A phase I clinical trial of PSMA-directed/TGFβ-insensitive CAR-T cells in metastatic castration-resistant prostate cancer

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Background: Prostate specific membrane antigen (PSMA) is a highly expressed tumor-associated antigen potentially amenable to chimeric antigen receptor-modified T (CAR-T) cell therapy for castration-resistant prostate cancer (CRPC). However, a primary challenge to the success of CAR-T therapy in CRPC is the immunosuppressive microenvironment, characterized by high levels of TGFβ. The immunosuppressive functions of TGFβ can be inhibited in T cells using a dominant negative TGFβ receptor (TGFβRdn), thereby enhancing antitumor immunity. Methods: We conducted a first-in-human phase 1 clinical trial to evaluate the feasibility, safety and preliminary efficacy of PSMA-directed/TGFβ-insensitive CAR-T cells (CART-PSMA-TGFβRdn) in patients with metastatic CRPC (NCT03089203). In a 3+3 dose-escalation design, patients received a single dose of 1-3 x 107/m2 (Cohort 1) or 1-3 x 108/m2 (Cohort 2) CART-PSMA-TGFβRdn cells without lymphodepleting (LD) chemotherapy. In Cohort 3, one patient received 1-3 x 108/m2 CART-PSMA-TGFβRdn cells following a LD chemotherapy regimen of cyclophosphamide and fludarabine (Cy/Flu). In Cohort -3, three patients received 1-3 x 107/m2 CART-PSMA-TGFβRdn cells following Cy/Flu. Patients underwent metastatic tumor biopsies at baseline and on day 10 following treatment. Quantitative PCR of CART-PSMA-TGFβRdn DNA was performed at serial timepoints to evaluate for CAR-T expansion and persistence in peripheral blood and trafficking to target tissues. Multiplex cytokine analysis assessed CART-PSMA-TGFβRdn bioactivity. Results: Ten patients received CART-PSMA-TGFβRdn therapy across dose-level cohorts. All CART-PSMA-TGFβRdn infusion products met target transduction efficiency. Evaluation of CAR-T cellular kinetics demonstrated dose-dependent peripheral blood T cell expansion, as well as tumor tissue trafficking in post-treatment tumor biopsies. At Cohort 2 and above, 5 of 7 treated patients developed grade ≥2 cytokine release syndrome (CRS). Marked increases in inflammatory cytokines (IL-6, IL-15, IL-2, IFNγ) correlated with high-grade CRS events. One grade 5 adverse event (sepsis) occurred in Cohort 3. PSA decline was observed in 6 of 10 patients (median decline -33.2%, range -11.6% to -98.3%), and PSA30 response occurred in 4 of 10 patients (including one patient achieving PSA < 0.1 ng/mL). Conclusions: Adoptive cellular therapy with CART-PSMA-TGFβRdn is safe and feasible in patients with metastatic CRPC. A dose-dependent and lymphodepletion chemotherapy-dependent relationship was observed with CART-PSMA-TGFβRdn cell expansion, cytokine expression, CRS, and anti-tumor effect. Correlative cell trafficking and paired tumor Nanostring analyses will be presented. Future clinical investigations seek to enhance anti-tumor efficacy, while optimizing the therapeutic window. Clinical trial information: NCT03089203.

Abstract IA01: Single cell analysis of CRISPR T cells

CRISPR-Cas9 gene editing provides a powerful tool to enhance the natural ability of human T cells to fight cancer. We report a first-in-human phase 1 clinical trial to test the safety and feasibility of multiplex CRISPR-Cas9 editing to engineer T cells in three patients with refractory cancer. Two genes encoding the endogenous T cell receptor (TCR) chains, TCRα (TRAC) and TCRβ (TRBC), were deleted in T cells to reduce TCR mispairing and to enhance the expression of a synthetic, cancer-specific TCR transgene (NY-ESO-1). Removal of a third gene encoding programmed cell death protein 1 (PD-1; PDCD1), was performed to improve antitumor immunity. Adoptive transfer of engineered T cells into patients resulted in durable engraftment with edits at all three genomic loci. Although chromosomal translocations were detected, the frequency decreased over time. Modified T cells persisted for up to 9 months, suggesting that immunogenicity is minimal under these conditions and demonstrating the feasibility of CRISPR gene editing for cancer immunotherapy.

Citation Format: Edward Stadtmauer, Joseph Fraietta, Ansuman Satpathy, Carl H. June. Single cell analysis of CRISPR T cells [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr IA01.

Antigen-specific B cell depletion with desmoglein 3 chimeric autoantibody receptor T cells (DSG3-CAART) for targeted therapy of mucosal pemphigus vulgaris

Chimeric autoantibody receptors (CAARs) direct T cells to kill autoantigen-specific B cells. We previously established proof-of-concept for the CAAR approach using gene-engineered T cells expressing CAARs comprising DSG3, the autoantigen in the autoimmune blistering disease mucosal pemphigus vulgaris, fused to CD137-CD3ζ signaling domains. Here, we present results of preclinical studies that supported the DSG3-CAART investigational new drug application.

DSG3-CAART demonstrated activity related to dose in a passive transfer polyclonal anti-DSG3 hybridoma mouse model of mucosal pemphigus vulgaris, resulting in reversal of the rising serum anti-DSG3 antibody titers, target cell burden, and IgG deposition in epithelial tissues, as well as increased DSG3-CAART engraftment relative to dose. We further evaluated DSG3-CAART efficacy in a novel exploratory active immune mouse model with physiologic levels of circulating anti-DSG3 IgG, which demonstrated decreased antibody responses against pathogenic DSG3 epitopes and autoantibody binding to epithelial tissues, leading to clinical and histologic resolution of blisters. High-throughput screening of a membrane protein array with soluble DSG3 CAAR did not identify verifiable off-target toxicities.

These preclinical studies have enabled a first-in-human clinical trial of DSG3-CAART in mucosal pemphigus vulgaris and provide a foundation that may inform the preclinical development of future CAAR T cell therapies for antigen-specific B cell depletion in other autoantibody-mediated diseases.

A phase I clinical trial of PSMA-directed/TGFβ-insensitive CAR-T cells in metastatic castration-resistant prostate cancer

TPS269

Background: Adoptive immunotherapy with Chimeric Antigen Receptor (CAR)-T cells is a novel approach for the treatment of prostate cancer. However, the prostate cancer immunosuppressive microenvironment, including high levels of TGFβ, may limit the therapeutic potential of re-directed T cells upon tumor infiltration. The inhibition of TGFβ signaling via co-expression of a dominant negative TGFβ receptor (TGFβRdn) can enhance antitumor immunity. Co-expression of TGFβRdn on PSMA-redirected CAR-T cells in in vivo disseminated tumor models led to increased T cell proliferation, enhanced cytokine secretion, resistance to exhaustion, long-term persistence, and greater induction of tumor eradication. Methods: We are conducting a first-in-human phase 1 clinical trial evaluating the safety and preliminary efficacy of lentivirally-transduced PSMA-redirected/TGFβ-insensitive CAR-T cells (CART-PSMA-TGFβRdn) in metastatic CRPC (NCT03089203). In a 3+3 dose-escalation design, patients received a single dose of 1-3 x 107/m2 (Cohort 1) or 1-3 x 108/m2 (Cohort 2) CART-PSMA-TGFβRdn cells without lymphodepleting chemotherapy. In Cohort 3, 1-3 x 108/m2 CART-PSMA-TGFβRdn cells are administered following a lymphodepleting chemotherapy regimen of cyclophosphamide and fludarabine (cy/flu). A currently accruing modified protocol seeks to optimize the therapeutic window with CART-PSMA-TGFβRdn (CAR-T dose of 1-3 x 107/m2 following lymphodepleting cy/flu). Eight patients have received a single dose of CART-PSMA-TGFβRdn. CAR-T expansion and persistence in peripheral blood and trafficking to target tissues is evaluated via quantitative PCR of CART-PSMA-TGFβRdn DNA. Bioactivity of CAR-T cells in peripheral blood is evaluated via multiplex immunoassays. Additional correlative analyses will interrogate the therapeutic contribution of TGFβRdn, as well as early markers of response and resistance to CART-PSMA-TGFβRdn therapy. Clinical trial information: NCT03089203.

Abstract IA20: Updates on CAR T Cells

The emergence of immune-oncology as the first broadly successful strategy for metastatic cancer will require clinicians to integrate this new pillar of medicine with the pillars of chemotherapy, radiation, and targeted small-molecule compounds. Chimeric antigen receptor (CAR) T cells have proven that engineered immune cells can serve as a powerful new class of cancer therapeutics. Adoptive immunotherapy retargeting T cells to CD19 via a chimeric antigen receptor (CAR) is an investigational treatment capable of inducing complete tumor regression of B-cell malignancies when there is sustained survival of infused cells. Clinical experience has helped to define the major challenges that must be met to make engineered T cells a reliable, safe, and effective platform that can be deployed against a broad range of tumors. The emergence of synthetic biology approaches for cellular engineering provides the field with a broadly expanded set of tools for programming immune cells. In this presentation, I will discuss how these tools could be used to design the next generation of smart T-cell precision therapeutics.

We have been exploring in preclinical models and clinical trials methods to synthetically enhance T-cell antitumor efficacy by transfer of genetically engineered T cells. Infusions of chimeric antigen receptor (CAR) T cells can result in remissions in patients with hematologic malignancies, but efficacy is often limited by the extent of expansion and persistence of engineered lymphocytes. In a patient with a delayed clinical response, we show that a complete and durable response to CAR T cell therapy resulted from a clonal expansion of a single CAR T cell. At the peak of the antitumor response, 94 percent of CD8+ CTL019 cells originated from a single clone in which proviral insertion disrupted the gene encoding the methylcytosine dioxygenase TET2. We conclude that loss of function of TET2 secondary to insertional mutagenesis promoted T-cell proliferation, and that the progeny of a single CAR T cell induced durable remission in refractory leukemia.

In solid tumors, we have observed antitumor activity in patients with ovarian cancer, pancreatic ductal adenocarcinoma, pleural mesothelioma, and glioblastoma following infusion of CAR T cells expressing scFv specific for mesothelin or EGFRvIII. However, this approach has not yet resulted in complete tumor eradication. Using genome-edited T cells, it may be possible to enhance and prolong the activity of T cells that have disrupted immune and metabolic checkpoints. In preclinical studies, we show that TCR-specific T cells have enhanced antitumor activity following disruption of TCR alpha and beta genes and the PD1 gene using CRISPR/Cas9. This approach is just entering a clinical trial. These findings provide insights into the immunobiology of effector T cells and demonstrate the potential of multiplexed CRISPR/Cas9 genome editing to synthetically enhance the efficacy of immunotherapy.

References:

1. Lim WA, June CH. The principles of engineering immune cells to treat cancer. Cell 2017;168(4):724-40.

2. Ruella M, Klichinsky M, Kenderian SS, et al. Overcoming the immunosuppressive tumor microenvironment of Hodgkin lymphoma using chimeric antigen receptor T cells. Cancer Discov 2017;Jun 2. pii: CD-16-0850. doi: 10.1158/2159-8290.CD-16-0850. [Epub ahead of print]

3. Maude S, Frey N, Shaw P, et al. Chimeric antigen receptor T cells for sustained remissions in leukemia. N Engl J Med 2014;371(16):1507-17.

4. Tanyi JL, Stashwick C, Plesa G, Morgan MA, Porter D, Maus MV, June CH. Possible compartmental cytokine release syndrome in a patient with recurrent ovarian cancer after treatment with mesothelin-targeted CAR-T cells. J Immunother 2017.

5. Beatty GL, Haas AR, Maus MV, et al. Mesothelin-specific chimeric antigen receptor mRNA-engineered T cells induce anti-tumor activity in solid malignancies. Cancer Immunol Res 2014;2(2):112-20.

6. Ruella M, Barrett DM, Kenderian SS, et al. Dual CD19 and CD123 targeting prevents antigen-loss relapses after CD19-directed immunotherapies. J Clin Invest 2016;126(10):3814-26.

7. Chong EA, Melenhorst JJ, Lacey SF, et al. PD-1 blockade modulates chimeric antigen receptor (CAR) modified T cells and induces tumor regression: Refueling the CAR. Blood 2016. doi: 10.1182/blood-2016-09-738245

8. Ren J, Liu X, Fang C, et al. Multiplex genome editing to generate universal CAR T cells resistant to PD1 inhibition. Clin Cancer Res 2016; Nov 4. 10.1158/1078-0432.ccr-16-1300. [Epub ahead of print].

9. June CH, Warshauer JT, Bluestone JA. Is autoimmunity the Achilles’ heel of cancer immunotherapy? Nat Med 2017;23(5):540-7.

10. O’Rourke DM, Nasrallah MP, Desai A, et al. A single dose of peripherally infused EGFRvIII-directed CAR T cells mediates antigen loss and induces adaptive resistance in patients with recurrent glioblastoma. Sci Transl Med 2017;9(399), pii: eaaa0984. doi: 10.1126/scitranslmed.aaa0984.

11. Sampson JH, Maus MV, June CH. Immunotherapy for brain tumors. J Clin Oncol 2017;35(21):2450-6.

Citation Format: Carl H. June, John Scholler, Marco Ruella, Joseph Fraietta, J. Jos Melenhorst, Jiangtao Ren, Yangbing Zhao. Updates on CAR T Cells [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr IA20.

Gene expression signatures of response to anti-CD19 chimeric antigen receptor (CAR) T-cell therapy in patients with CLL and ALL

137

Background: The adoptive transfer of autologous T cells genetically modified to express a CD19-specific, 4-1BB/CD3ζ-signaling CAR (CTL019) has shown remarkable activity and induces long-term remissions in a subset of patients with relapsed/refractory chronic lymphocytic leukemia (CLL) and acute lymphoblastic leukemia (ALL). In ALL, CTL019 induces a complete response (CR) in over 90% of patients while in CLL 25% of patients obtain a CR. It is not fully understood why only certain patients respond to therapy. Methods: We employed next generation sequencing of RNA (RNAseq) to identify predictive indicators of response to CTL019. We performed RNAseq on leukapheresis and manufactured product T cells prior to re-infusion from 35 CLL and 7 pediatric ALL patients with heavily pre-treated and high-risk disease. To characterize potency, we performed RNAseq on the infusion product after stimulation with the CAR. Results: We find that durable remission in CLL is associated with gene expression signatures of early memory and T-effector cells, while T cells from non-responding patients are enriched in signatures of T-regulatory cells, terminal differentiation, and exhaustion. In following the results from CLL, we find that pediatric ALL manufactured T cells are significantly enriched for an early memory, naïve T cell state and all achieved a CR. In parallel in vitro experiments, stimulation of the infusion product further demonstrated that CTL019 cells from CRs have an increased capacity for activation upon stimulation. We tested if we could extend these observations to identify a phenotype of T cells that is predictive of response prior to CTL019 manufacturing and find that the signatures predictive of response at the pre-infusion stage are also observed at the earlier leukapheresis time point. Conclusions: These findings suggest that intrinsic T cell fitness dictates response to CAR T cells. These gene expression signatures, along with additional immunological biomarkers, may be used to identify which patients are most likely to respond to adoptive transfer strategies and suggest manufacturing modifications that might potentiate the generation of maximally efficacious infusion products. Clinical trial information: NCT01029366, NCT01747486, NCT01626495.

Abstract B139: Toxicity testing of EGFRvIII CAR-based immunotherapy of glioblastoma: From bench to bedside

The purpose of this study was to generate a panel of donor-derived primary cells, expand them ex-vivo in to sufficient numbers to utilize as targets for evaluating potential normal tissue toxicity of epidermal growth factor receptor mutation variant three (EGFRvIII)-specific chimeric antigen receptors (CAR) prior to use in clinical trials for patients with glioblastoma (GBM). Nine cell types were obtained, including different epithelial, endothelial, bone, smooth muscle, cardiac, neural, hematopoetic, stem cells, and keratinocytes. Cells were expanded with individual specialized media and protocols for between 8-12 passages. After expansion, primary cell identity was confirmed by morphology, ICC and IHC for characteristic markers. Levels of EGFR and EGFRvIII in each cell type were determined by qRT-PCR. To evaluate potential normal-cell toxicity, CAR T cells were co-cultured with each type of primary cell and function was evaluated in two ways: i) T cell activation was measured by staining and flow cytometry of CD3+ T cells stained intracellularly for CD107a, or GzmB, TNFalpha, IFNgamma, IL-2 cytokines. ii) Target cell lysis was evaluated by labeling primary cells with 51Cr prior to 4 hour co-culture with increasing numbers of CAR T cells, and measuring chromium-release. None of the primary cells showed expression of EGFRvIII, although several, in particular keratinocytes and renal epithelial, had high levels of EGFR. In functional assays, while the EGFR CAR T cells recognized and lysed EGFR expressing cell types, EGFRvIII CARs showed T cell activation and target lysis only of EGFRvIII expressing tumors. EGFRvIII CAR 2173 was selected for use in clinical trials at UPENN and UCSD, treating patients with GBM. To date, 6 patients have been infused with 2173 EGFRvIII CAR T cells, with no observed toxicity. All patients had detectable expansion of CAR T cells in vivo in blood, and one patient with subsequent tumor resection had detectable intra-tumoral CAR T cells. These CARs appear to be safe, persist in vivo and traffic into GBM tumor. An update on the clinical trial will be presented at the conference.

Note:This abstract was not presented at the conference.

Citation Format: Alexandria P. Cogdill, Alina Boesteanu, Chong Xu, Kathleen Haines, John Scholler, Joseph Fraietta, Yangbing Zhao, Xiaojun Liu, Jennifer Morrissette, Bruce Levine, Simon Lacey, Andreas Loew, Reshma Singh, Jennifer Brogdon, Donald M. O'Rourke, Marcela V. Maus, Carl H. June, Laura A. Johnson. Toxicity testing of EGFRvIII CAR-based immunotherapy of glioblastoma: From bench to bedside. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B139.

Anti-HIV, anti-inflammatory and safety profile of the PDB microbicide candidate (HUM8P.342)

Topical microbicides (vaginal gels) are one mechanism to prevent sexual transmission of human immunodeficiency virus type 1 (HIV-1). We show here that a new class of microbicides, abasic phosphorothioate 2’ deoxyribose backbone (PDB) oligomers, has significant anti-HIV-1 activities in human PBMC cell cultures when either the virus or cells are pre-incubated with the compound. HIV infection is also inhibited in an explant model of human cervical tissue. A second function of PDB other than its anti-HIV activity is its capacity to inhibit HIV-triggered TLR7/9 activation. PDB suppresses the release of HIV-induced pro-inflammatory cytokines/chemokines in cultures of human PBMC and ectocervical tissues. We also demonstrated that PDB is safe and non-toxic in in vitro cell cultures and in an in vivo murine vaginal toxicity model. The effect of PDB is stable as this compound retains activity at pH 4.4 and after transition to a neutral pH, following incubation with biological fluids (seminal plasma, vaginal fluids) and a normal vaginal flora Lactobacillus strain. PDB does not affect the growth of Lactobacillus strains. Phosphorothioate 2’ deoxyribose oligomers are novel microbicide candidates with dual-acting anti-HIV and anti-inflammatory activities and an excellent safety and stability profile.

Type I interferon increases the sensitivity of human immunodeficiency virus (HIV)-specific CD8+ T lymphocytes to CD95/Fas-mediated apoptosis (42.22)

Innate immune responses elicited during acute and chronic HIV infection are critical to the control of viremia. Based on their well established antiviral effects, the production of type I interferon (IFN-alpha and IFN-beta) has long been considered a protective mechanism in HIV infection. However, it is possible that excessive IFN-alpha and IFN-beta production during HIV infection may impair HIV-specific CD8+ T cell responses and/or contribute to the loss of CD4+ T cells. We show here that CD4+ and CD8+ T lymphocytes from healthy donors and HIV+ patients are sensitized to CD95/Fas-induced death when pre-incubated with type I interferon for 72 hours. Importantly, IFN-alpha increased the sensitivity of HIV-specific CD8+ T cells from HIV+ individuals to CD95/Fas-mediated apoptosis. Apoptosis of CMV-specific and EBV-specific CD8+ T cells from the same patients was not augmented when exposed to IFN-alpha and subsequently stimulated with anti-CD95 antibody. Since CD4+ T cells and HIV-specific CD8+ T cells in HIV infection are known to be sensitive to CD95/Fas-mediated apoptosis, our studies suggest that these lymphocytes may be initially sensitized to CD95/Fas-induced death by type 1 interferon during acute HIV infection. The production of these anti-viral cytokines during chronic infection may further compromise CD4+ and HIV-specific CD8+ T cell survival.