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Treos Bio, Roche Begin Combination Immunotherapy Study in Microsatellite-Stable Colorectal Cancer

NEW YORK – Treos Bio said this week that it has dosed the first colorectal cancer patient in its Phase II clinical trial evaluating the off-the-shelf immunotherapy PolyPEPI1018 with Roche's anti-PD-L1 drug Tecentriq (atezolizumab). 

The trial, dubbed OBERTO 301, will enroll 28 patients with microsatellite-stable (MSS), metastatic colorectal cancer, who have previously received two or three lines of treatment. The study's primary goal is to assess the safety and tolerability of the immunotherapy combination, and the secondary aims include evaluating objective response rates, duration of response, progression-free survival, and overall survival. 

Treos developed PolyPEPI1018 using a computational tool dubbed PASCal, which identifies personal epitopes — or PEPIs — likely to induce tumor-specific T-cell responses. London-based Treos is using a PEPI test to identify personal epitopes in study participants. Researchers will also track patients' effector T-cell and memory T-cell responses to PolyPEPI1018 using ex vivo and in vitro stimulated ELISPOT assays, respectively. 

Colorectal cancer patients with MSS tumors tend to have lackluster responses to immune checkpoint blockade. Encouraging activity in earlier trials has suggested that adding PolyPEPI1018 to immunotherapy could turn a "cold" tumor "hot." 

In a Phase I/II trial, the company looked at the activity of PolyPEPI1018 as an add-on immunotherapy to standard-of-care maintenance therapy in metastatic colorectal cancer. The company is hoping to further explore the findings seen in this earlier trial in the Phase II study of PolyPEPI1018 and Tecentriq.

"We are humbled by the work in front of us in partnership with Roche as we explore the anti-tumor activity of our immunotherapy candidate in combination with atezolizumab to see if our exciting results in first-line maintenance therapy can be extended to advanced-stage disease by the use of this combination of therapies," Treos CEO Christopher Gallen said in a statement. 

The recently launched trial is the result of a collaboration between Treos and Roche, under the terms of which Treos is responsible for conducting the study and Roche is providing Tecentriq. Treos maintains full rights to PolyPEPI1018.