Design, synthesis, and biological evaluation of novel pyrazolo [3,4-d]pyrimidine derivatives as potent PLK4 inhibitors for the treatment of TRIM37-amplified breast cancer

Discovery of RP-1664: A First-in-Class Orally Bioavailable, Selective PLK4 Inhibitor

PLK4 is a cell cycle-regulated kinase important for the biogenesis of centrioles and is known to be synthetically lethal with TRIM37 gene amplification. Previous attempts to inhibit PLK4 have been hampered by selectivity or ADME liabilities. The known inhibitor Centrinone B, while potent and selective, is metabolically unstable and lacks oral bioavailability. Assisted by structure-based drug design (SBDD), dramatic improvements in potency, selectivity and ADME properties were made to this structure, resulting in the identification of RP-1664, a potent inhibitor of PLK4 with an excellent pharmacokinetic profile in preclinical species. Kinome profiling demonstrated exquisite selectivity over related kinases, including AURKA/B and PLK1. RP-1664 disrupts centriole biogenesis in cancer cells, modulates pharmacodynamic readouts of PLK4 activity in xenograft tumor tissues, and is efficacious in multiple TRIM37-amplified xenograft models. This first-in-class clinical candidate is currently being evaluated in Phase 1 clinical trials (NCT06232408) for treatment of advanced solid tumors.

Pyrazolopyrimidines: A Promising Frontier in Cancer Treatment-Reviewing Their Potential as Inhibitors of Serine/Threonine Kinases

Pyrazolopyrimidine derivatives have emerged as potent inhibitors targeting a broad spectrum of kinases, particularly serine/threonine kinases (STK). This review provides a comprehensive overview of the structural modifications and pharmacological relevance of pyrazolopyrimidine compounds in the realm of kinase inhibition. Specifically, the focus is placed on their inhibitory action against STK, key players in cell signaling and potential therapeutic targets in various diseases, especially cancer. The structure-activity relationship (SAR) of these derivatives highlights the importance of specific substituents in enhancing inhibitory activity, and pyrazolopyrimidine derivatives have shown promising inhibitory activity against certain STK. Challenges remain, including issues related to drug resistance, off-target effects, and potential toxicity. Future research is geared toward designing more selective derivatives with improved pharmacokinetic properties and reduced side effects.

Polo-like kinase 4 accelerates glioma malignant progression and vasculogenic mimicry by phosphorylating EphA2

Vasculogenic mimicry (VM), which involved the formation of vascular-like structures by highly invasive tumor cells, had been identified as one of the mechanisms contributing to resistance against anti-angiogenic therapy in patients with glioblastoma (GBM). Therefore, inhibition of VM formation may serve as an effective therapeutic strategy against angiogenesis resistance. Polo-like kinase 4 (PLK4), a protein kinase, had been linked to the progression of glioblastoma and was associated with an unfavorable prognosis. The integration of proteomics and phosphoproteomics revealed that PLK4 directly activated the PI3K-Akt and MAPK signaling cascades by phosphorylating the Ser901 and Ser897 of EphA2. In addition, EphA2 Ser901 phosphorylating catalyzed by PLK4 significantly enhanced the phosphorylation of its own Ser897 site, which is a hallmark of EphA2 activation. The PI3K-Akt signaling was intricately associated with the progression of VM. Thus, PLK4 influenced malignant progression and VM formation via stimulation of the EphA2 signal transduction. Moreover, the expression level of PLK4 protein positively correlated with the level of EphA2 phosphorylation in glioma tissues. These results highlighted the crucial significance of PLK4 phosphorylating EphA2 in the malignant progression and VM formation in GBM.

Current scenario of pyrazole hybrids with anti-breast cancer therapeutic applications

Breast cancer stands as the leading cause of cancer-related deaths among women globally, but current therapy is restricted to the serious adverse effects and multidrug resistance, necessitating the exploration of novel, safe, and efficient anti-breast cancer chemotherapeutic agents. Pyrazoles exhibit excellent potential for utilization as effective anti-breast cancer agents due to their ability to act on various biological targets. Particularly, pyrazole hybrids demonstrated the advantage of targeting multiple pathways, and some of them, which are exemplified by larotrectinib (pyrazolo[1,5-a]pyrimidine hybrid), can be applied for breast cancer therapy. Thus, pyrazole hybrids hold great promise as useful therapeutic interventions for breast cancer. The aim of this review is to summarize the current scenario of pyrazole hybrids with in vitro and/or in vivo anti-breast cancer potential, along with the modes of action and structure-activity relationships, covering articles published from 2020 to the present, to streamline the development of rational, effective and safe anti-breast cancer candidates.

Progress with polo-like kinase (PLK) inhibitors: a patent review (2018-present)

INTRODUCTION

Polo-like kinases (PLKs) have five isoforms, all of which play crucial roles in cell cycle and cell proliferation, offering opportunities for drug design and treatment of cancers and other related diseases. Notably, PLK1 and PLK4 have been extensively investigated as cancer drug targets. One distinctive feature of PLKs is the presence of a unique polo-box domain (PBD), which regulates kinase activity and subcellular localization. This provides possibilities for specifically targeting PLKs.

AREA COVERED

This article provides an overview of the roles of PLKs in various cancers and related diseases, as well as the drug development involving PLKs, with a particular focus on PLK1 and PLK4. It summarizes the PLK1 and PLK4 inhibitors that have been disclosed in patents or literature (from 2018 - present), which were sourced from SciFinder and WIPO database.

EXPERT OPINION

After two decades of drug development on PLKs, several drugs progressed into clinical trials for the treatment of many cancers; however, none of them has been approved yet. Further elucidating the mechanisms of PLKs and identifying and developing highly selective ATP-competitive inhibitors, highly potent drug-like PBD inhibitors, degraders, etc. may provide new opportunities for cancer therapy and the treatment for several nononcologic diseases. PLKs inhibition-based combination therapies can be another helpful strategy.

Therapeutic potential of targeting polo-like kinase 4

Polo-like kinase 4 (PLK4), a highly conserved serine/threonine kinase, masterfully regulates centriole duplication in a spatiotemporal manner to ensure the fidelity of centrosome duplication and proper mitosis. Abnormal expression of PLK4 contributes to genomic instability and associates with a poor prognosis in cancer. Inhibition of PLK4 is demonstrated to exhibit significant efficacy against various types of human cancers, further highlighting its potential as a promising therapeutic target for cancer treatment. As such, numerous small-molecule inhibitors with distinct chemical scaffolds targeting PLK4 have been extensively investigated for the treatment of different human cancers, with several undergoing clinical evaluation (e.g., CFI-400945). Here, we review the structure, distribution, and biological functions of PLK4, encapsulate its intricate regulatory mechanisms of expression, and highlighting its multifaceted roles in cancer development and metastasis. Moreover, the recent advancements of PLK4 inhibitors in patent or literature are summarized, and their therapeutic potential as monotherapies or combination therapies with other anticancer agents are also discussed.

Design, synthesis, and biological evaluation of a potent PLK4 inhibitor WY29 with 1H-pyrazolo[3,4-d]pyrimidine scaffold

Centriole duplication occurs once per cell cycle and is regulated by Polo-like kinase 4 (PLK4). Overexpression of PLK4 in somatic cells can lead to the excessive formation of centrioles, directly causing chromosome segregation errors and tumorigenesis. In this study, we described our efforts to develop a series of PLK4 inhibitors with 1H-pyrazolo[3,4-d]pyrimidine core, and further structure- and receptor-based design and optimization resulted in a potent inhibitor WY29 (IC₅₀  = 0.027 μM), which exhibited good selectivity to other PLK family members (PLK1-3). At the cellular level, compound WY29 showed excellent antiproliferative activity against three breast cancer cell lines (MCF-7, BT474, and MDA-MB-231) while weak inhibitory activity was found on normal cell line HUVECs. In addition, the in vitro preliminary drug-like properties evaluation of compound WY29 showed outstanding stability in human plasma and liver microsomes, and weak inhibitory activity against the major subtypes of human cytochrome P450. Also, the drug-like properties prediction of compound WY29 displayed remarkable drug-like properties (drug-likeness mode score: 1.06). In conclusion, these results support the further development of compound WY29 as a lead compound for PLK4-targeted anticancer drug discovery.

Discovery of CZS-241: A Potent, Selective, and Orally Available Polo-Like Kinase 4 Inhibitor for the Treatment of Chronic Myeloid Leukemia

Recent studies demonstrate that PLK4 has emerged as a therapeutic target for the treatment of multiple cancers owing to its indispensable role in cell division. Herein, starting from previously identified effective compound CZS-034, based on rational drug design strategies, tyrosine kinase receptor A (TRKA) selectivity- and metabolic stability-guided structure-activity relationship (SAR) exploration were carried out to discover a highly potent (IC₅₀ = 2.6 nM) and selective (SF = 1054.4 over TRKA) PLK4 inhibitor B43 (CZS-241) with acceptable human liver microsome stability (t_1/2 = 31.5 min). Moreover, compound B43 effectively inhibited leukemia cells in 29 tested cell lines, especially chronic myeloid leukemia (CML) cell lines K562 and KU-812. Pharmacokinetic characteristics revealed that compound B43 possessed over 4 h of half-life and 70.8% bioavailability in mice. In the K562 cells xenograft mouse model, a 20 mg/kg/day dosage treatment obviously suppressed tumor progression. As a potential and novel PLK4-targeted candidate drug for CML, compound B43 is undergoing extensive preclinical safety evaluation.