e16240 Background: PD-1/PD-L1-targeted immunotherapies have become critical roles in the treatment for many tumors. However, there is limited progress in gastrointestinal cancers, especially in pancreatic ductal adenocarcinoma (PDAC). PDAC is low immunogenicity. PDAC microenvironment is immunosuppressive. More than 70% PDACs have few or no CD8+ T cells around the tumor cell or in the tumor microenvironment. Therefore, immunotherapy like PD-1/PD-L1 antibody alone is rarely effective for PDACs. Methods: Some cytokine or analogs may activate CD8+ T cells. An analog specifically activating tumor antigen associated (TAA) CD8+ T cells was fused to anti-CLDN18.2 antibody. Results: The specific bi-functional molecule (Bis2) has high affinity to human anti-CLDN18.2 (14pM) and CD8+T cells. Bis2 shows significant in vivo efficacy at 0.1 mpk. The efficacy lasts for more than 24 days, only given two doses at day 1 and day 3, respectively. IHC shows that the tumor infiltrated CD8+T cells significantly increased and IFNγ secretion enhanced as well. The IHC results are consistent with the mechanism that Bis2 induces TAA CD8+ T cell proliferation and prevents CD8+T cells from IFNγ-mediated apoptosis. Moreover, Bis2 also shows 100% tumor inhibition in combination with either chem (L-OHP+5FU) or PD-1 antibody in vivo which is better than chem in combination with PD-1 antibody. Bis2 also shows 60% tumor inhibition at 1mpk in CLDN18.2 negative cell based in vivo model. Bis2 shows ADA in monkeys in two weeks by dosing weekly. The repeated doses toxicity study shows an increase of MONO and %MONO and decrease in RBC, HGB, HCT, and MCHC. The HNSTD was 3mpk. The T1/2 was 40h. Conclusions: The Phase I study in advanced solid tumors is ongoing. The study uses accelerated titration starting from 0.01mpk combined with a BOIN design, maximum patient size of 36. In the expansion part, two cohorts of 10 CLDN18.2+ pancreatic cancer patients are planned for the treatment of Bis2 alone or Bis2 in combination with chemotherapy, respectively.

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.

Metastasis of tumors requires angiogenesis, which is comprised of multiple biological processes that are regulated by angiogenic factors. The fibroblast growth factor (FGF) is a potent angiogenic factor and aberrant FGF signaling is a common property of tumors. Yet, how the aberration in cancer cells contributes to angiogenesis in the tumor is not well understood. Most studies of its angiogenic signaling mechanisms have been in endothelial cells. FGF receptor substrate 2α (FRS2α) is an FGF receptor-associated protein required for activation of downstream signaling molecules that include those in the mitogen-activated protein and AKT kinase pathways. Herein, we demonstrated that overactivation and hyperactivity of FRS2α, as well as overexpression of cJUN and HIF1α, were positively correlated with vessel density and progression of human prostate cancer (PCa) toward malignancy. We also demonstrate that FGF upregulated the production of vascular endothelial growth factor A mainly by increasing expression of cJUN and HIF1α. This then promoted recruitment of endothelial cells and vessel formation for the tumor. Tumor angiogenesis in mouse PCa tissues was compromised by tissue-specific ablation of Frs2α in prostate epithelial cells. Depletion of Frs2α expression in human PCa cells and in a preclinical xenograft model, MDA PCa 118b, also significantly suppressed tumor angiogenesis accompanied with decreased tumor growth in the bone. The results underscore the angiogenic role of FRS2α-mediated signaling in tumor epithelial cells in angiogenesis. They provide a rationale for treating PCa with inhibitors of FGF signaling. They also demonstrate the potential of overexpressed FRS2α as a biomarker for PCa diagnosis, prognosis and response to therapies.