Abstract 3766: Development of new FLT3/AXL dual inhibitor JRF104 with potent FLT3-TKD inhibition

Background: More than 30% of de novo AML patients were identified with FLT3 mutations. Two kinds of mutations, internal tandem duplication (ITD) and tyrosine kinase domain (TKD) mutations, account for 23% and 7% of all AML cases, respectively. FLT3 inhibitors, which have been recommended by both NCCN and ELN guidelines, are often used as single or combo agent to treat FLT3 m+ AML. However, primary and secondary acquired resistance to FLT3 inhibitors is a remarkable challenge. It has been revealed that AXL can activate FLT3, resulting in reduction of response to FLT3 inhibitors. Furthermore, TKD mutations can also lead to development of drug resistance. Therefore, FLT3/AXL dual inhibitor with potent FLT3-TKD inhibition may provide better efficacy as novel AML treatment option. Results: JRF104 is a potent FLT3/AXL dual inhibitor with a kinase inhibition IC50 value of 0.42 nM and 1.22 nM, respectively. In vitro studies suggested that JRF104 could potently inhibit the proliferation of MV4-11 and Molm-13 cells, which endogenously express FLT3-ITD mutation. JRF104 shows wide spectrum in vitro antiproliferation activity against all FLT3 mutation types, including the “gate-keeper” F691L mutation. JRF104 can effectively reduce MDA-MB-231 cell migration in vitro, accomplished by blocking tumor migration pathway regulated by AXL. In MV4-11 xenograft model, JRF104 inhibited tumor growth at the dose of 1 mg/kg, QD (TGI: 65%); significantly reduce tumor volume at 5 mg/kg, QD (TGI: 118%). In Molm-13 xenograft model, tumor volume was well controlled at 15 mg/kg, QD (TGI: 94%), and all tumor volume reduced to zero at 50 mg/kg, QD (TGI: 104%). In CT-26 syngeneic model, JRF104 enhanced anti-tumor growth effect when combined with anti-PD-1 antibody and suppressed pERK and pAKT in tumor tissues. Additionally, JRF104 demonstrated high oral bioavailability in mouse, rat, and dog. In 28 days pre-clinical toxicology studies, JRF104 was well tolerated in all tested rats. HNSTD and NOEAL were determined to be 20 mg/kg QD and 3 mg/kg QD, respectively. All results support that JRF104 with high efficacy and safety. Conclusion: JRF104 demonstrated consistently potent inhibition of FLT3 and strong antitumor efficacy against FLT3-driven tumors in preclinical studies. Based on these datas, JRF104 may overcome resistance caused by AXL and FLT3-TKD mutation, representing a novel promising clinical antitumor agent for treating AML patients with FLT3 mutations. Citation Format: yuquan wei, Xia