Abstract A220: Destabilizing domain technology facilitates exogenous regulation of IL15 and IL12 for adaptive T-cell therapy

Cytokines are messenger molecules that act as regulators of innate and adaptive immunity by propagating cell-cell immune signaling. Several cytokines have been approved for the treatment of metastatic renal cell cancer, advanced melanoma, and hairy cell leukemia (HCL) and can be particularly effective when combined with adoptive cell therapy. However, systemic delivery or constitutive expression of cytokines even at moderate levels can potentially lead to significant toxicity. These hurdles to enabling cytokine-enhanced adoptive cell therapy motivated us to implement destabilizing domain (DD) technology for regulating cytokines in chimeric antigen receptor (CAR) reprogrammed T-cells. The ability of CAR-T-cells to traffic to tumor sites enables localized co-delivery of cytokines for enhanced CAR-T-cell antitumor activity while improving safety. Obsidian Therapeutics’ DD technology enables titratable and reversible regulation of a protein of interest with FDA-approved small-molecule drugs in a time- and dose-dependent manner. Protein-fused DDs are misfolded in the absence of a stabilizing small-molecule ligand and are rapidly degraded by the proteasome. However, the addition of ligand restores the folding, stability, and function of the DD-protein fusion. We have generated IL-12 and membrane-bound IL15-IL15Ra (mbIL15) fused to DDs such as FK506 binding protein (FKBP), Escherichia coli dihydrofolate reductase (ecDHFR), as well as human protein substrates (huDDs) with clinically approved ligands. DD-IL12 and DD-mbIL15 fusions displayed ligand-dependent regulation of cytokine secretion or cell surface expression, respectively, in cell lines and primary human T-cells. We then tested DD regulation of IL12 or mbIL15 in vivo by injecting T-cells engineered with cytokine-fused DDs into NSG mice, followed by oral administration of vehicle or corresponding ligand. Vehicle-treated mice displayed low level expression of the respective cytokines, whereas ligand treatment robustly induced the expression of target cytokine within 4-6 hours after treatment. Cytokine expression returned to baseline levels 24 hours following ligand administration. These data demonstrate the feasibility of exogenous control over transgene-derived protein expression in primary human T-cells for the development of next-generation CAR-T-cell products with enhanced efficacy and more favorable safety profiles. Citation Format: Karen Tran, Kutlu Elpek, Tucker Ezell, Scott Heller, Mara Inniss, Abhishek Kulkarni, Dan Jun Li, Grace Olinger, Michelle Ols, Christopher Reardon, Dexue Sun, Tariq Kassum, Michael Briskin, Celeste Richardson, Vipin Suri, Steven Shamah, Michael Gilman. Destabilizing domain technology facilitates exogenous regulation of IL15 and IL12 for adaptive T-cell therapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A220.