As a novel and promising antitumor target, AXL plays an important role in tumor growth, metastasis, immunosuppression and drug resistance of various malignancies, which has attracted extensive research interest in recent years. In this study, by employing the structure-based drug design and bioisosterism strategies, we designed and synthesized in total 54 novel AXL inhibitors featuring a fused-pyrazolone carboxamide scaffold, of which up to 20 compounds exhibited excellent AXL kinase and BaF3/TEL-AXL cell viability inhibitions. Notably, compound 59 showed a desirable AXL kinase inhibitory activity (IC₅₀: 3.5 nmol/L) as well as good kinase selectivity, and it effectively blocked the cellular AXL signaling. In turn, compound 59 could potently inhibit BaF3/TEL-AXL cell viability (IC₅₀: 1.5 nmol/L) and significantly suppress GAS6/AXL-mediated cancer cell invasion, migration and wound healing at the nanomolar level. More importantly, compound 59 oral administration showed good pharmacokinetic profile and in vivo antitumor efficiency, in which we observed significant AXL phosphorylation suppression, and its antitumor efficacy at 20 mg/kg (qd) was comparable to that of BGB324 at 50 mg/kg (bid), the most advanced AXL inhibitor. Taken together, this work provided a valuable lead compound as a potential AXL inhibitor for the further antitumor drug development.

AXL作为一种新型、有前景的抗肿瘤靶点，在多种恶性肿瘤的肿瘤生长、转移、免疫抑制和耐药性中发挥着重要作用，近年来引起了广泛的研究兴趣。在本研究中，我们采用基于结构的药物设计和生物电子等排策略，设计并合成了总共54种以融合吡唑啉酮甲酰胺支架为特征的新型AXL抑制剂，其中多达20种化合物表现出优异的AXL激酶和BaF3/TEL-AXL细胞活力抑制。值得注意的是，化合物59表现出理想的AXL激酶抑制活性（IC ₅₀ ：3.5 nmol/L）以及良好的激酶选择性，并且它有效阻断细胞AXL信号传导。反过来，化合物59可以有效抑制BaF3/TEL-AXL细胞活力（IC ₅₀ ：1.5 nmol/L），并在纳摩尔水平显着抑制GAS6/AXL介导的癌细胞侵袭、迁移和伤口愈合。更重要的是，化合物59口服给药表现出良好的药代动力学特征和体内抗肿瘤效率，其中我们观察到显着的AXL磷酸化抑制，其20 mg/kg（qd）的抗肿瘤功效与50 mg/kg的BGB324相当（ bid），最先进的AXL抑制剂。总而言之，这项工作为进一步的抗肿瘤药物开发提供了一种有价值的先导化合物作为潜在的 AXL 抑制剂。