XBiotech Inc. (NASDAQ: XBIT) announced positive final efficacy results from the Phase II portion of the TASKIN clinical trial, an investigator-sponsored study evaluating its anti-IL-1α monoclonal antibody vilamakitug (Natrunix™, XB2001) in patients with refractory metastatic colorectal cancer (mCRC).

The study, funded by the French National Cancer Institute (INCa) and coordinated by the Centre Georges-François Leclerc (CGFL) in Dijon, France, met its pre-specified primary efficacy success criterion. At the 12-month landmark analysis, 49 of 80 evaluable patients (61.3%) in the vilamakitug arm were alive, exceeding the protocol-defined threshold of 42 or more surviving patients. In the control arm, 44 of 79 evaluable patients (55.7%) were alive at 12 months.

The 12-month time to strategy failure rate was 31.2% in the vilamakitug arm versus 20.3% in the control arm (log-rank p = 0.17). Median progression-free survival was 5.9 months for the vilamakitug arm compared to 5.6 months for the control arm (log-rank p = 0.42). The drug showed a 96.4% mean compliance rate for trifluridine/tipiracil and a 1.3% permanent discontinuation rate.

A prospective exploratory analysis of patients with right-sided primary tumors (n = 37) showed a statistically significant 62% reduction in the risk of death compared to the control arm (Hazard Ratio = 0.38; 95% CI: 0.14–0.99; log-rank p = 0.038). That subgroup also showed a 61% reduction in the risk of treatment strategy failure (HR = 0.39; 95% CI: 0.18–0.85; log-rank p = 0.014).

Sushma Shivaswamy, Ph.D., Chief Scientific Officer and Interim Chief Executive Officer of XBiotech, said the results "provide a focused and validated direction" as the company advances vilamakitug toward registrational clinical development.

The double-blind Phase II portion of the TASKIN trial (NCT05201352) enrolled heavily pre-treated mCRC patients randomized 1:1 to receive standard-of-care trifluridine/tipiracil with or without bevacizumab, combined with either vilamakitug or placebo.