Combination therapy with the oncolytic virus CF33-CD19 and blinatumomab for the treatment of advanced solid tumors.

TPS2687 Background: CF33-CD19 is a novel chimeric vaccinia virus that selectively replicates in tumor cells and can provoke anti-tumor immunity. CF33-CD19 expresses a truncated and non-signaling CD19 protein on the surface of infected tumor cells before virus-mediated tumor lysis, labeling them for CD19-targeted therapies. Preclinical studies with CF33-CD19 have shown that combination therapy with CD19 targeting chimeric antigen receptor T cells is more effective than either monotherapy in murine xenograft and syngeneic models 1. Likewise, combination therapy with bispecific T-cell engagers (BiTE)s that bind CD3-positive T cells and infected solid tumor cells that express de novo CD19, showed pronounced recruitment of T cells to the tumor microenvironment, resulting in tumor growth inhibition in mouse models. CD19xCD3 targeting BiTEs such as blinatumomab may offer an off-the-shelf alternative to adoptive cell therapies. This phase I study, called OASIS, dose escalates CF33-CD19 administered intravenously (IV) or intratumorally (IT) combined with blinatumomab in adults with advanced or metastatic solid tumors. Methods: The OASIS study (NCT06063317) is enrolling patients with advanced or metastatic solid tumors with ≥ 2 prior lines of therapy. Patients who have received prior treatment with a poxvirus based oncolytic virus or a bispecific CD19-directed CD3 T-cell engager are excluded. A safety run-in will evaluate the safety of CF33-CD19 monotherapy administered IT or IV before initiating the combination therapy regimen. Combination therapy will be administered in 28-day cycles with CF33-CD19 on days 1 and 15. Following viral transduction to promote de novo CD19 expression, blinatumomab is given on days 2-9 and 16-23 via a 7-day continuous infusion. Patients > 45 kg will receive 9 mcg of blinatumomab during the first week of cycle 1, then 28 mcg during the third week of cycle 1 and subsequent cycles. The study consists of two parts. Part 1 follows a 3+3 dose escalation scheme independently of each route of CF33-CD19 administration (IT and IV) with dose levels of CF33-CD19 ranging from 1.0x10 7 to 3.0x10 9 PFU. Part 2 is a cohort expansion in select indications at the optimal dose. The co-primary endpoints are safety and identification of the recommended phase 2 dose. Secondary endpoints include objective response rate according to RECIST v1.1 and iRECIST. Enrollment began in October 2023. 1. Park et al. Sci Transl Med. 2020 Sep 2;12(559):eaaz1863. doi: 10.1126/scitranslmed.aaz1863. PMID: 32878978. Clinical trial information: NCT06063317 .