Palbociclib has no clinically relevant effect on the QTc interval in patients with advanced breast cancer

Strategy of combining CDK4/6 inhibitors with other therapies and mechanisms of resistance

Cell cycle-dependent protein kinase 4/6 (CDK4/6) is a crucial kinase that regulates the cell cycle, essential for cell division and proliferation. Hence, combining CDK4/6 inhibitors with other anti-tumor drugs is a pivotal clinical strategy. This strategy can efficiently inhibit the growth and division of tumor cells, reduce the side effects, and improve the quality of life of patients by reducing the dosage of combined anticancer drugs. Furthermore, the combination therapy strategy of CDK4/6 inhibitors could ameliorate the drug resistance of combined drugs and overcome the CDK4/6 resistance caused by CDK4/6 inhibitors. Various tumor treatment strategies combined with CDK4/6 inhibitors have entered the clinical trial stage, demonstrating their substantial clinical potential. This study reviews the research progress of CDK4/6 inhibitors from 2018 to 2022, the related resistance mechanism of CDK4/6 inhibitors, and the strategy of combination medication.

Cardiac safety of ribociclib evaluated with 24-hour rhythm Holter electrocardiogram

OBJECTIVE

We aimed to evaluate cardiac safety profile of ribociclib with 24-h rhythm Holter ECG.

MATERIAL AND METHOD

Forty-two female metastatic breast cancer patients were included in the study. Rhythm Holter ECG was performed before starting treatment with ribociclib and after 3 months of the treatment initiation.

RESULTS

The mean age of the patients was 56.36 ± 12.73. 52.4% (n = 22) of the patients were using ribociclib in combination with fulvestrant and 47.6% (n = 20) with aromatase inhibitors. None of the patients developed cardiotoxicity. When the rhythm Holter results before and in third month of the treatment were compared, there was no statistically significant difference.

CONCLUSION

This is the first study evaluating effects of ribociclib treatment on cardiac rhythm with Holter ECG. The findings suggested ribociclib has a low risk of causing early cardiotoxicity.

Concentration-QTc Modeling of the DPP-4 Inhibitor HSK7653 in a First-in-Human Study of Chinese Healthy Volunteers

Cofrogliptin (HSK7653) is a long-acting dipeptidyl peptidase-4 inhibitor for the treatment of type 2 diabetes mellitus with a twice-monthly dosing regimen. This study included 62 participants (48 without food effect, 14 with food effect) receiving single doses of HSK7653 (5, 10, 25, 50, 100, and 150 mg) or placebo. Pharmacokinetic samples were collected over 24 hours postdosing and sampling times are aligned with 12-lead electrocardiograms (ECGs) which were derived from continuous ECG recordings. For the concentration-QT interval corrected for heart rate (C-QTc) analysis, we used linear mixed-effects modeling to characterize the correlation between plasma concentrations of HSK7653 and the change from baseline in the QT interval which was corrected by Fridericia's formula (ΔQTcF). The result showed that a placebo-corrected Fridericia corrected QT interval (ΔΔQTcF) prolongation higher than 10 milliseconds is unlikely at the mean maximum observed concentration (Cmax) (411 ng/mL) associated with the recommended therapeutic doses (25 mg twice-monthly), even at the highest supratherapeutic concentration (2425 ng/mL). Thus, HSK7653 does not significantly affect QT prolongation at either recommended doses or the highest supratherapeutic concentration.

Cardiovascular complications of ribociclib in breast cancer patients

Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors have unprecedentedly advanced hormone-dependent breast cancer treatment paradigm. In the metastatic setting, ribociclib has consistently demonstrated survival benefit in pre-, peri-, and postmenopausal patients, conjugating efficacy with health-related quality of life preservation. Accordingly, the emergence of cardiac and/or vascular adverse events related to this novel targeted agent is gaining significant interest. This narrative review provides an overview of the incidence and spectrum of cardiovascular toxicity, in both clinical trial framework and real-world evidence. The potential pathogenetic mechanism, along with the available diagnostic parameters including biomarkers, and proper management, are also summarized.

CDK4/6 inhibitors: basics, pros, and major cons in breast cancer treatment with specific regard to cardiotoxicity - a narrative review

Breast cancer is characterized by the uncontrolled proliferation of breast cells, with a high incidence reported in 2020 to have affected over 2 million women. In recent years, the conventional methods of treating breast cancer have involved radiotherapy and chemotherapy. However, the emergence of CDK4/6 inhibitors has shown potential as a promising cancer therapy. Cyclin-dependent kinases (CDK) inhibitors are a class of molecules that impede the formation of an active kinase complex, thereby hindering its activity and consequently halting the progression of the cell cycle. It was discovered that they have a significant impact on impeding the progression of the cancer. This is evident with the Food and Drug Administration's approval of drugs such as palbociclib, ribociclib, and abemaciclib for hormone receptor-positive metastatic breast cancer in combination with specific endocrine therapies. In spite of enormous success in breast cancer treatment, certain obstacles have emerged, such as therapy resistance, side effects, and most of all, cardiotoxicity. Some of these drawbacks have been successfully overcome by dosage reduction, different combinations of the drugs, and the assessment of each patient's condition and suitability prior to treatment. Yet other drawbacks still require tenacious research, especially certain cases of cardiotoxicities. This article delves into the biological mechanisms of CDK4/6 in the cell cycle and cancer, as well as the clinical advantages and most common adverse events (AEs) associated with CDK4/6 inhibitors. The primary objective of this review is to provide a comprehensive analysis of cardiotoxic AEs and elucidate the underlying pathophysiological mechanisms responsible for the cardiotoxicity of CDK4/6 inhibitors.

Concentration-QT modelling in early clinical oncology settings: Simulation evaluation of performance

AIMS

Concentration-QT modelling (C-QTc) of first-in-human data has been rapidly adopted as the primary evaluation of QTc interval prolongation risk. Here, we evaluate the performance of C-QTc in early oncology settings (i.e., patients, no placebo or supratherapeutic dose, 3 + 3 designs).

METHODS

C-QTc performance was evaluated across three oncology scenarios using a simulation-estimation approach: (scen1) typical dose-escalation testing six dose levels (n = 21); (scen2) small dose-escalation testing two dose levels (n = 9); (scen3) expansion cohorts at one dose level (n = 6-140). True ΔΔQTc effects ranged from 3 ms ("no effect") to 20 ms ("large effect"). Performance was assessed based on the upper limit of the ΔQTc two-sided 90% CI against a threshold of 10 or 20 ms.

RESULTS

The performance against the 10 ms threshold was limited based on C-QTc data from typical dose escalation (scen1) and acceptable performance was observed only for relatively large expansions (n ≥ 45; scen3). Performance against the 20 ms threshold was acceptable based on C-QTc data from a typical dose escalation (scen1) or dose expansion cohort n > 10 (scen3). In general, pooling C-QTc data from dose escalation and expansion cohorts substantially improved the performance and reduced the ΔQTc 90% CI width.

CONCLUSION

C-QTc performance appeared limited using a 10 ms threshold, but acceptable against a 20 ms threshold. Selection of threshold may be informed by the benefit-risk balance in a specific disease area. Acceptable precision (i.e., confidence intervals) of the estimated ΔQTc, regardless of its magnitude, can be facilitated by pooling data from dose escalation and expansion cohorts.

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.

Inhibiting CDK4/6 in Breast Cancer with Palbociclib, Ribociclib, and Abemaciclib: Similarities and Differences

The cyclin-dependent kinase (CDK) 4/6 inhibitors belong to a new class of drugs that interrupt proliferation of malignant cells by inhibiting progression through the cell cycle. Three such inhibitors, palbociclib, ribociclib, and abemaciclib were recently approved for breast cancer treatment in various settings and combination regimens. On the basis of their impressive efficacy, all three CDK4/6 inhibitors now play an important role in the treatment of patients with HR+, HER2- breast cancer; however, their optimal use still needs to be established. The three drugs have many similarities in both pharmacokinetics and pharmacodynamics. However, there are some differences on the basis of which the choice for a particular CDK4/6 inhibitor for an individual patient can be important. In this article, the clinical pharmacokinetic and pharmacodynamic profiles of the three CDK4/6 inhibitors are reviewed and important future directions of the clinical applicability of CDK4/6 inhibitors will be discussed.

Letrozole targets the human ether-a-go-go-related gene potassium current in glioblastoma

Aberrant expression of human ether-a-go-go-related gene (hERG) potassium channels has been implicated in the pathophysiology of glioblastoma (GBM). Letrozole has demonstrated efficacy in pre-clinical GBM models. The objective of this research was to assess the potential for hERG inhibition by letrozole to mediate efficacy in GBM. hERG currents were assessed using patch-clamp electrophysiology in an overexpression system during treatment with letrozole, exemestane or vehicle (dimethyl sulphoxide). Relative to vehicle, peak hERG tail current density was reduced when treated with 300 nmol/L and 1 µmol/L letrozole but not when treated with exemestane (up to 1 µmol/L). Cell proliferation was assessed in cultured glioblastoma cell lines (U87 and U373) treated with letrozole, exemestane, doxazosin (hERG blocker) or vehicle. Letrozole, but not exemestane, reduced cell proliferation relative to vehicle in U87 and U373 cells. The associations between expression of hERG (KCNH2), aromatase (CYP19A1) and the oestrogen receptors (ESR1 and ESR2) and time to all-cause mortality were assessed in GBM patients within The Cancer Genome Atlas (TCGA) database. hERG expression was associated with reduced overall survival in the TCGA GBM cohort. Future work is warranted to investigate hERG expression as a potential biomarker to predict the therapeutic potential of hERG inhibitors in GBM.

Talazoparib has no clinically relevant effect on QTc interval in patients with advanced solid tumors

Supplemental Digital Content is available in the text.

The aims of this study were (i) to evaluate the effect of talazoparib (1 mg once daily) on cardiac repolarization in patients with advanced solid tumors by assessing corrected QT interval (QTc) and (ii) to examine the relationship between plasma talazoparib concentration and QTc. In this open-label phase 1 study, patients had continuous 12-lead ECG recordings at baseline followed by time-matched continuous ECG recordings and collection of talazoparib plasma pharmacokinetic samples predose and at 1, 2, 4, and 6 h postdose on treatment days 1 and 22 and before talazoparib administration on day 2. ECG recordings were submitted for independent central review where triplicate 10-s ECGs, extracted up to 15 min before pharmacokinetic samples, were assessed for RR, PR, QRS, and QT intervals and ECG morphology. QT interval was corrected for heart rate using Fridericia’s (QTcF) and Bazett’s (QTcB) formulae. Linear mixed-effects modeling was used to examine the relationship between QTc and RR interval change from baseline and plasma talazoparib concentration. Thirty-seven patients received talazoparib. Mean change in QTcF from time-matched baseline ranged from −3.5 to 6.9 ms, with the greatest change 1 h postdose on day 22. No clinically relevant changes in PR, QRS, QTcB, QTcF, or RR intervals, heart rate, or ECG morphology were observed. No concentration-dependent effect on heart rate or QTc was observed. No deaths, permanent treatment discontinuations due to adverse events were reported. Talazoparib (1 mg once daily) had no clinically relevant effects on cardiac repolarization.

Palbociclib and beyond for the treatment of HR + HER2- metastatic breast cancer: an Asian-Pacific perspective and practical management guide on the use of CDK4/6 inhibitors

Breast cancer is the most frequent cancer amongst women worldwide including in Asia where the incidence rate is rapidly increasing. Even with treatment, around 30% of patients with early breast cancer progress to metastatic disease, with hormone receptor positive (HR+) and human epidermal growth factor receptor 2 negative (HER2-) breast cancer the most common phenotype. First-line endocrine therapy targeting the estrogen receptor signaling pathway provides a median progression-free survival or time to progression of 6-15 months in HR + HER2- metastatic breast cancer. Recently, cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, combined with endocrine therapy, have achieved more than two years median progression-free survival in HR + HER2- metastatic breast cancer. However, the characteristics of the Asian breast cancer population differ from those of Western populations and need to be considered when selecting a suitable treatment. Breast cancer is diagnosed at a younger age in Asian populations and late stage at presentation is generally more common in low-/middle-income countries than high-income countries. Consequently, the proportion of premenopausal women with metastatic breast cancer is higher in Asian compared with Western populations. While CDK4/6 inhibitors have been approved in the USA (FDA) since 2015, experience with them in Asia is more limited. We review the experience with the CDK4/6 inhibitor palbociclib in Asian patients with HR + HER2- metastatic breast cancer and provide guidance on the use of palbociclib in these patients.

Cardiac arrhythmia considerations of hormone cancer therapies

Breast and prostate cancers are among the most prevalent cancers worldwide. Oestradiol and progesterone are major drivers for breast cancer proliferation, and androgens for prostate cancer. Endocrine therapies are drugs that interfere with hormone-activated pathways to slow cancer progression. Multiple new breakthrough drugs improving overall survival have recently been developed within this class. As the use of these latter drugs grows, incidence of cardiac arrhythmias has emerged as an unappreciated complication. These changes are not surprising given that sex hormones alter ventricular repolarization. Testosterone shortens action potential duration and QT interval duration, while oestradiol has an opposite effect. In patients with breast cancer, selective oestrogen receptor modulators are associated with more reports for long QT and torsade de pointes (TdP) than aromatase inhibitors, likely through an oestradiol-like effect on the heart. Cyclin-dependent kinase 4/6 inhibitors, a new class of anticancer drugs used in combination with endocrine therapies in hormone receptor positive breast cancer, are also variably associated with drug-induced long QT, particularly with ribociclib. In prostate cancer, androgen deprivation therapy is associated with long QT and TdP, and possibly atrial fibrillation for abiraterone. In this review, we have summarized the clinical and preclinical data focusing on cardiac arrhythmia considerations of hormone cancer therapies.

Different Cardiotoxicity of Palbociclib and Ribociclib in Breast Cancer: Gene Expression and Pharmacological Data Analyses, Biological Basis, and Therapeutic Implications

Breast cancer is the most frequent tumor in women. The recent advent of cyclin-dependent kinase (CDK) 4/6 inhibitors palbociclib and ribociclib has represented a major step forward for patients with hormone receptor-positive breast cancer. These two agents have showed similar efficacy in terms of breast cancer outcome but different cardiotoxic effects. In particular, ribociclib, but not palbociclib, has been associated with QT interval prolongation, and the mechanisms underlying this event are still unclear. In order to clarify such difference, we matched the candidate genes associated with QT interval prolongation with genes whose expression is altered following palbociclib or ribociclib treatment. We also investigated whether pharmacokinetic and pharmacodynamic characteristics, such as IC₅₀ (hERG) [concentration of drug producing 50% inhibition (human ether-à-go-go related gene)] and maximum concentration (C_max), could justify the different effects on QT interval prolongation. Our results show that ribociclib, but not palbociclib, could act by down-regulating the expression of KCNH2 (encoding for potassium channel hERG) and up-regulating SCN5A and SNTA1 (encoding for sodium channels Nav1.5 and syntrophin-α1, respectively), three genes associated with long QT syndrome. Consistent with the cardiotoxicity induced by ribociclib, its IC₅₀ (hERG)/free concentration (C_{max free}) ratio is closer to the safety threshold than that of palbociclib. In summary, we hypothesize that the different cardiotoxicity associated with ribociclib and palbociclib could be due to the alteration of potassium and sodium channels induced by ribociclib. A better comprehension of the mechanisms of cardiac channelopathies and drug-induced QT interval prolongation will be fundamental to avoid serious and potentially lethal adverse events and, as a consequence, optimize the management of breast cancer patients.

Kinases as potential targets for treatment of pulmonary hypertension and right ventricular dysfunction

Pulmonary hypertension (PH) is a progressive pulmonary vasculopathy that causes chronic right ventricular pressure overload and often leads to right ventricular failure. Various kinase inhibitors have been studied in the setting of PH and either improved or worsened the disease, highlighting the importance of understanding the specific role of the respective kinases in a spatiotemporal cellular context. In this review, we will summarize the knowledge on the role of kinases in PH and focus on druggable targets for which certain criteria are met: (a) deregulation of the kinase in PH; (b) small-molecule inhibitors are available (e.g. from the oncology field); (c) preclinical studies have shown their efficacy in PH models; and (d) when available, therapeutic exploitation in human PH has been initiated. Along this line, clinical considerations such as personalized medicine approaches to predict therapy response and adverse side events such as cardiotoxicity together with their clinical management are discussed. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Cyclin-dependent kinase 4/6 inhibitors for the management of advanced or metastatic breast cancer in women

PURPOSE

The pharmacology, clinical activity, safety, and place in therapy of the cyclin-dependent kinase (CDK) inhibitors palbociclib, ribociclib, and abemaciclib are reviewed.

SUMMARY

CDK 4 and CDK 6 are downstream agents in the estrogen signaling pathway that control entry into the cell cycle. CDK4/6 inhibition may prevent tumor cell progression in the cell cycle. Three CDK4/6 inhibitors (palbociclib, ribociclib, and abemaciclib) are available for women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer. These medications' indications in the treatment of HR+/HER2- advanced breast cancer include use with an aromatase inhibitor (AI) as initial therapy in postmenopausal women and with fulvestrant in women whose disease progressed during endocrine therapy. Ribociclib is also indicated as initial therapy with an AI in premenopausal or perimenopausal women and as initial therapy with fulvestrant in postmenopausal women. Abemaciclib is also indicated as monotherapy in women with disease progression after endocrine therapy and prior chemotherapy. A significant increase in progression-free survival (PFS) was seen with use of all 3 agents as initial therapy with an AI in controlled trials. Each agent also was demonstrated to produce a significant increase in PFS when used with fulvestrant in women whose disease progressed with prior endocrine therapy. Neutropenia is a dose-limiting adverse effect of palbociclib and ribociclib. Fatigue is more common with use of palbociclib and abemaciclib, and gastrointestinal effects are more common with abemaciclib use.

CONCLUSION

CDK4/6 inhibitors have significant demonstrated clinical activity in combination with AIs or fulvestrant in women with HR+/HER2- advanced or metastatic breast cancer and are becoming a standard of care in these patients.

Treatment of Advanced Hormone Receptor-Positive (HR+) HER2-negative Breast Cancer

The article gives an overview of current treatment options for metastatic hormone receptor-positive and HER2-negative breast cancer. The focus is on combined therapies, e.g., with CDK4/6 inhibition compared with purely endocrine-based therapies in the pre- and postmenopause, presenting the latest study results. The addition of a CDK4/6 inhibitor to endocrine-based therapy with an aromatase inhibitor or fulvestrant leads to a marked improvement in progression-free survival and is independently beneficial whether palbociclib, ribociclib or abemaciclib is involved. The particular clinical status of inhibition of cyclin-dependent kinases argues for its use in the first-line treatment of women with metastatic, hormone receptor-positive and HER2-negative breast cancer compared with the available purely endocrine-based therapies.

Prevention, Monitoring, and Management of Cardiac Dysfunction in Patients with Metastatic Breast Cancer

Cardiac monitoring is becoming an important part of breast cancer care. Breast cancer and cardiovascular disease (CVD) share many common risk factors, and it is estimated that by the median age of diagnosis, many patients with breast cancer will have established or subclinical CVD. In addition, a number of treatments for metastatic breast cancer are known to have cardiac effects. As such, there is a clear need to prevent, identify, and effectively manage cardiovascular events in patients with breast cancer. Current clinical practice for patients with metastatic breast cancer involves a comprehensive set of assessments to ensure efficacy and safety of treatment. Adding cardiac monitoring to the assessments already required for patients with breast cancer may improve survival and quality of life. Currently, cardiac monitoring is recommended for several breast cancer treatments, and guidelines related to cardiac monitoring are available. Here, we review the risk of CVD in patients with breast cancer, providing an overview of the cardiac events associated with standard therapies for metastatic breast cancer. We also assess the current clinical recommendations relating to cardiac monitoring, and practical management strategies for oncologists. Cardio-oncology is a growing medical subspecialty that promotes the need for effective cancer therapy while minimizing cardiac effects. Integrating cardiac monitoring into routine clinical practice may safeguard patients with metastatic breast cancer against adverse cardiac effects. IMPLICATIONS FOR PRACTICE: This review details the common risk factors associated with cardiovascular disease that are frequently observed in patients with metastatic breast cancer, as well as the adverse cardiac effects of many therapies that are commonly prescribed. The review also provides a rationale for routine and comprehensive cardiovascular assessment of all patients at baseline, and during and after therapy depending on the treatment and presence of risk factors for cardiovascular disease. The medical discipline of cardio-oncology is increasingly being recognized as an important part of clinical practice to ensure effective cancer therapy while maintaining cardiac health.

Cyclin-Dependent Kinases 4/6 Inhibitors in Breast Cancer: Current Status, Resistance, and Combination Strategies

Dysregulated activation of the cyclin-dependent kinases (CDKs) 4/6, leading to uncontrolled cell division, is hallmark of cancers. Further study of the cell cycle will advance the cancer treatment. As powerful and effective drugs, inhibitors of CDK 4/6 have been widely used in clinical practice for several malignancies, particularly against breast cancers driven by the estrogen receptor (ER). Three CDK4/6 inhibitors, including palbociclib (PD0332991), ribociclib (LEE011) and abemaciclib (LY2835219), have been approved by the US Food and Drug Administration (FDA) for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced or metastatic breast cancer. However, CDK4/6 inhibitors act downstream of many mitogenic signaling pathways, and this has implications for resistance. It is worth to note that the mechanisms of resistance are not very clear. Up to now, a small number of preclinical and clinical studies have explored potential mechanisms of CDK4/6 inhibitors resistance in breast cancer. On this basis, rational and effective combination therapy is under development. Here we review the current knowledge about the mechanisms and efficacy of CDK4/6 inhibitors, and summarize data on resistance mechanisms to make future combination therapies more accurate and reasonable.

Cardiotoxicities of Modern Treatments in Breast Cancer

PURPOSE OF REVIEW

This paper will focus on novel breast cancer therapies used in clinical practice today, as well as review our understanding of standard therapies and their potential impact on cardiovascular health.

RECENT FINDINGS

Established and novel treatments such as anthracyclines, HER2-targeted agents, and immunotherapy have contributed to improvements in breast cancer outcomes; however, these treatments may be associated with an increased risk of cardiovascular injury. The number of available breast cancer treatments continues to expand, as does the need for health care providers to understand the potential impact of these treatments on cardiovascular health. Collaborative approaches in the development of risk stratification, prevention, and surveillance strategies for patients exposed to established and novel breast cancer treatments will facilitate improvements in patient outcomes without compromising their cardiovascular health.

Palbociclib and ribociclib in breast cancer: consensus workshop on the management of concomitant medication

Drug-drug interactions are of significant concern in clinical practice in oncology, particularly in patients receiving Cyclin-dependent kinase (CDK) 4/6 inhibitors, which are typically exposed to long-term regimens. This article presents the highlights from the 'First Workshop on Pharmacology and Management of CDK4/6 Inhibitors: Consensus about Concomitant Medications'. The article is structured into two modules. The educational module includes background information regarding drug metabolism, corrected QT (QTc) interval abnormalities, management of psychotropic drugs and a comprehensive review of selected adverse effects of palbociclib and ribociclib. The collaborative module presents the conclusions of the five working groups, each of which comprised five experts from different fields. From these conclusions positive lists of drugs for treating common comorbid conditions that can be safely administered concomitantly with palbociclib and/or ribociclib were developed.

Long-term Pooled Safety Analysis of Palbociclib in Combination With Endocrine Therapy for HR+/HER2- Advanced Breast Cancer

BACKGROUND

Palbociclib administered with endocrine therapy was tolerable when the overall incidence of toxicities was assessed separately for three PALOMA studies. This study analyzed pooled, longer-term PALOMA safety data longitudinally.

METHODS

Data were pooled from three randomized phase II and III studies (ClinicalTrials.gov: NCT00721409, NCT01740427, NCT01942135) of hormone receptor-positive/human epidermal growth factor receptor 2‒negative advanced breast cancer patients. Front-line patients were randomly assigned to receive letrozole with/without palbociclib (PALOMA-1) or letrozole plus palbociclib/placebo (PALOMA-2). In PALOMA-3, patients with prior endocrine resistance received fulvestrant plus palbociclib/placebo. The cumulative event rates of adverse events (AEs), reporting up to 50 months of treatment, were assessed over time.

RESULTS

Patients who received endocrine therapy (n = 1343) were included in this pooled analysis (872 were also treated with palbociclib, and 471 were not). The most common AEs with palbociclib plus endocrine therapy were neutropenia and infections (any grade, 80.6% and 54.7%, respectively), which were higher than in the endocrine monotherapy arm (any grade, 5.3% and 36.9%). The most common hematologic AEs (≥15.0% in the palbociclib arm) were more likely to be reported in the initial months of the study, after which time the cumulative event rate did not substantially increase. With palbociclib plus endocrine therapy, any grade AEs leading to permanent discontinuation over three years occurred in only 8.3% of patients.

CONCLUSIONS

Based on these long-term safety analyses, there is no evidence of specific cumulative or delayed toxicities with palbociclib plus endocrine therapy, supporting the ongoing investigation of palbociclib plus endocrine therapy in early breast cancer (NCT02513394).

Management of Adverse Events Due to Cyclin-Dependent Kinase 4/6 Inhibitors

Cyclin-dependent kinase (CDK) 4/6 inhibitors have become standard of care in the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer. They have been shown to double the efficacy of endocrine-based treatment. Three oral agents are available to date: palbociclib, ribociclib, and abemaciclib. The aim of this article is to give a short overview of the existing efficacy data, to summarize the recommended clinical monitoring procedures for patients under CDK4/6 inhibitors, and to shed light on the clinical management of the most common treatment-emergent adverse events. The hematological class side effect neutropenia as well as non-hematological toxicities (e.g., impaired liver function, prolonged QTc interval, and diarrhea) are discussed. In addition, the current knowledge about relevant drug interactions is reviewed.

Comparative efficacy of palbociclib, ribociclib and abemaciclib for ER+ metastatic breast cancer: an adjusted indirect analysis of randomized controlled trials

BACKGROUND

Several trials have demonstrated the benefit of anti-CDK4/6 inhibitors plus endocrine therapy in estrogen receptor-positive (ER+) advanced breast cancer (BC), in first or subsequent lines of therapy. However, due to the lack of direct/indirect comparisons, there are no data demonstrating the superiority of one drug over the other. We compared the effectiveness of palbociclib, ribociclib, and abemaciclib in advanced ER + BC via an indirect adjusted analysis.

METHODS

We performed electronic searches in the PubMed, EMBASE, and Cochrane databases for prospective phase 3 randomized trials evaluating anti-CDK4/6 inhibitors plus endocrine agents. We compared the results with an adjusted indirect analysis of randomized-controlled trials. Outcomes of interest were progression-free survival (PFS), overall response rate (ORR) and G3-4 toxicities occurring in ≥ 5% of patients.

RESULTS

Six trials and six treatment arms including a total of 3743 participants, were included. For PFS and ORR analysis, the three agents were similar in both first- and second-line studies. All G3-4 toxicities were similar, with reduced risk of diarrhea for palbociclib versus abemaciclib (relative risk [RR] 0.13, 95% CI 0.02-0.92; P = 0.04) and of QTc prolongation for palbociclib versus ribociclib (RR 0.02, 95% CI 0-0.83; P = 0.03). Despite different inclusion criteria and length of follow-up, similar features were noticed among second-line studies with the exception of increased risk of anemia G3-4 and diarrhea G3-4 for abemaciclib.

CONCLUSIONS

Based on PFS and ORR results of this indirect meta-analysis, palbociclib, ribociclib, and abemaciclib are equally effective in either first- or second-line therapy for advanced ER + BC. They, however, ported different toxicity profiles.

Hormone receptor positive, HER2 negative metastatic breast cancer: Impact of CDK4/6 inhibitors on the current treatment paradigm

Resistance to endocrine therapy is a significant therapeutic challenge in the treatment of women with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer. Cyclin-dependent kinase (CDK)4/6 inhibitors in combination with endocrine therapy have been shown to improve progression free survival, overall response rate and clinical benefit rate in women with HR+ HER2- metastatic breast cancer compared with endocrine therapy alone. This review examines the clinical evidence to support the use of CDK4/6 inhibitors in first and second line settings. Practical guidance is provided for the use of CDK4/6 inhibitors, including tolerability data, monitoring requirements and management of key toxicities for each of the available agents.

Updates on managing advanced breast cancer with palbociclib combination therapy

BACKGROUND

The objective of this study was to review the pharmacology, efficacy, and safety of palbociclib, a first-in-class cyclin-dependent kinase 4/6 inhibitor, for the management of advanced breast cancer (ABC).

METHODS

Pharmacokinetics and drug interactions associated with palbociclib are described. Recent clinical trial data are reviewed, including patient-reported outcomes and subgroup analyses.

RESULTS

Palbociclib is indicated in combination with an aromatase inhibitor as initial endocrine therapy (ET) or with fulvestrant for patients with disease progression following ET for hormone receptor positive, human epidermal growth factor receptor 2 negative ABC or metastatic breast cancer. Palbociclib inhibits cyclin-dependent kinases 4/6, resulting in a blockade of phosphorylation of the retinoblastoma protein, which hinders the activation of transcription factors involved in S-phase entry, thereby arresting cell cycle progression at G1 phase. The efficacy and safety of palbociclib in combination with ET was established in three randomized trials (PALOMA-1, -2, and -3); all studies met their primary endpoint of significantly prolonging investigator-assessed progression-free survival versus ET alone. Findings were similar in subgroup analyses of the three PALOMA studies. Palbociclib plus ET also maintained health-related quality of life (QoL) compared with ET alone in PALOMA-2 and -3. A long-term safety profile for palbociclib, up to 3 years, has been established. Neutropenia, the most common any-grade and grade 3 or higher adverse event associated with palbociclib, is consistent with the drug's mechanism of action and can be effectively managed with dose interruption, dose reduction, or delay in starting treatment cycles.

CONCLUSIONS

Palbociclib in combination with ET improved progression-free survival and QoL in patients with ABC, including in several patient subgroups.

Management of adverse events during cyclin-dependent kinase 4/6 (CDK4/6) inhibitor-based treatment in breast cancer

Cyclin-dependent kinase (CDK) 4/6 inhibitors have shown great results in numerous clinical trials and have improved the clinical outcome for patients with hormone-receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer significantly. To date, three CDK4/6 inhibitors are approved by the US Food and Drug Administration (FDA): palbociclib, ribociclib and abemaciclib; the first two compounds are aproved by the European Medicines Agency (EMA) as well. In combination with endocrine therapy, all of them led to significantly improved progression-free survival compared with endocrine therapy alone. The aim of this article is to give an overview of the efficacy data and to describe the CDK4/6 inhibitor-based treatment-associated adverse events, including hematological and nonhematological adverse events. In addition, it describes the corrrect approach to patient monitoring and adverse event mangement and summarizes the current recommendations for dose reductions and dose interruptions regarding the key adverse events, such as neutropenia, diarrhea, QTc prolongation and hepatobiliary toxicity. Accurate patient monitoring and management of the side effects is crucial, as several clinical trials in early breast cancer are in progress and may lead to an additional approval in the neo-/adjuvant setting.