T cell-engaging bispecific antibodies are a promising therapeutic approach for the treatment of multiple cancer types. Many formats are currently being tested in the clinic. Pfizer has developed several Fc-containing T cell-engaging bispecific antibody platforms, which increase the half-life and allow for conventional dosing. These platforms are currently being evaluated in the clinic. Here, we will compare these platforms, and the challenges and opportunities of each platform will be highlighted.

We present a new technology platform to fully automate both molecular design, as well as the integrated assessment of potency, efficacy, and developability profiling of large panels of bispecific candidates. We will present use cases showing how the platform allows for the systematic cloning, expression, purification, and characterization of complex multi-specific, CAR T and TCR modalities, with a focus on immuno-oncology applications.

Antibodies for immune checkpoint blockade have revolutionized cancer therapy but their use is oftentimes limited by toxicity, particularly when used in combination. The next generation of immunotherapies must address these toxicities to enable more potent combination therapies. Here, we describe a bispecific SNIPER™ antibody that selectively targets intratumoral regulatory T cells (Treg), diminishing the immunosuppressive tumor microenvironment without the toxicity associated with systemic Treg depletion. In vitro functional characterization of the engineered human SNIPERs™ identified a lead candidate that selectively binds Tregs localized in human tumors over those in systemic circulation. In vivo studies using a mouse surrogate SNIPER™ in CT26 tumor models revealed a dramatic reduction in Tregs in the tumors, with no change in the periphery. In an early CT26 model, a strong majority of mice receiving single agent therapy showed complete response and recovery. Combinations with immune stimulating agents against more advanced tumors led to similar efficacy.

Chimeric antigen receptors (CARs) are synthetic receptors for antigen that reprogram T cell specificity, function, and persistence. Despite remarkable complete response rates observed with patients suffering from B cell malignancies, relapses occur in a large fraction of patients, some of which are antigen-negative and others antigen-low. We explored multiple strategies of antigen dual targeting to improve CAR design with target-adapted co-stimulatory domains to prolong functional CAR T cell persistence and mitigate the risk of antigen escape.

Using computational modeling and protein engineering, we generated novel agents to redirect T cells to fight cancer. The designs provide for robust production of these novel agents. Impacts on epitope, affinity, and geometry will be discussed.

Our novel, automated high-throughput engineering platform enables fast generation of large panels of multi-specific variants (up to 10.000) giving rise to large data sets (more than 100.000 data points). We report on our visualization and data analysis workflows to improve understanding of our complex molecules and guide the engineering process.

T cell therapeutics have demonstrated clinical benefit in hematological malignancies and there is growing evidence of activity in solid tumors. This presentation will describe key findings from recent trials along with observations from nonclinical studies that inform on mechanism of action and approaches to address clinically observed challenges.

Using a unique sequence-based discovery approach along with proprietary transgenic rats, we have created a large collection of fully human anti-CD3 antibodies with diverse T cell agonist activities. Using machine learning tools, we were able to rapidly establish sequence-activity relationships and identify key residues in antibody sequences that had desired agonist behavior. The CD3 antibodies identified by our platform show diverse in vitro T cell activation profiles measured by CD69 upregulation, IL2, and IFNg production. We also generated human domain antibodies targeting a variety of tumor antigens that we combined with our unique CD3 antibodies to create bispecific molecules that mediate redirected T cell killing of tumor cells. In one particular example, we have created a panel of aCD3:aBCMA bispecific antibodies for the treatment of multiple myeloma that stimulate different levels of T cell activity. Using a multiple myeloma tumor cell line along with primary human PBMCs, we demonstrate a spectrum of in vitro tumor cell killing activity with varied levels of cytokine release using our bispecific molecules with diverse CD3 binding activities. Our lead program, TNB383B (BCMAxCD3) is currently in Phase I clinical studies. In summary, we have created a platform for tunable immune activation at the site of the tumor that works with a variety of tumor antigens.

CD3-engaging bispecifics mediate potent, redirected T cell killing in vitro and anti-tumor activity in vivo. However, their dosing is often limited by systemic cytokine release. While cytokine release effects can be mitigated through dosing strategies and anti-cytokine antibodies, an expansion of the therapeutic window of CD3-engaging bispecifics is desirable. Our studies suggest that modulating the affinity of CD3 engagement can reduce systemic cytokine secretion without compromising anti-tumor efficacy, and therefore might improve the activity and safety profile of next-generation CD3-engaging DART molecules.

Xencor has developed a robust platform for the creation of bispecific antibodies that recruit and activate immune cells to destroy tumors. This platform, importantly, includes the ability to explore different valencies and CD3 affinities to maximize selectivity and therapeutic index. Alternatively, checkpoint bispecific antibodies (e.g., PD1 x CTLA4) have been optimized to more safely target multiple checkpoint receptors, with potential to selectively activate endogenous tumor-reactive T cells. Finally, we have also applied our platform to create novel, reduced-potency IL15-Fc fusions with superior pharmacodynamic properties and improved therapeutic index.