A BIVALENT TIM-3/PD-1 BISPECIFIC ANTIBODY FOR THE TREATMENT OF PD-1 ANTIBODY RESISTANT OR REFRACTORY SOLID TUMORS

Abstract Background Immune checkpoint inhibitors (ICI) PD-1/PD-L1 antibody are key drugs for the treatment of cancer. Bispecific antibody is one of the strategies aimed to meet the clinical needs for cancer patients who are resistant to or refractory from ICI treatment. TIM-3, one of the next generation of ICI targets, co-expressed on exhausted T cells with PD-1. It is also expressed by innate immune populations, including NK and DC. Dual blocking PD-1 and TIM-3 not only on T cells but also on DC, NK cells may achieve better clinical benefit for patients who are resistant to or refractory from ICI treatment. Method A bivalent TIM-3 and PD-1 bispecific antibody (Bis5) was developed, a series of in vitro and in vivo efficacy, preclinical pharmacokinetic and toxicity studies were conducted. A Phase I, multicenter, open-label study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity and preliminary efficacy of Bis5 in patients with advanced and/or metastatic solid tumors is ongoing in China. Results Bis5 showed affinity of 5-8 nM to both TIM-3 and PD-1, with better cell activity than TIM-3 and PD-1 mAb combination to activated T cell as well as NK and DC, over the other clinical stage reference BsAb. In huPD-1/TIM-3 double knock in mice-CT26 tumor model, Bis5 showed significant tumor inhibition activity and doubled the survival rate, while neither PD-1 mAb, TIM-3 mAb nor PD-1 and TIM-3 antibody combination showed activity. The highest non-severe toxicity dose (HNSTD) was 200mg/kg in monkeys. Nine cohorts (0.001-15 mg/kg) are planned to be enrolled sequentially in the dose escalation part in the Phase I study, as of April 2023, seven cohorts enrollment have completed. No dose limiting toxicity was observed, and the optimal effective dose was not reached. No TRAE higher than grade 2 was observed. The TRAE with ≥10% Incidence was anemia. SD >4 or 2 months were shown in the suboptimal dose levels in NSCLC and CRC (0.3mg/kg, 1mg/kg). The Part 2 dose expansion will further characterize the safety profile and preliminary tumor response in several cohorts including NSCLC, CRC, ESCC etc. Conclusion Bis5 showed good preclinical efficacy and safety profile, its clinical performance is expected. Clinical trial information: NCT05357651.