I-Mab and ABL Bio Inc. jointly announced that the first patient has been dosed in a phase 1 trial for bispecific antibody TJ-L14B/ABL503. The phase 1 clinical trial is an open-label, multi-center, dose-escalation and dose-expansion study to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), preliminary antitumor activity, maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) of TJ-L14B/ABL503 in locally advanced or metastatic solid tumors (NCT04762641). Being developed jointly with ABL, TJ-L14B/ABL503 is a differentiated PD-L1-based bispecific antibody with the PD-L1 arm as the tumor-dependent T-cell activator and the 4-1BB arm as the conditional T cell activator upon tumor engagement.

Using ABL's ‘Grabody-T' bispecific antibody platform technology, TJ-L14B/ABL503 stimulates 4-1BB activation only in the presence of PD-L1 expressing tumor cells to minimize the risk of off-tumor toxicity. Preclinical studies have demonstrated that the bispecific antibody shows better anti-tumor activity than equimolar doses of single agents alone or in combination.