Abstract CT182: Oncolytic virus CF33-hNIS for the treatment of advanced cancer

Abstract Background: CF33-hNIS is a novel vaccinia virus engineered with the human sodium-iodide symporter (hNIS) gene. CF33-hNIS selectively replicates in tumor cells and promotes anti-tumor immunity. Here, we report results on a first-in-human phase 1 dose escalation study of CF33-hNIS, administered intratumorally (IT) or intravenously (IV) in adult patients with metastatic or advanced solid tumors (MAST). Methods: The MAST study is evaluating the safety of CF33-hNIS administered IT or IV, alone or in combination with pembrolizumab in patients with advanced or metastatic solid tumors with ≥ 2 prior lines of therapy (NCT05346484). CF33-hNIS is administered in 21-day cycles on C1D1 and C1D8, then D1 of each cycle thereafter. Pembrolizumab begins C2D1 for the combination groups and is administered Q3W. The study consists of two parts. Part 1 follows a 3+3 dose escalation scheme independent of each route of CF33-hNIS administration (IT and IV) and for each therapy regimen (monotherapy and combination therapy) with up to 7 dose levels of CF33-hNIS ranging from 8.6x105 to 3.0x109 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, and assessment of viral replication in tumor lesions via Single-Photon Emission Computerized Tomography (SPECT). Results: As of Dec 2023, 36 patients have been treated in Part 1 of the study with a median age of 59 (range 23-81). Twenty-two (61%) patients were heavily pretreated with ≥3 prior lines of systemic therapy, and 14 (39%) received prior treatment with checkpoint blockade. Treatment-related adverse events consisted predominantly of ‘flu-like’ symptoms, such as grade 1/2: fatigue (31%), pyrexia (22%), and chills (14%). No dose-limiting toxicities have occurred. The highest dose treated to date is 1.1x108 PFU by IT and IV delivery; dose escalation continues. In the IT cohorts (14 patients), 7 of 15 (47%) injected lesions had a reduction in tumor burden, three lesions were completely eradicated. Three patients (21%) had an objective response: one complete response by iRECIST in a patient with cholangiocarcinoma; and two partial responses in patients with melanoma by RECIST. In IV cohorts (17 patients), 53% of patients achieved stable disease as their best response. Patients who received prior checkpoint blockade therapy derived clinical benefit with and without pembrolizumab. Viral replication, assessed by SPECT was higher in patients that saw a reduction in tumor burden. Immunological changes in peripheral blood and tumor biopsies will be presented. Conclusions: CF33-hNIS alone or in combination with pembrolizumab is a safe treatment option for advanced cancer patients. Encouraging efficacy has warranted advancement to part 2 of this study with a cohort expansion of patients with cholangiocarcinoma and other tumor types. Citation Format: Daneng Li, Anthony F. Shields, Hirva Mamdani, Patrick Travis, Gavin Wright, Wallace Akerley, Alex Spira, Gregory Daniels, Jaime Merchan, Abhijeet Kumar, Emerson Lim, Colt Egelston, Oscar Flores, Stanley Hamilton, Janet Austria, Amanda Seiz, Sharon Yavrom, Seymour Fein, John Byon, Paul Woodard, Grey A. Wilkinson, Jennifer Leddon. Oncolytic virus CF33-hNIS for the treatment of advanced cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT182.