Bio-Thera Solutions has initiated dosing in a Phase I clinical trial of BAT8013, an antibody drug conjugate (ADC) designed to target cluster of differentiation 25 (CD25), in patients with advanced solid tumours.

The dose-escalation, open-label, multicentre study aims to assess the tolerability and safety of BAT8013 and identify the recommended dose for Phase II trials.

CD25 is also known as interleukin-2 receptor alpha chain (IL-2Rα).

Encoded by the IL2RA gene, this transmembrane glycoprotein is mainly found on activated T and B cells, regulatory T cells (Tregs), as well as certain haematologic cancers.

It is overexpressed on Tregs in the solid tumour microenvironment.

Bio-Thera Solutions has developed BAT8013 using its anti-CD25 antibody and linker-payload system, which includes a systemically stable and cleavable linker bound to a small molecule topoisomerase I inhibitor.

The compant noted that Tregs elimination with BAT8013 could enhance the efficacy of other immune-oncology agents such as PD-1 and PD-L1 monoclonal antibodies.

Preclinical research demonstrated apparent stability, safety, and strong anti-tumour activity for BAT8013, particularly when combined with the company's PD-1 inhibitor, BAT1308.

The topoisomerase I inhibitor payload has been described as having the capacity to penetrate cell membranes, potentially leading to the elimination of surrounding Treg cells through a bystander effect.

Study objectives for the current Phase I trial include determining the maximum tolerated dose, evaluating pharmacokinetics, and gathering preliminary data on efficacy in advanced solid tumour patients.

Bio-Thera Solutions is also working on other ADCs targeting Folate Receptor alpha, Her2, and Trop2, alongside early-stage clinical assets targeting immuno-oncology pathways such as bispecific antibodies for PD-L1/4-1BB and PD1/IL15.

The company is advancing more than 20 candidates in clinical development, focusing on immuno-oncology and targeted therapies, including ADCs.