Cowpea mosaic virus intratumoral immunotherapy maintains stability and efficacy after long‐term storage

Abstract

Abstract Cowpea mosaic virus (CPMV) has demonstrated superior immune stimulation and efficacy as an intratumoral immunotherapy, providing a strong argument for its clinical translation. One important consideration for any new drug candidate is the long‐term stability of the drug and its formulation. Therefore, our lab has evaluated the physical stability and biological activity, that is, anti‐tumor potency, of formulations of CPMV in buffer (with and without a sucrose preservative) in multiple temperature conditions ranging from ultralow freezers to a heated incubator over a period of 9 months. We found that non‐refrigerated temperatures 37°C and room temperature quickly led to CPMV destabilization, as evidenced by significant protein and RNA degradation after just 1 week. Refrigerated storage at 4°C extended physical stability, though signs of particle breakage and RNA escape appeared after 6 and 9 months. CPMV stored in frozen conditions, including −20°C, −80°C, and liquid N2, remained intact and matched the characteristics of fresh CPMV throughout the duration of the study. The biological activity was evaluated using a murine dermal melanoma model, and efficacy followed the observed trends in physical stability: CPMV stored in refrigerated and warmer conditions exhibited decreased anti‐tumor efficacy compared to freshly prepared formulations. Meanwhile, frozen‐stored CPMV performed similarly to freshly purified CPMV, resulting in reduced tumor growth and extended survival. Data, therefore, indicates that CPMV stored long‐term in cold or frozen conditions remains stable and efficacious, providing additional support to advance this powerful plant virus to translation.

Keywords

• cowpea mosaic virus
• intratumoral immunotherapy
• long‐term stability
• melanoma
• translational drug development