Cyclic Peptides as Adaptors for Universal CARs

SUMMARY Chimeric Antigen Receptor (CAR) T cell therapy has made a significant impact on the treatment of hematological malignancies and is poised to be directed toward solid tumors, autoimmune diseases, and chronic viral infections. CAR T cells recognize target antigens on cell surfaces, activating immune responses that lead to target cell destruction. Recently, we developed a programmable universal CAR, termed SNAP-CAR, that can be directed to any cell surface antigen of interest via covalent binding with benzylguanine (BG)-modified adaptor antibodies. Universal CARs offer significant therapeutic advantages by allowing a single receptor to target multiple antigens through interchangeable adaptors, addressing a key challenge of resistance due to target loss or heterogeneity in cancer treatment. However, antibody adaptors present limitations, including high production costs, intravenous administration, and difficulty in deactivation if adverse effects arise, especially in multi-antigen targeting scenarios. Additionally, chemical modifications required to convert antibodies into homogenous, tumorspecific adaptors are complex. To overcome these limitations, we propose the development of cyclic peptidebased adaptors for universal CARs. Cyclic peptides offer several significant advantages over protein-based adaptors, such as ease of development and production, synthetic versatility, and potential for oral administration. Given their successful use in clinical imaging, cyclic peptides may also provide diagnostic benefits. We aim to design and synthesize several cyclic peptide adaptors to program SNAP-CAR T cells to recognize prominent cancer antigens. We will test these adaptors, and their combinatorial use, in vitro and in vivo using human tumor xenograft models. The proposed NSG mouse xenograft models are necessary to demonstrate anti-tumor efficacy in a physiologically relevant system that captures the in vivo interaction between SNAP-CAR T cells and cyclic peptide adaptors. This system encompasses critical parameters such as adaptor biodistribution, bioavailability, and stability, CAR T cell trafficking, tumor infiltration, and persistence, and potential off-tumor ontarget toxicity, which cannot be adequately recapitulated in in vitro systems. This approach represents a novel and versatile strategy for advancing universal CAR T cell therapy, with broad applicability in targeting multiple cancer antigens. Project Number: 1R21CA304918-01A1 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Alexander Deiters (+1 co-PI) | Institution: UNIVERSITY OF PITTSBURGH AT PITTSBURGH, PITTSBURGH, PA | Award Amount: $379,644 | Activity Code: R21 | Study Section: Chemical Biology and Probes Study Section[CBP] View on NIH RePORTER: https://reporter.nih.gov/project-details/11382360