388 Engineering co-stimulation into TCR-T cells via a CD8–41BB fusion receptor enhances efficacy and durability in preclinical models of heme and solid tumor malignancies
Year: 2024
Type: conference-abstract
Abstract: Background Adoptive cell therapy using tumor antigen-targeting T cell receptors (TCRs) offers a compelling approach to treat both hematological cancers and solid tumors due to broad antigen accessibility and the ability to target specific cancer neoantigens. However, unlike clinically validated second generation CAR-T cells bearing built-in co-stimulatory signaling modules (i.e., 41BB or CD28), TCR-T cells receive little to no co-stimulation within most tumor microenvironments leading to relatively muted cellular responses. Additionally, HLA class I restricted TCRs, even those with high affinity, elicit minimal CD4+ T cell helper activity and thus do not maximally mobilize the CD8+TCR-T cells or host anti-tumor immune responses. Methods To address these limitations, we used CRISPR/Cas9 to engineer human T cells with site-specific insertion of synthetic chimeric CD8 constructs containing intracellular co-stimulatory domains along with transgenic TCRs targeting relevant shared tumor antigens (WT1 or PRAME). TCR-T cell potency was evaluated in-vitro against tumor cells in acute and long-term serial rechallenge cytotoxicity assays, proliferation assays, and cytokine release assays. T cell potency was evaluated in-vivo using challenging ovarian and AML tumor xenograft models and cell persistence monitored by ddPCR. Further mechanistic interrogation included cytokine profiling and multiparameter flow cytometric phenotyping. Results CRISPR/Cas9 mediated site-specific integration of wild type CD8αβ conferred robust CD4+ T helper and cytolytic activity to WT1-targeting TCR-T cells. However, this was insufficient to drive curative anti-tumor responses in challenging mouse models of ovarian cancer or AML. Systematic design and screening of CD8-co-stimulatory fusion constructs identified CD8-41BB designs with substantially increased activity relative to wild-type CD8αβ. WT1-TCR-T cells co-expressing these CD8-41BB receptors demonstrated several-fold improvement in CD4+ and CD8+ T cell activity, including increases in cell proliferation, long-term killing ability, and polarized Th1-type cytokine secretion. Remarkably, when combined with TGFβR2 gene disruption, WT1-TCR-T cells co-expressing CD8-41BB receptors were able to completely regress established large ovarian tumor xenografts, showed robust in-vivo expansion, and provided long-term protection from tumor rechallenge. Similarly, complete tumor clearance was achieved in an aggressive AML cell-line derived model. Importantly, the antigen specificity and HLA-A*02:01 restriction, did not change upon expression of CD8-41BB receptors. Lastly, the enhanced activity driven by the CD8-41BB receptor was confirmed in a second high avidity TCR targeting PRAME. Conclusions CRISPR/Cas9 based targeted integration of novel CD8-41BB fusion receptors represents a next-generation approach for enhancing the potency of TCR-based cell therapies. Ethics Approval Animal studies described here have been performed in compliance with protocols approved by Intellia Therapeutics’ IACUC (Institutional Animal Care and Use Committee).
Authors: Aaron Prodeus, Ivy Dutta, Justin Oh, Liz Cam, Allie Luther, Palak Sharma, Ishina Balwani, James Peter, Ian Miller, Lekshmi Maya, Elena Stampouloglou, James Bowen, Dai Liu, Eliana Ruggiero, Chiara Bonini, Birgit Schultes
Institution: Intellia Therapeutics (United States)
Language: English
Topic: CAR-T cell therapy research
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,490
OpenAlex ID: W4404064671