I-Mab announced multiple recent developments in TJ-L14B/ABL503, a differentiated PD-L1 x 4-1BB bispecific antibody developed in collaboration with ABL Bio. TJ-L14B/ABL503 is designed to address tumors resistant to PD-(L)1 antibodies through its unique ability to conditionally activate 4-1BB upon binding to its target, PD-L1. I-Mab owns 50% of the global rights of TJ-L14B/ABL503.

On September 7, 2023, TJ-L14B/ABL503 successfully obtained patent registration in eight Eurasian countries. The patent, officially named "Anti-PD-L1/Anti-4-1BB Bispecific Antibody and Its Applications," secures patent rights extending through 2039. Furthermore, this patent has already been granted in Chile, South Africa, and Japan.

Patent examinations are currently underway in over 20 countries, including the U.S., China, and Europe. TJ-L14B/ABL503 is currently being investigated in a Phase 1 dose-escalation study in patients with progressive, locally advanced or metastatic solid tumors who are relapsed or refractory following prior lines of treatment. The dose-expansion portion of the Phase 1 study is actively progressing in the U.S. and South Korea.

Currently, have observed 1 complete response, 1 partial response, and 2 patients who achieved an unconfirmed objective response upon recent enrollment. While preliminary efficacy signals have emerged, the maximum tolerated dose has not yet been reached. The Company anticipates presenting the top-line Phase 1 clinical data at a major medical conference in the first half of 2024.