Dalpiciclib plus letrozole or anastrozole versus placebo plus letrozole or anastrozole as first-line treatment in patients with hormone receptor-positive, HER2-negative advanced breast cancer (DAWNA-2): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial

Safety and quality of life of CDK4/6 inhibitors therapy for hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer: a multicenter cross-sectional survey in China

BACKGROUND

To investigate the treatment pattern, adverse events, and quality of life of Chinese patients treated with CDK4/6 inhibitors (CDK4/6i) for hormone receptor (HR)+/HER2- advanced breast cancer.

METHODS

This multicenter cross-sectional survey enrolled patients with HR+/HER2- advanced breast cancer currently treated with CDK4/6i. The patients reported adverse events and quality of life during CDK4/6i treatment with a questionnaire and EORTC QLQ-BR23. Meanwhile, the oncologists collected the treatment information, adverse events and patient characteristics from medical record.

RESULTS

The analysis included 1254 patients. Most patients received only one CDK4/6i, of which 38.92% received dalpiciclib, 35.81% received abemaciclib, 15.07% received palbociclib, and 0.47% received ribociclib, while 9.73% patients were treated with two CDK4/6i sequentially. The oncologists reported adverse events occurred in > 81.17% of patients, and most common AEs were leukopenia (63.30%) and neutropenia (58.73%). The most common symptomatic adverse events reported by the patients were fatigue (34.13%), alopecia (14.02%) and weakness (11.30%). The incidence of alopecia in patients receiving dalpiciclib was lower than in those receiving palbociclib (8.81% vs. 16.40%, P < 0.001) and abemaciclib (8.81% vs. 19.82%, P = 0.027). Regard to quality of life, breast symptom scores were lower in the palbociclib group than in the abemaciclib group (3.84 ± 8.57 vs. 5.70 ± 9.81, P = 0.047). Patient reported alopecia was associated with body image, systemic therapy side effects, breast symptoms, arm symptoms, and upset by hair loss (all P < 0.001).

CONCLUSIONS

The safety profile of different CDK4/6i varies and has different impacts on patients' quality of life, which needs more attention in clinical practice.

A phase I dose-escalation and dose-expansion study of tibremciclib, a novel CDK4/6 inhibitor, monotherapy and in combination with fulvestrant in HR-positive/HER2-negative advanced breast cancer

BACKGROUND

Tibremciclib (BPI-16350) is a novel potent selective inhibitor of cyclin-dependent kinase 4 and 6 (CDK4/6). This phase I, first-in-human study assessed the tibremciclib monotherapy and combined with fulvestrant in advanced breast cancer (ABC).

PATIENTS AND METHODS

This open-label, phase I study (NCT03791112) comprised dose escalation (phase Ia) and expansion (phase Ib). In phase Ia, Chinese patients with advanced solid tumors received tibremciclib monotherapy (50-500 mg orally once daily). Based on the tolerability and preliminary antitumor activity from phase Ia, two dose cohorts (300 or 400 mg orally once daily) were selected in phase Ib to combine with fulvestrant in patients with hormone receptor (HR)-positive/human epidermal growth receptor 2 (HER2)-negative ABC who failed endocrine therapy. The primary endpoints were safety and tolerability, and secondary endpoints included pharmacokinetics (PK) and antitumor activity.

RESULTS

In phase Ia, 24 patients with advanced tumors (23 ABC and 1 abdominal liposarcoma) received tibremciclib monotherapy, while in phase Ib, 78 patients with HR-positive/HER2-negative stage IV ABC received tibremciclib plus fulvestrant, with a median age of 56.0 (range 26-66) years and 53.5 (range 33-71) years, respectively. In phase Ia, one dose-limiting toxicity (grade 3 blood creatinine increased) occurred at 500 mg and the maximum tolerated dose was not reached. In phase Ib, the recommended phase II dose (RP2D) was tibremciclib 400 mg plus fulvestrant 500 mg. Frequently reported treatment-emergent adverse events of any grade were grade 1-2 blood creatinine increased, hypertriglyceridemia, and anemia. PK demonstrates dose proportionality, a half-life of ∼35.9-51.1 h, and no drug-drug interaction with fulvestrant. In phase Ia, one patient achieved partial response (PR), with a confirmed objective response rate (ORR) of 4.2% and a disease control rate (DCR) of 70.8%. In phase Ib, 42 patients achieved PR, with an ORR of 53.8% and a DCR of 87.2%.

CONCLUSIONS

Tibremciclib monotherapy or combined with fulvestrant was well tolerated with the RP2D set at 400 mg plus fulvestrant 500 mg. PK was consistent with dose proportionality. Both regimens showed preliminary antitumor activity in patients with HR-positive/HER2-negative ABC, supporting further evaluation in a phase III study (NCT05433480).

Efficacy and safety of first-line CDK4/6 inhibitors plus AI therapy for patients with HR +/HER2- advanced breast cancer: a network meta-analysis

BACKGROUND

CDK4/6 inhibitors plus aromatase inhibitors (AI) significantly improve the therapeutic effect of initial treatment for HR + /HER2- advanced breast cancer. However, there is a lack of head-to-head randomized controlled trials involving the four CDK4/6 inhibitors in current clinical treatments. This article aims to compare the efficacy and safety of the four CDK4/6 inhibitors in previously untreated HR + /HER2- advanced breast cancer for a better clinical medication selection.

METHODS

We performed a systematic search on databases published up to May 19, 2024 in the PubMed, Embase, and Cochrane library, and we focused on the data of phase II/III trials that met inclusion criteria. Pooled data on progression-free survival (PFS), objective response rate (ORR), clinical benefit rate (CBR), all adverse events (AE), and 3/4 adverse events were analyzed using the fixed-effect consistency models.

RESULTS

Dalpiciclib plus AI showed the best survival benefit in PFS (SUCRA value 77.9%) for all patients. In terms of ORR and CBR, Abemaciclib plus AI were ranked the best benefit (89.3% and 68.9%, respectively). Furthermore, Abemaciclib plus AI was ranked at the top for prolonging PFS in majority of the subgroups. In terms of AEs and grade 3/4 AEs, dalpiciclib plus AI had the greatest probability (91.3% and 99.8%). Ribociclib plus AI had lowest adverse events (29.3%), and grade 3/4 adverse events of abemaciclib plus AI were the least (26.2%).

CONCLUSION

There was no statistically significant difference in PFS among the four CDK4/6 inhibitors. Dalpiciclib has the best therapeutic effect in PFS. Meanwhile, dalpiciclib has the highest risk of adverse events and the 3/4 adverse events incidence compared with the others.

Cyclin-dependent kinase 4 and 6 inhibitors in breast cancer treatment

Breast cancer is the second largest cancer in the world, and it has highest mortality rate in women worldwide. The aberrant activation of the cyclin-dependent kinase 4 and 6 (CDK4/6) pathway plays an important role in uncontrolled breast cancer cell proliferation. Therefore, targeting CDK4/6 to improve overall survival rates has been a strong interest in breast cancer therapeutics. Till date, four CDK4/6 inhibitors have been developed and approved for hormone receptor-positive and human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer therapies with great success. However, acquired resistance to CDK4/6 inhibitors has emerged and limits their effectiveness in breast cancer. In this review, we systematically discussed the mechanisms of resistance to CDK4/6 inhibitors including the cell cycle-specific and cell cycle-nonspecific mechanisms. Also, we analyzed combination strategies with other signaling inhibitors in clinical and preclinical settings that further expand the clinical application of CDK4/6 inhibitors in future breast cancer therapies.

Cardiovascular Events Associated with CDK4/6 Inhibitors: A Safety Meta-Analysis of Randomized Controlled Trials and a Pharmacovigilance Study of the FAERS Database

BACKGROUND

CDK4/6 inhibitors are highly valued, but the incidence of cardiovascular adverse events (CVAEs) associated with CDK4/6 inhibitors is not clear.

OBJECTIVE

Our aim was therefore to assess the risk of developing CVAEs associated with CDK4/6 inhibitors, by conducting a systematic review and meta-analysis of randomized controlled trials (RCTs), along with a pharmacovigilance study of the FDA Adverse Event Reporting System (FAERS) database.

METHODS

Eligible CVAEs were extracted from the ClinicalTrials.gov registry. A systematic search of electronic databases (PubMed, Embase, Cochrane Library, and important meetings) until 3 September 2023 was conducted. A disproportionality analysis was performed from the first quarter (Q1) of 2013 to Q1 of 2023 using data from the FAERS database. Study heterogeneity was assessed using the I2 statistic. Using Peto odds ratio (Peto OR) and inverse variance methods to calculate the risk and incidence of CVAEs associated with CDK4/6 inhibitors.

RESULTS

In total, 17 RCTs with 23,437 patients were included in our meta-analysis. During the follow-up period of 8.4-34.0 months, CDK4/6 inhibitors significantly increased the risk of CVAEs (Peto OR, 1.86, 95% confidence interval, 1.30-2.68, P < 0.01). The rates of hypertension and QT prolongation were 68.07 (62.87-73.27) and 57.15 (50.83-63.48) per 1000 patients, respectively. Moreover, we identified nine CVAEs that were not reported in RCTs. These included acute coronary syndrome, arrhythmia, lymphoedema, hot flush, vein rupture, thrombophlebitis migrans, embolism venous, angiopathy and intracardiac thrombus, which were found to be strongly correlated with CDK4/6 inhibitors. Furthermore, the risk of CVAEs varied depending on the specific CDK4/6 inhibitors used, its combination with different endocrine therapies, and the patient's treatment stage.

CONCLUSION

CDK4/6 inhibitors increase the risk of CVAEs, some of which may lead to serious consequences. Early recognition and management of CVAEs is of great importance in clinical practice.

REGISTRATION

PROSPERO registration number CRD42023462059.

Dalpiciclib plus aromatase inhibitor versus neoadjuvant chemotherapy for ER-positive, HER2-negative breast cancer

Background

The combination of cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i) with endocrine therapy (ET) has emerged as an effective alternative to neoadjuvant chemotherapy (NCT) for patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2 (HER2) -negative breast cancer (BC). This single-center study retrospectively evaluated the efficacy and safety of dalpiciclib combined with an aromatase inhibitor (AI) compared to NCT.

Methods

The clinicopathological data and treatment details of patients with HR+ HER2 negative BC who underwent either neoadjuvant endocrine therapy (NET) or NCT were collected from the Fourth Hospital of Hebei Medical University. The primary endpoint of the study was the Residual Cancer Burden (RCB), while secondary endpoints included breast pathological complete response (bpCR), clinical response rates (ORR), proliferation markers, and safety profiles.

Results

Between May 2022 and June 2023, a total of 36 patients were treated with dalpiciclib plus AI, while 137 patients received NCT for the final analysis. Prior to propensity score matching (PSM), the rates of RCB 0 were 0% in the NET group and 7.3% in the NCT group (p=0.205). The rates of bpCR were 2.8% for the NET group and 13.1% for the NCT group (p=0.142). The ORR was comparable between the two groups (p=0.397), as were the rates of BCS (p=0.608). Both treatment groups demonstrated significant reductions in Ki-67 levels, although the extent of reduction was similar (p=0.174). Notably, a Ki-67 level of ≤ 10% post-treatment was more prevalent in the NET group (p<0.0001). Only two patients in the NET group achieved a Preoperative Endocrine Prognostic Index (PEPI) 0 score. The incidence of grade 3-4 toxicities was significantly higher in the NCT group compared to the NET group (p<0.05). Following PSM, patients treated with dalpiciclib plus AI exhibited comparable clinical responses and a safety advantage relative to those receiving NCT.

Conclusion

This study indicates that the combination of dalpiciclib and AI elicits comparable responses and demonstrates improved safety profiles when compared to NCT in patients with HR+ HER2 negative breast tumors. Furthermore, RCB and pCR may not serve as optimal endpoints for evaluating the efficacy of CDK4/6i-based NET.

Bireociclib plus fulvestrant for HR+/HER2- advanced female breast cancer progressed on or after endocrine therapy: phase 3 BRIGHT-2 study interim analysis

The BRIGHT-2 study (NCT05077449) is a randomized, double-blind, placebo-controlled, phase 3 trial evaluating the efficacy and safety of bireociclib plus fulvestrant (BF) vs. placebo plus fulvestrant (F) in Chinese female patients with hormone receptor-positive (HR+)/HER2-negative (HER2-) advanced breast cancer (ABC) who had progressed on or after prior endocrine therapy (ET). Interim results were analyzed after 70% of progression-free survival (PFS) events across 64 centers in China between December 8, 2021, and March 28, 2023. Patients were randomized (2:1) to receive BF or F, with stratification based on visceral involvement (yes/no) and resistance to prior primary or secondary ET. As the primary outcome, PFS was significantly prolonged in the BF group (n = 204) (12.94 months; 95% CI: 11.07-not reached) compared to 7.29 months (95% CI: 5.45-11.04) in the F group (n = 101) (hazard ratio, 0.56; 95% CI: 0.39-0.80; p = 0.001). The objective response rate in the BF group was 39.7% in the intention-to-treat population. Grade ≥3 adverse events were more frequent in the BF group (64.7%) than in the F group (18.8%), with neutropenia, leukopenia, and anemia being the most common. These findings suggest that BF is a promising therapeutic option for patients with HR+/HER2- ABC following ET failure.

Comparative analysis of CDKI-related adverse events in older patients: a real-world data from the FDA adverse event reporting system database

BACKGROUND

Cyclin-dependent kinase 4 and 6 inhibitors (CDKIs) are effective and safe against advanced and metastatic breast cancer; however, limited information is available for older patients. We conducted an analysis of real-world data pertaining to the safety of older patients using the Adverse Event Reporting System (FAERS) database of the FDA.

RESEARCH DESIGN AND METHODS

We performed a disproportionality analysis to evaluate CDKI-related adverse events (AEs) in older adults administered abemaciclib, palbociclib, and ribociclib.

RESULTS

Data were from 2132, 36916, and 4328 case reports on abemaciclib, palbociclib, and ribociclib in older patients, respectively. Disproportionality analysis revealed 242, 295, and 439 drug-AE signals. The numbers of system organ classes (SOC) for abemaciclib, palbociclib, and ribociclib were 25, 27, and 26, respectively. We found several expected AE signals consistent with those in the drug instructions, such as nausea, neutropenia, and fatigue, for all CDKIs. Interstitial lung disease, thromboembolic events, and cardiac toxicity were also noteworthy. Unexpected AE signals, such as acute kidney injury, atrial fibrillation, and memory impairment associated with abemaciclib, ribociclib, and palbociclib, respectively, were identified.

CONCLUSION

Our results aligned with clinical observations, emphasizing possible CDKI-related AEs. Conducting future clinical research is essential to confirm AE-related differences among CDKIs in older individuals.

CDK4/6 as a Therapeutic Target in HR+/HER2- Breast Cancer Cells-Current Treatment Status

Breast cancer is the most frequently diagnosed neoplasm in the world. It can be classified into four main subtypes, each of them showing differences in the expression of hormone receptor (HR), human epidermal growth factor receptor 2 (HER2), and in cell metabolism. Since 2015, when The U.S. Food and Drug Administration (FDA) approved the first cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor that regulates the cell cycle, treatment of HR+/HER2- BC has become much more effective. Currently, palbociclib, ribociclib, and abemaciclib are more often used both in combination with endocrine therapy as well as in monotherapy. Their application has been extensively verified in many clinical trials such as PALOMA-1,2,3, MONALEESA-1,2,3,7, and MONARCH-1,2,3, which allowed the verification of differences in their effectiveness, dosage, and adverse effects. Subsequent studies, MonarchE and NATALEE, examined the role of these inhibitors as adjuvant therapy, as well as at verifying their safety. Moreover, dalpiciclib is being investigated in HR+/HER2- BC treatment. This article will summarize clinical efficacy, recommendations, and differences in toxicity profile between palbociclib, ribociclib, and abemaciclib and will also discuss the possibility of using dalpiciclib in the treatment of breast cancer.

Application status and research progress of targeted therapy drugs for hormone receptor-positive breast cancer

Breast cancer (BC) is the most common malignant tumor in women and the leading cause of cancer-related deaths in women. As one of the most common subtypes of breast cancer, patients with hormone receptor-positive (HR+) breast cancer usually experience disease progression over an extended period of time, triggering the search for therapeutic strategies other than endocrine therapy. In recent years, continuous research on various targets has led to dramatic changes in the treatment of hormone receptor-positive breast cancer patients, resulting in prolonged clinical survival. With the redefinition of human epidermal growth factor-2 (HER2) expression, more precise and individualized treatment is possible. This review comprehensively reviews targeted therapies and critical clinical trials for HR+ breast cancer and tracks the latest advances. It also provides valuable insights into the future direction of targeted therapies.

A meta-analysis and systematic review of different cyclin-dependent kinase 4/6 inhibitors in breast cancer

Objective

The objective of this study was to assess the effectiveness and safety of CDK4/6 inhibitors in the treatment of hormone receptor-positive (HR+) breast cancer by using meta-analysis.

Methods

To gather comprehensive and reliable data for our analysis, we systematically searched multiple databases for relevant studies. We utilized RevMan5.3 software to perform the meta-analysis.

Results

Following a rigorous screening and evaluation process, we ultimately included a total of 13 studies in our analysis. Our findings showed that compared to endocrine therapy alone, the combination of CDK4/6 inhibitors with endocrine therapy significantly increased both PFS [HR 0.54 (95%CI: 0.50, 0.58), P<0.00001], OS [HR 0.77 (95%CI: 0.50, 0.58), P<0.00001] and ORR [RR 1.39 (95% CI: 1.21, 1.60), P<0.00001). However, it was also found that CDK4/6 inhibitors caused adverse drug reactions related to the blood system and digestive system (P<0.0001).

Conclusions

Our meta-analysis demonstrates that the addition of CDK4/6 inhibitors to endocrine therapy can result in improved PFS and OS for HR+ breast cancer patients. Meanwhile, we recommend close monitoring and management of these potential side effects when utilizing these inhibitors in breast cancer treatment.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42023490499.

Recent advances in regulating the cell cycle through inhibiting CDKs for cancer treatment

The inhibition of cyclin-dependent kinases (CDKs) is considered a promising strategy for cancer treatment due to their role in cell cycle regulation. However, CDK inhibitors with no selectivity among CDK families have not been approved. A CDK inhibitor with high selectivity for CDK4/6 exhibited significant treatment effects on breast cancer and has become a heavy bomb on the market. Subsequently, resistance gradually decreased the efficacy of selective CDK4/6 inhibitors in breast cancer treatment. In this review, we first introduce the development of selective CDK4/6 inhibitors and then explain the role of CDK2 activation in inducing resistance to CDK4/6 inhibitors. Moreover, we focused on the development of CDK2/4/6 inhibitors and selective CDK2 inhibitors, which will aid in the discovery of novel CDK inhibitors targeting the cell cycle in the future.

Hepatic adverse events with CDK4/6 inhibitors: a systematic review combining meta-analysis and FAERS database

BACKGROUND

Cell-cycle protein-dependent kinase 4 and 6 inhibitors (CDK4/6is) in combination with endocrine therapy (ET) are widely used in patients with early and advanced breast cancer (BC). CDK4/6is also lead to numerous side effects. This study aims to elucidate the relationship between CDK4/6is and hepatotoxicities.

RESEARCH DESIGN AND METHODS

As of 31 March 2024, we conducted a systematic search of PubMed, Embase, and the Cochrane Library databases, as well as several oncology conference proceedings. We included 20 randomized controlled trials (RCTs) with 24,342 breast cancer (BC) patients and 400 cases from the FDA Adverse Event Reporting System (FAERS). Fixed-effect and random-effect models were used to calculate odds ratios (ORs) of hepatotoxicity in the RCTs, while Reporting Odds Ratios (RORs) were calculated for the FAERS data.

RESULTS

Overall, CDK4/6 inhibitors (CDK4/6is) were associated with significant hepatotoxicities compared to controls (OR = 1.76, 95%CI 1.40-2.22, I2 = 75%). Palbociclib, ribociclib, and abemaciclib exhibited significant hepatotoxicities, while dalpiciclib did not. FAERS data showed significant liver enzyme and organ toxicity signals for ribociclib and abemaciclib but not for palbociclib.

CONCLUSIONS

CDK4/6is increase the risk of hepatotoxicities in patients with BC. Palbociclib, ribociclib, and abemaciclib caused liver damage, while dalpiciclib did not. The most common manifestations were elevated ALT and AST levels.

Clinical efficacy and therapy response prediction of neoadjuvant dalpiciclib plus letrozole in postmenopausal patients with HR+/HER2- stage II-III breast cancer (DARLING 01): a single-arm, open-label, exploratory study

BACKGROUND

Hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer is the most common subtype of breast cancer, yet its response to traditional chemotherapy remains limited, posing a challenge in achieving optimal therapeutic outcomes. In this study, we aimed to evaluate the clinical efficacy and safety of dalpiciclib, a novel CDK4/6 inhibitor, combined with letrozole as neoadjuvant therapy (NAT) in postmenopausal patients with HR+/HER2- stage II-III breast cancer. Additionally, we explored potential predictive biomarkers for treatment response using gene analysis.

METHODS

This single-arm, open-label, exploratory phase II trial involved 35 postmenopausal women with HR+/HER2- breast cancer (ClinicalTrials.gov identifier NCT05512780). Patients received four cycles of dalpiciclib (125 mg/day for 3 weeks, followed by 1 week off) plus continuous letrozole (2.5 mg/day). The primary endpoint was objective response rate (ORR), and secondary endpoints included changes in Ki-67 expression, complete cell cycle arrest (CCCA) rate, residual cancer burden (RCB), and safety profiles. Gene expression profiling and least absolute shrinkage and selection operator (LASSO) regression were conducted to identify biomarkers predictive of response to NAT.

RESULTS

Among the 35 enrolled patients, 31 completed the full treatment course. Of the 29 patients with evaluable response data after 4 cycles, 16 achieved partial response (PR), resulting in an ORR of 55.2%. Following two weeks of treatment, the mean Ki-67 expression significantly decreased from a baseline of 17.5-1.8%, and CCCA was observed in 75% of patients. Grade ≥ 3 treatment-emergent adverse events (TEAEs) were mainly decreased neutrophil count (45.7%), with a median duration of 3 days. The NAT predictive model, developed using gene expression analysis and clinicopathological factors, achieved an area under the curve (AUC) of 0.928, indicating that TFRC, SCUBE2, and MMP11A could serve as novel predictive biomarkers for response to NAT.

CONCLUSIONS

Dalpiciclib combined with letrozole demonstrated promising antitumor activity and an acceptable safety profile in postmenopausal patients with HR+/HER2- breast cancer. The identification of TFRC, SCUBE2, and MMP11A as predictive biomarkers provides insights into the potential for personalized neoadjuvant treatment strategies.

TMEM45A enhances palbociclib resistance and cellular glycolysis by activating AKT/mTOR signaling pathway in HR+ breast cancer

Palbociclib, a CDK4/6 inhibitor, plays a crucial role in the treatment of HR+ breast cancer. However, resistance to palbociclib is a significant concern that merits further investigation. Our investigation identifies TMEM45A as a potential driver of palbociclib resistance and its association with increased cellular glycolysis. We demonstrate that TMEM45A is highly expressed in palbociclib-resistant breast cancer (BRCA) cells, correlating with enhanced tumor progression. Silencing TMEM45A enhances sensitivity to palbociclib, promotes cell cycle arrest and apoptosis, and inhibits the proliferation of BRCA cells. Moreover, attenuation of TMEM45A expression reduces cancer aggressiveness by decreasing the expression of EMT and glycolysis-related proteins. Subsequent gene set enrichment analysis (GSEA) confirms that TMEM45A activates the AKT/mTOR signaling pathway, which is integral to cell cycle progression and glycolysis. In a cell line-derived xenograft (CDX) mouse model, TMEM45A knockdown significantly restores sensitivity to palbociclib and suppresses tumor growth. Additionally, the use of engineered exosomes loaded with siRNA targeting TMEM45A presents a promising strategy for enhancing CDK4/6 inhibitor sensitivity without observable toxic side effects in a patient-derived xenograft (PDX) model. Collectively, our findings suggest that TMEM45A may be a therapeutic target for overcoming palbociclib resistance, and exosomal siRNA delivery could be a viable strategy for precision medicine in HR+ breast cancer.

Efficacy and Safety of CDK4/6 Inhibitors: A Focus on HR+/HER2- Early Breast Cancer

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have revolutionized the treatment of hormone-receptor positive (HR+), HER2 negative (HER2-) metastatic breast cancer, and are now also established agents in the treatment of high-risk and intermediate-risk HR+ early breast cancer. Several strategies regarding CDK4/6i combinations or continuation beyond progression have been successfully evaluated in the metastatic setting, and are considered a standard of care. Mechanism of action of and resistance mechanisms against CDK4/6i in addition to endocrine resistance represent an important research topic, important for the treatment of HR+ breast cancer. Clinically, CDK4/6i are efficient substances that are usually well tolerated. However, side effects differing between the substances have been reported, and might lead to treatment discontinuation, including in the early disease setting. In the adjuvant setting, the addition of palbociclib to standard endocrine treatment has not improved outcomes, whereas large randomized phase III trials have demonstrated significant disease-free survival benefit for the addition of ribociclib (NATALEE trial) and abemaciclib (monarchE trial). Patient selection, treatment duration, endocrine backbone therapy, and other study details differ between these pivotal trials. This review focuses on both the scientific background as well as all available clinical data of CDK4/6i, with particular emphasis on their use in early breast cancer.

Targeting CDK4/6 in breast cancer

Dysregulation of the cell cycle machinery, particularly the overactivation of cyclin-dependent kinases 4 and 6 (CDK4/6), is a hallmark of breast cancer pathogenesis. The introduction of CDK4/6 inhibitors has transformed the treatment landscape for hormone receptor-positive breast cancer by effectively targeting abnormal cell cycle progression. However, despite their initial clinical success, drug resistance remains a significant challenge, with no reliable biomarkers available to predict treatment response or guide strategies for managing resistant populations. Consequently, numerous studies have sought to investigate the mechanisms driving resistance to optimize the therapeutic use of CDK4/6 inhibitors and improve patient outcomes. Here we examine the molecular mechanisms regulating the cell cycle, current clinical applications of CDK4/6 inhibitors in breast cancer, and key mechanisms contributing to drug resistance. Furthermore, we discuss emerging predictive biomarkers and highlight potential directions for overcoming resistance and enhancing therapeutic efficacy.

Influence of ethnicity on cyclin-dependent kinase inhibitor efficacy and toxicity: A systematic review and meta-analysis

BACKGROUND

The combination of cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) with endocrine therapy (ET) is the standard of care for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (aBC). While the efficacy and safety profiles of CDK4/6i and ET have been extensively evaluated in phase II and III trials worldwide, it remains unclear whether the response to CDK4/6i and toxicity profile vary among Asian and non-Asian patients. Therefore, we aimed to assess the treatment efficacy of ET with and without CDK4/6i by comparing outcomes in Asian and non-Asian subgroups included in these clinical trials. In addition, we evaluated the toxicity profiles of the treatments by estimating the risk of treatment-related adverse events (AEs).

METHODS

We conducted a meta-analysis including the most recent randomized trial data systematically searched from PubMed, Embase, Web of Science, Cochrane CENTRAL (from inception to May 31st, 2024) or presented in abstracts or oral presentations at the ESMO, ASCO, and SABCS international congresses. We included studies comparing CDK4/6i (palbociclib, ribociclib, abemaciclib, dalpiciclib) + ET versus placebo + ET. Progression-free survival (PFS) and overall survival (OS), hazard ratios (HR), and 95 % confidence intervals (CI) were extracted for the two subgroups of interest. To evaluate the treatment-related toxicity profiles, we extracted the number of side effects to estimate the risk of treatment-emergent AEs.

RESULTS

Eleven studies (n = 5129) were included in this meta-analysis. The addition of CDK4/6i to ET consistently improved PFS in both Asian (HR = 0.52, 95 % CI 0.47-0.60; p < 0.001) and non-Asian (HR = 0.58, 95 % CI 0.52-0.64; p < 0.001) groups. Similarly, the combination of CDK4/6i + ET led to an OS improvement in both Asian (HR = 0.75, 95 % CI 0.62-0.91; p = 0.003) and non-Asian (HR = 0.81, 95 % CI 0.73-0.89; p < 0.001) patients. The risk of treatment related toxicity was higher in the CDK4/6i + ET arm in both Asian and non-Asian groups. Interestingly, a numerically higher rate of treatment-related hematological toxicity was observed in Asian patients, although no significant interethnic difference was found in the relative risk of these events.

CONCLUSIONS

The combination of CDK4/6i and ET significantly improves PFS and OS compared to ET alone in both Asian and non-Asian patients with HR+/HER2-aBC. Although the magnitude of benefit appears to be independent of ethnicity, future clinical trials should devise a standardized method for stratifying patients by ethnicity to more effectively assess potential differences in treatment benefits.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42024543217.

Cyclin-dependent protein kinases and cell cycle regulation in biology and disease

Cyclin Dependent Kinases (CDKs) are closely connected to the regulation of cell cycle progression, having been first identified as the kinases able to drive cell division. In reality, the human genome contains 20 different CDKs, which can be divided in at least three different sub-family with different functions, mechanisms of regulation, expression patterns and subcellular localization. Most of these kinases play fundamental roles the normal physiology of eucaryotic cells; therefore, their deregulation is associated with the onset and/or progression of multiple human disease including but not limited to neoplastic and neurodegenerative conditions. Here, we describe the functions of CDKs, categorized into the three main functional groups in which they are classified, highlighting the most relevant pathways that drive their expression and functions. We then discuss the potential roles and deregulation of CDKs in human pathologies, with a particular focus on cancer, the human disease in which CDKs have been most extensively studied and explored as therapeutic targets. Finally, we discuss how CDKs inhibitors have become standard therapies in selected human cancers and propose novel ways of investigation to export their targeting from cancer to other relevant chronic diseases. We hope that the effort we made in collecting all available information on both the prominent and lesser-known CDK family members will help in identify and develop novel areas of research to improve the lives of patients affected by debilitating chronic diseases.

CDK4/6 Inhibitor Resistance in ER+ Breast Cancer

The cyclin-dependent kinases 4 and 6 inhibitors are the mainstay of treatment for patients with hormone receptor-positive and HER2-negative breast cancer. The ability of these drugs to improve the outcome of patients both in the metastatic and the early setting has been largely demonstrated. However, resistance, either de novo or acquired, represents a major clinical challenge. In the past years, efforts have been made to identify biomarkers that might help in a better selection of patients or to unravel the mechanisms leading to resistance in order to develop new therapeutic strategies to overcome it. Alterations of cell cycle-related genes and proteins are among the best characterized markers of resistance, and pathways impacting the cell cycle, including nuclear and growth factor receptors signaling, have been thoroughly investigated. Despite this, to date, cyclin-dependent kinases 4 and 6 inhibitors are administered based only on the hormone receptor and HER2 status of the tumor, and patients progressing on therapy are managed with currently available treatments. Here we summarize present knowledge on the cyclin-dependent kinases 4 and 6 inhibitors' mechanisms of action, efficacy data, and mechanisms of resistance.

Association between cyclin-dependent kinase 4/6 inhibitors and nephrotoxicity in patients with breast cancer: A Systematic Review and meta-analysis

Nephrotoxic adverse events (AEs) have been observed in patients with breast cancer receiving cyclin-dependent kinase (CDK) 4/6 inhibitors. This study aimed to evaluate the risk of nephrotoxicity associated with these inhibitors through a meta-analysis of 17 randomized controlled trials involving 19,638 patients. The results indicate a significant increase in all-grade nephrotoxic AEs, including elevated blood creatinine levels, acute kidney injury, and renal impairment (RR = 3.12, 95% CI [2.11, 4.63]). The incidence of grade 3 or higher nephrotoxicity was also more prevalent among treated patients (RR = 3.12, 95% CI [1.74, 5.58]). Subgroup analyses revealed varying risks among 4 different CDK 4/6 inhibitors. Furthermore, analysis of FDA Adverse Event Reporting System data corroborated these findings, emphasizing the occurrence of nephrotoxicity in real-world settings. Clinicians should remain vigilant in monitoring renal function indicators when prescribing CDK4/6 inhibitors.

Real-world comparison of palbociclib, abemaciclib, and dalpiciclib as first-line treatments for Chinese HR+/HER2-metastatic breast cancer patients: a multicenter study (YOUNGBC-28)

Background

In recent years, the combination of CDK4/6 inhibitors (CDK4/6i) and endocrine therapy (ET) has emerged as the standard first-line treatment for hormone receptor positive (HR+) and human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (MBC) patients. However, the comparison between the efficacy of CDK4/6i has been poorly explored before. Moreover, it remains unclear about the optimal choice of CDK4/6i in the first-line treatment for HR+/HER2- MBC patients in Asian, especially Chinese populations.

Objectives

Our study aims to compare the efficacy of three CDK4/6i widely used in the Chinese population (palbociclib, abemaciclib, and dalpiciclib) in the real world.

Design

From 2020 to 2023, the medical records of patients diagnosed with HR+/HER2- MBC were retrospectively assessed in seven institutions in China. Patients who received first-line palbociclib, abemaciclib, or dalpiciclib plus ET were included.

Methods

Demographic and clinical data were retrospectively collected and analyzed. Real-world progression-free survival (rwPFS), overall survival (OS), and objective response rate were used to analyze the clinical outcome.

Results

In total, 209 HR+/HER2- MBC patients were eligible for this study. Eighty-eight (42.1%), 79 (37.8%), and 42 (20.1%) patients were administered first-line palbociclib, abemaciclib, or dalpiciclib plus ET. The overall median rwPFS was 19 months, with no significant difference between these three CDK4/6i (p = 0.84). The results were similar even after propensity score matching. The median OS was not reached. Cox univariate and multivariate regression analysis identified that higher KI67 index, liver metastasis, and primary endocrine resistance were independent risk factors for rwPFS in patients with initial CDK4/6i plus ET.

Conclusion

This study presents a comparison of the real-world efficacy between three CDK4/6i widely used in the Chinese population. Palbociclib, abemaciclib, and dalpiciclib demonstrated comparable efficacy in Chinese patients with advanced HR+/HER2- MBC.

Trial registration

ClinicalTrials.gov identifier: NCT06344780.

Targeting RTKs/nRTKs as promising therapeutic strategies for the treatment of triple-negative breast cancer: evidence from clinical trials

The extensive heterogeneity and the limited availability of effective targeted therapies contribute to the challenging prognosis and restricted survival observed in triple-negative breast cancer (TNBC). Recent research indicates the aberrant expression of diverse tyrosine kinases (TKs) within this cancer, contributing significantly to tumor cell proliferation, survival, invasion, and migration. The contemporary paradigm shift towards precision medicine has highlighted TKs and their receptors as promising targets for pharmacotherapy against a range of malignancies, given their pivotal roles in tumor initiation, progression, and advancement. Intensive investigations have focused on various monoclonal antibodies (mAbs) and small molecule inhibitors that specifically target proteins such as epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor (VEGFR), cellular mesenchymal-epithelial transition factor (c-MET), human epidermal growth factor receptor 2 (HER2), among others, for combating TNBC. These agents have been studied both in monotherapy and in combination with other chemotherapeutic agents. Despite these advances, a substantial terrain of unexplored potential lies within the realm of TK targeted therapeutics, which hold promise in reshaping the therapeutic landscape. This review summarizes the various TK targeted therapeutics that have undergone scrutiny as potential therapeutic interventions for TNBC, dissecting the outcomes and revelations stemming from diverse clinical investigations. A key conclusion from the umbrella clinical trials evidences the necessity for in-depth molecular characterization of TNBCs for the maximum efficiency of TK targeted therapeutics, either as standalone treatments or a combination. Moreover, our observation highlights that the outcomes of TK targeted therapeutics in TNBC are substantially influenced by the diversity of the patient cohort, emphasizing the prioritization of individual patient genetic/molecular profiles for precise TNBC patient stratification for clinical studies.

Beyond clinical trials: CDK4/6 inhibitor efficacy predictors and nomogram model from real-world evidence in metastatic breast cancer

Background

CDK4/6 inhibitors (CDK4/6i) have shown promising results in the treatment of hormone receptor-positive (HR+) metastatic breast cancer (MBC) when combined with endocrine therapy (ET). It is crucial to evaluate the actual effectiveness and safety of CDK4/6i in clinical practice, as well as to analyze the factors that can predict their outcomes.

Methods

Patients with HR+ MBC who received CDK4/6i-based therapy between May 2016 and May 2023 at Hunan Cancer Hospital were evaluated for progression-free survival (PFS). Adverse reactions were assessed based on the National Cancer Institute Common Toxicity Criteria (version 5.0).

Results

This study included 344 patients, with a median PFS (mPFS) of 12.8 months (range: 10.4-15.2 months). After adjustment, Cox multivariate regression analysis revealed that visceral metastasis (specifically liver and brain metastases), Eastern Cooperative Oncology Group Performance Status (ECOG PS) ≥ 1, estrogen receptor ≤ 80%, progesterone receptor ≤ 10%, Ki-67 > 30%, and treatment in later stages were significant factors associated with reduced PFS. Based on this, we created a prognostic nomogram and validated its performance, obtaining a C-index of 0.714 (95% confidence interval: 0.640-0.787) as well as reliable calibration and clinical impact. The mPFS of CDK4/6i rechallenge was 7.7 months; for patients who initially discontinued CDK4/6i for reasons other than disease progression, CDK4/6i rechallenge still provided a mPFS of 11.4 months. The tolerability and safety of combining CDK4/6is with ET were manageable. Adverse events led to treatment discontinuation in 3.8% of patients. Neutropenia (29.1%), leukopenia (13.7%), and anemia (4.1%) were the primary grade 3/4 adverse reactions.

Conclusions

This real-world study highlights the ample efficacy and reasonable safety of combined CDK4/6i and ET in patients with HR+ MBC. Individualized treatment decisions and ongoing safety monitoring are important to optimize the therapeutic benefit of CDK4/6i treatment.

Dose reduction and discontinuation due to the combination of CDK4/6 inhibitors and endocrine drugs: a systematic review and meta-analysis

BACKGROUND

With the widespread use of CDK4/6 inhibitors, the number of discontinuations and reductions due to adverse events is increasing. Therefore, we examined the risk of dose reduction, discontinuation, and occurrence of serious adverse events and death due to adverse events when CDK4/6 inhibitors are combined with endocrine drugs.

METHODS

We searched English-language articles published up to February 10, 2024, using RR values (risk ratio) to indicate the risk of discontinuation, dose reduction, death, and the risk of serious adverse events.

RESULTS

When CDK4/6 inhibitors were used in combination with endocrine drugs, abemaciclib resulted in the highest risk of discontinuation, dose reduction, and serious adverse events. Ribociclib caused the highest risk of death.

CONCLUSION

When using CDK4/6 inhibitors in the clinical setting, a comprehensive evaluation should be performed to avoid dosage reductions and discontinuations and to choose the most appropriate treatment regimen.

Nanomaterials: breaking the bottleneck of breast cancer drug resistance

Drug resistance poses a significant challenge in the treatment of breast cancer. In recent years, a variety of nanomaterials have been discovered and synthesized that can selectively target tumor cells and play a crucial role in the advancement of breast cancer therapies. As our understanding of tumor heterogeneity deepens, the emerging potential of nanomaterials in addressing drug resistance has garnered considerable attention. These materials not only selectively target tumor cells but also possess unique properties that make them promising options for cancer treatment, including low toxicity, excellent biocompatibility, ease of preparation, the ability to carry antitumor drugs, and customizable surface functions. In this review, we will comprehensively summarize two key developments in breast cancer treatment: the application of antitumor drugs and nanomaterials. We will explore the mechanisms by which nanomaterials improve drug resistance in breast cancer, targeted nanotherapy strategies to mitigate this resistance, and recent research advancements in anticancer nanomaterials. This overview aims to highlight the significant role of nanomaterials in breast cancer treatment and provide a theoretical framework for identifying optimal treatment strategies in the future.

Low-dose apatinib in combination with chemotherapy for hormone receptor-positive, HER2-negative breast cancer with pulmonary lymphangitic carcinomatosis: A case report

RATIONALE

Hormone receptor-positive, HER2-negative advanced breast cancer complicated by pulmonary lymphangitic carcinomatosis (PLC) poses significant therapeutic challenges due to the lack of standardized treatment protocols. Despite various therapeutic interventions and supportive care, prognosis remains dismal.

PATIENT CONCERNS

Herein, a 48-year-old Chinese woman presented with a persistent cough, unresponsive to anti-infective treatment for 1 month. A computed tomography (CT) scan revealed lymphatic vessel infiltration and a diffuse nodular pattern, suggestive of PLC.

DIAGNOSES

Hormone receptor-positive, HER2-negative advanced breast cancer complicated by PLC.

INTERVENTIONS

The patient was treated with a regimen comprising low-dose apatinib, capecitabine, and albumin-bound paclitaxel.

OUTCOMES

The patient achieved a partial response, with a progression-free survival exceeding beyond ten months. Symptoms of dyspnea and dry cough significantly improved, alongside a notable reduction in lymphangitic carcinomatosis.

LESSONS

This case highlights the potential antitumor activity of apatinib in breast cancer patients with presenting with PLC. While further studies are necessary, this therapeutic approach could represent a viable option for managing breast cancer in the context of a visceral crisis. The case also emphasizes the importance of individualized treatment strategies and further research to substantiate these promising findings.

First- vs second-line CDK 4/6 inhibitor use for patients with hormone receptor positive, human epidermal growth-factor receptor-2 negative, metastatic breast cancer in the real world setting

PURPOSE

To compare CDK4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) in the first- versus second-line setting for treatment of hormone receptor positive (HR+), HER2 negative, metastatic breast cancer (MBC) using real-world evidence.

METHODS

Patients with HR+, HER2 negative MBC, diagnosed between 2/3/2015 and 11/2/2021 and having ≥ 3 months follow-up were identified from the nationwide electronic health record-derived Flatiron Health de-identified database. Treatment cohorts included: (1) first-line ET with a CDK 4/6i (1st-line CDK4/6i) versus (2) first-line ET alone followed by second-line ET with a CDK4/6i (2nd-line CDK4/6i). Differences in baseline characteristics were tested using chi-square tests and two-sample t-tests. Time to third-line therapy, time to start of chemotherapy, and overall survival were compared using Kaplan-Maier method.

RESULTS

The analysis included 2771 patients (2170 1st-line CDK4/6i and 601 2nd-line CDK4/6i). Patients receiving 1st-line CDK4/6i were younger (75% vs 68% < 75 years old, p = 0.0001), less likely uninsured or not having insurance status documented (10% vs. 13%, p = 0.04), of better performance status (50% vs 43% with ECOG 0, p = 0.03), and more likely to have de novo MBC (36% vs. 24%, p < 0.001). Time to third-line therapy (49 vs 22 months, p < 0.001) and time to chemotherapy (68 vs 41 months, p < 0.001) were longer in those receiving first-line CDK4/6i. Overall survival (54 vs 49 months, p = 0.33) was similar between groups.

CONCLUSION

Use of CDK4/6i with first-, vs second-, line ET was associated with longer time to receipt of 3rd-line therapy and longer time to receipt of chemotherapy.

Advances in the mechanism of CDK4/6 inhibitor resistance in HR+/HER2- breast cancer

Among women, breast cancer is the most prevalent form of a malignant tumour. Among the subtypes of breast cancer, hormone receptor (HR) positive and human epidermal growth factor receptor (HER2) negative kinds make up the biggest proportion. The advent of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, which are dependent on cell cycle proteins, has greatly enhanced the prognosis of patients with advanced HR+/HER2- breast cancer. This is a specific treatment that stops the growth of cancer cells by preventing them from dividing. Nevertheless, the drug resistance of the disease unavoidably impacts the effectiveness of treatment and the prognosis of patients. This report provides a thorough analysis of the current research advancements about the resistance mechanism of CDK4/6 inhibitors in HR+/HER2- breast cancer. It presents an in-depth discussion from numerous viewpoints, such as aberrant cell cycle regulation and changes in signalling pathways. In response to the drug resistance problem, subsequent treatment strategies are also being explored, including switching to other CDK4/6 inhibitor drugs, a combination of novel endocrine therapeutic agents, an optimal combination of targeted therapies and switching to chemotherapy. An in-depth study of the resistance mechanism can assist in identifying creative tactics that can overcome or postpone drug resistance, alleviate the problem of restricted treatment strategies following drug resistance and enhance the prognosis of patients.

Dalpiciclib in combination with letrozole/anastrozole or fulvestrant in HR-positive and HER2-negative advanced breast cancer: results from a phase Ib study

Background

Dalpiciclib is a novel cyclin-dependent kinase 4/6 inhibitor which showed tolerability and preliminary efficacy as monotherapy for pretreated advanced breast cancer (BC).

Objectives

To further assess dalpiciclib with endocrine therapy (ET) in hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative BC.

Design

A multicenter, open-label, phase Ib trial.

Methods

Patients with locally recurrent or metastatic BC were enrolled in five cohorts. Patients without prior treatment for advanced disease (cohorts 1-2) were given dalpiciclib (125 or 150 mg) plus letrozole/anastrozole; patients who progressed after ET (cohorts 3-5) were given dalpiciclib (125, 150, or 175 mg) plus fulvestrant. Dalpiciclib was administered orally once daily in 3-weeks-on/1-week off schedule. The primary endpoint was safety.

Results

A total of 58 patients received dalpiciclib with letrozole/anastrozole and 46 received dalpiciclib with fulvestrant. No maximum tolerated dose of dalpiciclib was reached with letrozole/anastrozole or fulvestrant. Across all cohorts, 86.7%-93.8% of patients had a grade ⩾3 adverse event, with the most common being neutropenia (grade 3, 40.0% for dalpiciclib 175 mg and 61.8%-87.5% for lower doses; grade 4, 46.7% and 4.2%-20.6%, respectively) and leukopenia (grade 3, 80.0% for 175 mg and 33.3%-54.2% for lower doses; grade 4, 0% for all doses). At tested dose levels, steady-state areas under the concentration curve and peak concentration of dalpiciclib increased with dose when combined with letrozole/anastrozole and fulvestrant. Dalpiciclib at 150 mg was associated with a numerically higher objective response rate in both patients untreated for advanced disease (67.6%; 95% confidence interval (CI) 49.5-82.6) and patients progressing after ET (53.3%; 95% CI 26.6-78.7); as of July 30, 2022, the median progression-free survival with dalpiciclib 150 mg was 24.1 months (95% CI 16.9-46.0) with letrozole/anastrozole and 16.7 months (95% CI 1.9-24.1) with fulvestrant.

Conclusion

Dalpiciclib plus letrozole/anastrozole or fulvestrant showed an acceptable safety profile. The recommended phase III dose of dalpiciclib was 150 mg.

Trial registration

ClinicalTrials.gov identifier: NCT03481998.

QTc prolongation across CDK4/6 inhibitors: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Cyclin-dependent kinases (CDK) 4/6 inhibitors have significantly improved outcomes for patients with ER+/HER2- breast cancer. Nevertheless, they differ from each other in terms of chemical, biological, and pharmacological features, as well as toxicity profiles. We aim to determine whether QTc prolongation is caused by CDK4/6i in general or if it is associated with ribociclib only.

METHODS

We systematically searched PubMed, Embase, and Cochrane Library for randomized controlled trials (RCTs) comparing the prevalence of QTc prolongation as an adverse event in HR+ breast cancer patients treated with CDK4/6i vs those without CDK4/6i. We pooled relative risk (RR) and mean difference (MD) with 95% confidence interval (CI) for the binary endpoint of QT prolongation.

RESULTS

We included 14 RCTs comprising 16 196 patients, of whom 8576 underwent therapy with CDK4/6i. An increased risk of QTc prolongation was associated with the use of CDK4/6i (RR = 2.35, 95% CI = 1.67 to 3.29, P < .001; I2 = 44%). Subgroup analyses revealed a significant increase in the QTc interval for the ribociclib and palbociclib cohorts. The ribociclib subgroup showed a relative risk of 3.12 (95% CI = 2.09 to 4.65, P < .001; I2 = 12%), whereas the palbociclib subgroup had a relative risk of 1.51 (95% CI = 1.05 to 2.15, P = .025; I2 = 0%).

CONCLUSION

Palbociclib was associated with QTc prolongation; however, the relative risk for any grade QTc was quantitively twice with ribociclib. Furthermore, grade 3 QTc prolongations were observed exclusively with ribociclib. These results are important for guiding clinical decision-making and provide reassurance regarding the overall safety profile of this drug class.

Mechanisms of sensitivity and resistance to CDK4/CDK6 inhibitors in hormone receptor-positive breast cancer treatment

Cell cycle dysregulation is a hallmark of cancer that promotes eccessive cell division. Cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6) are key molecules in the G1-to-S phase cell cycle transition and are crucial for the onset, survival, and progression of breast cancer (BC). Small-molecule CDK4/CDK6 inhibitors (CDK4/6i) block phosphorylation of tumor suppressor Rb and thus restrain susceptible BC cells in G1 phase. Three CDK4/6i are approved for the first-line treatment of patients with advanced/metastatic hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) BC in combination with endocrine therapy (ET). Though this has improved the clinical outcomes for survival of BC patients, there is no established standard next-line treatment to tackle drug resistance. Recent studies suggest that CDK4/6i can modulate other distinct effects in both BC and breast stromal compartments, which may provide new insights into aspects of their clinical activity. This review describes the biochemistry of the CDK4/6-Rb-E2F pathway in HR+ BC, then discusses how CDK4/6i can trigger other effects in BC/breast stromal compartments, and finally outlines the mechanisms of CDK4/6i resistance that have emerged in recent preclinical studies and clinical cohorts, emphasizing the impact of these findings on novel therapeutic opportunities in BC.

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.

CDK4/6 inhibitors plus endocrine therapy vs. placebo plus endocrine therapy for HR+/HER2- advanced breast cancer: a phase III RCTs based meta-analysis

BACKGROUND

Does incorporating Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors into endocrine therapy (ET) effectively enhance survival outcomes, notably overall survival (OS), among individuals with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer? This remains a clinical controversy. We compared the antitumor efficacy and adverse effects (AEs) between CDK4/6 inhibitors + ET (CET) and placebo + ET (PET) by conducting a phase III randomized controlled trials (RCTs) based meta-analysis.

METHODS

Seven databases were searched to identify eligible studies, comprising Phase III RCTs comparing CET to PET. The primary endpoints were OS and progression-free survival (PFS), with secondary endpoints including responses and adverse events (AEs).

RESULTS

Seven RCTs (DAWNA-2, MONALEESA-2, MONALEESA-3, MONALEESA-7, MONARCH-3, PALOMA-2, and PALOMA-4) were included. The CET group exhibited significantly improved OS (HR: 0.81 [0.74, 0.88]), PFS (HR: 0.57 [0.52, 0.63]), objective response rate (RR: 1.31 [1.20, 1.43]), and clinical benefit rate (RR: 1.11 [1.07, 1.15]). These benefits were consistent across almost all subgroups. Additionally, the CET group showed better overall survival rates (OSR) from 24 to 60 months (OSR 24-60 m) and progression-free survival rates (PFSR) from 6 to 60 months (PFSR 6-60 m). However, more total AEs, grade 3-5 AEs, and serious AEs were found in CET group. The top 5 grade 3-5 AEs in the CET group were neutropenia (59.39%), leukopenia (24.11%), decreased white blood cell count (12.99%), hypertension (7.03%), and increased alanine aminotransferase (5.91%).

CONCLUSIONS

The superiority of CET over PET in HR+/HER2- advanced breast cancer is evident, showing improved survival and responses. Nonetheless, the higher incidence of AEs, specifically hematologic AEs, requires cautious attention.

Comparative efficacy and safety of CDK4/6 inhibitors combined with endocrine therapies for HR+/HER2-breast cancer: Systematic review and network meta-analysis

BACKGROUND

In recent years, the combination of targeted drugs, such as Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, with endocrine therapy (ET), has emerged as a new research focus in the treatment of hormone receptor-positive (HR+) human epidermal growth factor receptor 2 negative (HER2-) breast cancer. This network meta-analysis aimed to systematically evaluate the efficacy and safety of CDK4/6 inhibitors combined with ET for HR+/HER2-breast cancer.

METHODS

A systematic search was conducted across PubMed, Web of Science, Cochrane Library, and GeenMedical databases to identify randomized controlled trials investigating the use of CDK4/6 inhibitors in combination with endocrine therapy for the treatment of HR+/HER2-breast cancer. The search period spanned from the inception of each database up to February 29, 2024. Data analysis was conducted using Stata 14.0 and R 4.1.0 software.

RESULTS

A total of 20 randomized controlled trials (RCTs) were included in this study, investigating the effectiveness of four CDK4/6 inhibitors-Abemaciclib, Dalpiciclib, Ribociclib, and Palbociclib-when combined with ET for the treatment of HR+/HER2-breast cancer. The results indicated that Abemaciclib + ET, Dalpiciclib + ET, Palbociclib + ET, and Ribociclib + ET exhibited similar therapeutic effects in terms of improving objective response rate (ORR), disease control rate (DCR) and reducing the occurrence of fatigue, all of which were superior to ET alone. However, in terms of prolonging progression-free survival (PFS) and overall survival (OS), Dalpiciclib + ET significantly improved PFS compared to Ribociclib + ET, Palbociclib + ET, Abemaciclib and Palbociclib. Ribociclib + ET significantly improved OS compared to Palbociclib + ET. Regarding overall adverse reaction events (AREs), Dalpiciclib + ET had a higher incidence compared to Ribociclib + ET. The incidence of neutropenia caused by Dalpiciclib + ET was significantly higher compared to Palbociclib + ET, Ribociclib + ET, Abemaciclib, and Palbociclib. Abemaciclib + ET demonstrated the worst safety profile concerning diarrhea.

CONCLUSION

Abemaciclib + ET likely represents the most effective option in terms of therapeutic effects, but it is prone to causing diarrhea and fatigue. On the other hand, Dalpiciclib + ET likely demonstrates the best efficacy in terms of PFS but exhibits the poorest safety profile, particularly in relation to neutropenia. Therefore, clinicians should exercise increased vigilance in monitoring and managing adverse effects when prescribing Abemaciclib + ET and Dalpiciclib + ET.

Abemaciclib plus endocrine therapy versus chemotherapy after progression on prior palbociclib in HR+/HER2- metastatic breast cancer: A single center real-world study in China

BACKGROUND

Cyclin-dependent kinase (CDK) 4/6 inhibitor plus endocrine therapy (ET) become standard-of-care for patients with hormone receptor-positive, human epidermal growth factor receptor-2 negative (HR+/HER2-) metastatic breast cancer (MBC). However, the optimal therapeutic paradigm after progression on CDK4/6 inhibitor remains unclear. This study aimed to evaluate the efficacy and safety of abemaciclib with switching ET versus chemotherapy after progression on prior palbociclib-based ET in Chinese patients with HR+/HER2- MBC.

METHODS

From 414 consecutive patients with HR+/HER2- MBC who had been treated with palbociclib plus ET from September 2018 to May 2022 in Peking University Cancer Hospital, we identified 80 patients who received abemaciclib plus switching ET or chemotherapy after progression on palbociclib, matched for age, original stage at diagnosis, disease-free interval, and tumor burden at 1:1 ratio. The primary endpoint was progression-free survival (PFS) compared using the Kaplan-Meier method. A Cox proportional hazard model was performed to identify clinical factors associated with PFS in the abemaciclib group.

RESULTS

The median PFS was 6.0 months (95% confidence interval [CI]: 3.94-8.06) in abemaciclib group and 4.0 months (95% CI, 2.52-5.49) in chemotherapy group (p = 0.667). And, there was no difference in median PFS between the sequential and nonsequential arm (6.0 vs. 6.0 months) in the abemaciclib group though fewer lines of prior systemic therapy and longer PFS from prior palbociclib in the sequential arm. However, patients with prior palbociclib as the first-line therapy had a significantly longer median PFS versus prior palbociclib as ≥2nd-line therapy (11.0 vs. 5.0 months, p = 0.043). Based on multivariable analysis, ER+/PR+ was an independent factor associated with longer PFS. There was no significant difference in overall survival between the abemaciclib and chemotherapy groups (p = 0.069).

CONCLUSION

Our findings indicate that abemaciclib plus switching ET might be one of feasible treatment options for Chinese patients with HR+/HER2- MBC after progression on prior palbociclib-based therapy in addition to chemotherapy.

Cost-effectiveness comparison of dalpiciclib and abemaciclib combined with an aromatase inhibitor as first-line treatment for HR+/HER2- advanced breast cancer

OBJECTIVES

CDK4/6 inhibitors dalpiciclib and abemaciclib have been approved by the Chinese National Medical Products Administration as first-line treatment for postmenopausal females with hormone receptor-positive (HR+) and human epidermal growth factor receptor-2 negative (HER2-) advanced breast cancer (ABC). We aimed to assess the cost-effectiveness of dalpiciclib plus letrozole/anastrozole (non-steroidal aromatase inhibitor [NSAI]) compared with abemaciclib plus NSAI as a first-line treatment for HR+/HER2- ABC in China.

METHODS

We constructed a Markov model with three health states to evaluate health and economic outcomes of first-line treatment with dalpiciclib plus NSAI and abemaciclib plus NSAI for HR+/HER2- ABC. Efficacy data was obtained from MONARCH3 and DAWNA-2 trials. Quality-adjusted life-years (QALYs) and incremental cost-effectiveness ratios (ICERs) were calculated.

RESULTS

Compared with abemaciclib plus NSAI, dalpiciclib plus NSAI resulted in 4.27 additional QALYs, with an ICER of $14827.4/QALY. At a willingness-to-pay threshold of 3 times gross domestic product per capita in China for 2023 ($37721.5/QALY), the cost-effectiveness probability of dalpiciclib plus NSAI was 77.42%.

CONCLUSIONS

From the perspective of Chinese payers, dalpiciclib plus NSAI appears to be a cost-effective strategy compared with abemaciclib plus NSAI for the first-line treatment of patients with HR+/HER2- ABC in China.

CLINICAL TRIAL REGISTRATION

MONARCH3, www.clinicaltrials.gov, identifier is NCT02246621 and DAWNA-2, www.clinicaltrials.gov, identifier is NCT03966898.

A pilot trial of neoadjuvant pyrotinib plus trastuzumab, dalpiciclib, and letrozole for triple-positive breast cancer

Triple-positive breast cancer (TPBC) poorly responds to current standard neoadjuvant therapy (trastuzumab plus pertuzumab and chemotherapy). Our previous MUKDEN 01 study showed a promising total pathological complete response (tpCR) rate of 30.4% with neoadjuvant pyrotinib (pan-human epidermal growth factor receptor tyrosine kinase inhibitor) plus dalpiciclib (cyclin-dependent kinase 4/6 inhibitor) and letrozole, but the efficacy remains suboptimal. This pilot study (NCT05228951) explored adding trastuzumab to this triplet neoadjuvant regimen in patients with stage II-III TPBC. The primary endpoint was tpCR (ypT0/is, ypN0) rate. Between February 2022 and June 2022, 12 patients were enrolled, and seven (58%; 95% confidence interval [CI], 27.7%-84.8%) patients achieved tpCR. The rate of residual cancer burden (RCB) 0-I was 75% (95% CI, 46.8%-91.1%). The objective response rate (ORR) was 92% (95% CI, 64.6%-98.5%). Mean Ki-67 level was significantly reduced from 45.0% (95% CI, 19.5%-70.5%) at baseline to 17.2% (95% CI, 0.7%-33.7%) after neoadjuvant therapy (p = 0.03). The most common grade 3 adverse events were diarrhea (four [33%]) and decreased neutrophil count (three [25%]). No grade 4 adverse events or treatment-related deaths occurred. This four-drug neoadjuvant regimen shows promising pathological response with an acceptable safety profile in patients with TPBC. A randomized controlled trial (NCT05638594) of this regimen is being conducted.

First-line CDK4/6 inhibitor-based combinations for HR+/HER2- advanced breast cancer: A Bayesian network meta-analysis

BACKGROUND

International guidelines recommend cyclin-dependent kinase 4/6 inhibitor (CDK4/6i)-based first-line therapy for hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC). However, direct drug comparisons are lacking. We aimed to identify the most effective and safe therapy through network meta-analysis (NMA).

METHODS

We searched PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials, and OpenGrey up to September 30, 2023. Eligible studies included randomized controlled trials (RCTs) assessing endocrine therapy alone or in combination with CDK4/6i as first-line endocrine treatment for HR+/HER2- ABC patients. The hazard ratios for progression-free survival (PFS) and overall survival (OS) and relative risks for objective response rate and adverse events (AEs) were available in selected trials. We performed a Bayesian NMA following PRISMA guidelines.

RESULTS

Thirteen RCTs, involving 10 treatments, were included. Most studies were at low risk of bias. Regarding PFS, ribociclib+fulvestrant ranked first with a surface under the cumulative ranking curve (SUCRA) of 85.0%, followed by dalpiciclib+nonsteroidal aromatase inhibitor (NSAI) (SUCRA = 78.9%). Considering OS, the top three ranked treatments were ribociclib+fulvestrant (SUCRA = 94.1%), abemaciclib+NSAI (SUCRA = 69.9%), and ribociclib+NSAI (SUCRA = 68.5%). Out of four CDK4/6is, ribociclib minimized the grade 3/4 AEs, while dalpiciclib demonstrated the worst safety. Publication bias could not be ignored in our analyses, and the certainty of evidence was downgraded primarily due to imprecision.

CONCLUSIONS

Ribociclib+fulvestrant probably represents the best option in a first-line setting. When combined with NSAI, dalpiciclib likely showed the best efficacy but the worst safety. Abemaciclib+NSAI and ribociclib+NSAI could also be promising treatments, while palbociclib presented inferiority. (PROSPERO Registration No. CRD42022370271).

A study protocol for an open-label, single-arm, single-center phase I clinical study on tolerability, safety, and efficacy of dalpiciclib combined with apatinib in the treatment of patients with advanced or metastatic sarcoma

INTRODUCTION

The prognosis of patients with advanced or metastatic sarcoma is very poor, and a new strategy for patients who fail systemic treatment is urgently required. Apatinib is a small molecule tyrosine kinase inhibitor of VEGFR-2, which can exert an antitumor effect by blocking downstream PI3K/AKT and VEGFR2/STAT3 signaling pathways of sarcoma. Dysregulation of the cyclin D (CCND)-cyclin-dependent kinase 4/6 (CDK4/6)-retinoblastoma 1 (Rb) pathway is highly prevalent in sarcoma. Thus, blocking VEGFR2 and CDK4/6 may exert a synergistic effect. We hypothesize that a combination of apatinib and dalpiciclib, an oral, highly effective, and selective small molecule CDK4/6 inhibitor, may result in higher antitumor efficacy in patients with refractory sarcoma.

METHODS

In this open-label, single-arm, single-center phase I trial, participants diagnosed with sarcoma who failed standard systemic treatment will be enrolled. Dose escalation will be conducted into three groups according to traditional 3 + 3 principle: dose 1, dalpiciclib 100 mg once daily oral d1-21+ apatinib 250 mg once daily oral d1-28, every 28 days as one cycle; dose 2, dalpiciclib 100 mg d1-21+ apatinib 500 mg d1-28; dose 3, dalpiciclib 150 mg d-21+ apatinib 500 mg d1-28. The primary endpoint is the safety and tolerability of combined treatment. The secondary endpoint is to evaluate the initial efficacy, including objective response rate (ORR), disease control rate (DCR), duration of response (DoR), and progression-free survival (PFS).

DISCUSSION

This trial will provide evidence of the tolerability, safety, and efficacy of dalpiciclib in combination with apatinib in metastatic sarcoma patients who have failed first-line systemic treatment.

Updates in the treatment of HR+HER2- breast cancer

PURPOSE OF REVIEW

Breast cancer (BC) is the most common cancer among women in the United States and the second leading cause of cancer death. BC research, diagnostics, drug development, and expansion of therapies for novel indications advances so rapidly that BC treatment standards change month-by-month. Herein we discuss notable advancements in the past year for hormone receptor positive (HR+) HER2 negative (HER2-) BC.

RECENT FINDINGS

Radiolabeled estradiol imaging and circulating tumor DNA (ctDNA) have changed our approach to metastatic BC (mBC) detection. Amongst an abundance of therapy options, treatment de-escalation to avoid toxicities is a priority. Promising results with CDK4/6 inhibitors in the curative setting have been demonstrated even as we await final data for use in the metastatic setting. Several novel endocrine therapies are expected to gain FDA-approval in the near future. Antibody-drug conjugates have expanded from other mBC types to HR+HER2- mBC. The PROMISE trial helped define disease recurrence outcomes for premenopausal women seeking pregnancy.

SUMMARY

The diagnostic and treatment landscape for HR+HER2- BC continues to rapidly evolve on multiple fronts.

The CDK4/6 inhibitors biomarker landscape: The most relevant biomarkers of response or resistance for further research and potential clinical utility

Cyclin-Dependent Kinase 4/6 inhibitors (CDK4/6is) in combination with Endocrine Therapy (ET) represent the standard frontline therapy for patients with Hormone Receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative metastatic Breast Cancer (mBC). Clinical activity and efficacy of CDK4/6is-based therapies have been proven both in the endocrine sensitive and resistant settings. Therapy resistance eventually underpins clinical progression to any CDK4/6is-based therapies, yet there is a lack of validated molecular biomarkers predictive of either intrinsic or acquired resistance to CDK4/6is in clinical practice. As the "post-CDK4/6is" landscape for the management of HR-positive/HER2-negative mBC is rapidly evolving with the introduction of novel therapies, there is an urgent need for the definition of clinically relevant molecular biomarkers of intrinsic/acquired resistance mechanisms to CDK4/6is. This narrative review outlines the role of currently approved CDK4/6is-based therapies, describes the most relevant molecular biomarkers of CDK4/6is-resistance, and ultimately provides a perspective on the clinical and research scenario.

Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors: existing and emerging differences

The cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors palbociclib, ribociclib, and abemaciclib are standard-of-care therapy for hormone receptor-positive advanced or metastatic breast cancer, based on randomized trials showing improved progression-free survival for all 3 drugs and overall survival for ribociclib and abemaciclib. Results in early breast cancer are discordant, with sustained improvement in invasive disease-free survival demonstrated for abemaciclib but not other CDK4/6 inhibitors to date. We review nonclinical studies exploring mechanistic differences between the drugs, the impact of continuous dosing on treatment effect, and translational research into potential resistance mechanisms and prognostic and predictive markers. We focus particularly on how emerging findings may help us understand similarities and differences between the available CDK4/6 inhibitors. Even at late-stage clinical development, there remains much to learn about how agents in this class exert their varying effects.