Anti-CD70 monoclonal antibody, clone FR70

Purpose: Given that heterogeneous expression and variants of antigens on solid tumors are responsible for relapse after chimeric antigen receptor (CAR)-T cell therapy, we hypothesized that combinatorial targeting two tumor-associated antigens would lessen this problem and enhance the antitumor activity of T cells. Methods: The co-expression level of CD70 and B7-H3 was analyzed in multiple tumor tissue samples. Further, two putative antigens were identified in The Cancer Genome Atlas and Gene Expression Profiling Interactive Analysis database. Two CD70 targeted CARs with different antigen binding domain, truncated CD27 and CD70 specific single-chain antibody fragment (scFv), were designed to screen a more suitable target-antigen binding moiety. Accordingly, we designed a bivalent tandem CAR (TanCAR) and further assessed the anti-tumor efficacy of TanCAR-T cells in vitro and in vivo. Results: Our results indicated that co-expression of CD70 and B7-H3 was observed on multiple tumor types including kidney, breast, esophageal, liver, colon cancer, glioma as well as melanoma. The CD70 targeted CAR-T cells with binding moiety of CD70 specific scFv exhibit a higher affinity and antitumor effect against CD70(+) tumor cells. TanCAR-T cells induced enhanced ability of cytolysis and cytokine release over unispecific CAR-T cells when encountering tumor cells expressing two target-antigens. Further, low doses of TanCAR-T cells could also effectively control the lung cancer and melanoma xenografts and improved overall survival of the treated animals. Conclusion: TanCAR-T cells targeting CD70 and B7-H3 exhibit enhanced antitumor functionality and improve the problem of antigenic heterogeneity and variant in the treatment against solid tumor and melanoma.

Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment for hematologic and immunologic diseases. However, graft-versus-host disease (GVHD) may develop when donor-derived T cells recognize and damage genetically distinct normal host tissues. In addition to TCR signaling, costimulatory pathways are involved in T cell activation. CD27 is a TNFR family member expressed on T cells, and its ligand, CD70, is expressed on APCs. The CD27/CD70 costimulatory pathway was shown to be critical for T cell function and survival in viral infection models. However, the role of this pathway in allo-HCT is previously unknown. In this study, we have examined its contribution in GVHD pathogenesis. Surprisingly, Ab blockade of CD70 after allo-HCT significantly increases GVHD. Interestingly, whereas donor T cell-or bone marrow-derived CD70 plays no role in GVHD, host-derived CD70 inhibits GVHD as CD70(-/-) hosts show significantly increased GVHD. This is evidenced by reduced survival, more severe weight loss, and increased histopathologic damage compared with wild-type hosts. In addition, CD70(-/-) hosts have higher levels of proinflammatory cytokines TNF-alpha, IFN-gamma, IL-2, and IL-17. Moreover, accumulation of donor CD4(+) and CD8(+) effector T cells is increased in CD70(-/-) versus wild-type hosts. Mechanistic analyses suggest that CD70 expressed by host hematopoietic cells is involved in the control of alloreactive T cell apoptosis and expansion. Together, our findings demonstrate that host CD70 serves as a unique negative regulator of allogeneic T cell response by contributing to donor T cell apoptosis and inhibiting expansion of donor effector T cells.