ABL Bio announced on the 9th via a regulatory filing that it has applied for an amendment to the Investigational New Drug (IND) application for its bispecific antibody immuno-oncology drug 'ABL503'. This filing is a correction to the previous submission dated the 4th, with the key change being the addition of the US Food and Drug Administration (FDA) as a clinical trial regulatory authority.

According to the company, ABL503, a bispecific antibody immuno-oncology drug targeting 4-1BB and PD-L1, is a Phase 1 clinical trial evaluating monotherapy and combination therapy in patients with progressive locally advanced (unresectable) or metastatic solid tumors. The updated regulatory authorities now include the Korean Ministry of Food and Drug Safety (MFDS) and the US FDA, with clinical trials expected to be conducted at approximately eight or more institutions across the United States and South Korea in the future.

Under the requested amendment, the existing monotherapy dose escalation and expansion parts will remain unchanged, but the target cancer types in the monotherapy tumor expansion part will be modified. Additionally, new combination therapy dose escalation and expansion parts have been added. The primary objectives of the clinical trial are to evaluate the safety and tolerability of ABL503, and to determine the Maximum Tolerated Dose (MTD) and the Recommended Phase 2 Dose (RP2D). In particular, the combination therapy portion will evaluate preliminary anti-tumor activity alongside safety and tolerability.

The target number of subjects consists of approximately 36 in the monotherapy dose escalation part, approximately 111 in the monotherapy tumor expansion part, about 20 in the combination therapy dose escalation part, and about 20 in the combination therapy dose expansion part. The monotherapy dose expansion part will involve approximately 6 to 20 participants per cohort.

ABL Bio stated that following the initial submission of the clinical trial plan to the Korean MFDS on June 4, 2026, it completed an additional submission to the US FDA on June 9, 2026. Once the amendment is approved, the company plans to immediately disclose the details through a regulatory filing.

Meanwhile, the company noted as an investment risk that the clinical trial and product approval process may yield unfavorable results, and that the statistical probability of successful final drug approval is only around 10%.