CTLA-4 and CD28 exemplify a co-inhibitory and co-stimulatory signaling axis that dynamically sculpts the interaction of antigen-specific T cells with antigen-presenting cells. Anti-CTLA-4 antibodies enhance tumor-specific immunity through a variety of mechanisms including: blockade of CD80 or CD86 binding to CTLA-4, repressing regulatory T cell function and selective elimination of intratumoral regulatory T cells via an Fcγ receptor-dependent mechanism. AGEN1884 is a novel IgG1 antibody targeting CTLA-4. It potently enhanced antigen-specific T cell responsiveness that could be potentiated in combination with other immunomodulatory antibodies. AGEN1884 was well-tolerated in non-human primates and enhanced vaccine-mediated antigen-specific immunity. AGEN1884 combined effectively with PD-1 blockade to elicit a T cell proliferative response in the periphery. Interestingly, an IgG2 variant of AGEN1884 revealed distinct functional differences that may have implications for optimal dosing regimens in patients. Taken together, the pharmacological properties of AGEN1884 support its clinical investigation as a single therapeutic and combination agent.
5529 Background: The development and clinical application of immune checkpoint inhibitors has transformed the therapeutic landscape for cancer treatment in recent years. Balstilimab (AGEN2034) is a fully human, monoclonal IgG4 antibody that binds with high affinity to programmed death 1 (PD-1), thus preventing the interaction between this receptor and its ligands programmed death ligand 1 and 2 (PD-L1, PD-L2). Emerging evidence suggests that balstilimab exhibits a differentiated activity profile compared to currently approved anti-PD-1 agents, including pembrolizumab and nivolumab. Methods: Balstilimab as monotherapy was evaluated in a large phase 2 study in patients (pts) with recurrent/metastatic cervical cancer who had relapsed after a platinum-based treatment regimen for advanced disease. Pts were dosed at 3 mg/kg once every 2 weeks for up to 24 months and antitumor activity was assessed using RECIST v1.1. The tumor cell killing activity of balstilimab was evaluated preclinically in a human co-culture system of (1) primary T cells engineered to recognize NY-ESO-1 and (2) NY-ESO-1+ cancer cell lines, including PD-L1 and/or PD-L2-deficient engineered lines. The co-culture system was maintained for ̃ two weeks to drive partial T cell exhaustion; a state where cytotoxicity is compromised but recoverable with PD-1 blockade. Cytotoxicity of these partially exhausted T cells was quantified against PD-L1/L2 double positive, single positive, or double negative cancer cells in the presence or absence of PD-(L)1 antibodies. Results: In the second-line treatment setting for pts with advanced cervical cancer, balstilimab showed a numerically higher objective response rate (ORR) in subjects with PD-L1+, squamous cell carcinoma (SCC) tumors (21%, 95% CI, 12.7-32.6%) than those reported for pembrolizumab. Unlike pembrolizumab, balstilimab showed activity in PD-L1(-) pts, and irrespective of tumor histology (ORR 7.9%, 95% CI, 2.7-20.8%). Despite lower overall PD-L1 positivity compared to SCC (41.7 v 72.9%), an ORR of 12.5% (95% CI, 5.9-24.7%) was observed in the subset of pts with a poorer prognosis, those with cervical adenocarcinoma. Concordant with clinical observations, balstilimab demonstrated superior rescue of antigen-specific T cell cytotoxicity in vitro relative to pembrolizumab, nivolumab, or atezolizumab. Balstilimab also induced cytotoxicity against PD-L1 and/or PD-L2 deficient target cancer cells. Conclusions: Taken together, these data suggest functional differentiation of balstilimab from other PD-1 inhibitors with potentially important implications for extending the therapeutic reach of anti-PD-1 therapy. Investigation of the underlying mechanistic basis for these findings is ongoing. Clinical trial information: NCT03104699.
Immune checkpoint blockade (ICB) of cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death receptor 1 (PD-1) have shown durable responses in cancer patients. However, responses have been limited to a small subset of patients, and resistance to ICB therapy continues to be a limiting factor to achieving broad and more durable clinical benefit. Considering the emerging hallmarks of response to ICB, we investigated how response to anti-PD-1 and anti-CTLA-4 therapy could be improved through antibody engineering and combination with other therapeutic approaches such as with novel immune checkpoint inhibitors (e.g. TIGIT, LAG-3), adoptive T cell therapy (ACT), cancer vaccines or focal radiation. In preclinical studies, we demonstrated that anti-CTLA-4 antibodies engineered to selectively enhance binding to human FcyRIIIA or mouse FcyRIV, respectively, significantly improve T cell effector function and tumor clearance in preclinical models that are known to have high immunogenicity and responsiveness to ICB single therapy such as MC-38 and CT-26. To identify novel T cell-intrinsic resistance mechanisms to current ICB therapies, we emulated a progressive anti-PD-1 refractory state in primary CD4- and CD8-positive NY-ESO-1 TCR-transduced T cells upon repeat co-culture with an antigen-expressing glioblastoma cell line. In this model, the addition of anti-CTLA-4, anti-LAG-3, or anti-TIGIT enhanced T cell cytotoxicity and killing of tumor target cells. Gene expression signatures associated with the anti-PD-1 refractory state in this system predicted anti-PD-1 response in melanoma patients. Combination therapy with anti-PD-1 was further validated in a PD-1 refractory mouse syngeneic tumor models demonstrating improved tumor control. Finally, to further address resistance mechanisms to ICB therapy, we evaluated the combination potential of anti-PD-1 and Fc-engineered anti-CTLA-4 with tumor targeted therapies in syngeneic tumor models such as B16 melanoma which are resistant to co-blockade of PD-1 and CTLA-4. In these studies, anti-PD-1 and Fc-engineered anti-CTLA-4, promoted significantly improved tumor control when combined together or with CD4 or CD8 ACT, low dose focal radiation (10 Gy), or an antigen-specific heat shock protein-based (HSC70) cancer vaccine as compared to either therapy alone. Our preclinical data suggest that the limited activity of anti-PD-1 can be addressed by combining with a Fc engineered anti-CTLA4 antibody or with select novel ICB. Furthermore, we have demonstrated that PD1-CTLA4 activity could be further improved when combined with conventional focal radiation or other immune-modulating targeted therapies such as ACT or vaccines to significantly enhance tumor antigenicity and overcome resistance to conventional ICB. Citation Format: Antoine J. Tanne, Sylvia Vincent, Benjamin Duckless, Elena Paltrinieri, Simarjot Pabla, Andrew Basinski, Sudesh Pawaria, Vidur Patel, Margaret Wilkens, Bishnu Joshi, Matthew Hancock, Daniel Levey, Thomas Horn, Cailin Joyce, David Savitsky, Cori Gorman, Jennifer Buell, Dhan Chand. Expanding the therapeutic potential of anti-PD-1 and anti-CTLA-4 therapy with innovative Fc engineering and rationale combinations for the treatment of solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 922.
There is an urgent need to develop vaccines against bacteria due to the rise of Multi-drug resistant (MDR & XDR) organisms. To date, it has been difficult to produce protective vaccines against bacterial pathogens; there is a danger of outgrowth of fast growing attenuated bacterial strains while polysaccharide cell walls are poorly immunogenic and subunit vaccines are ineffective, generating TI (T-independent) immune responses, characterized by low affinity, short lived, non-class switched IgM antibodies. We are developing technologies for generating vaccines in mice against multiple pathogen species, including bacterial; MDR E. coli, MRSA, MTb LAM, Viral; HIV gp120, parasitic; P. falciparum and fungal; C. albicans. We capture pathogens using FcMBL Opsonin technology (which binds more than 90 different pathogen species), and present the killed pathogens in an immune modulating biomaterial system. This lyophilized product provides long-lasting protection with a single dose through a novel self-boosting mechanism of action. Our vaccines can protect mice against MDR strains of E. coli which are lethal within 12 hours. We have raised antibodies with titers which are sustained beyond 90 days (to date) with a single vaccination (the biomaterial system has demonstrated titers beyond 1 year in other indications). Using this opsonin and immune modulating technology, E. coli can be captured from the blood and tissues of one animal and used to vaccinate other animals.
BackgroundAnti-PD-1 therapies have achieved durable clinical responses in a wide range of malignancies, but responses are limited to a small subset of patients. Expression of PD-L1 on tumor cells by immunohistochemistry (IHC) has been applied as a companion diagnostic for anti-PD-1 therapy. However, recent studies have called in to question the reliability of this method to predict response.MethodsHere we developed a novel platform that integrates in vitro pharmacogenomic and functional data with clinical pharmacodynamic responses to immunotherapy using proprietary in silico approaches. The data originate from a long-term co-culture of primary antigen-specific T cells and cancer cells which drives T cells to a terminally dysfunctional, PD-1 refractory state. T cell effector functions and gene expression changes were monitored in the presence or absence of anti-PD-1 antibody or genetic knockouts. RNA expression signatures were refined with a randomized sliding window approach to generate a deep learning neural network for PD-1 response prediction.ResultsWe defined five T cell states associated with distinct phenotypic and molecular features - naïve, active, effector, transition and dysfunction. Among the genes that were selectively expressed in the dysfunction state, we identified a 96-gene signature that is closely associated with clinical outcomes to anti-PD-1 therapy. In PD-1 treated patients across multiple solid tumor indications, this signature correlates with objective response rate and outperforms traditional metrics such as tumor mutation burden or PD-L1 IHC signal. Moreover, this signature combines with tumor sequencing data to generate a powerful machine-learning model that predicts anti-PD-1 responses in metastatic melanoma patients with significantly higher accuracy than PD-L1 IHC. Having established that the T cell states in our co-culture relate to clinical outcomes, we leveraged the system to investigate the molecular basis for PD-1 responses. Single cell mapping of transition state T cells in the presence of anti-PD-1 revealed an expanded population of T cells that co-expresses PD-1, TIGIT and activation markers. Likewise, PD-L1 knockout on cancer cells identified the TIGIT ligand, CD155, as a potential tumor escape mechanism to anti-PD-1 therapy. Consistent with this, the combination of PD-1 and TIGIT blockade enhanced T cell cytotoxicity of tumor cells relative to monotherapies.ConclusionsAgenus’ T cell dysfunction platform combines deep in vitro profiling and AI-based approaches to predict clinical outcomes. Here, we defined a predictive biomarker signature that outperforms standard PD-L1 IHC. Further, we identified known (TIGIT) and potentially novel combination partners predicted to enhance the durability of anti-PD-1 responses.Ethics ApprovalNot ApplicableConsentNot Applicable
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