The Helsinki-based company, which develops intravenously delivered cancer immunotherapies, evaluated TILT-123 (igrelimogene litadenorepvec) together with MSD’s anti-PD-1 therapy Keytruda (pembrolizumab) and pegylated liposomal doxorubicin in the PROTA study.

Of fourteen patients treated, nine could be evaluated at the time of data cut-off. Four of them achieved confirmed partial responses, an overall response rate of 44%. Two of these patients later converted to complete responses. A third had an ongoing response that had lasted twelve months at the time of analysis, and the fourth patient’s disease progressed twenty-one months after the start of treatment. Of the remaining five patients, three had stable disease, giving a disease control rate of 78%. The combination was well tolerated, with no dose-limiting toxicities and no unexpected safety signals.

“We have been struck by both the high frequency of responses to the regimen used in this clinical trial and the durable nature of those responses. Multiple patients have reported good tolerability of this approach,” says Dr. Matthew S. Block, a medical oncologist at the Mayo Clinic and lead investigator of the PROTA trial.

Enrollment in the Phase Ib study was completed in January 2026. Some patients are still receiving therapy because they continue to benefit from it.

“The combination of TILT-123, pembrolizumab, and chemotherapy has demonstrated durable responses, along with a favorable safety profile, in a patient population facing limited treatment options. This further supports our strategy of combining TILT-123 with established immunotherapies and standard-of-care agents to improve outcomes for patients with difficult-to-treat solid tumors,” says Akseli Hemminki, Founder and CEO, TILT Biotherapeutics.