CD19-targeted chimeric antigen receptor (CAR)-engineered T/NK-cell therapies can result in durable clinical responses in B-cell malignancies. However, CAR-based immunotherapies have been less successful in solid cancers. This is partly due to specificity for shared tumor antigens also present on normal host tissues that leads to ‘on-target/off-tumor’ toxicity. We therefore developed a non-viral approach using repeated infusions of mesothelin-specific messenger RNA (mRNA) CAR-transfected T cells to permit prospective control of ‘on-target/off-tumor’ toxicity. Early trials provided preliminary evidence of the safety and anti-tumor activity of this strategy, but the ex vivo selection, activation and expansion of lymphocytes is laborious and expensive. We therefore explored the feasibility of using a rapid, automated, closed system for cGMP-compliant mRNA CAR transfection into freshly isolated peripheral blood mononuclear cells for clinical scale manufacture (CARMA). The resulting cryopreserved cellular product expressed CAR in >95% of cells, and recognized and lysed tumor cells in an antigen-specific manner. Expression of CAR was detectable for 5-7 days in vitro, with a progressive decline of CAR expression related to in vitro cell expansion. In a murine ovarian cancer model, a single intra-peritoneal (IP) injection of CARMA resulted in the dose-dependent inhibition of tumor growth and prolonged the overall survival (OS) of mice. Multiple weekly IP injections of the optimal CARMA dose enhanced disease control and further prolonged OS, both of which improved with an increasing number of injections. No significant off-tumor toxicities were observed. These data support further investigation of serial IP CARMA administration as a potential treatment for ovarian cancer and other mesothelin-expressing tumors involving the peritoneum, and provide preclinical proof of principle of CARMA for solid tumors.

Citation Format: Chien-Fu Hung, Xuequn Xu, Linhong Li, Ying Ma, Qiu Jin, Angelia Viley, Cornell Allen, Pachai Natarajan, Rama Shivakumar, Madhusudan V. Peshwa, Leisha A. Emens. Development of anti-human mesothelin chimeric antigen receptor (CAR) messenger RNA (mRNA) transfected peripheral blood mononuclear cells (CARMA) for the treatment of mesothelin-expressing cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3748. doi:10.1158/1538-7445.AM2017-3748