A phase 1, first-in-human (FIH) study of adenovirally transduced autologous macrophages engineered to contain an anti-HER2 chimeric antigen receptor (CAR) in subjects with HER2 overexpressing solid tumors.

TPS668 Background: Adoptive T cell therapies have led to remarkable advances among patients with hematologic malignancies, but not in those with solid tumors. Macrophages are actively recruited into, and are abundantly present in the solid tumor microenvironment (sTME). Tumor- associated macrophages typically display immunosuppressive behavior, but when engineered to be proinflammatory, may be an ideal vector to administer adoptive cellular therapy in solid tumors. Furthermore, insertion of a CAR on the macrophages allow them to selectively recognize and phagocytose antigen overexpressing cancer cells. CAR macrophages reprogram the sTME and present neoantigens to T cells, leading to epitope spreading and immune memory. Human Epidermal Growth Factor Receptor 2 (HER2) overexpression promotes tumorigenesis in many cancers (Table). CT-0508 is a cell product comprised of autologous monocyte-derived pro-inflammatory macrophages expressing an anti-HER2 CAR. Pre-clinical studies have shown that CT-0508 induced targeted cancer cell phagocytosis while sparing normal cells, decreased tumor burden and prolonged survival in relevant models. CT-0508 cells were safe and effective in a semi-immunocompetent mouse model of human HER2 overexpressing ovarian cancer. Methods: This is a FIH Phase 1 study to evaluate safety, tolerability, cell manufacturing feasibility, trafficking and preliminary evidence of efficacy of investigational product CT-0508 in 18 subjects with locally advanced (unresectable) or metastatic solid tumors overexpressing HER2, who have failed available therapies, including anti-HER2 therapies when indicated. Filgrastim is being used to mobilize autologous hematopoietic progenitor cells for monocyte collection by apheresis. The CT-0508 CAR macrophage product is manufactured, prepared and cryopreserved from mobilized peripheral blood monocytes. Group 1 subjects receive CT-0508 infusion split over D1, 3 and 5. Dose limiting toxicities will be observed and addressed by a Safety Review Committee. Group 2 subjects will receive the full CT-0508 infusion on D1. Pre and post treatment biopsies and blood samples will be collected to investigate correlates of safety (immunogenicity), trafficking (PCR, RNA scope), CT-0508 persistence in blood and in the tumor, target antigen engagement, TME modulation (single cell RNA sequencing), immune response (TCR sequencing) and others. Clinical trial information: NCT04660929. [Table: see text]