LAUSR

Background: MEM-288 is a conditionally-replicative oncolytic adenovirus expressing human IFNβ and a recombinant membrane-stable form of CD40L (MEM40). Preclinical studies show MEM-288 induces robust dendritic cell-mediated systemic T cell responses capable of inhibiting abscopal tumor growth as monotherapy and synergizes with immune checkpoint inhibitors (ICI). Methods: Safety, antitumor and immunologic activity of MEM-288 are being evaluated in this Phase 1, multicenter, open-label trial (NCT05076760). Pts with select solid tumors including NSCLC (a) refractory to standard therapy and (b) with a tumor lesion deemed feasible for biopsy and MEM-288 intratumoral injection are eligible. The primary objective is to determine a recommended phase 2 dose of MEM-288 monotherapy across 3 dose levels (DL1-3) spanning 1e10 to 1e11 viral particles by intratumoral injection once every 3 weeks, for up to 6 injections, using a BOIN design. Secondary objectives include efficacy assessment (including response rate of injected and non-injected tumors assessed separately). Tumor biopsies immediately prior to the 1st and 2nd injections, and peripheral blood at serial timepoints, are used to explore biomarkers and anti-tumor immune responses. Results: As of Jan 2023, the study is ongoing with the DL3 high-dose cohort completing accrual. 11 pts (10 NSCLC and 1 pancreatic) enrolled and received ≥1 dose of MEM-288 (n=3 DL1, n=5 DL2, n=3 DL3). No dose limiting toxicities have been reported to date and no pts have discontinued treatment due to toxicity. Treatment-related adverse events observed in >1 pt include grade 1 injection site reaction (45%) and chills (18%). Of 7 pts evaluable for response, 3 had shrinkage of injected tumor (range -40 to -54%), and multiple pts also had stabilization or shrinkage of distal non-injected lesions with best RECIST response in uninjected tumors as 2 SD and 5 PD. After a single MEM-288 injection, biopsies show decreased tumor cell percentage concomitant with substantial increases in overall CD8+ T cells, increased T clonotype diversity in both tumor and peripheral blood, and increased TCF1+ stem-like CD8+ T cells that are strongly associated with response to ICIs. Plasma cytokine analysis showed increases in IFNγ and of IFN-inducible cytokines and chemokines, supportive of stimulation of systemic response after MEM-288. Of note, a pt with strong stimulation of tumor and systemic T cell immunity after MEM-288 had a subsequent CR (ongoing >6 months) to docetaxel + ramucirumab following prior treatment failure with platinum doublet + ICI received before MEM-288. Conclusions: Preliminary safety, antitumor and immune response data are encouraging. Updated results and immune data will be presented. An expansion arm is planned with combination MEM-288 and anti-PD1 antibody in pts with advanced NSCLC refractory to ICI. Citation Format: Andreas N. Saltos, Christy Arrowood, Georgia Beasley, James Ronald, Ghassan El-Haddad, Uzma Khan, Luiziane Guerra-Guevara, Steven Wolf, Lin Gu, Xiaofei F. Wang, Dana Foresman, Xiaoqing Yu, Mark J. Cantwell, Scott J. Antonia, Amer A. Beg, Neal E. Ready. A phase 1 first-in-human study of MEM-288 oncolytic virus in solid tumors including non-small cell lung cancer (NSCLC): impact on tumor and systemic T cell immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT103.