AB002

Although tyrosine kinase inhibitor therapy and immunotherapy have significantly improved lung cancer management, many patients do not benefit or become resistant to treatment, highlighting the need for novel treatments. We found elevated CD73 expression to be prevalent in non–small cell lung cancer (NSCLC) including those harboring the RAS- or RTK (EGFR, EML4-ALK) oncogenes. CD73 expression is enriched closely with the transcriptome signature of epithelial–mesenchymal transition and the immune-tolerant tumor microenvironment, which are increasingly relevant for disease progression and therapy resistance. We developed two novel series of CD73 antibody, Ab001/Ab002 and humanized version Hu001/Hu002, which demonstrated high CD73 binding affinity, potent enzyme inhibition, and efficiently protected effector T lymphocyte function from adenosine/cancer-imposed toxicity. Hu001/Hu002 inhibited growth of RAS-mutant NSCLC tumors in mice via enhanced antibody-dependent cell-mediated cytotoxicity and multifaceted remodeling of the tumor immune environment, reflecting diminished levels of tumor-associated macrophages, myeloid-derived suppressor cells, and tumor vasculature. A novel MMAE-conjugated CD73-ADC (Hu001–MMAE) elicited potent cytotoxicity against CD73-high expressing tumor cells (IC50<0.1 nmol/L) and suppressed in vivo growth of multiple NSCLC and glioma tumors, including the RAS-mutant models [minimum effective dose <1 mg/kg]. Treatment with CD73–ADC triggered a robust intratumoral accumulation of proinflammatory macrophages and activated dendritic cells (DC), which were not observed with naked CD73 antibody or standard chemotherapy. Studies with human PBMC-derived systems confirmed CD73-ADC as fully functional in protecting effector T cells and stimulating DCs thus providing dual benefits in killing CD73-high tumors and improving cancer immunity response. These results warrant clinical investigation of CD73-targeted antibody and ADC for treating advanced lung cancer.

Although thrombin is a key enzyme in the coagulation cascade and is required for both normal hemostasis and pathologic thrombogenesis, it also participates in its own negative feedback via activation of protein C, which downregulates thrombin generation by enzymatically inactivating factors Va and VIIIa. Our group and others have previously shown that thrombin’s procoagulant and anticoagulant activities can be effectively disassociated to varying extents through site-directed mutagenesis. The thrombin mutant W215A/E217A (WE thrombin) has been one of the best characterized constructs with selective activity toward protein C. Although animal studies have demonstrated that WE thrombin acts as an anticoagulant through activated protein C (APC) generation, the observed limited systemic anticoagulation does not fully explain the antithrombotic potency of this or other thrombin mutants. AB002 (E-WE thrombin) is an investigational protein C activator thrombin analog in phase 2 clinical development (clinicaltrials.gov NCT03963895). Here, we demonstrate that this molecule is a potent enzyme that is able to rapidly interrupt arterial-type thrombus propagation at exceedingly low doses (<2 µg/kg, IV), yet without substantial systemic anticoagulation in baboons. We demonstrate that AB002 produces APC on platelet aggregates and competitively inhibits thrombin-activatable fibrinolysis inhibitor (carboxypeptidase B2) activation in vitro, which may contribute to the observed in vivo efficacy. We also describe its safety and activity in a phase 1 first-in-human clinical trial. Together, these results support further clinical evaluation of AB002 as a potentially safe and effective new approach for treating or preventing acute thrombotic and thromboembolic conditions. This trial was registered at www.clinicaltrials.gov as #NCT03453060.