BT7480, a novel fully synthetic Bicycle tumor-targeted immune cell agonist™ (Bicycle TICA™) induces tumor localized CD137 agonism

Abstract

BackgroundCD137 (4-1BB) is an immune costimulatory receptor with high therapeutic potential in cancer. We are creating tumor target-dependent CD137 agonists using a novel chemical approach based on fully synthetic constrained bicyclic peptide (Bicycle®) technology. Nectin-4 is overexpressed in multiple human cancers that may benefit from CD137 agonism. To this end, we have developed BT7480, a novel, first-in-class, Nectin-4/CD137 Bicycle tumor-targeted immune cell agonist™ (Bicycle TICA™).MethodsNectin-4 and CD137 co-expression analyses in primary human cancer samples was performed. Chemical conjugation of two CD137 Bicycles to a Nectin-4 Bicycle led to BT7480, which was then evaluated using a suite of in vitro and in vivo assays to characterize its pharmacology and mechanism of action.ResultsTranscriptional profiling revealed that Nectin-4 and CD137 were co-expressed in a variety of human cancers with high unmet need and spatial proteomic imaging found CD137-expressing immune cells were deeply penetrant within the tumor near Nectin-4-expressing cancer cells. BT7480 binds potently, specifically, and simultaneously to Nectin-4 and CD137. In co-cultures of human peripheral blood mononuclear cells and tumor cells, this co-ligation causes robust Nectin-4-dependent CD137 agonism that is more potent than an anti-CD137 antibody agonist. Treatment of immunocompetent mice bearing Nectin-4-expressing tumors with BT7480 elicited a profound reprogramming of the tumor immune microenvironment including an early and rapid myeloid cell activation that precedes T cell infiltration and upregulation of cytotoxicity-related genes. BT7480 induces complete tumor regressions and resistance to tumor re-challenge. Importantly, antitumor activity is not dependent on continuous high drug levels in the plasma since a once weekly dosing cycle provides maximum antitumor activity despite minimal drug remaining in the plasma after day 2. BT7480 appears well tolerated in both rats and non-human primates at doses far greater than those expected to be clinically relevant, including absence of the hepatic toxicity observed with non-targeted CD137 agonists.ConclusionBT7480 is a highly potent Nectin-4-dependent CD137 agonist that produces complete regressions and antitumor immunity with only intermittent drug exposure in syngeneic mouse tumor models and is well tolerated in preclinical safety species. This work supports the clinical investigation of BT7480 for the treatment of cancer in humans.

Discovery and Optimization of a Synthetic Class of Nectin-4-Targeted CD137 Agonists for Immuno-oncology

“…As the lead Bicycle TICA candidate, BCY11863 was more extensively profiled in vitro and in vivo. 24 In additional studies using the CT26 model described earlier, it was observed that the antitumor activity for BCY11863 could be achieved even when dosed Q3D. 24 This indicated that a positive pharmacologic effect with Bicycle TICAs can be achieved without sustained plasma concentrations, which is markedly different from the exposure approaches taken with the recombinant bispecific CD137 agonists currently under clinical development.…”

“… 24 In additional studies using the CT26 model described earlier, it was observed that the antitumor activity for BCY11863 could be achieved even when dosed Q3D. 24 This indicated that a positive pharmacologic effect with Bicycle TICAs can be achieved without sustained plasma concentrations, which is markedly different from the exposure approaches taken with the recombinant bispecific CD137 agonists currently under clinical development. The reasonably short-circulating half-life of BCY11863 in mice ( Figure 8 B, 2.3 h after IP injection) therefore permits a further exploration of the effect of intermittent plasma exposure on antitumor activity.…”

“…BCY11863 (1:2) was also evaluated in the CT26-Nectin-4/huCD137 mouse model and, at 5 mg/kg QD, significant antitumor activity was observed. 24 Based on these preliminary in vivo activity results, both compounds were further profiled to identify the lead candidate.…”

“…Pharmacokinetic data from follow-up studies of BCY11863 in NHPs are described elsewhere. 24 BCY11863 exhibited linear pharmacokinetics in doses ranging from 1 to 30 mg/kg in mouse, enabling the development of exposure-response models in the preclinical efficacy models ( Figure 9 B).…”

“…The pharmacology of BT7480 has recently been described and it is currently undergoing clinical trial (ClinicalTrials.gov Identifier: NCT05163041). 24 …”