[ABL Bio Submits Application for Phase 1 Clinical Trial Change Approval for ABL503]

ABL Bio announced on the 4th through a regulatory filing that it has applied to the Korean Ministry of Food and Drug Safety (MFDS) for a change approval for the Phase 1 clinical trial plan (IND) of its bispecific antibody immuno-oncology drug, 'ABL503'. Both the application date and the date of occurrence are June 4, 2026.

This application for change approval pertains to the monotherapy and combination therapy clinical trials of ABL503 in patients with progressive or metastatic solid tumors. ABL503 is a bispecific antibody that simultaneously targets 4-1BB and PD-L1, and the Phase 1 clinical trial is planned to be conducted at approximately 8 or more institutions in the United States and South Korea. However, the number of institutions and subjects may change during the course of the trial.

This change adds a 'combination therapy part' to the existing Phase 1 clinical plan, representing a modification to the existing IND rather than a new approval. Through this clinical trial, the company plans to evaluate the safety and tolerability of the monotherapy and determine the maximum tolerated dose (MTD) and the recommended Phase 2 dose (RP2D). In the tumor expansion part, preliminary anti-tumor activity will be confirmed, while in the newly added combination therapy part, the safety, tolerability, and preliminary anti-tumor activity during combination administration will be evaluated through dose escalation and expansion to derive the RP2D.

• The clinical trial will be conducted as a single-arm, open-label, multi-center study, with the target number of subjects as follows:
• Monotherapy dose escalation: Approximately 36 subjects
• Monotherapy dose expansion: Approximately 6 to 20 subjects per cohort
• Monotherapy tumor expansion: Approximately 111 subjects
• Combination therapy dose escalation: Approximately 20 subjects
• Combination therapy dose expansion: Approximately 20 subjects (including patients administered the recommended dose determined in the dose escalation part)

Regarding the reason for the change application, the company explained, "The monotherapy dose escalation and expansion parts are proceeding without changes, while the monotherapy tumor expansion part has modified the cancer types targeted in the existing clinical trial." It added that this change approval application was submitted to further proceed with the addition of the combination therapy escalation and expansion parts.

Meanwhile, the company informed investors as a precautionary note that the clinical trial and product approval processes may yield disappointing results, and the probability of a new drug reaching final approval is typically around 10%. Once the approval for the future clinical trial plan change is completed, the company plans to submit an additional regulatory filing.