[Efficacy analysis of chemotherapy and endocrine therapy combined with targeted drugs after progression on cyclin-dependent kinase 4/6 inhibitor treatment in hormone receptor positive/human epidermal growth factor receptor 2-low metastatic breast cancer].

Objective: To evaluate the efficacy of chemotherapy and endocrine therapy combined with targeted drugs after progression on cyclin-dependent kinase 4/6 (CDK4/6) inhibitor treatment in hormone receptor (HR) positive/human epidermal growth factor receptor 2 (HER2)-low metastatic breast cancer. Methods: Patients with metastatic breast cancer diagnosed with HR positive/HER2 low expression at the Fifth Medical Center of PLA General Hospital from October 1, 2018 to September 30, 2023 were retrospectively included. All patients received sequential chemotherapy or sequential endocrine therapy combined with targeted drugs after progression on CDK4/6 inhibitor treatment.The median follow-up was 9 months, and the follow-up ended on October 31, 2023. The patients were divided into chemotherapy group (receiving sequential chemotherapy) and endocrine therapy group (receiving sequential endocrine therapy combined with targeted drugs), according to the treatment plan. Information on demographic data, clinical and pathological diagnosis, treatment regimen, and efficacy evaluation was collected. The basic conditions of patients who may affect the curative effect of different treatment schemes were preset as stratified subgroups, including age, progesterone receptor (PR) status, HER2 status, disease-free survival, number of previous endocrine therapy and chemotherapy, and visceral metastasis. The primary endpoint was progression-free survival (PFS), the secondary endpoints were objective response rate (ORR), clinical benefit rate(CBR) and PFS based on stratification factors. The survival curve was plotted by Kaplan-Meier method, the comparison of PFS between groups was performed by log-rank test, and the comparison of ORR and CBR between groups were performed by χ2 test. Results: A total of 188 patients were included, including 126 patients in the chemotherapy group [all females, aged 29-74 (51±10) years] and 62 patients in the endocrine therapy group [1 male and 61 female, aged 29-77 (51±12) years]. ORR of chemotherapy group was 23.0% (29/126), higher than that of endocrine treatment group [3.2% (2/62)] (P<0.001); The CBR of chemotherapy group and endocrine therapy group were 46.8% (59/126) and 33.9% (21/62), respectively, with no statistical significance (P=0.091). The median PFS of chemotherapy group and endocrine therapy group were 5.0 (95%CI: 4.3-5.7) and 4.0 (95%CI: 1.6-6.4) months, respectively, with no statistical significance (P=0.484). In the preset stratified subgroups, the median PFS of chemotherapy [6.0 (95%CI: 5.4-6.6) months] was longer than that of endocrine combined with targeted therapy [2.0 (95%CI: 1.8-2.2) months] (P<0.001) in PR negative patients; In patients who had progressed on over 2 previous endocrine treatments, the median PFS of chemotherapy [5.0 (95%CI: 3.8-6.2) months] was longer than that of endocrine combined with targeted therapy [2.0 (95%CI: 0.6-3.4) months] (P=0.045). Conclusions: After progression on treatment with CDK4/6 inhibitors for HR-positive/HER2-low expression metastatic breast cancer, both chemotherapy and endocrine therpy combined with targeted drugs are viable treatment options. However, for patients with PR negative or ≥2 lines of endocrine therapy previously, priority should be accorded to chemotherapy.

Real-World Treatment Patterns and Clinical Outcomes among Patients Receiving CDK4/6 Inhibitors for Metastatic Breast Cancer in a Canadian Setting Using AI-Extracted Data.

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) are widely used in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) advanced/metastatic breast cancer (ABC/MBC) in first line (1L), but little is known about their real-world use and clinical outcomes long-term, in Canada. This study used Pentavere's previously validated artificial intelligence (AI) to extract real-world data on the treatment patterns and outcomes of patients receiving CDK4/6i+endocrine therapy (ET) for HR+/HER2- ABC/MBC at Sinai Health in Toronto, Canada. Between 1 January 2016 and 1 July 2021, 48 patients were diagnosed with HR+/HER2- ABC/MBC and received CDK4/6i + ET. A total of 38 out of 48 patients received CDK4/6i + ET in 1L, of which 34 of the 38 (89.5%) received palbociclib + ET. In 2L, 12 of the 21 (57.1%) patients received CDK4/6i + ET, of which 58.3% received abemaciclib. In 3L, most patients received chemotherapy (10/12, 83.3%). For the patients receiving CDK4/6i in 1L, the median (95% CI) time to the next treatment was 42.3 (41.2, NA) months. The median (95% CI) time to chemotherapy was 46.5 (41.4, NA) months. The two-year overall survival (95% CI) was 97.4% (92.4, 100.0), and the median (range) follow-up was 28.7 (3.4-67.6) months. Despite the limitations inherent in real-world studies and a limited number of patients, these AI-extracted data complement previous studies, demonstrating the effectiveness of CDK4/6i + ET in the Canadian real-world 1L, with most patients receiving palbociclib as CDK4/6i in 1L.

Absolute lymphocyte count and neutrophil-to-lymphocyte ratio as predictors of CDK 4/6 inhibitor efficacy in advanced breast cancer.

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) are the standard agents for treating patients with estrogen receptor-positive and human epidermal growth factor receptor 2-negative advanced breast cancer (ER + HER2 - ABC). However, markers predicting the outcomes of CDK4/6i treatment have yet to be identified. This study was a single-center retrospective cohort study. We retrospectively evaluated 101 patients with ER + HER2 - ABC receiving CDK4/6i in combination with endocrine therapy at Fukuyama City Hospital between November 2017 and July 2021. We investigated the clinical outcomes and the safety of CDK4/6i treatment, and the absolute lymphocyte count (ALC) and neutrophil-to-lymphocyte ratio (NLR) as predictive markers for CDK4/6i. We defined the cut-off values as 1000/µL for ALC and 3 for NLR, and divided into "low" and "high" groups, respectively. We evaluated 43 and 58 patients who received abemaciclib and palbociclib, respectively. Patients with high ALC and low NLR had significantly longer overall survival than those with low ALC and high NLR (high vs. low; ALC: HR 0.29; 95% CI 0.12-0.70; NLR: HR 2.94; 95% CI 1.21-7.13). There was no significant difference in efficacy between abemaciclib and palbociclib and both had good safety profiles. We demonstrated that ALC and NLR might predict the outcomes of CDK4/6i treatment in patients with ER + HER2 - ABC.

Predicting drug-drug interactions in breast cancer patients treated with CDK4/6 inhibitors and forward planning.

INTRODUCTION: Cyclin-dependent kinase (CDK) 4/6 inhibitors are cornerstones in the treatment of Hormone Receptor (HR) positive and Human Epidermal Growth factor (HER2) negative metastatic breast cancer. Given their widespread use in the metastatic setting and emerging use in the adjuvant setting, studying drug-drug interactions (DDI) of these medications is of utmost importance. AREAS COVERED: This review provides key background information on the CDK4/6 inhibitors, palbociclib, ribociclib, and abemaciclib. We discuss drug-drug interactions including those with proton pump inhibitors as well as CYP3A substrates, inhibitors, and inducers. We describe the effect of these drugs on membrane transporters and their substrates as well as those drugs that increase risk of CDK4/6 toxicities. Finally, we explore future directions for strategies to minimize drug-drug interactions. EXPERT OPINION: It is crucial to be mindful of medications that may interfere with drug absorption, such as proton pump inhibitors, as well as those that interfere with drug metabolism, such as CYP3A4 inhibitors and inducers. Additionally, special consideration should be given to populations at higher risk for polypharmacy, such as older patients with greater comorbidities. These interactions and patient characteristics should be considered when developing individual treatment plans with CDK4/6 inhibitors.

Comprehensive Transcriptomic Analysis of EWSR1::WT1 Targets Identifies CDK4/6 Inhibitors as an Effective Therapy for Desmoplastic Small Round Cell Tumors.

Desmoplastic small round cell tumors (DSRCT) are a type of aggressive, pediatric sarcoma characterized by the EWSR1::WT1 fusion oncogene. Targeted therapies for DSRCT have not been developed, and standard multimodal therapy is insufficient, leading to a 5-year survival rate of only 15% to 25%. Here, we depleted EWSR1::WT1 in DSRCT and established its essentiality in vivo. Transcriptomic analysis revealed that EWSR1::WT1 induces unique transcriptional alterations compared with WT1 and other fusion oncoproteins and that EWSR1::WT1 binding directly mediates gene upregulation. The E-KTS isoform of EWSR1::WT1 played a dominant role in transcription, and it bound to the CCND1 promoter and stimulated DSRCT growth through the cyclin D-CDK4/6-RB axis. Treatment with the CDK4/6 inhibitor palbociclib successfully reduced growth in two DSRCT xenograft models. As palbociclib has been approved by the FDA for the treatment of breast cancer, these findings demonstrate the sensitivity of DSRCT to palbociclib and support immediate clinical investigation of palbociclib for treating this aggressive pediatric cancer. SIGNIFICANCE: EWSR1::WT1 is essential for desmoplastic small round cell tumors and upregulates the cyclin D-CDK4/6-RB axis that can be targeted with palbociclib, providing a targeted therapeutic strategy for treating this deadly tumor type.

Oral SERDs alone or in combination with CDK 4/6 inhibitors in breast cancer: Current perspectives and clinical trials.

Over the past few decades, first-line therapy for treating advanced and metastatic HR+/HER2-breast cancer has transformed due to the introduction of adjuvant endocrine therapy with cyclin-dependent kinase 4/6 inhibitors (CDK 4/6i). However, there is an unmet need for novel classes of endocrine therapy with superior efficacy to improve treatment outcomes and overcome CDK4/6i resistance. New generation selective estrogen receptor degraders (SERDs), orally administered and with higher bioavailability, could potentially be the novel compounds to meet this emerging need. In this paper, we review accredited clinical studies on the combining effects of CDK4/6 inhibitors and oral SERDs, report efficacy of treatment data when available, and provide a framework for future research focusing on these promising agents.

Bruceantinol works as a CDK2/4/6 inhibitor to inhibit the growth of breast cancer cells.

Bruceantinol (BOL), isolated from the dried fruit of the Brucea javanica (L.) Merr., exhibits cytotoxic effects on breast cancer cells. However, the underlying mechanism remains to be fully addressed. In this paper, the MCF-7 and MDA-MB-231 human breast cancer cell lines were used as experimental models to uncover how BOL inhibits breast cancer cell growth. The effects of BOL on cell growth, proliferation, the cell cycle, and apoptosis were investigated using the MTT assays, EdU incorporation assays, and flow cytometry, respectively. Bioinformatics techniques were applied to predict the key targets of BOL in breast cancer. Subsequent validation of these targets and the anti-breast cancer mechanism of BOL was conducted through Western blotting, RT-PCR, siRNA transfection, and molecular docking analysis. The results demonstrated that BOL dose- and time-dependently reduced the growth of both cell lines, impeded cell proliferation, disrupted the cell cycle, and induced necrosis in MCF-7 cells and apoptosis in MDA-MB-231 cells. Furthermore, CDK2/4/6 were identified as BOL targets, and their knockdown reduced cell sensitivity to BOL. BOL was found to potentially bind with CDK2/4/6 to facilitate protein degradation through the proteasome pathway. Additionally, BOL activated ERK in MDA-MB-231 cells, and this activation was required for BOL's functions in these cells. Collectively, BOL may act as an inhibitor of CDK2/4/6 to exert anti-breast cancer effects. Its effects on cell growth and CDK2/4/6 expression may also depend on ERK activation in HRs-HER2- breast cancer cells. These results suggest the potential of using BOL for treating breast cancer.

Overcoming BRAF and CDK4/6 inhibitor resistance by inhibiting MAP3K3-dependent protection against YAP lysosomal degradation.

Transcriptional programs governed by YAP play key roles in conferring resistance to various molecular-targeted anticancer agents. Strategies aimed at inhibiting YAP activity have garnered substantial interest as a means to overcome drug resistance. However, despite extensive research into the canonical Hippo-YAP pathway, few clinical agents are currently available to counteract YAP-associated drug resistance. Here, we present a novel mechanism of YAP stability regulation by MAP3K3 that is independent of Hippo kinases. Furthermore, we identified MAP3K3 as a target for overcoming anticancer drug resistance. Depletion of MAP3K3 led to a substantial reduction in the YAP protein level in melanoma and breast cancer cells. Mass spectrometry analysis revealed that MAP3K3 phosphorylates YAP at serine 405. This MAP3K3-mediated phosphorylation event hindered the binding of the E3 ubiquitin ligase FBXW7 to YAP, thereby preventing its p62-mediated lysosomal degradation. Robust YAP activation was observed in CDK4/6 inhibitor-resistant luminal breast cancer cells. Knockdown or pharmacological inhibition of MAP3K3 effectively suppressed YAP activity and restored CDK4/6 inhibitor sensitivity. Similarly, elevated MAP3K3 expression supported the prosurvival activity of YAP in BRAF inhibitor-resistant melanoma cells. Inhibition of MAP3K3 decreased YAP-dependent cell proliferation and successfully restored BRAF inhibitor sensitivity. In conclusion, our study reveals a previously unrecognized mechanism for the regulation of YAP stability, suggesting MAP3K3 inhibition as a promising strategy for overcoming resistance to CDK4/6 and BRAF inhibitors in cancer treatment.

Supramolecular nanodrug targeting CDK4/6 overcomes BAG1 mediated cisplatin resistance in oral squamous cell carcinoma.

Chemoresistance to cisplatin remains a significant challenge affecting the prognosis of advanced oral squamous cell carcinoma (OSCC). However, the specific biomarkers and underlying mechanisms responsible for cisplatin resistance remain elusive. Through comprehensive bioinformatic analyses, we identified a potential biomarker, BCL2 associated athanogene-1 (BAG1), showing elevated expression in head and neck squamous cell carcinoma (HNSCC). Since OSCC represents the primary pathological type of HNSCC, we investigated BAG1 expression in human tumor tissues and cisplatin resistant OSCC cell lines, revealing that silencing BAG1 induced apoptosis in cisplatin-resistant cells both in vitro and in vivo. This effect led to impaired cell viability of cisplatin resistant OSCC cells and indicated a positive correlation between BAG1 expression and the G1/S transition during cell proliferation. Based on these insights, the administration of a CDK4/6 inhibitor in combination with cisplatin effectively overcame cisplatin resistance in OSCC through the CDK4/6-BAG1 axis. Additionally, to enable simultaneous drug delivery and enhance synergistic antitumor efficacy, we developed a novel supramolecular nanodrug LEE011-FFERGD/CDDP, which was validated in an OSCC orthotopic mouse model. In summary, our study highlights the potential of a combined administration of CDK4/6 inhibitor and cisplatin as a promising therapeutic regimen for treating advanced or cisplatin resistant OSCC.

Visceral obesity and sarcopenia as predictors of efficacy and hematological toxicity in patients with metastatic breast cancer treated with CDK 4/6 inhibitors.

PURPOSE: We aimed to investigate whether visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and skeletal muscle area (SMA) index are predictive for efficacy and hematological toxicity in ER + HER2-metastatic breast cancer (BC) patients who received CDK 4/6 inhibitors. METHODS: This retrospective cohort study analyzed 52 patients who were treated with CDK 4/6 inhibitors between January 2018 and February 2021. The values of VAT, SAT, SMA indices and hematological parameters were noted before the start, at the third and sixth months of this treatment. The skeletal muscle area (SMA) and adipose tissue measurements were calculated at the level of the third lumbar vertebra. A SMA-index value of <40 cm2/m2 was accepted as the threshold value for sarcopenia. RESULTS: Patients with sarcopenia had a worse progression-free survival (PFS) compared to patients without sarcopenia (19.6 vs. 9.0 months, p = 0.005). Patients with a high-VAT-index had a better PFS (20.4 vs. 9.3 months, p = 0.033). Only the baseline low-SMA- index (HR: 3.89; 95% CI: 1.35-11.25, p = 0.012) and baseline low-VAT-index (HR: 2.15; 95% CI: 1.02-4.53, p = 0.042) had significantly related to poor PFS in univariate analyses. The low-SMA-index was the only independent factor associated with poor PFS (HR: 3.99; 95% CI: 1.38-11.54, p = 0.011). No relationship was observed between body composition parameters and grade 3-4 hematological toxicity. CONCLUSION: The present study supported the significance of sarcopenia and low visceral adipose tissue as potential early indicators of poor PFS in patients treated with CDK 4/6 inhibitors.

Impact of HER2-low expression on the efficacy of endocrine therapy with or without CDK4/6 inhibitor in HR-positive/HER2-negative metastatic breast cancer: A prospective study.

BACKGROUND: CDK4/6 inhibitors in combination with traditional endocrine therapy (ET) have become the recommended first-line therapy for HR-positive/HER2-negative metastatic breast cancer (MBC). The aim of this prospective study was to evaluate the relationship between HER2-low expression and clinical outcomes in HR-positive/HER2-negative MBC patients receiving ET with or without CDK4/6 inhibitors. METHODS: Between April 2016 and November 2019, 233 women with HR-positive/HER2-negative MBC who received ET with or without CDK4/6 inhibitors were enrolled into the study. The primary endpoint was progression-free survival (PFS). Statistical analysis included descriptive statistics, Kaplan-Meier curves, and Cox proportional hazards models. RESULTS: HER2-low and HER2-zero subgroups in the CDK4/6 inhibitor plus ET cohort showed no significant difference in the median PFS (10.9 vs. 8.0 months; hazard ratio: 0.92; 95% confidence interval [CI]: 0.64-1. 30; p = 0.65), while HER2-low subgroup showed a significantly shorter median PFS compared to the HER2-zero subgroup in the ET alone cohort (5.6 vs. 17.0 months; hazard ratio: 2.82; 95% CI: 1.34-5.93; p = 0.0044). Moreover, the objective response rate was significantly lower in the HER2-low subgroup than the HER2-zero subgroup in the ET alone cohort (10.5% vs. 40.0%, p = 0.047). Lastly, no significant difference was observed in the overall survival between the HER2-low and HER2-zero subgroups in both cohorts. CONCLUSION: This study suggested that HER2-low expression may predict the efficacy of ET but not that of CDK4/6 inhibitor plus ET in HR-positive/HER2-negative MBC patients. The results of this study highlight the importance of integrating HER2 status in tailoring personalized treatment strategies for HR-positive MBC.

The effects of low HER2 expression on survival in patients with metastatic breast cancer treated with CDK 4/6 inhibitors: a multicenter retrospective study.

PURPOSE: Endocrine therapy (ET) in combination with CDK 4/6 inhibitors (CDK 4/6i) is the standard treatment modality for hormone receptor (HR)-positive and HER2-negative metastatic breast cancer (mBC). There is uncertainty about the prognostic and predictive value of HER2-low status and whether HER2-low BC is an individual biologic subtype. In this study, we aimed to investigate the prognostic effect of HER2 expression status on survival in mBC patients treated with first-line ET plus CDK 4/6i. METHODS: This multicenter retrospective study included patients with HR + /HER2-negative mBC cancer who were treated with first-line CDK 4/6i in combination with ET from January 2016 to March 2023. Patients were divided into two groups (HER2-low and zero), and survival and safety analyses were performed. RESULTS: A total of 201 patients were included in this study; of these, 73 (36.3%) had HER2-low disease and 128 (63.7%) had HER2-zero. There were 135 patients (67.2%) treated with ribociclib and 66 (32.8%) with palbociclib. Most of the patients (75.1%) received aromatase inhibitors as combination-endocrine therapy. Baseline characteristics were similar between the two groups. The median follow-up was 19.1 months (range: 2.5-78.4). The most common side effect was neutropenia (22.4%). The frequency of grade 3-4 toxicity was similar between the HER2-zero and low patients (32% vs 31.5%; p = 0.939). Visceral metastases were present in 44.8% of patients. Between the HER2-low and zero groups, median PFS (25.2 vs 22.6 months, p = 0.972) and OS (not reached vs 37.5 months, p = 0.707) showed no statistically significant differences. CONCLUSION: The prognostic value of HER2-low status remains controversial. Our study showed no significant effect of HER2 low expression on survival in patients receiving CDK 4/6i plus ET.

Cyclin-dependent kinase 4/6 inhibitors in the treatment of advanced or metastatic breast cancer.

OBJECTIVE: Despite the relatively high cure rates in early-stage breast cancer, advanced and metastatic breast cancer cases are associated with more inauspicious patient outcomes. Fortunately, with the advent of cyclin-dependent kinase (CDK)4/6 inhibitors (e.g. palbociclib, ribociclib, and abemaciclib) with endocrine therapy, survival in advanced and metastatic breast cancer has appreciably improved. In the current review, we discuss these distinctions and the concomitant implications associated with the individual CDK4/6 inhibitors. DATA SOURCES: We conducted an extensive PubMed search comprising several review articles on the topic of advanced or metastatic breast cancer treatment, with specific terms that included CDK4/6 inhibitors, treatment, and breast cancer. DATA SUMMARY: Palbociclib, ribociclib, and abemaciclib have exhibited superior progression-free survival differences compared to endocrine therapy alone. However, there are differences among the various CDK4/6 inhibitors with regard to overall survival, tolerability and quality of life. CONCLUSIONS: Ribociclib may be indicated for pre/perimenopausal patients, whereas abemaciclib is potentially recommended to address endocrine-resistant or visceral disease. Alternatively, palbociclib is associated with lower discontinuation rates than abemaciclib and unlike ribociclib, QTc prolongation is not observed with palbociclib.

Selective CDK7 Inhibition Suppresses Cell Cycle Progression and MYC Signaling While Enhancing Apoptosis in Therapy-resistant Estrogen Receptor-positive Breast Cancer.

PURPOSE: Resistance to endocrine therapy (ET) and CDK4/6 inhibitors (CDK4/6i) is a clinical challenge in estrogen receptor (ER)-positive (ER+) breast cancer. Cyclin-dependent kinase 7 (CDK7) is a candidate target in endocrine-resistant ER+ breast cancer models and selective CDK7 inhibitors (CDK7i) are in clinical development for the treatment of ER+ breast cancer. Nonetheless, the precise mechanisms responsible for the activity of CDK7i in ER+ breast cancer remain elusive. Herein, we sought to unravel these mechanisms. EXPERIMENTAL DESIGN: We conducted multi-omic analyses in ER+ breast cancer models in vitro and in vivo, including models with different genetic backgrounds. We also performed genome-wide CRISPR/Cas9 knockout screens to identify potential therapeutic vulnerabilities in CDK4/6i-resistant models. RESULTS: We found that the on-target antitumor effects of CDK7 inhibition in ER+ breast cancer are in part p53 dependent, and involve cell cycle inhibition and suppression of c-Myc. Moreover, CDK7 inhibition exhibited cytotoxic effects, distinctive from the cytostatic nature of ET and CDK4/6i. CDK7 inhibition resulted in suppression of ER phosphorylation at S118; however, long-term CDK7 inhibition resulted in increased ER signaling, supporting the combination of ET with a CDK7i. Finally, genome-wide CRISPR/Cas9 knockout screens identified CDK7 and MYC signaling as putative vulnerabilities in CDK4/6i resistance, and CDK7 inhibition effectively inhibited CDK4/6i-resistant models. CONCLUSIONS: Taken together, these findings support the clinical investigation of selective CDK7 inhibition combined with ET to overcome treatment resistance in ER+ breast cancer. In addition, our study highlights the potential of increased c-Myc activity and intact p53 as predictors of sensitivity to CDK7i-based treatments.

Cracking the Genomic Code of CDK4/6 Inhibitor Resistance.

The therapeutic approach to metastatic hormone receptor-positive, human epidermal growth factor-2-negative metastatic breast cancer (HR+/HER2- MBC) has evolved rapidly over recent years. The cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have become first-line targeted agents of choice, in combination with an antiestrogen. Simultaneously, the clinical landscape of therapeutic options has been rapidly shifting, with novel antiestrogens, signal transduction inhibitors, and next-generation CDK inhibitors in various stages of development. Given these dynamic changes, understanding the genomic and molecular landscape of resistance to currently available antiestrogen therapy and CDK4/6 inhibitors represents a major focus of translational breast cancer research globally. See related article by Goetz et al., p. 2233.

Efficacy of CDK4/6 inhibitors combined with endocrine therapy in HR+/HER2- breast cancer: an umbrella review.

BACKGROUND: The use of Cyclin-Dependent kinase 4 and 6 (CDK4/6) inhibitors has profoundly changed the challenge of endocrine therapy (ET) resistance in hormone receptor-positive (HR+)/HER2-negative (HER2-) breast cancer. However, there is currently no comprehensive evaluation of the evidence for the efficacy of CDK4/6 inhibitors. We conducted an umbrella review to explore the impact of CDK4/6 inhibitor combined with ET on breast cancer by summarizing and assessing the meta-analysis (MA) and systematic review (SR) evidence. METHODS: Cochrane, PubMed, Embase, and Web of Science databases were searched from inception to August 1st, 2022. Eligible studies were assessed for methodological quality, report quality, and evidence quality using the AMSTAR-2 scale, PRISMA 2020, and GRADE grading systems, respectively. We summarized all efficacy outcomes of CDK4/6 inhibitors for breast cancer and reported them in narrative form. RESULTS: Our study included 24 MAs and SRs. The strongest evidence demonstrated that CDK4/6 inhibitor combined with ET significantly improved progression-free survival (PFS), overall survival (OS) in advanced breast cancer (ABC). A large body of moderate to high evidence showed a significant association between combination therapy and objective response rate (ORR), and clinical benefit response (CBR) benefit in ABC. Low evidence suggested some degree of benefit from combination therapy in second progression-free survival (PFS2) and time to subsequent chemotherapy (TTC) outcomes in ABC and invasive disease-free survival (IDFS) outcomes in early breast cancer. CONCLUSIONS: Based on current evidence, CDK4/6 inhibitors combined with ET have great confidence in improving PFS, OS, ORR, and CBR outcomes in patients with ABC, which provides more rational and valid evidence-based medicine for CDK4/6 inhibitor promotion and clinical decision support.

CDK4/6-Inhibitors Versus Chemotherapy in Advanced HR+/HER2-Negative Breast Cancer: Results and Correlative Biomarker Analyses of the KENDO Randomized Phase II Trial.

BACKGROUND: The optimal treatment approach for hormone receptor-positive/HER2-negative metastatic breast cancer (HR+/HER2-negative MBC) with aggressive characteristics remains controversial, with lack of randomized trials comparing cyclin-dependent kinase (CDK)4/6-inhibitors (CDK4/6i) + endocrine therapy (ET) with chemotherapy + ET. MATERIALS AND METHODS: We conducted an open-label randomized phase II trial (NCT03227328) to investigate whether chemotherapy + ET is superior to CDK4/6i + ET for HR+/HER2-negative MBC with aggressive features. PAM50 intrinsic subtypes (IS), immunological features, and gene expression were assessed on baseline samples. RESULTS: Among 49 randomized patients (median follow-up: 35.2 months), median progression-free survival (mPFS) with chemotherapy + ET (11.2 months, 95% confidence interval [CI]: 7.7-15.4) was numerically shorter than mPFS (19.9 months, 95% CI: 9.0-30.6) with CDK4/6i + ET (hazard ratio: 1.41, 95% CI: 0.75-2.64). Basal-like tumors under CDK4/6i + ET exhibited worse PFS (mPFS: 11.4 months, 95% CI: 3.00-not reached [NR]) and overall survival (OS; mOS: 18.8 months, 95% CI: 18.8-NR) compared to other subtypes (mPFS: 20.7 months, 95% CI: 9.00-33.4; mOS: NR, 95% CI: 24.4-NR). In the chemotherapy arm, luminal A tumors showed poorer PFS (mPFS: 5.1 months, 95% CI: 2.7-NR) than other IS (mPFS: 13.2 months, 95% CI: 10.6-28.1). Genes/pathways involved in BC cell survival and proliferation were associated with worse outcomes, as opposite to most immune-related genes/signatures, especially in the CDK4/6i arm. CD24 was the only gene significantly associated with worse PFS in both arms. Tertiary lymphoid structures and higher tumor-infiltrating lymphocytes also showed favorable survival trends in the CDK4/6i arm. CONCLUSIONS: The KENDO trial, although closed prematurely, adds further evidence supporting CDK4/6i + ET use in aggressive HR+/HER2-negative MBC instead of chemotherapy. PAM50 IS, genomic, and immunological features are promising biomarkers to personalize therapeutic choices.

Dual Inhibition of CDK4/6 and XPO1 Induces Senescence With Acquired Vulnerability to CRBN-Based PROTAC Drugs.

BACKGROUND & AIMS: Despite the increasing number of treatment options available for liver cancer, only a small proportion of patients achieve long-term clinical benefits. Here, we aim to develop new therapeutic approaches for liver cancer. METHODS: A compound screen was conducted to identify inhibitors that could synergistically induce senescence when combined with cyclin-dependent kinase (CDK) 4/6 inhibitor. The combination effects of CDK4/6 inhibitor and exportin 1 (XPO1) inhibitor on cellular senescence were investigated in a panel of human liver cancer cell lines and multiple liver cancer models. A senolytic drug screen was performed to identify drugs that selectively killed senescent liver cancer cells. RESULTS: The combination of CDK4/6 inhibitor and XPO1 inhibitor synergistically induces senescence of liver cancer cells in vitro and in vivo. The XPO1 inhibitor acts by causing accumulation of RB1 in the nucleus, leading to decreased E2F signaling and promoting senescence induction by the CDK4/6 inhibitor. Through a senolytic drug screen, cereblon (CRBN)-based proteolysis targeting chimera (PROTAC) ARV-825 was identified as an agent that can selectively kill senescent liver cancer cells. Up-regulation of CRBN was a vulnerability of senescent liver cancer cells, making them sensitive to CRBN-based PROTAC drugs. Mechanistically, we find that ubiquitin specific peptidase 2 (USP2) directly interacts with CRBN, leading to the deubiquitination and stabilization of CRBN in senescent liver cancer cells. CONCLUSIONS: Our study demonstrates a striking synergy in senescence induction of liver cancer cells through the combination of CDK4/6 inhibitor and XPO1 inhibitor. These findings also shed light on the molecular processes underlying the vulnerability of senescent liver cancer cells to CRBN-based PROTAC therapy.

A real-world analysis of trametinib in combination with hydroxychloroquine or CDK4/6 inhibitor as third- or later-line therapy in metastatic pancreatic adenocarcinoma.

BACKGROUND: There are no standard third-line treatment options for metastatic pancreatic ductal adenocarcinoma (mPDAC). Trametinib in combination with hydroxychloroquine (HCQ) or CDK4/6 inhibitors for pancreatic adenocarcinoma showed promising efficacy in preclinical studies. However, the regimens have not been well examined in patients with mPDAC. METHODS: Patients with mPDAC who received the combination of trametinib and HCQ or CDK4/6 inhibitors as third- or later-line therapy were reviewed. The efficacy and prognosis were further analyzed. RESULTS: A total of 13 mPDAC patients were enrolled, of whom 8 and 5 patients were treated with trametinib plus HCQ or a CDK4/6 inhibitor (palbociclib or abemaciclib), respectively. All enrolled patients had either KRAS G12D or G12V mutations and had received a median of 3 prior lines of therapy (range, 2-6). The median trametinib treatment duration was 1.4 months. Of the 10 patients with measurable disease, only 1 patient achieved stable disease, and the remaining patients had progressive disease. Moreover, in patients treated with trametinib plus HCQ and a CDK4/6 inhibitor, the median progression-free survival was 2.0 and 2.8 months, respectively, and the median overall survival was 4.2 and 4.7 months, respectively. Moreover, 5 (50%) patients experienced grade 3-4 adverse events in 10 patients with available safety data. CONCLUSIONS: The combination of trametinib and HCQ or CDK4/6 inhibitors may not be an effective later-line treatment for mPDAC, and the current preliminary findings need to be confirmed by other studies with larger sample sizes.

CDK4/6 inhibitors for hormone receptor-positive/human epidermal growth factor receptor 2 negative advanced breast cancer: A rapid health technology assessment.

OBJECT: Based on the best available evidence, rapid health technology was used to assess 4 CDK4/6 inhibitors approved for marketing in China. This assessment aims to provide a reference basis for the selection of drugs by medical institutions in China and to promote the rational use of drugs in the clinic. METHODS: Depending on the Rapid Guidelines for Drug Evaluation and Selection in Chinese Medical Institutions (the Second Edition), a percentage quantitative scoring approach was used to objectively score the pharmacological properties, efficacy, safety, economy, and other attributes of CDK4/6 inhibitors. RESULTS: The composite score rankings were, in descending order, 78.09 points for abemaciclib, 78.04 points for palbociclib, 72.15 points for dalpiciclib, and 69.24 points for ribociclib by integrating the result of the 5 dimensions. CONCLUSION: Until the clinical studies, guideline recommendations, prices, and many other aspects of this assessment are updated, abemaciclib and palbociclib, which have the top 2 scores, can be used as a priority recommendation for Chinese medical institutions to select CDK4/6 inhibitors and optimize the use of the drug catalog based on the scoring results of this assessment.