CDK4/6 inhibitors in breast cancer: differences in toxicity profiles and impact on agent choice. A systematic review and meta-analysis

Recent progress of CDK4/6 inhibitors' current practice in breast cancer

Dysregulated cellular proliferation represents a hallmark feature across all cancers. Aberrant activation of the cyclin-dependent kinase 4 and 6 (CDK4/6) pathway, independent of mitogenic signaling, engenders uncontrolled breast cancer cell proliferation. Consequently, the advent of CDK4/6 inhibition has constituted a pivotal milestone in the realm of targeted breast cancer therapy. The combination of CDK4/6 inhibitors (CDK4/6i) with endocrine therapy (ET) has emerged as the foremost therapeutic modality for patients afflicted with hormone receptor-positive (HR + )/HER2-negative (HER2-) advanced breast cancer. At present, the Food and Drug Administration (FDA) has sanctioned various CDK4/6i for employment as the primary treatment regimen in HR + /HER2- breast cancer. This therapeutic approach has demonstrated a substantial extension of progression-free survival (PFS), often amounting to several months, when administered alongside endocrine therapy. Within this comprehensive review, we systematically evaluate the utilization strategies of CDK4/6i across various subpopulations of breast cancer and explore potential therapeutic avenues following disease progression during application of CDK4/6i therapy.

A real-world pharmacovigilance study of QT interval prolongation and Torsades de Pointes associated with CDK4/6 inhibitors in breast cancer patients: findings from the FDA adverse event reporting system

BACKGROUND

The aim of this study was to evaluate the association between CDK4/6 inhibitors and QT interval prolongation (QTp) and Torsades de Pointes (TdP) in breast cancer patients.

METHOD

The cases with breast cancer from 2015 to 2022 were extracted from the FDA adverse event database (FARES) and further divided into a CDK4/6 inhibitor group and a positive control group. The associations between CDK4/6 inhibitors and QTp and TdP adverse events were evaluated using the reporting odds ratio (ROR) and the information component (IC).

RESULTS

A total of 172,266 breast cancer patients were included. A total of 234 QTp/TdP events occurred in the CDK4/6 inhibitor group. Disproportionality analysis revealed that ribociclib was related to QTp/TdP. The ROR was 10.10 (95% 8.56-11.92), and the IC was 2.84 (95% 2.28-3.32). Palbociclib and abemaciclib had no correlation with QTP/TDP events.

CONCLUSION

Based on this real-world pharmacovigilance analysis, this study demonstrated a significant association between ribociclib and QTp/TdP events, which should attract clinical attention. The QT interval was monitored before and after medication. Attention should be given to adjusting the drugson time.

Comparative analysis of adverse events associated with CDK4/6 inhibitors based on FDA's adverse event reporting system: a case control pharmacovigilance study

BACKGROUND

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors marked a milestone in the breast cancer treatment. Due to the potential impact of adverse effects on treatment decisions and patient outcomes, careful consideration of the varying toxicities of CDK4/6 inhibitors is crucial, as three inhibitors-palbociclib, abemaciclib, and ribociclib-have been approved with differences in adverse event profiles. However, limitations in clinical trials call for urgent real-world safety studies to evaluate and compare the risk of adverse events (AEs) among these CDK4/6 inhibitors. Therefore, this study aimed to analyze AEs of CDK4/6 inhibitors and provide insights for clinical drug selection, using real world database.

METHODS

The AEs of CDK4/6 inhibitors in the FDA Adverse Event Reporting System (2015-2022) were analyzed. Four disproportionality methods were used to detect safety signals: reporting odds ratio (ROR), proportional reporting ratio, Bayesian Confidence Neural Network Propagation, and Multi-Item Gamma Poisson Shrinker. Venn analysis was used to compare and select common and specific AEs.

RESULTS

This study included 73,042 patients treated with palbociclib, 25,142 with ribociclib, and 7563 with abemaciclib. All three inhibitors had 27 common AEs. Palbociclib exhibited the highest ROR for hematologic toxicities, while ribociclib showed the highest ROR for macrocytosis, nail disorders, and hepatic lesions. Abemaciclib displayed the highest ROR for mucosal toxicity. Common signals for both palbociclib and ribociclib included hematologic toxicities, decreased immune responsiveness, and aphthous ulcers. Myelosuppression, oral pain, and pseudocirrhosis were common signals for palbociclib and abemaciclib. Anemia, hepatotoxicity, and pneumonitis were observed as common signals for ribociclib and abemaciclib. Furthermore, specific AEs associated with palbociclib included fatigue, alopecia, and stomatitis. For ribociclib, specific AEs included electrocardiogram QT prolongation, thrombocytopenia, and decreased hemoglobin. Abemaciclib was specifically linked to diarrhea, vomiting, and interstitial lung disease.

CONCLUSION

Our analysis revealed that palbociclib showed a higher risk of hematologic toxicity. Ribociclib showed higher risks of hepatotoxicity, nephrotoxicity, and QT prolongation. Abemaciclib showed higher risks of hepatotoxicity, gastrointestinal effects, interstitial lung disease, and thrombosis. These findings provide valuable insights for CDK4/6 inhibitor selection.

A disproportionality analysis of CDK4/6 inhibitors in the FDA Adverse Event Reporting System (FAERS)

OBJECTIVE

The FDA Adverse Event Reporting System (FAERS) was used to mine and evaluate adverse events (AEs) associated with cyclin-dependent kinase (CDK) 4/6 inhibitors, thereby providing a reference for clinical rational drug use.

METHODS

AE data related to CDK4/6 inhibitors from the first quarter of 2015 to the first quarter of 2023 were acquired from FAERS, while the signal mining was processed using the reporting odds ratio (ROR) method and Bayesian confidence propagation neural network (BCPNN) method.

RESULTS

The number of AE reports for CDK4/6 inhibitors was, respectively, 132,494 for palbociclib, 56,151 for ribociclib, and 7,014 for abemaciclib. The corresponding numbers of AE signals were 319, 517, and 59, with the number of involved System Organ Class (SOC) being 23, 23, and 15, mainly involving blood and lymphatic system disorders, respiratory, thoracic and mediastinal disorders, hepatobiliary disorders, skin and subcutaneous tissue disorders, etc.

CONCLUSION

CDK4/6 inhibitors could lead to pulmonary toxicity, myelosuppression, skin reactions, etc. Special attention should be paid to abemaciclib for interstitial lung disease (ILD), erythema multiforme, and thrombosis risk; ribociclib for cardiac toxicity, hepatotoxicity, and musculoskeletal toxicity; palbociclib for neurocognitive impairment and osteonecrosis of the jaw.

Confirming the efficacy and safety of CDK4/6 inhibitors in the first-line treatment of HR+ advanced breast cancer: a systematic review and meta-analysis

Objective: Cyclin-dependent kinase (CDK) 4 and 6 inhibitors (abemaciclib, palbociclib and ribociclib) have been recommended in the first-line treatment of hormone receptor-positive (HR+) breast cancer in China. Our study aims to evaluate the efficacy and safety of CDK4/6 inhibitors by processing survival data using fractional polynomial modeling methods. Methods: Phase II or III randomized controlled trials in treatment-naive HR + patients with advanced breast cancer were systematically searched through the preset search strategy. The fractional polynomial (FP) model was used to relax the proportional hazard assumption and obtain time-varying hazard ratio (HR). Progression-free life years (PFLYs) and life years (LYs) were calculated from the area under curve (AUC) of the predicted progression-free survival (PFS) and overall survival (OS) curves to evaluate the long-term efficacy benefit. Odds ratio (OR) of grade≥3 adverse events were analyzed for safety outcomes. Results: 6 randomized controlled trials with 2,638 patients were included. The first-order FP model (p = -1) and the first-order FP model (p = 1) were used to calculate the time-varying HR of PFS and OS, respectively. Extrapolating to 240 months, abemaciclib obtained a PFS benefit of 3.059 PFLYs and 6.275 LYs by calculating the AUC of the PFS and OS curves. Palbociclib obtained 2.302 PFLYs and 6.351 LYs. Ribociclib obtained 2.636 PFLYs and 6.543 LYs. In terms of safety, the use of CDK4/6 inhibitors resulted in a higher risk of adverse events (OR = 9.84, 95% CI: 8.13-11.95), especially for palbociclib (OR = 14.04, 95% CI: 10.52-18.90). Conclusion: The use of CDK4/6 inhibitors in treatment-naive patients with HR + advanced breast cancer significantly improves survival, but also increases the risk of adverse events. Abemaciclib and ribociclib may be the best options for prolonging PFS and OS in treatment-naïve patients, respectively.

Spectrum of psychiatric adverse reactions to cyclin-dependent kinases 4/6 inhibitors: A pharmacovigilance analysis of the FDA adverse event reporting system

BACKGROUND

The emergence of cyclin-dependent kinases 4/6 inhibitors (CDK4/6i) represented a major breakthrough in the treatment of breast cancer over the past decade. In both clinical trials and real-world settings, it was observed that patients using CDK4/6i might experience psychiatric adverse events (PAEs). Herein, we conducted a pharmacovigilance study to comprehensively assess the correlation between CDK4/6i and PAEs.

METHOD

We obtained individual case safety reports submitted to the FDA Adverse Events Reporting System (FAERS) during the period from January 2015 to December 2023. In disproportionality analysis, the reporting odds ratio (ROR) and information component (IC) values were calculated for each adverse event-drug combination. Univariate logistic regression analysis was utilized to explore factors associated with PAEs following CDK4/6i treatment.

RESULTS

A total of 95,591 reports related to CDK4/6i were identified, with 6.72% reporting PAEs, and this proportion exhibited an annual upward trend. Based on the ROR and IC values, 17 categories of PAEs were defined as CDK4/6i-related PAEs. Among these PAEs, insomnia, stress, eating disorder, depressed mood, and sleep disorder were very common, each accounting for over 10% of CDK4/6i reports. Ribociclib showed the highest risk signal of CDK4/6i-related PAEs (ROR = 1.89[1.75-2.04], IC025 = 0.79), followed by palbociclib (ROR = 1.47[1.41-1.53], IC025 = 0.49), while abemaciclib did not exhibit a significant signal (ROR = 0.52[0.44-0.62], IC025 = -1.13). Female sex, younger age and weight exceeding 80 kg were significant risk factors for the incidence of CDK4/6i-related PAEs.

CONCLUSIONS

Using data from a real-world, large-scale spontaneous reporting system for adverse drug reactions, our study delineated the spectrum of PAEs to CDK4/6i. This potentially offered valuable insights for healthcare professionals to manage the risk of PAEs in patients receiving CDK4/6i treatment, particularly those with psychiatric disorders.

Real-world effectiveness of palbociclib in HR+/HER2- metastatic breast cancer: a literature review

Approximately 70% of newly diagnosed breast cancers are of the HR+/HER2- subtype. For the treatment of patients with HR+/HER2- metastatic breast cancer, current guidelines recommend the use of a CDK4/6 inhibitor (palbociclib, ribociclib or abemaciclib) in combination with endocrine therapy. In this review we assess existing literature concerning real-world effectiveness of palbociclib. Survival outcomes in terms of progression-free survival and overall survival are discussed and compared among the included real-world studies and in relation to the phase III PALOMA trials.

The Use of Cyclin-Dependent Kinase 4/6 Inhibitors in Elderly Breast Cancer Patients: What Do We Know?

BACKGROUND

Breast cancer (BC) incidence increases with age, particularly in HR-positive/HER2-negative subtypes. Cyclin-dependent kinase 4 and 6 inhibitors (CDK 4/6is) alongside endocrine therapy (ET) have emerged as promising treatments for HR-positive/HER2-negative advanced and early BC. However, their efficacy, safety, and impact on quality of life (QoL) in older and frail patients remain underexplored.

METHODS

This position paper assesses the existing literature from 2015 to 2024, focusing on CDK4/6is use in patients aged 65 years and older with HR-positive/HER2-negative BC.

RESULTS

Our analysis methodically addresses critical questions regarding the utilization of CDK4/6is in the elderly BC patient population, organizing findings from the metastatic and adjuvant settings. In the metastatic setting, CDK4/6is significantly improve progression-free survival (PFS), paralleling benefits observed in younger patients, and suggest potential overall survival (OS) benefits, warranting further investigation. Despite an increased incidence of grade ≥ 3 adverse events (AEs), such as neutropenia and asthenia, CDK4/6is present a markedly lower toxicity profile compared to traditional chemotherapy, with manageable side effects. QoL analysis indicates that integrating CDK4/6is into treatment regimens does not significantly impact elderly BC patients' daily life and symptom management. Special attention is given to frail subgroups, and personalized approaches are recommended to balance efficacy and adverse effects, such as starting with ET alone and introducing CDK4/6is upon progression in patients with a low disease burden. Transitioning to the adjuvant setting, early results, particularly with abemaciclib, indicate positive effects on disease-free survival (DFS), emphasizing the need for continued analysis to validate these findings and assess long-term implications. However, data on older patients are insufficient to conclude whether they truly benefit from this treatment.

CONCLUSION

Overall, CDK4/6is present a favorable benefit-risk profile in older BC patients, at least in advanced BC; however, further research is warranted to optimize treatment strategies and improve outcomes in this population.

CDK4/6 inhibitors in drug-induced liver injury: a pharmacovigilance study of the FAERS database and analysis of the drug-gene interaction network

Objective

The aim of this study was to investigate the potential risk of drug-induced liver injury (DILI) caused by the CDK4/6 inhibitors (CDK4/6is abemaciclib, ribociclib, and palbociclib by comprehensively analyzing the FDA Adverse Event Reporting System (FAERS) database. Moreover, potential toxicological mechanisms of CDK4/6is-related liver injury were explored via drug-gene network analysis.

Methods

In this retrospective observational study, we collected reports of DILI associated with CDK4/6i use from the FAERS dated January 2014 to March 2023. We conducted disproportionality analyses using the reporting odds ratio (ROR) with a 95% confidence interval (CI). Pathway enrichment analysis and drug-gene network analyses were subsequently performed to determine the potential mechanisms underlying CDK4/6i-induced liver injury.

Results

We found positive signals for DILI with ribociclib (ROR = 2.60) and abemaciclib (ROR = 2.37). DILIs associated with liver-related investigations, signs, and symptoms were confirmed in all three reports of CDK4/6is. Moreover, ascites was identified as an unlisted hepatic adverse effect of palbociclib. We isolated 189 interactive target genes linking CDK4/6 inhibitors to hepatic injury. Several key genes, such as STAT3, HSP90AA1, and EP300, were revealed via protein-protein analysis, emphasizing their central roles within the network. KEGG pathway enrichment of these genes highlighted multiple pathways.

Conclusion

Our study revealed variations in hepatobiliary toxicity among the different CDK4/6 inhibitors, with ribociclib showing the highest risk of liver injury, followed by abemaciclib, while palbociclib appeared relatively safe. Our findings emphasize the need for cautious use of CDK4/6 inhibitors, and regular liver function monitoring is recommended for long-term CDK4/6 inhibitor use.

A comparison between the adverse event profiles of patients receiving palbociclib and abemaciclib: analysis of two real-world databases

BACKGROUND

Palbociclib and abemaciclib are cyclin-dependent kinase (CDK) 4/6 inhibitors currently used to treat breast cancer. Although their therapeutic efficacies are considered comparable, differences in adverse event (AE) profiles of the two drugs remain unclear.

AIM

We analysed two real-world databases, the World Health Organization's VigiBase and the Food and Drug Administration Adverse Event Reporting System (FAERS), to identify differences in AE profiles of palbociclib and abemaciclib.

METHOD

Data of patients with breast cancer receiving palbociclib or abemaciclib recorded until December 2022 were extracted from the VigiBase and FAERS databases. In total, 200 types of AEs were analysed. The reporting odds ratios were calculated using a disproportionality analysis.

RESULTS

Cytopenia was frequently reported in patients receiving palbociclib, whereas interstitial lung disease and diarrhoea were frequently reported in those receiving abemaciclib. Moreover, psychiatric and nervous system disorders were more common in the palbociclib group, whereas renal and urinary disorders were more common in the abemaciclib group.

CONCLUSION

This study is the first to show comprehensively the disparities in the AE profiles of palbociclib and abemaciclib. The findings highlight the importance of considering these differences when selecting a suitable CDK4/6 inhibitor to ensure safe and favourable outcomes for patients with breast cancer.

Liver toxicity with ribociclib in a patient with metastatic hormone receptor positive postmenopausal breast cancer

INTRODUCTION

In recent years, highly selective reversible CDK4/6 inhibitors have been combined with aromatase inhibitors for their efficacy and ease of application in the treatment of advanced stage of hormone-responsive breast cancers. Oral use of these drugs facilitates patient compliance. However, adverse drug reactions are reported due to these drugs, in the literature. Diverse adverse reactions such as skin reactions, liver toxicity, and vitiligo with ribociclib have been reported.

CASE REPORT

In this study, we present of liver toxicity due to the use of ribociclib in a case of advanced breast cancer with metastases. It is noteworthy that the patient did not have any other concomitant disease and did not take any other medication.

MANAGEMENT AND OUTCOME

After the 600 mg initial dose of ribociclib, neutropenia occurred at the beginning of the therapy, the dose was reduced to 400 mg, and liver enzymes started to rise in the second month of the therapy. In the fifth month of the intermittent treatment period, liver toxicity was grade 3.

DISCUSSION

Liver adverse reaction occurred due to ribociclib use in the patient who had no history of any other disease. The Naranjo algorithm score was evaluated as 9. Considering the excretion of ribociclib by sulfation, cysteine conjugation, and glucuronidation, which are phase II reactions, n-acetyl cysteine (NAC) treatment (600 mg/day) was started for the patient. NAC therapy is recommended to reduce elevated liver enzymes in the case. The patient's treatment has been continuing with palbociclib for 5 months. No increase in liver enzymes was observed.

Ribociclib-induced liver injury: a case report

Background

Idiosyncratic drug-induced liver injury (DILI) is a rare, unpredictable hepatic adverse event and the most common cause of acute liver failure in Europe and the US. Ribociclib is a potent Cyclin-dependent kinase 4 and 6 (CDK4/6)-inhibitor administered for advanced hormone-receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Previous reports have shown hepatotoxicity without liver necrosis related to ribociclib.

Case presentation

A 41-year-old female patient with primary metastatic HR-positive, HER2-negative breast cancer developed liver enzyme elevation under treatment with ribociclib. Ribociclib was withdrawn 8 weeks after initiation due to liver enzyme elevation. A liver biopsy, performed due to further enzyme increase (peak ALT 2836 U/l), onset of jaundice (peak bilirubin 353 µmol/l) and coagulopathy (INR 1.8) two weeks later, revealed acute hepatitis with 30% parenchymal necrosis. Roussel Uclaf Causality Assessment Method (RUCAM) score was 7 points (probable). Under treatment with prednisone (60mg), initiated 2 weeks after drug withdrawal, and subsequently N-acetylcysteine (Prescott regimen) liver enzymes normalized within 8 weeks along with prednisone tapering.

Conclusion

This case illustrates the development of a severe idiosyncratic hepatocellular pattern DILI grade 3 (International DILI Expert Working Group) induced by ribociclib. Routine liver enzyme testing during therapy, immediate hepatologic work-up and treatment interruption in case of liver enzyme elevation are highly recommended. Corticosteroid treatment should be considered in cases of severe necroinflammation.

CDK4/6 inhibitors in metastatic breast cancer, a comparison of toxicity and efficacy across agents in a real-world dataset

INTRODUCTION

CDK4/6 inhibitors (ribociclib, palbociclib and abemaciclib) are 1st line therapy in metastatic breast cancer (MBC). No comparative data exists between agents regarding toxicity or efficacy.

METHODS

A retrospective study was performed at our tertiary referral centre evaluating patients on a CDK4/6 inhibitor for MBC between July 2017 and December 2021. Toxicity was evaluated along with variability in full blood counts and liver function over the first 12 weeks of therapy.

RESULTS

Two hundred and seventeen patients were treated (palbociclib 59%, abemaciclib 25% and ribociclib 16%). 86% received the agent as 1st line therapy. Most patients were white women with a median age of 61 years (32-95) and ECOG 0/1. Twelve patients were switched to an alternative CDK4/6 inhibitor due to toxicity and two did not tolerate this. Toxicity profiles of agents were consistent with published trials. However, there was greater overlap in hepatitis, diarrhoea and bone marrow suppression. Blood results indicated a minimum of four weeks treatment before development of neutropenia. Forty percent of patients went onto have subsequent lines of therapy. The progression-free survival per agent was palbociclib 27.9 months (95% CI 23-32.5), ribociclib 29 months (95% CI 21.5-37.0) and abemaciclib 20.6 months (95% CI 15.0-26.0). The overall survival was palbociclib 38.0 months (95% CI 33.5-42.5), ribociclib 33.9 months (95% CI 26.7-41.1) and abemaciclib 27.3 months (95% CI 22.5-32.1).

CONCLUSIONS

Toxicity across CDK4/6 inhibitors overlaps. The optimal sequence of therapies post CDK4/6 inhibitors remains unknown but rechallenge with an alternative agent is possible.

CDK4/6 inhibitors in the treatment of metastatic breast cancer: Focus on toxicity and safety

The development of oral cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors, including palbociclib, ribociclib, and abemaciclib, has revolutionized the treatment landscape for patients with hormone-receptor-positive (HR+) and human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (BC). When combined with an aromatase inhibitor or fulvestrant, these agents have been approved as first-line therapy in the metastatic setting. Abemaciclib has also gained FDA approval for patients with HR-positive, HER2-negative, node-positive, early BC at high risk of recurrence. Moreover, ribociclib has recently improved disease-free survival in patients with stage II or III HR+/HER2-negative early BC. CDK4/6 inhibitors have favorable safety profiles. However, the available agents have different toxicity profiles that must be clearly discussed with the patients for optimal clinical decisions. This manuscript aims to review CDK4/6 inhibitor-related treatment-associated adverse events, identify risk factors for intolerable adverse events, and assess their safety in special patient populations such as the elderly and those with renal insufficiency. Enhanced knowledge and understanding of CDK4/6 inhibitor-related toxicities can improve treatment strategies and ultimately enhance patient care.

Immune responses and clinical outcomes following the third dose of SARS-CoV-2 mRNA-BNT162b2 vaccine in advanced breast cancer patients receiving targeted therapies: a prospective study

Purpose

Metastatic breast cancer patients are the most prevalent oncology population with advanced disease facing COVID-19 pandemic. Immune responses after mRNA-based vaccination during treatment with CDK4/6 inhibitors or HER2-directed agents remain unclear. We conducted a prospective analysis to elucidate changes in antibody titers and lymphocyte counts following full course of mRNA-BNT162b2 (tozinameran) vaccination in recipients undergoing these targeted therapies.

Methods

Patients who had received a booster dosing and had been treated for at least 6 months were eligible. Antibody titers against SARS-CoV-2 spike protein were measured at four subsequent time points. Immunophenotyping of circulating lymphocytes was performed before the third dose of tozinameran and four weeks later to quantify the absolute counts of CD3+CD4+ T-helper cells, CD3+CD8+ T-cytotoxic cells, CD19+ B cells, and CD56+CD16+ NK cells. We also assessed the incidence of breakthrough infections and investigated whether immune changes affect time-to-treatment failure (TTF) after booster vaccination.

Results

The current analysis included 69 patients, of whom 38 (55%) and 31 (45%) were being treated with CDK4/6 inhibitors and HER2-targeted therapies, respectively. All participants received a third dose of tozinameran between September 23 and October 7, 2021. Multivariate analysis revealed that CDK4/6 inhibition predicted a significantly impaired humoral response after the booster dose. This detrimental effect was also evident for T-helper cell counts before the third immunization, but it disappeared in the subsequent evaluation. After a median follow-up of 22.3 months, we observed 19 (26%) cases of COVID-19 outbreaks, all experiencing favorable clinical outcomes. Univariate analysis showed a significant association between the onset of SARS-CoV-2 infections and the use of CDK4/6 inhibitors, as well as with an impaired antibody and T-helper cell response. Only the last two covariates remained independent predictors after multivariate testing. Dynamic variations in antibody titers and T-helper cell counts did not affect TTF in multivariate regression analysis.

Conclusions

Our results confirm that the immune response to tozinameran is impaired by CDK4/6 inhibitors, increasing the odds of breakthrough infections despite the third vaccine dose. Current evidence recommends maintaining efforts to provide booster immunizations to the most vulnerable cancer patients, including those with advanced breast cancer undergoing CDK4/6 inhibition.

Late onset toxicities associated with the use of CDK 4/6 inhibitors in hormone receptor positive (HR+), human epidermal growth factor receptor-2 negative (HER2-) metastatic breast cancer patients: a multidisciplinary, pan-EU position paper regarding their optimal management. The GIOCONDA project

The personalization of therapies in breast cancer has favoured the introduction of new molecular-targeted therapies into clinical practice. Among them, cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors have acquired increasing importance, with the approval in recent years of palbociclib, ribociclib, and abemaciclib in combination with endocrine therapy. Currently, no guidelines are available to monitor and manage potential long-term toxicities associated with the use of these drugs. A multidisciplinary panel of European oncologists, was supported by a pharmacologist, a hematologist, a hepatologist and a pulmonologist to discuss the management of long-term toxicities, based on the literature review and their clinical experience. The panel provided detailed roadmaps to manage long-term toxicities associated with the use of CDK4/6 inhibitors in clinical practice. Knowing the frequency and characteristics of the toxicity profile associated with each CDK4/6 inhibitor is important in the decision-making process to match the right drug to the right patient.

Safety and feasibility of CDK4/6 inhibitors treatment combined with radiotherapy in patients with HR-positive/HER2-negative breast cancer. A systematic review and meta-analysis

BACKGROUND AND PURPOSE

The addition of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) to endocrine therapy in hormone receptor-positive (HR+) human epidermal growth factor 2-negative (HER2-) breast cancer has led to practice-changing improvements in overall survival. However, there are conflicting data concerning the safety of CDK4/6i combination with radiotherapy, and no consensus guidelines exist to guide practice. We conducted a meta-analysis to assess the safety and feasibility of CDK4/6i treatment with radiotherapy.

MATERIALS AND METHODS

A comprehensive search was performed in PubMed/MEDLINE, Web of Science, and Scopus, for studies in advanced/metastatic breast cancer receiving CDK4/6i and radiotherapy with the provided safety data on the occurrence of toxicity. The main outcomes were safety (grade 3-5 adverse events), CDK 4/6i dose reduction, and the discontinuation rate due to toxicity.

RESULTS

Fifteen studies comprising 1133 patients with HR+/HER2- breast cancer patients were included. Among them, 617 pts received CDK4/6i and radiotherapy; the median follow-up was 17.0 months (IQR 9.2 - 18.0), and the median age was 58.8 years (IQR 55.5---62.5). The pooled prevalence of severe hematologic toxicity was 29.4% (95% CI 14.0% - 47.4%; I2 = 93%; τ2 = 0.084; p < 0.01 and severe non-hematologic toxicity was 2.8% (95% CI 1.1% - 4.8%; I2 = 0%; τ2 = 0.0; p = 0.67). The pooled prevalence of CDK4/6i dose reduction was 24.0% (95% CI 11.1% - 39.4%; I2 = 90%; τ2 = 0.052; p < 0.01) with no difference between CDK4/6i plus RT vs. CDK4/6i (odds ratio of 0.934; 95% CI 0.66 - 1.33; I2 = 0%; τ2 = 0.0; p = 0.56). The pooled prevalence of CDK4/6i discontinuation due to toxicity was 2.3% (95% CI 0.4% - 5.2%; I2 = 23%; τ2 = 0.002; p = 0.24).

CONCLUSION

The findings of this study suggest that radiotherapy in addition to CDK4/6i treatment in breast cancer patients is generally safe and well tolerated and remains a viable treatment option.

Hematological Events Potentially Associated with CDK4/6 Inhibitors: An Analysis from the European Spontaneous Adverse Event Reporting System

Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors are a recent targeted therapy approved for patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer. Abemaciclib, palbociclib and ribociclib demonstrated great efficacy and safety during clinical studies. However, differences in their adverse-event profiles have been observed. This work aims to describe the suspected adverse drug reactions (ADRs), such as leukopenia and thrombocytopenia, reported for each CDK4/6 inhibitor in the EudraVigilance (EV) database. Data on individual case safety reports (ICSRs) were obtained by accessing the European spontaneous reporting system via the EV website. Information on concomitant drug therapy, including fulvestrant, letrozole, anastrozole and exemestane, was also analyzed. A total of 1611 ICSRs were collected from the EV database. Most reports of palbociclib and ribociclib were classified as serious cases for both suspected leukopenia and thrombocytopenia ADRs. However, most patients had their leukopenia and thrombocytopenia recovered/resolved. On the contrary, reports of abemaciclib were mostly characterized as non-serious cases. Abemaciclib and palbociclib were often combined with fulvestrant, while ribociclib was generally associated with letrozole. Pharmacovigilance studies are crucial for the early identification of potential ADRs and to better differentiate the toxicity profile of the different CDK4/6 inhibitors, particularly in a real-world setting.

Safety profile of cyclin-dependent kinase (CDK) 4/6 inhibitors with concurrent radiation therapy: A systematic review and meta-analysis

The cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) have become the standard of care for hormone receptor-positive (HR + ) and human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer, improving survival outcomes compared to endocrine therapy alone. Abemaciclib and ribociclib, in combination with endocrine therapy, have demonstrated significant benefits in invasive disease-free survival for high-risk HR+/HER2- early breast cancer patients. Each CDK4/6i-palbociclib, ribociclib, and abemaciclib-exhibits distinct toxicity profiles. Radiation therapy (RT) can be delivered with a palliative or ablative intent, particularly using stereotactic body radiation therapy for oligometastatic or oligoprogressive disease. However, pivotal randomized trials lack information on concomitant CDK4/6i and RT, and existing preclinical and clinical data on the potential combined toxicities are limited and conflicting. As part of a broader effort to establish international consensus recommendations for integrating RT and targeted agents in breast cancer treatment, we conducted a systematic review and meta-analysis to evaluate the safety profile of combining CDK4/6i with palliative and ablative RT in both metastatic and early breast cancer settings.

Cyclin-Dependent Kinase 4/6 Inhibitors and Dermatologic Adverse Events: Results from the EADV Task Force "Dermatology for Cancer Patients" International Study

BACKGROUND

The introduction of cyclin-dependent kinase inhibitors (CDK4/6i) was a great advance in therapeutics for patients with estrogen receptor+/human epidermal growth factor receptor (HER2) locally advanced and metastatic breast cancer. Despite the increasing use of these agents, their adverse drug-related events have not yet been fully characterized. We describe the spectrum of cutaneous adverse reactions occurring in advanced breast cancer patients treated with cyclin-dependent kinase inhibitors, analyzing types, severity, time to onset, and possible treatment outcomes.

METHODS

We performed a multicentric retrospective study including patients with advanced breast cancer who developed cutaneous lesions during treatment with CDK4/6i in the period from June 2020 to June 2021. Patients > 18 years were recruited at eleven onco-dermatology units located in Albania (1), Argentina (1), France (1), Greece (3), Italy (3), and Spain (2). We evaluated patients' epidemiological and clinical characteristics, types of cutaneous adverse events, their time to onset, and treatment outcomes. The severity of the skin reactions was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 score.

RESULTS

Seventy-nine patients (median age: 62.3 years; range 39-83 years) were included in the study, and, collectively, we recorded a total of 165 cutaneous adverse events during follow-up visits. The most frequent cutaneous reactions were pruritus (49/79 patients), alopecia (25/79), and eczematous lesions (24/79). Cutaneous toxicities were usually mild in severity (>65%) and occurred after a median of 6.5 months. Only four patients (5%) required treatment discontinuation due to the severity of the skin lesions. The majority of the skin reactions were managed with topical treatments.

CONCLUSIONS

To the best of our knowledge, we present the largest case series of cutaneous adverse events developing in advanced breast cancer patients treated with CDK4/6i. We showed that cutaneous toxicities are usually mild in severity, and manageable with standard supportive care; however, in selected cases, they can lead to treatment discontinuation with possible implications for patients' clinical outcomes.

Ribociclib in newly diagnosed hepatitis B infection: A case report

Breast cancer is the most frequently diagnosed cancer in women worldwide. Actually CDK4/6 inhibitor Ribociclib is approved for the treatment of metastatic hormone-positive and human epidermal growth factor receptor 2 (HER 2)-negative breast cancer, but comorbidities like infectious or cardiovascular diseases may limit its use.

Case report

A 45-year-old woman was diagnosed with metastatic breast cancer in September 2021; also, her hepatitis screening resulted positive for hepatitis B infection. Patient assumed eradicative therapy for hepatitis and bit after started oncological therapy with Ribociclib.

Outcome

Frequent check of hepatological function was observed since start of eradicative therapy; liver transaminases and bilirubin kept to not rise despite start of oncological treatment with Ribociclib. Patient's Performance Status was also not compromised and revaluation at 4, 9 and 13 months showed partial response and then stable disease.

Discussion

hepatotoxicity of Ribociclib is reported as a possible side effect, and often positivity for hepatitis is cause of exclusion from therapy; in our case, no hepatotoxicity was noted and patient obtained response in terms of control of both infectious and oncological diseases.

Effect of adenosine triphosphate on ribociclib-induced skin toxicity in rats

PURPOSE

Ribociclib is a CDK4/6 inhibitor approved for the treatment of breast cancer; it inhibits the activity of CDK4/6 by competitively binding to adenosine 5'-triphosphate (ATP) binding sites. Although generally well-tolerated, ribociclib has been connected to a number of serious dermatologic complications. This study explored the effects of ATP on ribociclib-induced skin damage.

MATERIALS AND METHODS

Using a rat model, ATP 25 mg/kg was injected intraperitoneally in the ATP + Ribociclib (ATR) group (n = 6). Distilled water as solvent was applied to the healthy control (HC) group (n = 6) and ribociclib (RCB) group (n = 6). One hour after ATP and solvent administration, ribociclib (200 mg/kg) suspension prepared in distilled water was administered to the stomach by gavage (ATR and RCB groups). This was repeated once a day for 15 d. After that period, biochemical markers were studied in the skin tissues and histopathological evaluations were conducted.

RESULTS

In the histopathological evaluation of the RCB group, dermal necrosis, degeneration in hair follicles, and pycnosis in keratinocytes were observed. Only mild degeneration was observed in the ATR group; the HC group had a normal histological appearance. The malondialdehyde (MDA) values were significantly higher and the superoxide dismutase (SOD), catalase (CAT), and total glutathione (tGSH) levels were significantly lower in the RCB group in comparison to the HC group (p < .001). ATP reduced the ribociclib-induced increases in the MDA values and decreased the SOD, CAT, and tGSH levels in the ATR group (p < .001).

CONCLUSION

ATP may be useful in the treatment of ribociclib-induced skin damage.

Sticking to the Rules: Outcome and Success Rate of Guideline-Based Diarrhea Management in Metastatic Breast Cancer Patients Treated with Abemaciclib

In clinical trials testing abemaciclib in patients with hormone-receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer, diarrhea is a very common adverse event (occurring in approximately 85% of patients, any grade). Nonetheless, this toxicity leads to abemaciclib discontinuation in a small proportion of patients (approximately 2%) thanks to the use of effective loperamide-based supportive therapy. We aimed to determine whether the incidence of abemaciclib-induced diarrhea in real-world trials was higher than the one reported in clinical trials, where patients are highly selected, and to evaluate the success rate of standard supportive care in this setting. We conducted a retrospective, observational, monocentric study including 39 consecutive patients with HR+/HER2- advanced breast cancer treated with abemaciclib and endocrine therapy at our institution from July 2019 to May 2021. Overall, diarrhea of any grade occurred in 36 patients (92%), of whom 6 (17%) had diarrhea of grade ≥3. In 30 patients (77%), diarrhea was associated with other adverse events, including fatigue (33%), neutropenia (33%), emesis (28%), abdominal pain (20%), and hepatotoxicity (13%). Loperamide-based supportive therapy was administered to 26 patients (72%). Abemaciclib dose was reduced in 12 patients (31%) due to diarrhea, and treatment was permanently discontinued in 4 patients (10%). In 58% of patients (15/26), diarrhea was effectively managed with supportive care and did not require abemaciclib dose reduction and/or discontinuation. In our real-world analysis, we observed a higher incidence of diarrhea related to abemaciclib compared to data from clinical trials, and a higher rate of permanent treatment discontinuation due to gastrointestinal toxicity. Better implementation of guideline-based supportive care could help to manage this toxicity.

An experimental study: the effect of S. boulardii on abemaciclibinduced diarrhea

BACKGROUND

In our study, we aimed to investigate the protective effects of Saccharomyces boulardii on abemaciclib-induced diarrhea model, which is a commonly used drug in breast cancer.

METHODS

Thirty rats were divided into 3 groups as control (Group 1), abemaciclib (Group 2), and abemaciclib + Saccharomyces boulardii (Group 3) groups. The clinical status, body weight, and defecation status were monitored daily. At the end of the 15-day experiment period, the rats were killed with high-dose anesthesia and the resected small intestine segments were evaluated histopathologically. Lesions were classified according to thickening of the villus, inflammation and edema of mucosa and intraepithelial leukocyte accumulation. Then, mean values of both crypt depths and villi thicknesses were calculated for each rat. Normal distribution assumption was controlled with the Shapiro-Wilk test. One-way analysis of variance for normally distributed variables in the comparisons of more than two independent groups and Kruskal-Wallis test for nonnormally distributed variables were used. The significance value was accepted as 0.05.

RESULTS

: There was one death in Group 3, but none in the others. There were no findings of mucositis in Group I. There was mild diarrhea and weight loss in only one rat in Group 1. For the comparison of the severity of diarrhea (72.5%/39%) and weight loss (72.5%/45%), a decrease was found in Group 3 according to Group 2 (p < 0.01). Histopathological findings such as edema, inflammation, and intraepithelial leukocyte accumulation also showed a decrease in Group 3 compared to Group 2 (p < 0.01).

DISCUSSION

Saccharomyces boulardii should be considered as a treatment option in abaemaciclib (chemotherapy)-induced diarrhea. Further comparative studies and in vivo human randomized controlled studies can be conducted in the future.

The likelihood of being helped or harmed as a patient-centred tool to assess cyclin dependent kinase 4/6 inhibitors clinical impact and safety in metastatic breast cancer: a systematic review and sensitivity-analysis

Background

In hormone-receptor positive/HER2-negative metastatic breast cancer (mBC) no randomized comparisons are available between CDK4/6 inhibitors. We undertook this systematic review and meta-analysis to assess the reliability of the likelihood of being helped or harmed (LHH).

Methods

PubMed, CENTRAL, Embase and oncological meetings websites were searched to September 13th, 2022. We included phase III randomized controlled trials (RCTs) investigating palbociclib, ribociclib and abemaciclib in addition to endocrine therapy (ET) compared to placebo in hormone-receptor positive/HER2-negative advanced or mBC. Outcomes were progression-free survival (PFS), overall survival (OS), adverse events (AEs), dose reductions and discontinuations. Hazard ratios (HRs) and risk differences were computed with a random effect model to estimate the number needed to treat/harm (NNT/NNH). LHH was computed as (1/NNT)/(1/NNH). PROSPERO registration number: CRD42022362417.

Findings

2204 records were screened and seven RCTs (4415 patients) were included. A significant PFS benefit was observed in patients treated with a CDK4/6 inhibitor compared to placebo (HR 0.549; 0.508-0.594, I 2  = 0). Palbociclib, ribociclib and abemaciclib had similar NNTs (4.4, 5.0 and 4.4). Palbociclib and ribociclib showed lower LHHs for grade 3-4 neutropenia (0.33 and 0.35) and febrile neutropenia ([FN], 14.27 and 15.52), while abemaciclib the lowest LHH for any grade diarrhea (0.42). Abemaciclib had a lower LHH for grade 3-4 fatigue (9.92) and the highest LHH for all grade 3-4 AEs (0.62), while ribociclib the lowest LHH (1.75) for grade 3-4 hepatotoxicity. Palbociclib had the highest LHH for dose reductions and discontinuations (0.65 and 6.17). Considering OS, an overall benefit was observed (HR 0.788, 0.727-0.856, I 2  = 0%); ribociclib and abemaciclib had lower NNTs (9.7 and 10.0). Ribociclib showed the highest LHH for diarrhea (1.29), fatigue (7.37), dose reductions (0.28) and discontinuations (2.40), while abemaciclib the highest LHHs for neutropenia (0.40), FN (12.53) and hepatotoxicity (2.23).

Interpretation

Palbociclib and ribociclib showed lower LHHs for haematological toxicities and abemaciclib for diarrhea. Palbociclib confirmed to be a manageable drug. The LHH appears to be a reliable synthesis tool for balancing risks and benefits of experimental drugs when head-to-head comparisons are missing.

Funding

None.

Haematopoietic cytopenia associated with cyclin-dependent kinase 4/6 inhibitors: A real-world study of data from the food and drug administration adverse event reporting system database

OBJECTIVE

The haematopoietic cytopenia (HC) of the cyclin-dependent kinase (CDK)4/6 inhibitors was evaluated using the Food and Drug Administration Adverse Event Reporting System (FAERS).

METHOD

Data from 1 January 2015 to 31 December 2021 has been retrieved from the FAERS database. Disproportionality analysis and Bayesian analysis were utilized in the data mining. The reporting odds ratio (ROR) with 95% confidence interval (CI) for HC was calculated for each CDK 4/6 inhibitor agent. Clinical features of the patients were collected and compared between death outcome and non-death outcome groups. Time to onset (TTO), proportion of deaths, life-threatening and hospitalizations of CDK 4/6 inhibitors-associated HC were also studied.

RESULTS

A total of 17,235 cases of HC associated with CDK 4/6 inhibitors were identified with a median age of 65 years (interquartile range [IQR] 57-73). Palbociclib appeared the strongest signal, with the highest (ROR 9.64, 95% CI 9.46-9.83), followed by ribociclib (ROR 6.38, 95% CI 6.04-6.73) and then abemaciclib (ROR 2.72, 95% CI 2.49-2.97). Patients aged 18-64 had a higher proportion of deaths than those aged 65-84 (12.21% vs. 9.91%, p = 0.001). In Africa and Asia, the proportions of deaths were higher (31.65% and 26.13%, respectively). The median TTO was 26 days (IQR 14-65) for abemaciclib, 33 days (IQR 15-134) for palbociclib and 23 days (IQR 14-69) for ribociclib, respectively. The highest proportion of deaths, life-threatening and hospitalizations all occurred in abemaciclib (13.00%, 5.42% and 44.04%, respectively).

CONCLUSIONS

Greater proportions of deaths occurred in Africa and Asia. HC may occur early in any CDK 4/6 inhibitor regimen. Abemaciclib had the highest proportion of deaths, life-threatening and hospitalizations. Health care workers should be more concerned about CDK 4/6 inhibitors. The higher proportions of serious events, including deaths, from Africa and Asia, as well as for abemaciclib, deserve further investigations through additional pharmacoepidemiological approaches.

CDK4/6 Inhibitors as Upfront Treatment in a Patient with Breast Cancer Presenting with a Clinical Critic Situation: A Case Report and Review of the Literature

CDK4/6 inhibitors have revolutionized the treatment algorithm of luminal metastatic breast cancer, becoming the recommended first-line therapy in association with endocrine therapy. However, due to its theoretically greater and more rapid tumor shrinkage, the upfront use of chemotherapy is considered in some clinical situations like visceral crisis. At the state of the art level, a paucity of data is available about the use of CDK4/6 inhibitors in patients presenting with visceral crisis or with life-threatening conditions since this population was historically excluded from clinical trials. In addition, data regarding direct comparison between combinations of chemotherapy and CDK4/6 inhibitors in terms of efficacy, rapidity of responses and long-term outcomes are lacking. We report the case of a 68-year-old woman with luminal metastatic breast cancer presenting at diagnosis with a critical and potentially life-threatening condition. The patient was treated with first-line Abemaciclib plus letrozole and achieved a rapid partial response with sudden clinical stabilization. Although the patient did not technically present with a visceral crisis, this case presentation also endorsed the upfront use of CDK4/6 inhibitor combinations in critical clinical situations in the absence of severe organ dysfunction and after multidisciplinary discussion.

The role of HER2 alterations in clinicopathological and molecular characteristics of breast cancer and HER2-targeted therapies: a comprehensive review

Breast cancer (BC) is the most common malignancy in women and one of the leading causes of cancer mortality, despite significant treatment advancements over the last decades. Human epidermal growth factor receptor-2 (HER2) is a member of the ERBB family of receptor tyrosine kinases which have long been known to mediate cancer cell growth and invasion through constitutive activation of oncogenic downstream signaling, such as PI3K/Akt/mTOR and MAPK. Overexpression/amplification of HER2 in various tumors, especially BC, offers the possible therapeutic potential for target therapies. HER2-targeted therapies, either with a combination of chemotherapy or through multi-anti-HER2 therapies without chemotherapy, have significantly improved the prognosis of HER2-positive tumors. In recent years, novel anti-HER2 agents and combination therapies have garnered much attention, especially for heavily treated advanced or metastatic BCs. HER2-positive BC is biologically a heterogeneous group depending on HER2 activation mechanisms, hormone receptor status, genome variations, tumor heterogeneity, and treatment resistance, which affect the treatment benefit and patients' outcomes. This review will discuss HER2 alternations (gene amplification or receptor overexpression) in BC, their correlation with clinicopathological characteristics and molecular characteristics, and HER2-based therapies in tumors with HER2 overexpression/amplification.

Theranostics platform of Abemaciclib using magnetite@silica@chitosan nanocomposite

The current study was designed to synthesize a nanoformula comprising of magnetite nanoparticles (MN) with mesoporous silica (MS), which was in turn coated with chitosan (CS) and further loaded with a chemotherapeutic agent, Abemaciclib (ABE). The prepared formula, MN@MS@CS@ABE, was characterized by XRD, FTIR, HRTEM, FESEM, DLS, VSM, BET, and BJH. The ABE loading capacity and entrapment efficiency were calculated, and an in vitro drug release experiment was conducted. Cytoxicity was studied by the MTT assay. The formula was investigated as an anticancer agent versus MCF-7 cells by performing Annexin V-FITC flow cytometry and cell cycle analysis. Furthermore, we examine the formula as a contrast agent in magnetic resonance imaging (MRI). ABE loading and encapsulation efficiency were 24.2 % and 63.4 %, respectively. The formula demonstrated sustained drug release behavior for 72 h. The MTT assay revealed a higher cytotoxicity of free ABE in MCF-7 cells compared to MN@MS@CS@ABE. Flow cytometry revealed early and late phases of apoptosis and necrosis with different percentages. The formula stimulated a reduction in signal intensity in the MR T2-weighted imaging technique. In conclusion, the current study developed a nanoformula which could be a promising theranostic agent in cancer therapy and diagnosis.

CDK4/6 inhibitors versus PI3K/AKT/mTOR inhibitors in women with hormone receptor-positive, HER2-negative metastatic breast cancer: An updated systematic review and network meta-analysis of 28 randomized controlled trials

Background

Updated evidence was required to compare the efficacy and safety of cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) inhibitors for patients with hormone receptor-positive and HER2-negative metastatic breast cancer.

Methods

A systematic review and network meta-analysis was conducted utilizing data from randomized controlled trials (RCTs) that contained interventions of CDK4/6 inhibitors or PI3K/AKT/mTOR inhibitors. Progression-free survival (PFS), overall survival (OS), and treatment-related adverse events (TRAEs) were primary outcomes of interest. Pooled hazard ratios (HRs) and odds ratios (ORs) with 95% credible intervals (CrIs) were used to assess the survival outcomes and safety profiles, respectively.

Results

A total of 28 RCTs with 12,129 participants were included. Pooled analysis showed that CDK4/6 inhibitors significantly prolonged PFS than PI3K/AKT/mTOR inhibitors (HR, 0.81; 95% CrI, 0.69–0.94), whereas no significant differences were detected regarding OS. After balancing the treatment lines and metastatic sites, the superiority of CDK4/6 inhibitors only appeared in the visceral and non-visceral subgroups. Among CDK4/6 inhibitors, abemaciclib was significantly better than others in ≥3 grade neutropenia (OR, 0.04; 95% CrI, 0.01–0.15). The incidence of stomatitis and digestive disorders was different among diverse kinds of PI3K/AKT/mTOR inhibitors. Discrepancies appeared regarding TRAEs of hepatotoxicity, diarrhea, and hyperglycemia among different interventions.

Conclusions

CDK4/6 inhibitors showed better efficacy in PFS, but the benefits disappeared when taking treatment line into consideration. Specific and discrepant safety profiles were found in two categories of agents.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42022321172.

Precision Medicine Highlights Dysregulation of the CDK4/6 Cell Cycle Regulatory Pathway in Pediatric, Adolescents and Young Adult Sarcomas

Simple Summary

This review provides an overview of clinical features and current therapies in children, adolescents, and young adults (AYA) with sarcoma. It highlights the basic and clinical findings on the cyclin-dependent kinases 4 and 6 (CDK4/6) cell cycle regulatory pathway in the context of the precision medicine-based molecular profiles of the three most common types of pediatric and AYA sarcomas—osteosarcoma (OS), rhabdomyosarcoma (RMS), and Ewing sarcoma (EWS).

Abstract

Despite improved therapeutic and clinical outcomes for patients with localized diseases, outcomes for pediatric and AYA sarcoma patients with high-grade or aggressive disease are still relatively poor. With advancements in next generation sequencing (NGS), precision medicine now provides a strategy to improve outcomes in patients with aggressive disease by identifying biomarkers of therapeutic sensitivity or resistance. The integration of NGS into clinical decision making not only increases the accuracy of diagnosis and prognosis, but also has the potential to identify effective and less toxic therapies for pediatric and AYA sarcomas. Genome and transcriptome profiling have detected dysregulation of the CDK4/6 cell cycle regulatory pathway in subpopulations of pediatric and AYA OS, RMS, and EWS. In these patients, the inhibition of CDK4/6 represents a promising precision medicine-guided therapy. There is a critical need, however, to identify novel and promising combination therapies to fight the development of resistance to CDK4/6 inhibition. In this review, we offer rationale and perspective on the promise and challenges of this therapeutic approach.

CDK4/6 inhibitors improve the anti-tumor efficacy of lenvatinib in hepatocarcinoma cells

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer with a poor prognosis and limited treatment options. Considering that alterations of the CDK4/6-cyclin D-Rb pathway occur frequently in HCC, we tested the efficacy of two CDK4/6 inhibitors, abemaciclib and ribociclib, in combination with lenvatinib, a multi-kinase inhibitor approved as first-line therapy for advanced HCC, in a panel of HCC Rb-expressing cell lines. The simultaneous drug combinations showed a superior anti-proliferative activity as compared with single agents or sequential schedules of treatment, either in short or in long-term experiments. In addition, the simultaneous combination of abemaciclib with lenvatinib reduced 3D cell growth, and impaired colony formation and cell migration. Mechanistically, these growth-inhibitory effects were associated with a stronger down-regulation of c-myc protein expression. Depending on the HCC cell model, reduced activation of MAPK, mTORC1/p70S6K or src/FAK signaling was also observed. Abemaciclib combined with lenvatinib arrested the cells in the G1 cell cycle phase, induced p21 accumulation, and promoted a stronger increase of cellular senescence, associated with elevation of β-galactosidase activity and accumulation of ROS, as compared with single treatments. After drug withdrawal, the capacity of forming colonies was significantly impaired, suggesting that the anti-tumor efficacy of abemaciclib and lenvatinib combination was persistent.

Our pre-clinical results demonstrate the effectiveness of the simultaneous combination of CDK4/6 inhibitors with lenvatinib in HCC cell models, suggesting that this combination may be worthy of further investigation as a therapeutic approach for the treatment of advanced HCC.

Treatment patterns, effectiveness, and patient-reported outcomes of palbociclib therapy in Chinese patients with advanced breast cancer: A multicenter ambispective real-world study

BACKGROUND

Palbociclib was the only available cyclin-dependent kinase 4/6 inhibitor in China until very recently, and its effect has not been systemically evaluated among Chinese patients. This study aims to assess the efficacy, safety and patient-reported outcomes (PROs) of palbociclib plus endocrine therapy (ET) in real-world China.

METHODS

An ambispective cohort study was conducted on patients with advanced HR+HER2- breast cancer who received palbociclib between July 2018, and November 2020 and were enrolled from 12 hospitals. Treatment patterns, survival outcomes, and safety events were documented, and PROs (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 items [EORTC QLQ-C30] and EuroQoL 5 dimensions [EQ-5D]) were analyzed. The Kaplan-Meier method was used to visualize and estimate the median progression-free survival (mPFS). Log-rank tests, Cox regressions, t tests, and chi-square tests were performed for comparison.

RESULTS

A total of 190 patients (median follow-up of 18.0 months) were enrolled. Palbociclib was mostly combined with aromatase inhibitors (66.3%), fulvestrant (32.6%), and tamoxifen (1.1%). The mPFS values were 21.0, 14.0, and 7.0 months with palbociclib administered in first- (n = 83), second- (n = 41) and subsequent-line settings (n = 66), respectively. Endocrine sensitivity was significantly associated with patient prognosis (mPFS: 23.0, 12.0, and 6.0 months for endocrine naïve, acquired, and primary resistant patients, respectively, p < 0.01). The outcome was worse for patients who failed to meet the inclusion criteria of PALOMA-3 than for those who met the criteria (later-line: 6.0 months vs. 9.0 months). The most common adverse events (AEs) were neutropenia (74.2%; grade 3/4: 30.0%), fatigue (48.4%), anemia (32.6%), and thrombocytopenia (22.1%). PRO data suggested that palbociclib plus ET significantly improved cognitive and emotional function, pain symptoms, and overall quality of life.

CONCLUSIONS

Palbociclib is effective for front-line use and for treating endocrine-sensitive patients in real-world China and is generally well tolerated. The prevalence of AEs in the Chinese population is different from that reported in the PALOMA-2/3 trials.

Harnessing the immunotherapeutic potential of CDK4/6 inhibitors in melanoma: is timing everything?

CDK4/6 inhibitors (CDK4/6i) were developed as a cancer therapeutic on the basis of their tumor-intrinsic cytostatic potential, but have since demonstrated profound activity as immunomodulatory agents. While currently approved to treat hormone receptor-positive breast cancer, these inhibitors are under investigation in clinical trials as treatments for a range of cancer types, including melanoma. Melanoma is a highly immunogenic cancer, and has always been situated at the forefront of cancer immunotherapy development. Recent revelations into the immunotherapeutic activity of CDK4/6i, therefore, have significant implications for the utility of these agents as melanoma therapies. In recent studies, we and others have proven the immunomodulatory effects of CDK4/6i to be multifaceted and complex. Among the most notable effects, CDK4/6 inhibition induces transcriptional reprogramming in both tumor cells and immune cells to enhance tumor cell immunogenicity, promote an immune-rich tumor microenvironment, and skew T cell differentiation into a stem-like phenotype that is more amenable to immune checkpoint inhibition. However, in some contexts, the specific immunomodulatory effects of CDK4/6i may impinge on anti-tumor immunity. For example, CDK4/6 inhibition restricts optimal T cells expansion, and when used in combination with BRAF/MEK-targeted therapies, depletes immune-potentiating myeloid subsets from the tumor microenvironment. We propose that such effects, both positive and negative, may be mitigated or exacerbated by altering the CDK4/6i dosing regimen. Here, we discuss what the most recent insights mean for clinical trial design, and propose clinical considerations and strategies that may exploit the full immunotherapeutic potential of CDK4/6 inhibitors.

Safety in Japanese Advanced Breast Cancer Patients Who Received Abemaciclib in MONARCH 2 and MONARCH 3: Assessment of Treatment-Emergent Neutropenia, Diarrhea, and Increased Alanine Aminotransferase and Aspartate Aminotransferase Levels

Purpose

Our objective was to gain a better understanding of the safety of abemaciclib in Japanese patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer.

Patients and Methods

Treatment-emergent adverse events (TEAEs) were assessed in pooled Japanese subpopulation data from two phase 3 studies assessing abemaciclib/placebo in combination with fulvestrant (MONARCH 2; M2) or non-steroidal aromatase inhibitors (MONARCH 3; M3). For common, clinically relevant TEAEs, event characteristics and management were summarized by study.

Results

In the Japanese safety subpopulation (abemaciclib: N=101; placebo: N=46), all patients experienced ≥1 TEAE (Grade ≥ 3: abemaciclib, 71.3%; placebo, 23.9%; no Grade 5). Clinically relevant TEAEs that were more frequent in abemaciclib-treated Japanese patients compared to the overall safety populations included diarrhea (any grade, 95.0%; Grade ≥ 3, 12.9%), neutropenia (any grade, 75.2%; Grade 3–4, 35.6%), increased alanine aminotransferase (ALT; any grade, 39.6%; Grade 3–4, 14.9%), and increased aspartate aminotransferase (AST; any grade, 37.6%; Grade 3–4, 8.9%). Diarrhea was Grade ≤3 and successfully managed with medications (≥87%) and dose reductions (≤25%) and/or omissions (≤23.3%). Most Grade ≥2 diarrhea occurred in the first treatment cycle, declining thereafter. Neutropenia, the most common Grade ≥3 TEAE in abemaciclib-treated Japanese patients, was generally manageable with dose omissions (M2: 42.0%; M3: 23.1%) and/or reductions (M2: 16%; M3: 15.4%). Neutrophil counts plateaued after Cycle 2, recovering to pretreatment levels after discontinuation of abemaciclib. Hepatic events were managed with medication (≤21%) and dose adjustments (≤33.3%), with most Grade ≥2 events occurring in early treatment cycles. Discontinuation of any study treatment in Japanese patients occurred more frequently due to increased ALT/AST (M2: 9.1%/10.5%; M3: 16.7%/10.5%) compared with diarrhea (M2: 0%; M3: 2.8%) or neutropenia (M2: 0%; M3: 3.8%).

Conclusion

Abemaciclib was well tolerated in Japanese patients in MONARCH 2 and MONARCH 3, with common, clinically relevant TEAEs manageable with appropriate interventions.

Endocrine Treatment for Breast Cancer Patients Revisited-History, Standard of Care, and Possibilities of Improvement

PURPOSE OF REVIEW

Due to the findings of current studies and the approval of novel substances for the therapy of hormone-receptor-positive breast cancer patients, the established standards of endocrine treatment are changing. The purpose of this review is to give an overview of the history of endocrine treatment, to clarify its role in the present standard of care, and to discuss the possibilities of improvement.

RECENT FINDINGS

Tamoxifen, aromatase inhibitors, and fulvestrant are the main drugs that have been used for decades in the therapy of hormone-receptor-positive breast cancer patients. However, since a relevant number of women suffer at some point from disease recurrence or progression, several novel substances are being investigated to overcome resistance mechanisms by interfering with certain signaling pathways, such as the PI3K/AKT/mTOR or the CDK4/6 pathways. mTOR and CDK4/6 inhibitors were the first drugs approved for this purpose and many more are in development.

SUMMARY

Endocrine treatment is one of the best tolerable cancer therapies available. Continuous investigation serves to improve patients' outcomes and modernize the current standard of care. Considering the resistance mechanisms and substances analyzed against these, endocrine treatment of hormone-receptor-positive breast cancer is on the brink of a new era.

SARS-CoV-2 neutralizing antibodies after first vaccination dose in breast cancer patients receiving CDK4/6 inhibitors

Undoubtedly, the development of COVID-19 vaccines displays a critical step towards ending this devastating pandemic, considering their protective benefits in the general population. Yet, data regarding their efficacy and safety in cancer patients are limited. Herein we provide the initial analysis of immune responses after the first dose of vaccination in 21 breast cancer patients receiving cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors. The levels of neutralizing antibodies post vaccination were similar to the matched healthy controls, whereas no safety issues have been raised. Further exploration is needed to reduce the uncertainty of SARS-CoV-2 immunity among cancer patients under treatment.

•

Data on the efficacy and safety of COVID-19 vaccines in cancer patients are limited.

•

21 breast cancer patients under CDK4/6 inhibition enrolled to our prospective study.

•

Nearly 30% of them developed favorable viral inhibition after the first dose.

•

Immune responses did not differ between patient cohort and healthy controls.

Clinical and Pharmacologic Differences of CDK4/6 Inhibitors in Breast Cancer

Targeted therapies such as Cyclin Dependent Kinase 4 and 6 (CDK 4/6) inhibitors have improved the prognosis of metastatic hormone receptor (HR) positive breast cancer by combating the resistance seen with traditional endocrine therapy. The three approved agents currently in the market are palbociclib, ribociclib and abemaciclib. Besides the overall similarities associated with CDK4/6 inhibition, there are differences between the three approved agents that may explain the differences noted in unique clinical scenarios- monotherapy, patients with brain metastases or use in the adjuvant setting. This review article will explore the preclinical and pharmacological differences between the three agents and help understand the benefits seen with these agents in certain subgroups of patients with metastatic HR positive breast cancer.

Epigenetically Mediated Ciliogenesis and Cell Cycle Regulation, and Their Translational Potential

Primary cilia biogenesis has been closely associated with cell cycle progression. Cilia assemble when cells exit the cell cycle and enter a quiescent stage at the post-mitosis phase, and disassemble before cells re-enter a new cell cycle. Studies have focused on how the cell cycle coordinates with the cilia assembly/disassembly process, and whether and how cilia biogenesis affects the cell cycle. Appropriate regulation of the functions and/or expressions of ciliary and cell-cycle-associated proteins is pivotal to maintaining bodily homeostasis. Epigenetic mechanisms, including DNA methylation and histone/chromatin modifications, are involved in the regulation of cell cycle progression and cilia biogenesis. In this review, first, we discuss how epigenetic mechanisms regulate cell cycle progression and cilia biogenesis through the regulation of DNA methylation and chromatin structures, to either promote or repress the transcription of genes associated with those processes and the modification of cytoskeleton network, including microtubule and actin. Next, we discuss the crosstalk between the cell cycle and ciliogenesis, and the involvement of epigenetic regulators in this process. In addition, we discuss cilia-dependent signaling pathways in cell cycle regulation. Understanding the mechanisms of how epigenetic regulators contribute to abnormal cell cycle regulation and ciliogenesis defects would lead to developing therapeutic strategies for the treatment of a wide variety of diseases, such as cancers, polycystic kidney disease (PKD), and other ciliopathy-associated disorders.

CDK4/6 Inhibitors and Arthralgia: A Single Institution Experience

Background: Aromatase inhibitors (AIs) are associated with musculoskeletal pain in one third (20–47%) of breast cancer patients. Recently, CDK4/6 inhibitors have emerged as a new therapeutic approach in hormone receptor (HR)-positive breast cancer. While hematological and gastrointestinal toxicities are frequently reported during treatment with CDK4/6 inhibitors, musculoskeletal symptoms are less commonly encountered. Methods: Herein, we present a retrospective study of 47 breast cancer patients who received CDK4/6 inhibitors along with endocrine therapy in our department between 01/01/2018 and 01/09/2020. Results: Median age at diagnosis was 58 years (29–81). Median duration of treatment was 8.76 months (SD: 7.68; 0.47–30.13 months). Median PFS was 24.33 months (95% CI; 1.71–46.96). Overall, toxicity was reported in 61.7% of the cases (29/47). Arthralgia was reported in 6.4% (3/47) of the patients. Hematological toxicity was reported in 51.1% (24/47) of the patients. Neutropenia was the main hematological toxicity observed (86.8%; 22/47) along with anemia (4.3%; 2/47), thrombocytopenia (2.1%; 1/47), and leukopenia (4.2%; 1/24). Conclusions: Though our data reflect a small sample size, we report a reduced arthralgia rate (6.4%) during treatment with CDK4/6 inhibitors compared with that reported in studies of AIs (20–47%).

Thromboembolic Events with Cyclin-Dependent Kinase 4/6 Inhibitors in the FDA Adverse Event Reporting System

Simple Summary

This post-marketing research addressed the role of cyclin-dependent kinase 4/6 inhibitors, relatively new anticancer drugs approved for advanced breast cancer in cancer-associated thrombosis. We used the Food and Drug Administration pharmacovigilance database to retrospectively assess thromboembolic events in the real world. A potential class effect was found for venous thrombosis, whereas distinctive arterial events emerged for ribociclib. These signals call for both prospective research and early proactive monitoring by oncologists, also in patients without apparent risk factors. These findings strengthen the role of timely pharmacovigilance to detect and characterize post-marketing adverse events of special interest, thus supporting patient care.

Abstract

We analyzed thromboembolic events, recognized (AESIs), with cyclin-dependent kinase (CDK)4/6 inhibitors, using the Food and Drug Administration adverse event reporting system. Methods: Thromboembolic events were characterized in terms of spectrum [venous and arterial thromboembolism (VTE; ATE)] and clinical features by combining the disproportionality approach [reporting odds ratio (ROR) with 95% confidence interval (CI)] with individual case assessment. Results: A total of 1722 thromboembolic events were retained. Increased VTE reporting emerged for CDK4/6 inhibitors in the exploratory analyses (n = 659; ROR = 1.51; 95% CI = 1.39–1.63), with consistent disproportionality in the consolidated analyses (e.g., deep vein thrombosis with abemaciclib: 17; 1.98; 1.22–3.19). Higher-than-expected ATE reporting was found for ribociclib, including myocardial infarction (41; 1.82; 1.33–2.48), with rapid onset (median latency 1 vs. 6 months for other CDK4/6 inhibitors). Causality was highly probable or probable in 83.2% of cases, with a negligible proportion of pre-existing drug- and patient-related risk factors except for cardiovascular comorbidities (26%). Conclusions: Although causal association cannot be firmly inferred, oncologists should proactively monitor the occurrence of VTE with CDK4/6 inhibitors. The unexpected distinctive increased ATE reporting with ribociclib deserves urgent clarification though large comparative population-based studies. We support pharmacovigilance for the post-marketing characterization of AESIs, thus promoting real-time safe prescribing in oncology.