ABL Bio is pushing its bispecific antibody ABL103 into a new phase 1b/2 trial with MSD’s (Merck & Co. in the U.S. and Canada) Keytruda (pembrolizumab) and a taxane-based chemotherapy. 

The study, targeting advanced or metastatic solid tumors, will run in Korea, the U.S., and Australia, with up to 20 trial sites. ABL Bio submitted the trial plans to the FDA for review on Wednesday. 

ABL103, a B7-H4 and 4-1BB bispecific antibody, is designed to better stimulate T cells and limit tumor growth while improving toxicity. 

A monotherapy trial is already underway, but ABL Bio is expanding into a combination study to explore whether pairing the drug with Keytruda and chemotherapy enhances efficacy.

The trial will start with two safety lead-in parts: one to evaluate ABL103 with Keytruda alone and another to determine the recommended dose when adding taxane-based chemo. A dose-expansion phase will follow, focusing on specific tumor types. The company plans to enroll around 30 patients for the safety phase and another 40 for dose expansion.

ABL Bio CEO Lee Sang-hoon called the investigational new drug (IND) submission a key step in bringing ABL103 to more solid tumor patients and noted that its other 4-1BB bispecifics—ABL111 (givastomig), ABL503 (ragistomig), and ABL105—are progressing in trials. ABL111 is moving fastest, with top-line results from a phase 1b combo study expected this year.