ABL Bio Inc. announced the publication of pre-clinical data highlighting the safety and anti-tumor efficacy of ABL503/TJ-L14B in the Journal for ImmunoTherapy of Cancer(JITC). Jointly developed with I-Mab, ABL503 is a bispecific antibody combining PD-L1 checkpoint pathway with 4-1BB agonistic activity to overcome the current limitation of PD-(L)1 therapy and 4-1BB related toxicity. Using ABL's Grabody-T bispecific antibody platform technology, ABL503 induces 4-1BB activation only in the presence of PD-L1 expressing tumors to minimize the risk of 4-1BB related peripheral toxicity. ABL503 is currently being evaluated in a Phase 1 study in the U.S. in patients with locally advanced or metastatic solid tumors (NCT04762641). In the study, ABL503 induced complete tumor regression in humanized mice, which was superior to anti-PD-L1 or anti-4-1BB monotherapy. Moreover, no tumor growth was observed in these mice when they were rechallenged at 40 days after their first ABL503 treatment, demonstrating that ABL503 treatment yields a prolonged anti-tumor response despite a short-term administration schedule. In addition, ABL503 was well-tolerated following a repeated high dose administration of ABL503 in monkeys. Monkeys treated with ABL503 exhibited overall good tolerance with normal liver functions.