Bryan D. Choi

EGFRvIII mCAR-modified T-cell therapy cures mice with established intracerebral glioma and generates host immunity against tumor-antigen loss

Purpose: Chimeric antigen receptor (CAR) transduced T cells represent a promising immune therapy that has been shown to successfully treat cancers in mice and humans. However, CARs targeting antigens expressed in both tumors and normal tissues have led to significant toxicity. Preclinical studies have been limited by the use of xenograft models that do not adequately recapitulate the immune system of a clinically relevant host. A constitutively activated mutant of the naturally occurring epidermal growth factor receptor (EGFRvIII) is antigenically identical in both human and mouse glioma, but is also completely absent from any normal tissues. Experimental Design: We developed a third-generation, EGFRvIII-specific murine CAR (mCAR), and performed tests to determine its efficacy in a fully immunocompetent mouse model of malignant glioma. Results: At elevated doses, infusion with EGFRvIII mCAR T cells led to cures in all mice with brain tumors. In addition, antitumor efficacy was found to be dependent on lymphodepletive host conditioning. Selective blockade with EGFRvIII soluble peptide significantly abrogated the activity of EGFRvIII mCAR T cells in vitro and in vivo, and may offer a novel strategy to enhance the safety profile for CAR-based therapy. Finally, mCAR-treated, cured mice were resistant to rechallenge with EGFRvIIINEG tumors, suggesting generation of host immunity against additional tumor antigens. Conclusion: All together, these data support that third-generation, EGFRvIII-specific mCARs are effective against gliomas in the brain and highlight the importance of syngeneic, immunocompetent models in the preclinical evaluation of tumor immunotherapies. Clin Cancer Res; 20(4); 972–84. ©2013 AACR.

EGFRvIII-targeted vaccination therapy of malignant glioma

Given the highly infiltrative growth pattern of malignant glioma and the lack of specificity associated with currently available treatment regimens, alternative strategies designed to eradicate cancer cells while limiting collateral toxicity in normal tissues remain a high priority. To this end, the development of specific immunotherapies against targeted neoplastic cells represents a promising approach.

Systemic administration of a bispecific antibody targeting EGFRvIII successfully treats intracerebral glioma

Bispecific antibodies (bscAbs), particularly those of the bispecific T-cell engager (BiTE) subclass, have been shown to effectively redirect T cells against cancer. Previous efforts to target antigens expressed in both tumors and normal tissues have produced significant toxicity, however. Moreover, like other large molecules, bscAbs may be restricted from entry into the “immunologically privileged” CNS. A tumor-specific mutation of the epidermal growth factor receptor, EGFRvIII, is a constitutively activated tyrosine kinase not found in normal tissues but frequently expressed in glioblastomas and many other neoplasms. Because it is localized solely to tumor tissue, EGFRvIII presents an ideal target for immunotherapy. Here we report the preclinical evaluation of an EGFRvIII-targeted BiTE, bscEGFRvIIIxCD3. Our results show that bscEGFRvIIIxCD3 activates T cells to mediate potent and antigen-specific lysis of EGFRvIII-expressing gliomas in vitro (P < 0.001) at exceedingly low concentrations (10 ng/mL) and effector-to-target ratios (2.5:1). Treatment with i.v. bscEGFRvIIIxCD3 yielded extended survival in mice with well-established intracerebral tumors (P < 0.05) and achieved durable complete cure at rates up to 75%. Antitumor efficacy was significantly abrogated on blockade of EGFRvIII binding, demonstrating the need for target antigen specificity both in vitro and in vivo. These results demonstrate that BiTEs can be used to elicit functional antitumor immunity in the CNS, and that peptide blockade of BiTE-mediated activity may greatly enhance the safety profile for antibody-redirected T-cell therapies. Finally, bscEGFRvIIIxCD3 represents a unique advancement in BiTE technology given its exquisite tumor specificity, which enables precise elimination of cancer without the risk of autoimmune toxicity.

Bispecific antibodies engage T cells for antitumor immunotherapy

Introduction: Although considerable evidence supports the hypothesis that T cells play a critical role in the immune response against cancer, the ability to mount and sustain tumor-specific cellular responses in vivo remains a challenge. A strategy that harnesses the cytotoxic advantage of T cell therapy is the use of bispecific antibodies designed to engage and activate endogenous polyclonal T cell populations via the CD3 complex, but only in the presence of a tumor antigen. While antibody constructs with dual specificity were first described as anticancer therapeutics over 25 years ago, it was not until recently that one subclass of bispecific single-chain antibody, the bispecific T cell engager (BiTE), emerged as superior to previous iterations in achieving efficacy in animal models and early clinical trials. Areas covered: The evolution of bispecific antibodies in antitumor immunotherapy is reviewed and the greatest hurdles impeding their clinical translation are discussed, specifically in the context of immunoprivileged sites as is the case for intracerebral malignancy. Expert opinion: The BiTE platform has great potential in the treatment of malignant disease. Despite burgeoning interest in bispecific antibodies and permutations thereof, the issues of stability and cost-effective production persist as obstacles.

Intracerebral delivery of a third generation EGFRvIII-specific chimeric antigen receptor is efficacious against human glioma

Chimeric antigen receptors (CAR)-transduced T cells hold great promise in the treatment of malignant disease. Here, we demonstrate that intracerebral injection with a human, epidermal growth factor receptor variant III (EGFRvIII)-specific, third generation CAR successfully treats glioma in mice. Importantly, these results endorse clinical translation of this CAR in patients with EGFRvIII-expressing brain tumors.

Myeloablative Temozolomide Enhances CD8+ T-Cell Responses to Vaccine and Is Required for Efficacy against Brain Tumors in Mice

Temozolomide (TMZ) is an alkylating agent shown to prolong survival in patients with high grade glioma and is routinely used to treat melanoma brain metastases. A prominent side effect of TMZ is induction of profound lymphopenia, which some suggest may be incompatible with immunotherapy. Conversely, it has been proposed that recovery from chemotherapy-induced lymphopenia may actually be exploited to potentiate T-cell responses. Here, we report the first demonstration of TMZ as an immune host-conditioning regimen in an experimental model of brain tumor and examine its impact on antitumor efficacy of a well-characterized peptide vaccine. Our results show that high-dose, myeloablative (MA) TMZ resulted in markedly reduced CD4+, CD8+ T-cell and CD4+Foxp3+ TReg counts. Adoptive transfer of naïve CD8+ T cells and vaccination in this setting led to an approximately 70-fold expansion of antigen-specific CD8+ T cells over controls. Ex vivo analysis of effector functions revealed significantly enhanced levels of pro-inflammatory cytokine secretion from mice receiving MA TMZ when compared to those treated with a lower lymphodepletive, non-myeloablative (NMA) dose. Importantly, MA TMZ, but not NMA TMZ was uniquely associated with an elevation of endogenous IL-2 serum levels, which we also show was required for optimal T-cell expansion. Accordingly, in a murine model of established intracerebral tumor, vaccination-induced immunity in the setting of MA TMZ–but not lymphodepletive, NMA TMZ–led to significantly prolonged survival. Overall, these results may be used to leverage the side-effects of a clinically-approved chemotherapy and should be considered in future study design of immune-based treatments for brain tumors.

Immunotherapy for malignant glioma

Malignant gliomas (MG) are the most common type of primary malignant brain tumor. Most patients diagnosed with glioblastoma (GBM), the most common and malignant glial tumor, die within 12–15 months. Moreover, conventional treatment, which includes surgery followed by radiation and chemotherapy, can be highly toxic by causing nonspecific damage to healthy brain and other tissues. The shortcomings of standard-of-care have thus created a stimulus for the development of novel therapies that can target central nervous system (CNS)-based tumors specifically and efficiently, while minimizing off-target collateral damage to normal brain. Immunotherapy represents an investigational avenue with the promise of meeting this need, already having demonstrated its potential against B-cell malignancy and solid tumors in clinical trials. T-cell engineering with tumor-specific chimeric antigen receptors (CARs) is one proven approach that aims to redirect autologous patient T-cells to sites of tumor. This platform has evolved dramatically over the past two decades to include an improved construct design, and these modern CARs have only recently been translated into the clinic for brain tumors. We review here emerging immunotherapeutic platforms for the treatment of MG, focusing on the development and application of a CAR-based strategy against GBM.

Factors influencing fellowship selection, career trajectory, and academic productivity among plastic surgeons.

Background: Several factors influence the career trajectory of graduating plastic surgeons, and the authors’ study sought to capture characteristics of plastic surgery trainees as they relate to outcomes, including fellowship selection, career choice, and academic productivity. Methods: Anonymous online survey data were obtained from members of the American Society of Plastic Surgeons. Correlative analysis was performed implementing the Pearson chi-square test, the Mann-Whitney test, and the Kendall tau-b correlation to determine significant correlations defined by values of p < 0.05. Results: Of 4543 survey invitations sent, a total of 624 plastic surgeons (13.7 percent) completed the study. Greater numbers of publications on entering residency (p < 0.05) and on graduating from residency (p < 0.0001), stronger perceived mentorship during residency (p < 0.01), graduating from an integrated program (p < 0.01), and fellowship training (p < 0.001) were all correlated with a future career in academia. In addition, fellowship training and number of publications during and before residency were correlated with eventual academic productivity (p < 0.05). Lastly, individual tendency to prioritize economics (p < 0.01) or geographic location (p < 0.05) was associated with eventual private practice, whereas prioritization of research (p < 0.01) and culture of training institute (p < 0.001) predicted academic careers. Conclusions: Graduating plastic surgery residents from integrated programs, with greater numbers of publications, stronger mentor relationships, and fellowship training were more likely to become academic surgeons. Among this academic cohort, fellowship training and greater numbers of publications before and during residency were significantly correlated with increased academic productivity as an attending surgeon.

Human regulatory T cells kill tumor cells through granzyme-dependent cytotoxicity upon retargeting with a bispecific antibody

Regulatory T cells play a central role in tumor escape from immune-mediated rejection. Using a bispecific antibody targeting the tumor-specific mutation of the EGF receptor, EGFRvIII, Choi and colleagues describe a new mechanism they identified by which regulatory T cells can be redirected to elicit potent antitumor activity. A major mechanism by which human regulatory T cells (Treg) have been shown to suppress and kill autologous immune cells is through the granzyme-perforin pathway. However, it is unknown whether Tregs also possess the capacity to kill tumor cells using similar mechanisms. Bispecific antibodies (bscAb) have emerged as a promising class of therapeutics that activate T cells against tumor antigens without the need for classical MHC-restricted T-cell receptor (TCR) recognition. Here, we show that a bscAb targeting the tumor-specific mutation of the EGF receptor, EGFRvIII, redirects human CD4+CD25+FoxP3+ Tregs to kill glioblastoma cells. This activity was significantly abrogated by inhibitors of the granzyme-perforin pathway. Notably, analyses of human primary glioblastoma also displayed diffused infiltration of granzyme-expressing FoxP3+ T cells. Together, these data suggest that despite their known suppressive functions, tumor-infiltrating Tregs possess potent cytotoxic mechanisms that can be co-opted for efficient tumor cell lysis. Cancer Immunol Res; 1(3); 163–7. ©2013 AACR.

Regulatory T cells are redirected to kill glioblastoma by an EGFRvIII-targeted bispecific antibody.

Regulatory T cells (Tregs) play a central role in in tumor escape from immunosurveillance. We report that a bispecific T-cell engager (BiTE) targeting a mutated form of the epidermal growth factor receptor, i.e., EGFRvIII, potently redirects Tregs to kill glioblastoma through the granzyme-perforin pathway.