidify its selection.
Xencor plans to discuss potential accelerated approval pathways with the FDA for patient populations who have exhausted standard clinical options.
In pooled analyses, patients with prior exposure to checkpoint inhibitors and multiple VEGFR inhibitors achieved a 45% confirmed response rate.
Furthermore, Xencor aims to initiate a global randomized trial evaluating XmAb819 against tivozanib to pursue full regulatory approval as a monotherapy.
Ongoing sub-studies continue testing subcutaneous delivery and combination therapies for earlier-stage disease.
Analyst View
William Blair on Monday wrote, “Overall, we believe XmAb819 is showing an unprecedented profile in ccRCC…”
Analyst Matt Phipps wrote, “We continue to believe the discussant of the data at the ESMO conference summed it up appropriately in saying the results presented at the conference are likely the “floor” in terms of efficacy for XmAb819, and can further improve as management of CRS improves and the therapy advances to less heavily pretreated patient populations.”
XNCR Price Action: Xencor shares were up 20.25% at $30.27 at the time of publication on Monday. The stock is trading near its 52-week high of $30.61, according to Benzinga Pro data.
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