Oncolytics Biotech reports 33% ORR and 19.5-month DOR with pelareorep plus FOLFIRI and bevacizumab in second-line RAS-mutant MSS metastatic colorectal cancer, supporting further development.
Written by: Karthik Teja Macharla PharmD
Reviewed By: Pharmacally Editorial Team
Oncolytics Biotech Inc. today announced updated clinical results demonstrating durable responses in patients with second-line RAS-mutant microsatellite stable (MSS) metastatic colorectal cancer (mCRC) treated with its investigational immuno-oncolytic virus pelareorep in combination with FOLFIRI chemotherapy and bevacizumab.
The data were generated from the open-label, early-phase REO 022 study evaluating pelareorep in patients who progressed following first-line oxaliplatin-based chemotherapy. The study reported a 33% objective response rate (ORR) and a median duration of response (DOR) of 19.5 months.
While cross-trial comparisons should be interpreted with caution, these outcomes exceed historical benchmarks in this setting, where ORR typically ranges from 6% to 11% and median DOR is approximately 4 to 6 months. The observed duration of response represents an approximate three- to four-fold improvement over historical expectations, suggesting the potential for sustained clinical benefit in a patient population with limited treatment options.
“These findings demonstrate clinically meaningful and durable responses in a setting where outcomes have historically been poor,” said Jared Kelly, Ph.D., president and chief executive officer of Oncolytics Biotech. “We believe these data support further development of pelareorep and ongoing discussions with regulators regarding a potential path forward.”
RAS-mutant MSS metastatic colorectal cancer represents a large and difficult-to-treat subgroup of colorectal cancer. MSS tumors are generally less responsive to immune checkpoint inhibitors, and patients who progress after first-line therapy have limited effective options. The combination of pelareorep with chemotherapy and anti-angiogenic therapy is intended to enhance tumor immunogenicity and promote immune infiltration, potentially improving treatment response.
Pelareorep is a systemically delivered oncolytic virus designed to selectively replicate in cancer cells with activated RAS pathways, leading to tumor cell lysis and stimulation of innate and adaptive immune responses.
The safety profile observed in the study was consistent with the known effects of FOLFIRI and bevacizumab, with no new safety signals attributed to pelareorep. Reported adverse events were manageable and aligned with prior experience.
Oncolytics Biotech stated that it is engaging with the U.S. Food and Drug Administration (FDA) to explore a potential regulatory pathway, including the possibility of accelerated approval. The company is currently enrolling patients in a randomized phase 2 trial designed to validate response rates and assess progression-free and overall survival.
Colorectal cancer remains a leading cause of cancer-related mortality worldwide. Approximately 85% of metastatic colorectal cancers are MSS, and a substantial proportion harbor RAS mutations, both associated with resistance to many existing therapies. If confirmed in randomized studies, these findings could represent a meaningful advancement in this setting.
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About the Writer
Karthik Teja Macharla, PharmD is a Pharm.D. graduate with a strong interest in clinical research, pharmacovigilance, and medical writing. In his words, he is passionate about converting complex medical information into clear, evidence-based scientific communication, committed to contributing to patient safety and advancing healthcare through accurate and impactful medical content.