Bio-Thera Solutions, Ltd. (SH: 688177), a commercial-stage pharmaceutical company, announced that dosing has begun in a Phase 1 clinical study evaluating BAT8013, an antibody drug conjugate (ADC) that targets CD25.  The clinical trial is a multicenter, open-label Phase 1 clinical study in patients with advanced solid tumors to evaluate the safety and tolerability of BAT8013 and to determine the recommended Phase 2 dose.

CD25, also known as interleukin-2 receptor alpha chain (IL-2Rα), is a 55 kDa transmembrane glycoprotein encoded by the IL2RA gene, predominantly expressed on activated T and B cells, regulatory T cells (Tregs), and various hematologic malignancies. BAT8013 was developed using Bio-Thera's anti-CD25 antibody and Bio-Thera's proprietary ADC linker-payload combination that includes a systemically stable and cleavable linker and a small molecule topoisomerase I inhibitor. CD25 is differentially overexpressed on Tregs in the solid tumor microenvironment.  Eliminating Tregs using BAT8013 is expected to potentiate the efficacy of other immune-oncology agents like PD-1 and PD-L1 mAbs.

A series of preclinical studies have shown that BAT8013 has good stability and safety and has high anti-tumor activity in combination with Bio-Thera's PD-1 inhibitor, BAT1308. The small molecule topoisomerase I inhibitor payload carried by BAT8013 has a strong cell membrane penetration ability, so when the target Treg cells are killed, the payload can be released and further kill nearby Treg cells, producing a bystander. BAT8013 has demonstrated high anti-tumor activity and good safety in both in vitro and in vivo pharmacological studies and is a potential "best-in-class" ADC that targets CD25, representing another important milestone in the company's research and development in the field of innovative oncology drugs.

The Phase 1, multi-center, open-label, dose-escalation clinical trial of BAT8013 is designed to assess the safety and tolerability of BAT8013. Key objectives of the study are to determine the maximum tolerated dose and recommended Phase 2 dose (RP2D), and to evaluate pharmacokinetics and preliminary efficacy in patients with advanced solid tumor.  In addition, Bio-Thera Solutions is developing several additional ADCs targeting Folate Receptor alpha, Trop2 and Her2 along with additional innovative oncology assets directed at important IO targets, including novel bispecific targeting PD-L1/4-1BB and PD1/IL15, all in early-stage clinical studies.