Rimas J. Orentas

Bio: Rimas J. Orentas is an academic researcher from University of Washington. The author has contributed to research in topics: Chimeric antigen receptor & Antigen. The author has an hindex of 33, co-authored 94 publications receiving 7302 citations. Previous affiliations of Rimas J. Orentas include Medical College of Wisconsin & Miltenyi Biotec.

4-1BB costimulation ameliorates T cell exhaustion induced by tonic signaling of chimeric antigen receptors

Abstract: Chimeric antigen receptors (CARs) targeting CD19 have mediated dramatic antitumor responses in hematologic malignancies, but tumor regression has rarely occurred using CARs targeting other antigens. It remains unknown whether the impressive effects of CD19 CARs relate to greater susceptibility of hematologic malignancies to CAR therapies, or superior functionality of the CD19 CAR itself. We show that tonic CAR CD3-ζ phosphorylation, triggered by antigen-independent clustering of CAR single-chain variable fragments, can induce early exhaustion of CAR T cells that limits antitumor efficacy. Such activation is present to varying degrees in all CARs studied, except the highly effective CD19 CAR. We further determine that CD28 costimulation augments, whereas 4-1BB costimulation reduces, exhaustion induced by persistent CAR signaling. Our results provide biological explanations for the antitumor effects of CD19 CARs and for the observations that CD19 CAR T cells incorporating the 4-1BB costimulatory domain are more persistent than those incorporating CD28 in clinical trials.

CD22-targeted CAR T cells induce remission in B-ALL that is naive or resistant to CD19-targeted CAR immunotherapy.

Abstract: Chimeric antigen receptor (CAR) T cells targeting CD19 mediate potent effects in relapsed and/or refractory pre-B cell acute lymphoblastic leukemia (B-ALL), but antigen loss is a frequent cause of resistance to CD19-targeted immunotherapy. CD22 is also expressed in most cases of B-ALL and is usually retained following CD19 loss. We report results from a phase 1 trial testing a new CD22-targeted CAR (CD22-CAR) in 21 children and adults, including 17 who were previously treated with CD19-directed immunotherapy. Dose-dependent antileukemic activity was observed, with complete remission obtained in 73% (11/15) of patients receiving ≥1 × 106 CD22-CAR T cells per kg body weight, including 5 of 5 patients with CD19dim or CD19- B-ALL. Median remission duration was 6 months. Relapses were associated with diminished CD22 site density that likely permitted CD22+ cell escape from killing by CD22-CAR T cells. These results are the first to establish the clinical activity of a CD22-CAR in B-ALL, including leukemia resistant to anti-CD19 immunotherapy, demonstrating potency against B-ALL comparable to that of CD19-CAR at biologically active doses. Our results also highlight the critical role played by antigen density in regulating CAR function.

CAR T Cells Targeting B7-H3, a Pan-Cancer Antigen, Demonstrate Potent Preclinical Activity Against Pediatric Solid Tumors and Brain Tumors.

Abstract: Purpose: Patients with relapsed pediatric solid tumors and CNS malignancies have few therapeutic options and frequently die of their disease. Chimeric antigen receptor (CAR) T cells have shown tremendous success in treating relapsed pediatric acute lymphoblastic leukemia, but this has not yet translated to treating solid tumors. This is partially due to a paucity of differentially expressed cell surface molecules on solid tumors that can be safely targeted. Here, we present B7-H3 (CD276) as a putative target for CAR T cell therapy of pediatric solid tumors, including those arising in the central nervous system. Experimental Design: We developed a novel B7-H3 CAR whose binder is derived from a monoclonal antibody that has been shown to preferentially bind tumor tissues and has been safely used in humans in early phase clinical trials. We tested B7-H3 CAR T cells in a variety of pediatric cancer models. Results: B7-H3 CAR T cells mediate significant anti-tumor activity in vivo, causing regression of established solid tumors in xenograft models including osteosarcoma, medulloblastoma, and Ewing sarcoma. We demonstrate that B7-H3 CAR T cell efficacy is largely dependent upon high surface target antigen density on tumor tissues and that activity is greatly diminished against target cells that express low levels of antigen, thus providing a possible therapeutic window despite low-level normal tissue expression of B7-H3. Conclusions: B7-H3 CAR T cells could represent an exciting therapeutic option for patients with certain lethal relapsed or refractory pediatric malignancies which should be tested in carefully designed clinical trials.

Adhesion receptors of the immune system.

Abstract: The adhesive interactions of cells with other cells and with the extracellular matrix are crucial to all developmental processes, but have a central role in the functions of the immune system throughout life Three families of cell-surface molecules regulate the migration of lymphocytes and the interactions of activated cells during immune responses

Tisagenlecleucel in Children and Young Adults with B-Cell Lymphoblastic Leukemia

Abstract: Background In a single-center phase 1–2a study, the anti-CD19 chimeric antigen receptor (CAR) T-cell therapy tisagenlecleucel produced high rates of complete remission and was associated with serious but mainly reversible toxic effects in children and young adults with relapsed or refractory B-cell acute lymphoblastic leukemia (ALL) Methods We conducted a phase 2, single-cohort, 25-center, global study of tisagenlecleucel in pediatric and young adult patients with CD19+ relapsed or refractory B-cell ALL The primary end point was the overall remission rate (the rate of complete remission or complete remission with incomplete hematologic recovery) within 3 months Results For this planned analysis, 75 patients received an infusion of tisagenlecleucel and could be evaluated for efficacy The overall remission rate within 3 months was 81%, with all patients who had a response to treatment found to be negative for minimal residual disease, as assessed by means of flow cytometry The rates of event-f

Specificities of secretion and uptake of exosomes and other extracellular vesicles for cell-to-cell communication.

Abstract: The ability of exosomes to transfer cargo from donor to acceptor cells, thereby triggering phenotypic changes in the latter, has generated substantial interest in the scientific community. However, the extent to which exosomes differ from other extracellular vesicles in terms of their biogenesis and functions remains ill-defined. Here, we discuss the current knowledge on the specificities of exosomes and other types of extracellular vesicles, and their roles as important agents of cell-to-cell communication.