Background CD39-Adenosine and transforming growth factor-β (TGFβ) are two key immune suppressive pathways within the tumor microenvironment (TME). Given that TGFβ effector cells (immune cells and stroma cells) and CD39 expressing cells are highly correlated in localized microenvironment of tumors, it is thus possible to design an inhibitory molecule to enrich inhibit TGFβ function in location where it matters by using CD39 targeting. We have since developed a bifunctional antibody-ligand trap called ES014 which comprises an antibody targeting CD39 fused to a TGFβ receptor II ectodomain, resulting in inhibition of TGFβ activity in the vicinity of CD39 expressing stroma cells and immune cells.

Methods Single cell RNAseq analysis was used to analyze CD39 and TGFβ expression across different tumor types and cell types. Immunohistochemistry method were performed to test CD39 expression pattern on primary tumor tissue of NSCLC and SCLC patients. The pharmacokinetics (PK), plasma TGFβ, CD39 target occupancy and safety profile were assessed in cynomolgus monkeys after intravenous administration of ES014. The immunological function of ES014 was studied using malignant pleural effusions (MPE) collected from lung cancer patients.

Results The single cell RNAseq and IHC result indicated that CD39 mainly expressed in intratumoral immune cells (macrophagesSCs, DCs, B cells, Tregs and exhausted T cells), cancer associated fibroblasts (CAFs) and endothelial cells, but not on tumor cells. CD39 and TGFβ are highly elevated in several tumors including SCLC, breast cancer and HNSCC, indicating these indications are ideal intervention candidates for ES014 bispecific antibody. By using malignant pleural effusions (MPE) lung cancer patients, it is found that ES014 treatment promotes M1 macrophage differentiation and promotes CD8+ T cells survival and tumor killing. In cynomolgus monkeys, TGFβ neutralization in the periphery and full CD39 target occupancy on peripheral blood CD11b+ granulocytes were observed after dosing, and the drug duration time increased along with doses. ES014 was well tolerated in cynomolgus monkeys, no severe adverse effects were observed up to 90 mg/kg.

Conclusions ES014 bispecific antibody is a first-in-class bi-specific antibody that demonstrated strong immune-promoting effect, resulting in killing of tumor cells. It inhibits both CD39-adenosine and TGFβ pathway within the TME. ES014 has a favorable preclinical PK and safety profile in monkey study. A phase 1 study is ongoing to investigate the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary clinical activity of ES014 in patients with advanced solid tumors.