Oncolytics Biotech Inc. (Nasdaq: ONCY) announced on March 2, 2026, the formal initiation of REO-033, a randomized Phase 2 clinical trial evaluating pelareorep in combination with bevacizumab (Avastin®) and FOLFIRI versus bevacizumab and FOLFIRI alone in patients with second-line (2L) RAS-mutated, microsatellite-stable (MSS) metastatic colorectal cancer (mCRC). First site activation is expected later in March 2026, with preliminary data targeted before the end of 2026.
The trial advances on a foundation of compelling prior evidence: the REO-022 study in this same population demonstrated a median overall survival (OS) of 27 months, a median progression-free survival (PFS) of 16.6 months, and an objective response rate (ORR) of 33%* with the pelareorep combination — against respective standard-of-care benchmarks of 11.2 months OS, 5.7 months PFS, and approximately 10% ORR (Bennouna et al., 2012; Iwamoto et al., 2015).
By every critical efficacy metric, pelareorep roughly doubled or tripled outcomes in a population that has historically been among the most resistant to immune-based intervention.
The announcement comes less than four weeks after the FDA granted Fast Track Designation to pelareorep plus bevacizumab and FOLFIRI in 2L KRAS-mutant MSS mCRC — a regulatory acknowledgment that this combination addresses a serious unmet medical need and that a credible development pathway exists toward approval.
You can read more about the FDA Fast Track Designation on OncoDaily.
REO-033 Trial Design: Powered for Statistical Significance
REO-033 is a company-sponsored, randomized, controlled Phase 2 study with a regulatory-grade design. Key parameters:
- Population: 2L RAS-mutated (including KRAS), MSS mCRC patients who have progressed on first-line platinum-based chemotherapy
- Randomization: Control arm (bevacizumab + FOLFIRI) vs. experimental arm (pelareorep + bevacizumab + FOLFIRI)
- Enrollment: ~30 patients per arm (60 total), powered for statistical significance
- Primary Endpoint: Objective Response Rate (ORR)
- Secondary Endpoints: Progression-free survival (PFS), overall survival (OS), safety, and biomarker analysis
- Lead Investigator: Dr. Sanjay Goel, M.D., M.S., FASCO — Professor of Medicine, Rutgers Cancer Institute of New Jersey
- Preliminary Data Expected: By end of 2026
The decision by Oncolytics to self-sponsor rather than pursue an investigator-sponsored trial is significant. Company-sponsored trials allow for tighter protocol control, proprietary data ownership, greater analytical rigor, and the ability to communicate findings at the company’s discretion — all factors that support regulatory submissions and future partnership discussions.
Dr. Goel, the lead investigator, spoke to the scientific continuity:
I am honored to lead this study as I have a long track record working with pelareorep and have witnessed its ability to improve patient outcomes in a meaningful way, the colorectal cancer data we recorded in the REO 022 study continues to be compelling to this day, as evidenced by the Fast Track Designation, and I hope we can generate additional exciting data in this new trial to support registration.
Dr. Sanjay Goel, M.D., M.S., FASCO
Regulatory Context: What FDA Fast Track Means Here
By granting Fast Track status, the FDA has formally acknowledged that pelareorep’s REO-022 data in 2L KRAS-mutant MSS mCRC meets that threshold.
Practically, Fast Track status accelerates FDA collaboration, including more frequent meetings, the ability to submit a rolling NDA, and eligibility for Priority Review if criteria are met. Combined with the randomized Phase 2 design of REO-033, the company is building a regulatory dossier consistent with a pivotal program.
Jared Kelly, CEO of Oncolytics Biotech, framed the stakes clearly following the Fast Track announcement:
Adding pelareorep to the standard-of-care in this underserved segment of colorectal cancer patients results in a doubling or tripling of critical clinical endpoints, including overall survival, progression-free survival, and objective response rate in a market that is estimated to be worth several billion dollars. Pelareorep offers the potential to help a meaningful number of patients, and I look forward to continuing to collaborate with the FDA to address this treatment gap as expeditiously as possible.
Prior Clinical Evidence: REO-022 Data in Full Context
The REO-022 dataset merits emphasis because REO-033 is explicitly designed to confirm and extend it in a controlled setting:
| Endpoint | Pelareorep + Bev + FOLFIRI (REO-022) | SOC: Bev + FOLFIRI |
| Median OS | 27.0 months | ~11.2 months |
| Median PFS | 16.6 months | ~5.7 months |
| ORR | 33% | ~10% |
These are striking differentials. A 2.4-fold improvement in median OS, a nearly 3-fold improvement in median PFS, and a 3-fold improvement in ORR from an additive immunotherapy intervention in a population previously considered immune-therapy-resistant would, if confirmed in a randomized trial, constitute a clinically practice-changing dataset.
Dr. Van Morris, Associate Professor in GI Medical Oncology at MD Anderson Cancer Center, underscored the global relevance:
The potential to improve clinical outcomes compared to the standard-of-care in the second-line setting would have the potential to benefit patients around the world who are affected by colorectal cancer.
Van Morris/faculty.mdanderson.org
Competitive Landscape: No Approved Immunotherapy in MSS mCRC
The competitive environment in MSS mCRC immunotherapy development is active but largely unproven. Several programs have attempted to unlock checkpoint inhibitor activity in MSS disease, through combinations with MEK inhibitors, TGF-beta blockade, VEGF inhibition, but none have demonstrated the magnitude of benefit reported in REO-022. Post-second-line options like regorafenib and trifluridine/tipiracil offer modest OS benefits with significant toxicity and are not immune-based strategies.
Pelareorep’s approach, viral immunosensitization concurrent with anti-VEGF therapy, is mechanistically distinct from most competing programs and benefits from evidence directly in the RAS-mutant MSS subpopulation that constitutes the clinical majority of the disease.
The oncolytic virus field broadly has struggled to translate preclinical promise into pivotal wins. The approval of T-VEC (talimogene laherparepvec) in melanoma established regulatory precedent for oncolytic agents, but pelareorep’s intravenous delivery in a systemic metastatic disease model represents a fundamentally different and more scalable clinical proposition.
Strategic Implications: What REO-033 Means for Oncolytics and the Field
If REO-033 reproduces the REO-022 efficacy signal with statistical significance, Oncolytics will possess a company-owned, Phase 2-validated, FDA Fast Track-designated dataset in one of the largest unmet-need populations in solid tumor oncology. That data package would be highly attractive to large pharma partners with established GI oncology commercial infrastructure. The colorectal cancer treatment market is projected to expand at a 4.7% CAGR through 2033, with second-line RAS-mutant MSS mCRC representing a clinically and commercially significant addressable segment.
For the broader oncology landscape, the implications extend further. If pelareorep can demonstrably convert MSS mCRC into an immunotherapy-responsive disease, it raises a foundational question about whether similar viral immunosensitization strategies might work in other cold tumor types (pancreatic cancer, microsatellite-stable gastric cancer, and beyond) where pelareorep already has active clinical programs and additional FDA Fast Track designations.
The hypothesis that oncolytic viruses can functionally reprogram the immunosuppressive tumor microenvironment of MSS solid tumors is one of the most important open questions in immuno-oncology today. REO-033, with preliminary data expected before year-end 2026, is among the best-positioned trials in position to answer it.
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Written by: Semiramida Nina Markosyan, Editor, OncoDaily Canada