CDK4/6 inhibitors in the treatment of hormone receptor-positive, HER2-negative advanced breast cancer

Endocrine therapy(ET)is the therapy backbone of hormone receptor(HR)-positive and human epidermal growth factor receptor 2(HER2)-negati ve advanced breast cancer.However,there are about 20%HR positive patients with no response to ET due to primary or acquired ET resistance.In this background,many agents have been studied to overcome ET resistance and of which the important agents are cyclin-dependent kinase 4/6(CDK4/6)inhibitors.The prognosis of advanced breast cancer has been improved by combing ET with CDK4/6 inhibitors.In this review,we mainly focused on the CDK4/6 inhibitors in the treatment of HR-positive,HER2-negative advanced breast cancer and discussed the action mechanisms of CDK4/6 inhibitors alone or combined with ET.We also summarized several molecular features that would predict response or resistance to CDK4/6 inhibitors.In addition,we put forward possible strategies to overcome CDK4/6 inhibitor resistance according to the latest research.

Insights into the Use of CDK 4/6 Inhibitors in Patients with HR-positive Advanced or Metastatic Breast Cancer

Hormone receptor(HR)-positive breast cancer(BC)is the most common subtype of BC and some patients with such tumors experience recurrences.Endocrine-based therapy(ET)(e.g.,tamoxifen,aromatase inhibitors(AIs),and fulvestrant)that has improved outcomes in such patients represents the initial therapy for women with HR-positive/human epidermal growth factor receptor 2(HER2)-negative BC(considering no evidence of visceral crisis).However,the resistance to ET can occur in almost 50%of HR-positive BCs.In order to improve outcomes of patients with HR-positive metastatic BC,new treatment strategies are required.One such therapy is the new class of medications,cyclin-dependent kinase(CDK)4/6 inhibitors,that have improved the outcomes in such patients(both endocrine-sensitive and endocrine-resistant).This article presents evidence from the main clinical trials,which led to the approval of palbociclib,ribociclib,and abemaciclib.These three CDK 4/6 inhibitors have shown a significant improvement of the progression-free survival(PFS)in patients with HR-positive/HER2-negative metastatic BC when used in combination with selected ETs.In addition,some important patient management considerations,when choosing a particular CDK 4/6 inhibitor for an individual patient are presented.Furthermore,a need to find biomarkers for CDK 4/6 inhibitor sensitivity,efficacy,and resistance,to be able to precisely select the best patientcandidates for this treatment is highlighted.

Progress of CDK4/6 inhibitors in the treatment of malignant tumors

CDK4/6 inhibitor acts on cell cycle.It can be used alone or in combination to treat lung cancer,liver cancer,pancreatic cancer and other cancers by restoring normal cell cycle,triggering anti-tumor immunity and changing the microenvironment of tumors.It has a certain therapeutic effect,and has a certain inhibitory effect on the proliferation and development of malignant tumors.The combination of other antineoplastic drugs can effectively reduce the emergence of drug resistance and synergistically enhance the clinical efficacy.This article reviews the related research results of CDK4/6 inhibitors,as well as the literature,and summarizes the mechanism and clinical application of CDK4/6 inhibitors.Cyclin dependent kinase(CDK)is a group of serine/threonine protein kinases.The chemical action of CDK on serine/threonine protein is the key to driving cell cycle.The typical biological feature of cancer is cell cycle disorder.As the engine of cell cycle,CDK and its regulators play an important role in tumorigenesis and development.In modern times,cancer has gained a deeper understanding at the level of biomolecule.For cell receptors,more and more drugs are used for key genes.The new generation of CDK4/6 inhibitors cut into the cell cycle to treat malignant tumors,prevent cells from G1 phase to S phase.They have good clinical efficacy for ER+breast cancer patients.They are also used in clinical trials of lung cancer,melanoma and other malignant tumors to treat malignant tumors.Therapy provides a new way.

Impact of Drug-Drug Interaction between CDK4/6 Inhibitors and Proton Pump Inhibitors on Survival Outcomes in the Treatment of Metastatic Breast Cancer—Real World Data from a Portuguese Center

Introduction: Proton pump inhibitors (PPi) are widely prescribed, including in patients undergoing treatment for advanced breast cancer (ABC). Due to the pharmacokinetic characteristics of the CDK4/6 inhibitor (Ci) palbociclib a drug interaction with PPi was hypothesized. It was shown in a retrospective study that this association was an independent predictive factor for worse progression-free survival (PFS). Objective: To verify the impact of concomitant administration of PPi with Ci on overall survival (OS) and PFS. Material and Methods: This is a retrospective cohort study of patients treated with Ci for HR+HER2-ABC in the period from Feb/2017 to Aug/2020. SPSS software was used for data processing. Univariate analysis was done by the Kaplan-Meier method and log-rank test, and multivariate analysis by COX regression. P-value < 0.05 was considered significant. Results: 80 patients were included. The median age at diagnosis of ABC was 56 years (25 - 75). Treatment with Ci was 1st line for ABC in 68.8%. Choice of Ci was palbociclib in 73.8% (n = 59) and ribociclib in 26.3% (n = 21). The hormone partner was a nonsteroidal aromatase inhibitor in 45.0%, and fulvestrant in 55.0% of cases. 37.5% of patients were on PPi, and 70.0% of them were during the entire treatment (23.3% omeprazole, 73.4% pantoprazole, 3.3% others). Patients taking concomitant PPi and Ci had lower OS (OS-3 years 42.6% vs. 63.4%, p = 0.254) and PFS (PFS med 15 m. vs. 21 m., p = 0.733), although with no statistically significant difference. Discussion: In the sample, there was a numerical difference, without the statistical significance in the use of PPi in the survival of patients under Ci. This difference could be more evident with a longer follow-up and a larger sample size. This study intends to alert to the growing importance of checking for drug interactions. Polymedication, advanced age and the presence of several comorbidities are real problems in patients with ABC. Conclusion: Real-world data from this center demonstrate a negative, non-statistically significant impact of PPi treatment on survival outcomes, in patients treated with Ci for HR+HER2-ABC.

A Systematic Review of Economic Evaluation of CDK4/6 Inhibitors in HR+/HER2-Advanced Breast Cancer

Objective To review the domestic and foreign economic studies on CDK4/6 inhibitors in first-line or second-line treatment of HR+/HER2-advanced breast cancer,and to analyze the main methodologies and research results.Methods Systematic literature review was used to search PubMed,EMBASE,Cochrane Library,CNKI,CBM,and Wanfang database.The incremental cost-effectiveness ratio was taken as the main outcome index,and all pharmacoeconomic evaluations with CDK4/6 inhibitors as intervention measures were included,such as Palbociclib,Ribociclib,and Abemaciclib.According to the Quality of Health Economic Studies Instrument,the quality of the included articles was evaluated,and then the included literature was analyzed.Results and Conclusion A total of 16 pharmacoeconomic evaluation studies were included,mainly from the perspective of national healthcare systems or third-party payers.Only 2 studies focused on second-line treatment,and the remaining treatment levels were first-line treatment.In terms of model structure,7 studies adopted the Markov model,6 studies adopted the PSM model,and 3 studies adopted the DES model.The basic analysis results showed that CDK4/6 inhibitor combined with endocrine regimen was not economical compared with endocrine alone regimen when the threshold was the conventional willingness to pay(WTP)value of each country.The uncertainty analysis included deterministic sensitivity analysis and probability sensitivity analysis.The included studies are all Cost-Utility Analysis with high-quality evaluation,which can provide evidence support for health-related decision-makers in decision-making.It can also provide methodological reference for the economic evaluation of other targeted drugs.

CDK4/6抑制剂所致药物不良反应文献分析及思考

目的分析CDK4/6抑制剂在临床应用中所致不良反应(ADR)的特点,为临床安全用药提供参考。方法检索维普、中国知网、万方、Web of Science、PubMed等数据库中关于CDK4/6抑制剂致ADRs的文献并进行分析。结果CDK4/6抑制剂致ADRs的个案报道共34例;患者平均年龄约63.5岁,ADRs多发生在用药4个月内(29例,85.29%);CDK4/6抑制剂致ADRs主要以皮肤及其附件损害(14例,41.18%)、呼吸系统损害(6例,17.65%)、肝胆系统损害(4例,11.76%)为主;经停药和/或对症治疗后达到症状好转或治愈的有31例;3例最终死亡。结论临床使用CDK4/6抑制剂时应加强用药监测,开展多学科患者管理,而CDK4/6抑制剂的ADR发生机制尚需进一步研究。

Overexpressed Cyclin D1 and CDK4 proteins are responsible for the resistance to CDK4/6 inhibitor in breast cancer that can be reversed by PI3K/mTOR inhibitors

CDK4/6 inhibitors are the standard treatment in advanced HR+/HER2-breast cancer patients.Nevertheless,the resistance to CDK4/6 inhibitors is inevitable and the strategies to overcome resistance are of great interest.Here,we show that the palbociclibresistant breast cancer cells expressed significantly higher levels of Cyclin D1 and CDK4 proteins because of upregulated protein synthesis.Silencing Cyclin D1 or CDK4 led to cell cycle arrest while silencing Cyclin E1 or CDK2 restored the sensitivity to palbociclib.Furthermore,PI3K/mTOR pathway was hyper-activated in palbociclib-resistant cells,leading to more phosphorylated 4E-BP1 and higher levels of Cyclin D1 and CDK4 translation.Targeting PI3K/mTOR pathway with a specific PI3Kαinhibitor(BYL719)or an mTOR inhibitor(everolimus)reduced the protein levels of Cyclin D1 and CDK4,and restored the sensitivity to palbociclib.The tumor samples expressed significantly higher levels of Cyclin D1,CDK4,p-AKT and p-4E-BP1 after progression on palbociclib treatment.In conclusion,our findings suggest that overexpressed Cyclin D1 and CDK4 proteins lead to the resistance to CDK4/6 inhibitor and PI3K/mTOR inhibitors are able to restore the sensitivity to CDK4/6 inhibitors,which provides the biomarker and rationale for the combinational use of CDK4/6 inhibitors and PI3K/mTOR inhibitors after CDK4/6 inhibitor resistance in breast cancer.

FSIP1 enhances the therapeutic sensitivity to CDK4/6 inhibitors in triple-negative breast cancer patients by activating the Nanog pathway

CDK4/6 inhibitors are routinely recommended agents for the treatment of advanced HR+HER2-breast cancer.However,their therapeutic effectiveness in triple-negative breast cancer(TNBC)remains controversial.Here,we observed that the expression level of fibrous sheath interacting protein 1(FSIP1)could predict the treatment response of TNBC to CDK4/6 inhibitors.High FSIP1 expression level was related to a poor prognosis in TNBC,which was associated with the ability of FSIP1 to promote tumor cell proliferation.FSIP1 downregulation led to slowed tumor growth and reduced lung metastasis in TNBC.FSIP1knockout caused cell cycle arrest at the G0/G1 phase and reduced treatment sensitivity to CDK4/6 inhibitors by inactivating the Nanog/CCND1/CDK4/6 pathway.FSIP1 could form a complex with Nanog,protecting it from ubiquitination and degradation,which may facilitate the rapid cell cycle transition from G0/G1 to S phase and exhibit enhanced sensitivity to CDK4/6 inhibitors.Our findings suggest that TNBC patients with high FSIP1 expression levels may be suitable candidates for CDK4/6 inhibitor treatment.

Palbociclib:周期蛋白依赖性激酶4/6抑制剂治疗乳腺癌

乳腺癌在我国发病率位居女性恶性肿瘤的第1位。针对雌激素受体(Estrogen receptor,ER)、孕激素受体(Progesterone receptor,PR)的内分泌治疗可延长激素受体(Hormone receptor,HR)阳性乳腺癌患者的生存,是乳腺癌治疗方案的重要组成部分。研究发现HR阳性的乳腺癌生长依赖细胞周期蛋白依赖性激酶(cyclin-dependent kinase,CDK),尤其是CDK4和CDK6,它们可以加快细胞从细胞周期的G1期进入S期的进程,导致细胞的增殖失控。Palbociclib(PD-0332991,lbrance)是一种口服CDK4/6小分子抑制剂。在体外实验和临床试验中,都显示出对于HR阳性乳腺癌生长的抑制,并且与内分泌治疗有协同作用。2015年2月美国FDA批准其联合来曲唑(Letrozole)用于HR阳性和HER2阴性的绝经后晚期(转移性)乳腺癌患者的一线治疗。也有临床试验支持其联合氟维司群应用。本文综述了Palboeiclib的作用机制,体外实验及临床试验。

Abemaciclib, a Recent Novel FDA-Approved Small Molecule Inhibiting Cyclin-Dependant Kinase 4/6 for the Treatment of Metastatic Breast Cancer: A Mini-Review

Abemaciclib (Verzerio®) is a cell cycle inhibitor of both CDK4 and CDK6. In 2017, abemaciclib was approved by the Food and Drug Administration (FDA) and, in 2018 by the European Medicines Agency (EMA) for the treatment of postmenopausal women with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2−) advanced breast cancer. In this mini-review, we provide a series of information for respectively their targets and its selectivity, results on preclinical trial, clinical phase I, II and III trials, and some perspectives. We also describe the batch and flow steps used for the synthesis of this cancer drug.

LA-D-B1,a novel Abemaciclib derivative,exerts anti-breast cancer effects through CDK4/6

Background:Regulatory proteins involved in human cellular division and proliferation,cyclin-dependent kinases 4 and 6(CDK4/6)are overexpressed in numerous cancers,including triple-negative breast cancer(TNBC).TNBC is a common pathological subtype of breast cancer that is prone to recurrence and metastasis,and has a single treatment method.As one of the CDK4/6 inhibitors,abemaciclib can effectively inhibit the growth of breast tumors.In this study,we synthesized LA-D-B1,a derivative of Abemaciclib,and investigated its anti-tumor effects in breast cancer.Methods:Cellular viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay.Cell cloning and migration abilities were determined by colony formation assay and wound healing assay.Cell invasion abilities and adhesion were determined by cell invasion assay and cell adhesion assay.The impact of compound LA-D-B1 on cell proliferation and the cell cycle was analyzed through Western blotting,which quantified the levels of proteins associated with the cyclin-dependent kinase(CDK)4/6-cyclin D-Rb-E2F pathway.The in vivo anti-tumor activity of compound LA-D-B1 was investigated using a chick chorioallantoic membrane(CAM)model.Results:The study demonstrated that LA-D-B1 effectively suppressed breast cancer cell proliferation,induced apoptosis,and caused cell cycle arrest.Furthermore,LA-D-B1 reduced the expression of key proteins in the CDK4/6-cyclin D-Rb-E2F pathway,including CDK4,CDK6 and E2F1.The results also indicated significant antitumor activity of LA-D-B1 in a transplanted tumor model.Conclusion:In this study,LA-D-B1 demonstrated a potent anti-tumor effect by effectively suppressing cell proliferation and inhibiting cell cycle progression in breast cancer.These findings highlight the potential of LA-D-B1 as a valuable compound for enhancing therapeutic outcomes and controlling the progression of breast cancer.

Liquid biopsies to predict CDK4/6 inhibitor efficacy and resistance in breast cancer

Cyclin-dependent kinase 4 and 6(CDK4/6)inhibitors combined with endocrine therapy have transformed the treatment of estrogen receptor-positive(ER+)and human epidermal growth factor receptor 2 negative(HER2-)metastatic breast cancer.However,some patients do not respond to this treatment,and patients inevitably develop resistance,such that novel biomarkers are needed to predict primary resistance,monitor treatment response for acquired resistance,and personalize treatment strategies.Circumventing the spatial and temporal limitations of tissue biopsy,newly developed liquid biopsy approaches have the potential to uncover biomarkers that can predict CDK4/6 inhibitor efficacy and resistance in breast cancer patients through a simple blood test.Studies on circulating tumor DNA(ctDNA)-based liquid biopsy biomarkers of CDK4/6 inhibitor resistance have focused primarily on genomic alterations and have failed thus far to identify clear and clinically validated predictive biomarkers,but emerging epigenetic ctDNA methodologies hold promise for further discovery.The present review outlines recent advances and future directions in ctDNA-based biomarkers of CDK4/6 inhibitor treatment response.

Acid-activatible micelleplex delivering siRNA-PD-L1 for improved cancer immunotherapy of CDK4/6 inhibition

Cyclin-dependent kinases 4 and 6 inhibitors(CDK4/6i)have been demonstrated to trigger antitumor immunity for tumor regression.However,the therapeutic performance of CDK4/6i-meadiated cancer immunotherapy was impaired by the immunosuppressive tumor microenvironment(ITM)due to overexpression of programmed death ligand 1(PD-L1)on the surface of cancer cell membrane.To improve the immunotherapeutic performance of CDK4/6i,we herein developed endosomal acidactivatable micelleplex for si RNA delivery and PD-L1 knockdown in the tumor cells in vitro and in vivo.We further demonstrated that the combination of PD-L1 knockdown and CDK4/6 inhibition facilitated intratumoral infiltration of cytotoxic T lymphocytes(CTLs),and elicited protective immune response and efficiently suppressed tumor growth in vivo.This study revealed the importance of molecular design of the micelleplex for highly efficient si RNA delivery,which might provide a novel insight for RNAi-based cancer immunotherapy.

Cell cycle regulation and anticancer drug discovery

Cellular growth,development,and differentiation are tightly controlled by a conserved biological mechanism:the cell cycle.This cycle is primarily regulated by cyclin-dependent kinase(CDK)-cyclin complexes,checkpoint kinases,and CDK inhibitors.Deregulation of the cell cycle is a hallmark of the transformation of normal cells into tumor cells.Given its importance in tumorigenesis,several cell cycle inhibitors have emerged as potential therapeutic drugs for the treatment of cancers-both as singleagent therapy and in combination with traditional cytotoxic or molecular targeting agents.In this review,we discuss the mechanisms underlying cell cycle regulation and present small-molecule anticancer drugs that are under development,including both pan-CDK inhibitors and CDK4/6-selective inhibitors.In addition,we provide an outline of some promising CDK inhibitors currently in preclinical and clinical trials that target cell cycle abnormalities in various cancers.

立博昔利布:细胞周期蛋白依赖性激酶4/6抑制剂类抗癌新药

立博昔利布是一种口服的小分子细胞周期蛋白依赖性激酶4/6抑制剂,通过抑制肿瘤细胞由G1期向S期转换达到抑制肿瘤发展的目的。立博昔利布和来曲唑联用已于2017年3月13日在美国获批,作为激素受体阳性/人表皮生长因子2受体阴性的晚期和转移性乳腺癌患者的治疗药物。临床研究表明该药对晚期和转移性肿瘤有明显的抑制作用;与来曲唑联用较单独使用来曲唑能显著延长患者的无恶化生存期。该药不良反应发生率较高,但是耐受性较好。介绍该药的药效学、药动学、临床观察和不良反应研究进展。

Effects of palbociclib on oral squamous cell carcinoma and the role of PIK3CA in conferring resistance

Objective: Lack of effective therapies remains a problem in the treatment of oral squamous cell carcinoma(OSCC), especially in patients with advanced tumors. OSCC development is driven by multiple aberrancies within the cell cycle pathway, including amplification of cyclin D1 and loss of p16. Hence, cell cycle inhibitors of the CDK4/6-cyclin D axis are appealing targets for OSCC treatment. Here, we determined the potency of palbociclib and identified genetic features that are associated with the response of palbociclib in OSCC.Methods: The effect of palbociclib was evaluated in a panel of well-characterized OSCC cell lines by cell proliferation assays and further confirmed by in vivo evaluation in xenograft models. PIK3CA-mutant isogenic cell lines were used to investigate the effect of PIK3CA mutation towards palbociclib response.Results: We demonstrated that 80% of OSCC cell lines are sensitive to palbociclib at sub-micromolar concentrations.Consistently, palbociclib was effective in controlling tumor growth in mice. We identified that palbociclib-resistant cells harbored mutations in PIK3CA. Using isogenic cell lines, we showed that PIK3CA mutant cells are less responsive to palbociclib as compared to wild-type cells with concurrent upregulation of CDK2 and cyclin E1 protein levels. We further demonstrated that the combination of a PI3 K/mTOR inhibitor(PF-04691502) and palbociclib completely controlled tumor growth in mice.Conclusions: This study demonstrated the potency of palbociclib in OSCC models and provides a rationale for the inclusion of PIK3CA testing in the clinical evaluation of CDK4/6 inhibitors and suggests combination approaches for further clinical studies.

转移性激素受体阳性乳腺癌内分泌治疗耐药及治疗决策进展

内分泌治疗已成为转移性激素受体(hormone receptor,HR)阳性乳腺癌的治疗基础。内分泌耐药的发生使得很多新型内分泌治疗药物或药物组合被研发出来。细胞周期蛋白依赖性激酶(cyclin-dependent protein kinase,CDK)4/6抑制剂的应用可显著延长内分泌耐药患者的无进展生存时间。有多项关于使用磷脂酰肌醇3激酶(phosphatidylinositol 3-kinase,PI3K)抑制剂和哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)抑制剂作为后续治疗方案的研究,特别是针对内分泌耐药的情况,应基于合并症、既往辅助治疗、患者的生活质量、不良反应及无病间隔期的情况,选择治疗方案的最佳顺序。对转移性乳腺癌的特定生物标志物检测以及新型基因检测对预测治疗效果、耐药性以及预后均具有重要意义,有助于进一步推动精准治疗的发展。

Targeted lapatinib anti-HER2/ErbB2 therapy resistance in breast cancer:opportunities to overcome a difficult problem

Approximately 20%of invasive breast cancers have upregulation/gene amplification of the oncogene human epidermal growth factor receptor-2(HER2/ErbB2).Of these,some also express steroid receptors(the so-called Luminal B subtype),whereas others do not(the HER2 subtype).HER2 abnormal breast cancers are associated with a worse prognosis,chemotherapy resistance,and sensitivity to selected anti-HER2 targeted therapeutics.Transcriptional data from over 3000 invasive breast cancers suggest that this approach is overly simplistic;rather,the upregulation of HER2 expression resulting from gene amplification is a driver event that causes major transcriptional changes involving numerous genes and pathways in breast cancer cells.Most notably,this includes a shift from estrogenic dependence to regulatory controls driven by other nuclear receptors,particularly the androgen receptor.We discuss members of the HER receptor tyrosine kinase family,heterodimer formation,and downstream signaling,with a focus on HER2 associated pathology in breast carcinogenesis.The development and application of anti-HER2 drugs,including selected clinical trials,are discussed.In light of the many excellent reviews in the clinical literature,our emphasis is on recently developed and successful strategies to overcome targeted therapy resistance.These include combining anti-HER2 agents with programmed cell death-1 ligand or cyclin-dependent kinase 4/6 inhibitors,targeting crosstalk between HER2 and other nuclear receptors,lipid/cholesterol synthesis to inhibit receptor tyrosine kinase activation,and metformin,a broadly inhibitory drug.We seek to facilitate a better understanding of new approaches to overcome anti-HER2 drug resistance and encourage exploration of two other therapeutic interventions that may be clinically useful for HER+invasive breast cancer patients.