Efficient tumor killing and minimal cytokine release with novel T-cell agonist bispecific antibodies

Abstract

T-cell-recruiting bispecific antibodies (T-BsAbs) have shown potent tumor killing activity in humans, but cytokine release-related toxicities have affected their clinical utility. The use of novel anti-CD3 binding domains with more favorable properties could aid in the creation of T-BsAbs with improved therapeutic windows. Using a sequence-based discovery platform, we identified new anti-CD3 antibodies from humanized rats that bind to multiple epitopes and elicit varying levels of T-cell activation. In T-BsAb format, 12 different anti-CD3 arms induce equivalent levels of tumor cell lysis by primary T-cells, but potency varies by a thousand-fold. Our lead CD3-targeting arm stimulates very low levels of cytokine release, but drives robust tumor antigen-specific killing in vitro and in a mouse xenograft model. This new CD3-targeting antibody underpins a next-generation T-BsAb platform in which potent cytotoxicity is uncoupled from high levels of cytokine release, which may lead to a wider therapeutic window in the clinic.

Antibody Structure and Function: The Basis for Engineering Therapeutics

“…BsAb architecture can vary the orientation of the binders, linkers, valency, functional activity, and developability [539]. The role of the anti-CD3-binding domains in BsAb with a broader range of T cell agonism has been shown to have a potential wider therapeutic index [541]. In addition, the choice of the BsAb subtype can affect T cell redirection activity [389].…”

Mechanistic Quantitative Pharmacology Strategies for the Early Clinical Development of Bispecific Antibodies in Oncology

“…Mechanisms for mitigating CRS in the clinic have been implemented, including a “priming” dose strategy (i.e., a lower initial dose followed by a higher maintenance dose), timely supportive care, corticosteroids administered prophylactically or upon onset of symptoms, and IL6/IL6R mAbs (e.g., tocilizumab) upon onset of CRS 66,67 . New generation CD3 bsAbs are being designed with reduced CD3 affinity, or with novel CD3 epitopes that limit cytokine release but maintain cytotoxic activity, or with different mAb formats to reduce potential for CRS 68 . However, predicting the incidence and severity of CRS from preclinical experiments remains a challenge and selection of dose priming regimens in the clinic is mostly based on an empirical trial and error approach.…”

Perspective: Designing T-Cell Engagers With Better Therapeutic Windows

“…Most importantly, these new CD3 antibodies are meant to be "fit-for-purpose, " designed and functionally screened specifically for optimal behavior in TCE bispecific antibodies. Toward this goal, we at Teneobio (Newark, CA) have discovered numerous novel human anti-CD3 binding domains through sequence-based discovery of fixed light chain transgenic rats (30).…”

“…Based on the previous work of Faroudi et al (9), our goal was to identify leads which preferentially trigger the cytolytic activity of T-cells and avoid the production and secretion of large quantities of pro-inflammatory cytokines. Characteristic of one of the CDR families (F2) was that its members uniquely bound a conformational epitope that recognizes the CD3δε heterodimer preferentially over CD3γε and over a wide range of affinities from low to high nanomolar (30). Importantly, in the context of human IgG heterodimeric bispecific antibodies, F2 family members retained full efficacy against cancer target cells while demonstrating low levels of cytokine release (30).…”

“…Characteristic of one of the CDR families (F2) was that its members uniquely bound a conformational epitope that recognizes the CD3δε heterodimer preferentially over CD3γε and over a wide range of affinities from low to high nanomolar (30). Importantly, in the context of human IgG heterodimeric bispecific antibodies, F2 family members retained full efficacy against cancer target cells while demonstrating low levels of cytokine release (30). Consistent with our results, recent studies by Zuch de Zafra et al (31) and Li et al (32) also demonstrated that T-cell mediated cytotoxicity can be decoupled from cytokine release when using TCEs.…”