Caitlin Stashwick

B7-H4 as a potential target for immunotherapy for gynecologic cancers: A closer look

B7-H4 is a transmembrane protein that binds an unknown receptor on activated T cells resulting in inhibition of T-cell effector function via cell cycle arrest, decreased proliferation, and reduced IL-2 production. B7-H4 is up-regulated on the surface of cancer cells and immunosuppressive tumor-associated macrophages (TAMs) in a variety of human cancers. Notably, B7-H4 expression levels inversely correlate with patient survival in ovarian cancer, making B7-H4 an attractive candidate for therapeutic intervention. Here, we summarize the experimental data and methodologies that have revealed B7-H4s mRNA and protein expression and function in both mice and humans since its discovery in 2003, with a specific focus on B7-H4s role in ovarian cancer. We also underscore the discrepancies in published data due to high variability in methodology and use of different antibodies, most of which are not commercially available. Finally, since B7-H4 is expressed on tumor cells and TAMs in various cancer types, directing therapeutics against B7-H4 could have tremendous synergistic outcomes in favorably altering the tumor micro-environment and eliminating cancer cells. We highlight the therapeutic potential of targeting B7-H4, both by comparing other negative immune modulators such as PD-1 and CTLA-4 and by identifying novel methods to target B7-H4 directly or indirectly to overcome B7-H4-mediated T-cell inhibition.

Mesothelin as a target for chimeric antigen receptor-modified T cells as anticancer therapy

Mesothelin is a promising target for immune-based therapy, specifically for mesothelioma and pancreatic and ovarian cancers that have high levels of mesothelin expression. Many preclinical and clinical studies that target tumors with high mesothelin expression with antibodies, immunotoxins, antibody-drug conjugates and vaccines have shown the potential of mesothelin as a target. Studies of T cells genetically modified with chimeric antigen receptors (CAR) report significant efficacy in hematologic malignancies, and antimesothelin CAR T cells are currently being investigated in clinical studies. Here we outline the rationale for using mesothelin as a target for immunotherapy, review the clinical and preclinical studies evaluating mesothelin-directed therapies and explore the promise of CAR T cells directed against mesothelin for immunotherapy in the future.

Follicle-Stimulating Hormone Receptor as a Target in the Redirected T-cell Therapy for Cancer

Ovarian cancers, and possibly tumor-associated vasculature, express follicle-stimulating hormone receptors (FSHRs), a potential target for antitumor immunity. T cells expressing anti-FSHR receptors killed tumors expressing the FSHR in vitro and reduced tumor growth in mouse models. Adoptive transfer of T cells engineered to express chimeric immunoreceptors is an effective strategy to treat hematologic cancers; however, the use of this type of therapy for solid cancers, such as ovarian cancer, remains challenging because a safe and effective immunotherapeutic target has not yet been identified. Here, we constructed and evaluated a novel redirected T-cell–based immunotherapy targeting human follicle-stimulating hormone receptor (FSHR), a highly conserved molecule in vertebrate animals with expression limited to gonadal tissues, ovarian cancer, and cancer-associated vasculature. Receptor ligand–based anti-FSHR immunoreceptors were constructed that contained small binding fragments from the ligand for FSHR, FSH, fused to T-cell transmembrane and T-cell signaling domains. Human T cells transduced to express anti-FSHR immunoreceptors were specifically immunoreactive against FSHR-expressing human and mouse ovarian cancer cell lines in an MHC-nonrestricted manner and mediated effective lysis of FHSR-expressing tumor cells, but not FSHR-deficient targets, in vitro. Similarly, the outgrowth of human ovarian cancer xenografts in immunodeficient mice was significantly inhibited by the adoptive transfer of FSHR-redirected T cells. Our experimental observations show that FSHR is a promising immunotherapeutic target for ovarian cancer and support further exploration of FSHR-targeted immune therapy approaches for patients with cancer. Cancer Immunol Res; 3(10); 1130–7. ©2015 AACR.

Abstract CT105: Safety and feasibility of chimeric antigen receptor modified T cells directed against mesothelin (CART-meso) in patients with mesothelin expressing cancers

A phase I study to evaluate the safety and feasibility of an intravenous infusion of autologous T cells transduced to express a chimeric antigen receptor directed against mesothelin (CART-meso) in patients with mesothelin expressing tumors is being conducted at the University of Pennsylvania. Here we report on the first five patients treated with CART-meso T cell infusion. Five patients with recurrent advanced stage cancers (two serous ovarian, two epithelial mesothelioma, and one pancreatic) who had received 4-12 prior regimens, were treated with a single infusion of CART-meso cells. Apheresed autologous T cells were transduced with a lentiviral vector expressing the CAR construct composed of an extracellular anti-mesothelin single chain variable fragment derived from mouse monoclonal antibody (SS1) fused to the intracellular signaling domains of 4-1BB (CD137) and TCRzeta. Each patient received a single dose of 1-3 × 10^7 CART-meso cells/m2. No lymphodepletion with chemotherapy was given prior to infusion. All subjects enrolled were successfully infused and there were no acute adverse events (AE) with infusion. To date, Grade 4 AEs have included sepsis(1), anemia(1), pleural effusions(1), tachypnea(1), dyspnea(1), and aspiration(1) and Grade 3 AEs have included sepsis(1), leukocytosis(2), DIC(1), tachycardia(1), dyspnea(1), hypotension(1), dusky extremities(1), fatigue(1), ascites(1), peritonitis(1), elevated LFTs(1), portal vein hypertension(1), and acute kidney injury(1). After infusion, CART-meso T cells were transiently detectable by PCR in the peripheral blood in all patients up to Day 21-28 after infusion. CART-meso cells were found to traffic to tumor sites within the peritoneum and liver, as well as to off-tumor on-target sites such as pericardial fluid, but without clinical toxicity of pericarditis. Expansion of CART-meso cells was also observed in the pleural fluid of one patient who had a known malignant pleural effusion. Cytokine profiling of the peripheral blood revealed elevations of IL-6 and VEGF with significant elevations seen in the one patient with malignant pleural effusion. No elevations in TNFα or IFNγ were found. Anti-tumor efficacy is suggested by the clearing of malignant cells in the pleural fluid of one patient on Day 21 and Day 26 after infusion, as well as radiological and clinical evidence of stable to decreased burden of disease in one patient. Patient follow-up for 1-3 months post infusion has revealed no evidence of long-term toxicities to date. These interim results suggest that intravenous infusion of CART-meso T cells without lymphodepletion is feasible and safe. In these five patients with metastatic mesothelin expressing cancers, the infusion was well tolerated with no off-tumor on-target toxicities. Laboratory and clinical findings suggest infused T cells are effective and functional. Citation Format: Janos L. Tanyi, Andrew R. Haas, Gregory L. Beatty, Mark A. Morgan, Caitlin J. Stashwick, Mark H. O9Hara, David L. Porter, Marcela V. Maus, Bruce L. Levine, Simon F. Lacey, Anne Marie Nelson, Maureen McGarvey, Naseem DS Kerr, Gabriela Plesa, Carl H. June. Safety and feasibility of chimeric antigen receptor modified T cells directed against mesothelin (CART-meso) in patients with mesothelin expressing cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT105. doi:10.1158/1538-7445.AM2015-CT105

Targeted cancer immunotherapy via combination of designer bispecific antibody and novel gene-engineered T cells

BackgroundRedirection of T lymphocytes against tumor antigens can induce dramatic regression of advanced stage malignancy. The use of bispecific antibodies (BsAbs) that bind both the T-cell receptor (TCR) and a target antigen is one promising approach to T-cell redirection. However, BsAbs indiscriminately bind all CD3+ T-cells and trigger TCR activation in the absence of parallel costimulatory signals required to overcome T-cell unresponsiveness or anergy.MethodsTo address these limitations, a combination platform was designed wherein a unique BsAb referred to as frBsAb exclusively engages T-cells engineered to express a novel chimeric receptor comprised of extracellular folate receptor fused to intracellular TCR and CD28 costimulatory signaling domains in tandem; a BsAb-binding immune receptor (BsAb-IR). As a surrogate TCR, the BsAb-IR allows for concomitant TCR and costimulatory signaling exclusively in transduced T-cells upon engagement with specific frBsAbs, and can therefore redirect T-cells on command to desired antigen. Human primary T-cells were transduced with lentiviral vector and expanded for 14–18 days. BsAb-IRs were harvested and armed with frBsAbs to test for redirected cytotoxicity against CD20 positive cancer cell lines.ResultsUsing frBsAbs specific for CD20 or HER2, the lytic activity of primary human T-cells expressing the BsAb-IR was specifically redirected against CD20+ leukemic cells or HER2+ epithelial cancer cells, respectively, while non-engineered T-cells were not activated. Notably, elimination of the CD28 costimulatory domain from the BsAb-IR construct significantly reduced frBsAb-redirected antitumor responses, confirming that frBsAbs are capable of delivering simultaneous TCR activation and costimulatory signals to BsAb-IR T-cells.ConclusionIn summary, our results establish the proof of concept that the combination of BsAbs with optimized gene-engineered T-cells provides the opportunity to specify and augment tumor antigen-specific T-cell activation and may improve upon the early success of conventional BsAbs in cancer immunotherapy.

Possible Compartmental Cytokine Release Syndrome in a Patient With Recurrent Ovarian Cancer After Treatment With Mesothelin-targeted Car-t Cells

Cytokine release syndrome (CRS) is a potentially severe systemic toxicity seen after adoptive T-cell therapy and caused by T-cell activation and proliferation and is associated with elevated circulating levels of cytokines such as C-reactive protein, interleukin-6 (IL-6), and interferon-γ and has previously been described as a systemic response in hematologic malignancies. A 52-year-old woman with BRCA 1 mutation positive heavily pretreated advanced recurrent serous ovarian cancer was treated under a compassionate use protocol with autologous mesothelin-redirected chimeric antigen receptor T cells (CART-meso). Autologous T cells were transduced to express a receptor composed of an extracellular antimesothelin single-chain variable fragment fused to 4-1BB and TCR-zeta signaling domain. This patient was infused with 3×10 CART-meso T cells/m without lymphodepletion and developed compartmental CRS confined to the pleural cavities. The compartmental CRS was evidenced by an increase in IL-6 and accumulation of CART-meso T cells in pleural fluid compared with peripheral blood and was successfully treated the anti-IL6 receptor antagonist tocilizumab on D21 after the T-cell infusion. This is the first description of a compartmental CRS in a patient with solid malignancy. This response could be due to malignant pleural fluid creating an environment where T cells could interact with tumor cells and suggests localized on-target CAR-T-cell activation.

Tumor Regression and Delayed Onset Toxicity Following B7-H4 CAR T Cell Therapy.

B7-H4 protein is frequently overexpressed in ovarian cancer. Here, we engineered T cells with novel B7-H4-specific chimeric antigen receptors (CARs) that recognized both human and murine B7-H4 to test the hypothesis that B7-H4 CAR T cell therapy can be applied safely in preclinical models. B7-H4 CAR T cells specifically secreted IFN-γ and lysed B7-H4(+) targets. In vivo, B7-H4 CAR T cells displayed antitumor reactivity against B7-H4(+) human ovarian tumor xenografts. Unexpectedly, B7-H4 CAR T cell treatment reproducibly showed delayed, lethal toxicity 6-8 weeks after therapy. Comprehensive assessment of murine B7-H4 protein distribution uncovered expression in ductal and mucosal epithelial cells in normal tissues. Postmortem analysis revealed the presence of widespread histologic lesions that correlated with B7-H4(+) expression, and were inconsistent with graft versus host disease. Lastly, expression patterns of B7-H4 protein in normal human tissue were comparable to distribution in mice, advancing our understanding of B7-H4. We conclude that B7-H4 CAR therapy mediates control of cancer outgrowth. However, long-term engraftment of B7-H4 CAR T cells mediates lethal, off-tumor toxicity that is likely due to wide expression of B7-H4 in healthy mouse organs. This model system provides a unique opportunity for preclinical evaluation of safety approaches that limit CAR-mediated toxicity after tumor destruction in vivo.

Overcoming barriers of car T-cell therapy in patients with mesothelin-expressing cancers.

One obstacle to the application of immunotherapy to solid malignancies is to overcome the existing tolerance to self-antigens. Vaccine strategies aimed at harnessing endogenous antitumor T cells are limited by the T-cell receptor repertoire, which can be detected within the thymus as central tolerance or rendered nonfunctional by post-thymic mechanisms of peripheral tolerance. Adoptive immunotherapy can overcome these obstacles, since therapeutically effective T cells can be engineered to recognize tumors. Continued advancements in novel treatments, including immunotherapy, in solid malignancies are imperative. While mesothelin is an attractive target for cancer immunotherapy given its normal expression is limited to mesothelial cells, the breakthrough for chimeric antigen receptor T-cell treatment against this antigen is still forthcoming.

206. Follicle-Stimulating Hormone Receptor as a Target in the Redirected T-Cell Therapy for Cancer

Adoptive transfer of T-cells engineered to express chimeric immune receptors is an effective strategy to treat hematological cancers, however, such therapy for solid cancers such as ovarian cancer remains challenging because a safe and effective immunotherapeutic target has not yet been identified. Here, we constructed and evaluated a novel redirected T-cell-based immunotherapy targeting human follicle-stimulating hormone receptor (FSHR), a highly conserved molecule in vertebrate animals with expression limited to gonadal tissues, ovarian cancer and cancer-associated vasculature. Receptor ligand-based anti-FSHR immune receptors were constructed that contained small binding fragments from the ligand for FSHR, follicle stimulating hormone (FSH), fused to T-cell transmembrane and T-cell signaling domains. Human T-cells transduced to express anti-FSHR immune receptors were specifically immunoreactive against FSHR-expressing human and mouse ovarian cancer cell lines in a MHC-non-restricted manner, and produced more than one Th1 type of proinflammatory cytokine. This observation is of special interest, as it provides the opportunity to address potential, but unpredicted, toxicity issues associated with targeting of FSHR in preclinical in vivo studies. Moreover, anti-FSHR-IR T-cells specifically upregulated surface expression of the activation marker CD69 in the presence of FSHR positive targets, but not FSHR-deficient the 293T cell line. Additionally, specific activation of anti-FSHR-IR T-cells by FSHR expressed on tumor cell surface led to efficient tumor cell killing in vitro. Furthermore, to assess the anti-tumor effect of anti-FSHR T-cells, we established human OvCa xenografts in NSG mice by subcutaneous flank injection of CaOV3 cancer cell line followed by two intravenous redirected T-cell administrations. As shown by caliper measurements, FSHR-redirected T-cells elicited anti-tumor potential with suppressed outgrowth of established tumor. Tumor growth was statistically reduced in comparison to control, GFP engineered T-cell treated group or PBS treated animals. These data suggest that systemic delivery of anti-FSHR T-cells to mice bearing FSHR-expressing tumors may result in tumor trafficking, activation, and lysis at location of tumor.In summary, we have successfully exploited for the first time a novel therapeutic antigen, the FSHR protein, expressed on tumor cell surface, to deliver T-cell based immune-therapy of cancer. Given its highly restricted expression in cancer, cancer-associated vessels and gonadal tissues, the rationale for FSHR targeting is strong and supports further exploration of FSHR-targeted immune therapy approaches for cancer patients.

Abstract POSTER-THER-1433: Overcoming resistance to antibody targeted therapy in ovarian cancer

Targeted therapies utilizing monoclonal antibodies (mAbs) are now the major class of successful therapeutics for treating a variety of malignancies. Mechanistically, mAbs can have direct antitumoral activity but often their effectiveness relies upon antibody-dependent cellular cytotoxicity (ADCC). For instance, Trastuzumab is a therapeutic monoclonal antibody directed against HER2 that is well-tolerated and useful in the treatment of HER2-positive breast cancer, where efficacy is mediated in part by ADCC. In contrast, Trastuzumab is relatively ineffective in the treatment of epithelial ovarian cancer (EOC) where virtually all cancer cells express detectable levels of HER2. Poor response to mAb therapy in EOC and other types of cancers may be explained in part by diminished numbers and cytotoxic potential of NK cells in cancer patients, compared to healthy individuals. Therefore, reports of poor antitumor effect of Ab-therapy in cancer led us to hypothesize that the development of potent effector cells with the capacity to bind tumor-bound mAb and mediate strong antibody-directed cellular cytotoxicity would markedly improve the efficacy of mAb-targeted therapy for EOC. In order to expand applications for T cell-based immunotherapy and to enhance ADCC, we developed novel effector T cells engineered to express Fc binding immune receptors (FcIR) containing human Fc receptor of low FcγRIIIA (CD16), intermediate FcγRIIA (CD32) or high affinity FcγRI (CD64) molecules fused to intracellular TCR and co-stimulatory signaling domains in order to enable cytotoxic T cells to mediate strong mAb-directed cytotoxicity against antigen-expressing tumor cells. Following FcIR gene transduction, all forms of FcγRs were efficiently expressed on the surface of primary human T cells which allowed these cells to be armed with mAb. Trastuzumab-armed FcIR T cells specifically recognized HER2+ cancer cells, as did unarmed FcIRs but only when the cancer cells were first pre-bound with Trastuzumab. Addition of a CD28 cytoplasmic domain juxtaposed to the TCR CD3z signaling moiety increased IFN-g secretion by FcIR-28z transduced T cells following encounter with antigen-bound mAb on the cancer cell surface. Notably, T cells expressing a high affinity FcIRI (CD64) demonstrated the greatest specific anti-tumor reactivity in comparison to cells expressing FcγRIIA (CD32) or FcγRIIIA (CD16) FcIRs. In addition, FcIRI (CD64) T cells exhibited stronger specific lytic activity than NK cells, even at low antibody concentrations. Further, co-administration of FcIRI (CD64) FcIR-28z T cells with immunotherapeutic mAb, Trastuzumab, exerted strong antitumor activity in vivo, completely eliminating HER2+ tumor. In summary, our results show that ADCC can be enhanced by human T cells engineered to express an FcIR and that this novel approach may overcome issues of resistance to mAb-targeted therapies including those utilizing Trastuzumab. Citation Format: Katarzyna Urbanska, Mathilde Poussin, Caitlin Stashwick, Jenessa B. Smith, Daniel J. Powell Jr. Overcoming resistance to antibody targeted therapy in ovarian cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-THER-1433.