mRNA/LNP CAR-M Shows Promise for Treating Solid Tumors in Preclinical Research

A novel approach to treating solid tumors with a chimeric antigen receptor macrophage/monocyte (CAR-M) therapy generated in vivo with the use of mRNA delivered in lipid nanoparticles (LNPs) was shown to be feasible in preclinical research conducted by Carisma Therapeutics as part of a collaboration with Moderna.^1,2 Results from the research were presented in a late-breaking session at the Society for Immunotherapy of Cancer’s (SITC) 38th Annual Meeting, held November 1-5, 2022, in San Diego, California, by Bindu Varghese, PhD, the senior director of in vivo CAR-M therapies, at Carisma Therapeutics.

The feasibility of the CAR mRNA/LNP approach to modifying macrophages/monocytes was initially tested in vitro and it was found to produce high CAR expression, in the realm of 80% to 90%, and to enable antigen-targeted killing of tumor cells. Varghese noted that unmodified control monocytes showed no antitumor activity. Further in vitro experiments with in situ mRNA/LNP reprogramming of macrophages in tumor spheroids showed dose-dependent shrinking of the spheroids. The CAR-M cells also showed the ability to secrete a broad range of proinflammatory cytokines.

Afterwards, the in vivo potential of the CAR mRNA/LNP approach was evaluated in vivo with mouse models. In wild-type, immune-competent mice, it was found that administration of CAR mRNA/LNP lead to high expression of the CAR on macrophages, monocytes, and dendritic cells, but low or minimal expression in T-cells, natural killer cells, B-cells, and nonleukocytes. These results were corroborated in in vitro testing with human peripheral blood mononuclear cells.

antiHER2 CAR mRNA/LNP was also administered to a CD34+ humanized NSG-S mouse model of lung cancer that overexpressed HER2. It was found that local administration of CAR mRNA/LNP to the tumor lead to a robust reduction in tumor burden over time. Meanwhile, mice that received administration of control mRNA did not experience a reduction in tumor burden. Systemic administration of CAR mRNA/LNP compared to systemic administration of control mRNA was also evaluated in a CD34+ humanized NSG-S mouse model of aggressive pancreatic cancer. It was found that mice who received the control mRNA showed aggressive tumor growth, while mice who received the CAR mRNA/LNP showed a slower increase in tumor burden over time. In the same mouse model, it was also found that CAR mRNA/LNP delivered intravenously reduced lung metastasis and cleared liver metastasis.

"The data presented at SITC is incredibly exciting as it demonstrates that we have the ability to make CAR-M directly in vivo with mRNA/LNP technology, leading to robust and targeted antitumor activity," Michael Klichinsky, PharmD, PhD, the co-founder and chief scientific officer of Carisma, said in a statement released prior to the presentation. "This off-the-shelf approach to treat cancer with engineered myeloid cells, developed in collaboration with Moderna, has the potential to transform the CAR field and be applied to numerous cancer targets and indications."

In terms of safety, it was noted that repeated administration of CAR mRNA/LNP was well-tolerated by mice and that no indication of toxicity was observed. Varghese concluded her presentation by summarizing key advantages of the CAR mRNA/LNP modality, pointing out that it uses autologous cells despite being an off-the-shelf therapy, does not require a viral vector, and is redosable. She also noted that the platform has the potential to be adapted to a wide range of antigens for the purpose of treating various indications.

"We are pleased to share data about the successful application of our mRNA platform to advance in vivo cell therapy," Lin Guey, PhD, the chief scientific officer of external research ventures at Moderna, added to the statement.² "We look forward to the continuation of our preclinical work with Carisma and are optimistic that the joint scientific knowledge of both companies will accelerate the development of novel in vivo CAR-M therapies for patients."

REFERENCES
1. Varghese B, Mori S, Pierini S, et al. In vivo CAR-M: redirecting endogenous myeloid cells with mRNA for cancer immunotherapy. Presented at: SITC 38th Annual Meeting, held November 1-5, 2022, in San Diego, California. Abstract #1514
2. Carisma presents pre-clinical proof of concept for in vivo CAR-M using mRNA platform in collaboration with Moderna at SITC. News release. Carisma Therapeutics Inc. October 31, 2023. Accessed November 3, 2023. https://ir.carismatx.com/news-releases/news-release-details/carisma-presents-pre-clinical-proof-concept-vivo-car-m-using