SHP2, a cytoplasmic protein-tyrosine phosphatase encoded by the PTPN11 gene, is involved in multiple cell signaling processes including Ras/MAPK and Hippo/YAP pathways. SHP2 has been shown to contribute to the progression of a number of cancer types including leukemia, gastric, and breast cancers. It also regulates T-cell activation by interacting with inhibitory immune checkpoint receptors such as the programmed cell death 1 (PD-1) and B- and T-lymphocyte attenuator (BTLA). Thus, SHP2 inhibitors have drawn great attention by both inhibiting tumor cell proliferation and activating T cell immune responses toward cancer cells. In this study, we report the identification of an allosteric SHP2 inhibitor 1-(4-(6-bromonaphthalen-2-yl)thiazol-2-yl)-4-methylpiperidin-4-amine (23) that locks SHP2 in a closed conformation by binding to the interface of the N-terminal SH2, C-terminal SH2, and phosphatase domains. Compound 23 suppresses MAPK signaling pathway and YAP transcriptional activity and shows antitumor activity in vivo. The results indicate that allosteric inhibition of SHP2 could be a feasible approach for cancer therapy.
Background MCL-1 is an important anti-death BCL-2 family protein and plays a key role in blocking apoptosis in cancer cells. MCL-1 gene is located in one of the most frequently amplified locus in various hematologic malignancies and solid tumors, including prostate, lung, pancreatic, breast, ovarian and cervical cancers, as well as melanoma, B-cell chronic lymphocytic leukemia (B-CLL), acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL)); moreover, MCL-1 overexpression is implicated as a resistance factor for multiple therapies including widely prescribed microtubule-targeted agents for breast cancers. Therefore, MCL-1 is an attractive therapeutic target for the treatment of cancers. In this study, we discovered the lead preclinical compound APG-3526, from its chemical synthesis optimization to potent antiproliferative and antitumor activity using multiple in vitro and in vivo xenograft models, respectively. Methods and Experiments APG-3526 was chemically synthesized by using one convergent multistep synthesis in gram scale. The binding affinity of APG-3526 was determined by a FP assay using a fluorescein labelled peptide (FAM-Bid) which binds to the MCL-1 protein leading to an increased anisotropy measured in milli-polarization (mP) values. The effect of APG-3526 on cell viability was determined using CCK-8 assay and its antitumor activities were tested in NCI-H929 and OPM-2 multiple myeloma (MM) xenograft SCID mice model (dosed i.v. at 50 mg/kg and p.o. at 25 mg/kg). Results Our biochemical study has demonstrated that APG-3526 binds to MCL-1 with a nanomolar affinity (IC50 = 7 nM). It is highly potent in inhibition of cell growth in MCL-1-dependent multiple myeloma cell lines (NCI-H929 cells: IC50 = 14 nM; OPM-2 cells: IC50 = 62 nM). Administration of APG-3526 (p.o. at 25 mg/kg, QDx14D, or i.v. at 50 mg/kg, once) achieved complete tumor regression in both NCI-929 and OPM-2 multiple myeloma xenograft models. The pharmacodynamics (PD) study using tumor samples further revealed caspase 3 activation and PARP cleavage triggered by APG-3526. MCL-1 complex MSD assay confirmed that APG-3526 disrupted MCL-1:BIM binding thus freeing BIM to initiate the apoptotic cascade. In conclusion, we have developed a novel and highly potent MCL-1 inhibitor, APG-3526, which displays clinically relevant pharmacokinetic properties and elicits potent antiproliferative and antitumor activities via disrupting MCL-1 complex and triggering caspase activation, especially in MCL-1 driven MM models. These results support APG-3526 as a promising MCL-1inhibitor for further clinical development. Citation Format: Jianyong Chen, Chengzhe Wu, Lingling Jiao, Leilei Zhao, Yunlong Zhou, Dongbo Li, Guozhi Tang, Shoulai Gu, Jing Deng, Guangfeng Wang, Douglas D. Fang, Shaomeng Wang, Dajun Yang, Yifan Zhai. Development of APG-3526 as a novel and highly efficacious MCL-1 inhibitor [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 73.
Follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) are among the most prevalent B-lymphocyte neoplasms with Bruton’s tyrosine kinase (BTK) often found abnormally activated in these patients. BTK inhibitor ibrutinib has showed proven efficacy in both indications, but its clinical application is limited to gradually acquired resistance. Recent studies reported that ibrutinib-resistant cells exhibited higher BCL-2 expression and therefore increase their sensitivity to BCL-2 inhibitors. In this study, using a BCL-2 selective inhibitor APG-2575, we asked whether its combination with ibrutinib enhanced antitumor activity in FL and DLBCL in preclinical studies. Indeed, the combination treatment with APG-2575 and ibrutinib synergistically enhanced antitumor activity in DOHH2 cell-derived FL xenograft models. Similarly, enhanced activity was achieved in DLBCL xenograft models derived from OCI-LY1 cells. Interestingly, in OCI-LY1 xenografts, the combination treatment achieved a 100 % response rate, which include partially (PR) and complete tumor regression (CR), with ~80 % of CR and ~20 % of PR recorded. Durable response was continuously observed till the end of the study after dose suspension. Pharmacokinetic studies revealed that there were no significant changes in drug concentrations between single agents and the combination treatment, suggesting there was no drug-drug interaction between these two agents. On-target pharmacodynamic (PD) modulations of BTK and apoptosis pathways were observed in corresponding tumor tissues co-treated with ibrutinib and APG-2575. An increase in the levels of cleaved PARP-1 protein was observed under the combination treatment suggesting enhanced induction of apoptosis occurred, which may be the biological event contributing to the synergistic effect of the combination treatment. In summary, our study suggests that APG-2575 may be applied to the combination therapy with ibrutinib in the treatment of FL and DLBCL. Citation Format: Douglas D. Fang, Guoqin Zhai, Shoulai Gu, Ran Tao, Qiuqiong Tang, Ping Min, Qixin Wang, Dongmei Yang, Jiaxing Gu, Yinfeng Li, Dingxiong Chen, Jiajun Li, Guangfeng Wang, Dajun Yang, Yifan Zhai. BCL-2 selective inhibitor APG-2575 synergizes with BTK inhibitor in preclinical xenograft models of follicular lymphoma and diffuse large B-cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2058.
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