Orum Therapeutics said it has voluntarily terminated the U.S. phase 1 clinical trial of its lead breast cancer candidate ORM-5029, sending its shares plummeting to the lower limit on the Kosdaq market. 

On Monday afternoon, Orum’s shares dropped by 7,650 won ($5.32), or 30 percent, marking a 52-week low.

ORM-5029, developed through Orum’s proprietary degraducer-antibody conjugate (DAC) platform, was pushed as a treatment for HER2-positive metastatic breast cancer and other HER2-overexpressing malignancies. Orum is recognized as the world’s first company to develop a DAC, a novel subclass of antibody-drug conjugates (ADCs) that links antibodies to targeted protein degraders (TPDs) instead of traditional cytotoxic payloads.

The company’s decision follows a serious adverse event (SAE) reported last November during the phase 1 trial in the U.S., where a patient died from liver failure. Following the incident, Orum had already suspended the enrollment of new patients.

SAE is defined as an event that results in death, is life-threatening, requires hospitalization or prolongs an existing hospital stay, causes significant disability, or leads to a congenital anomaly, among other serious outcomes.

Previously, Orum had indicated that a decision regarding the future of ORM-5029 would be made after discussions with the U.S. FDA later this year. However, the company has now officially announced the discontinuation of the program, citing a comprehensive evaluation of clinical safety, pharmacokinetic, and pharmacodynamic data.

“The decision reflects our commitment to prioritizing patient safety and developing therapeutics with a clear risk-benefit profile,” Orum Therapeutics said in a statement. “We will strategically reallocate resources to next-generation candidates based on its proprietary platform technology.

ORM-5029 was considered a core program for Orum, having secured FDA clearance to initiate a phase 1 trial in 2022.

With its discontinuation, the company will focus on advancing ORM-1023, a second-line treatment for small cell lung cancer, and ORM-1153, a candidate for blood cancer therapies.