A phase I/II study of Pexa-Vec oncolytic virus in combination with immune checkpoint inhibition in refractory colorectal cancer.

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Abstract
117 Background: The benefit of immune checkpoint inhibition is limited to the small percentage of advanced colorectal cancer (CRC) patients whose tumors present mismatch repair (MMR) gene abnormalities; immunotherapy has not shown benefit in patients with MMR proficient CRC. Oncolytic immunotherapy represents a unique therapeutic platform. This phase I trial tests the safety of the combination of pexastimogene devacirepvec (Pexa-Vec) plus durvalumab (durva) in patients with locally advanced or metastatic CRC. Methods: Eligible patients with advanced proficient mixed match repair (pMMR) CRC received intravenous infusion of Pexa-Vec at dose level 3 x 108 plaque forming units (pfu) (DL1) or at 109 pfu (DL2) every 2 weeks for 4 doses and durva 1500 mg every 28 days. Response was assessed with CT every 8 weeks. Adverse events were recorded and managed. The primary endpoint included safety, tolerability and feasibility of this combination therapy. Samples of tumor and peripheral blood were collected for assessment of immune parameters. Results: Sixteen patients (6 males and 10 females) enrolled with a median age of 52.1 years (range 39-69) from Dec, 2017 to Oct, 2018. Four patients were treated with Pexa-Vec at DL1 and durva;twelve patients were treated with Pexa-Vec at DL2 and durva.The most common treatment related adverse events (TRAE) included fever 15/16 (94 %), hypotension 12/16 (75 %), chills 12/16 (75%), fatigue 8/16 (50%), sinus tachycardia 7/16 (44%) and rash 6/16 (38%). Grade 3/4 TRAEs were reported in 8/16 (50%)patients; the most common were fever 7/16 (44 %), lymphopenia 2/16 (13%), neutropenia 1/16 (6%) and anemia 1/16 (6%). 14 patients were evaluable for response analysis; one patient 1/14 (7 %) achieved a confirmed partial response (lasting 7.1 months) and continues to receive treatment, while 13 patients had progressive disease. The median progression free survival (PFS) was 2.2 months (95% CI: 2.2-2.3 months) and the median overall survival (OS) was 7.5 months (CI: 4.9-10.1 months). Conclusions: Combination therapy of Pexa-Vec with durva ICI issafe, well tolerated and demonstrates possible activity in patients with advanced pMMR CRC. Clinical trial information: NCT03206073.
Funding Information
  • U.S. National Institutes of Health