Abemaciclib plus endocrine therapy for HR+, HER2-, node-positive, high-risk early breast cancer: a plain language summary of the monarchE study.

WHAT IS THIS SUMMARY ABOUT?: This article summarizes the most recent results of the monarchE study. This study was completed in participants with a type of breast cancer called HR+, HER2-, node-positive, high-risk early breast cancer. In this study, abemaciclib, a non-chemotherapy treatment, was administered with standard of care endocrine therapy after curative surgery. Most participants had received prior chemotherapy and/or radiotherapy. The study investigated if abemaciclib helped participants live longer without their cancer returning compared with participants who only received standard of care endocrine therapy. The study participants were assigned to 1 of 2 treatment groups. Participants in Group A were assigned to receive standard of care endocrine therapy with abemaciclib for 2 years, followed by endocrine therapy for a total of at least 5 years. Participants in Group B were assigned to receive standard of care endocrine therapy only for at least 5 years. The effect of treatment was compared between these 2 groups. WHAT WERE THE RESULTS?: Overall, the results showed that the cancer was 34% less likely to come back after surgery in the participants in Group A (abemaciclib plus endocrine therapy) compared with those in Group B (endocrine therapy only). At 4 years since the start of the study treatment, more participants who received the combination of abemaciclib plus endocrine therapy remained free of cancer compared with participants who received endocrine therapy alone (86% versus 79%). Participants who received abemaciclib plus endocrine therapy had more side effects than those who received endocrine therapy alone, but most of these effects were mild to moderate and reversible upon the end of therapy. The most common side effects in the abemaciclib group were diarrhea, infections, low number of white blood cells, and tiredness. WHAT DO THE RESULTS MEAN?: This study found that administering abemaciclib in combination with standard endocrine therapy after curative breast surgery helped lower the risk of cancer returning in people with HR+, HER2-, node-positive, high-risk early breast cancer. Abemaciclib is a new treatment option for people with this diagnosis. People with high-risk early breast cancer should always talk to their doctors and nurses before making any decisions about their treatment.Clinical Trial Registration: NCT03155997 (monarchE study).

CDK4/6 inhibitors as adjuvant therapy in early breast cancer? Uncertain benefits, guaranteed harms.

CDK4/6 inhibitors are oral agents inhibiting key molecules of the cell cycle regulation. In patients with endocrine receptor positive (ER+), human epidermal growth factor receptor 2 negative (HER2-) breast cancer, the combination of CDK4/6 inhibitors with endocrine therapy is an effective treatment in the metastatic setting. Now, two studies in the adjuvant setting - MonarchE (2 years of abemaciclib) and NATALEE (3 years of ribociclib) - report positive invasive disease-free survival. Here, we re-evaluate these seminal trials. First, an excess drop-out or loss-to-follow up occurred early in the control arms of both studies. Since both trials are open-label, there is concern that the patients who drop-out do not do so at random but based on socioeconomic factors and alternative options. Is it possible that the results merely appear favorable due to loss to follow up? Based on re-constructed Kaplan-Meier curves, we concluded the results of these studies remain fragile, being prone to informative censoring. Secondly, adverse events were notably higher in both trials, and some of them, like COVID-19 related deaths in NATALEE, raise serious concerns. Third, the potential costs associated with CDK4/6 inhibition given as adjuvant therapy are unprecedented. The NATALEE strategy, in particular, could affect up to 35 % of patients with newly diagnosed breast cancer, which is the cancer with the highest incidence worldwide. Without confirmatory data based on a placebo-controlled trial, or better identification of patients that would benefit from the addition of CDK4/6 inhibitors in the adjuvant setting, we argue against their routine use as adjuvant therapy in ER+ /HER2- early breast cancer.

Development of a Radiolabeled Cyclin-Dependent Kinases 4 and 6 (CDK4/6) Inhibitor for Brain and Cancer PET Imaging.

The synthesis, biochemical evaluation and radiosynthesis of a cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor and radioligand was performed. NT431, a newly synthesized 4-fluorobenzyl-abemaciclib, exhibited high potency to CDK4/6 and against four cancer cell lines with IC50 similar to that of the parent abemaciclib. We performed a two-step one-pot radiosynthesis to produce [18F]NT431 with good radiochemical yield (9.6 ± 3%, n = 3, decay uncorrected), high radiochemical purity (>95%), and high molar activity (>370 GBq/µmol (>10.0 Ci/µmol). In vitro autoradiography confirmed the specific binding of [18F]NT431 to CDK4/6 in brain tissues. Dynamic PET imaging supports that both [18F]NT431 and the parent abemaciclib crossed the BBB albeit with modest brain uptake. Therefore, we conclude that it is unlikely that NT431 or abemaciclib (FDA approved drug) can accumulate in the brain in sufficient concentrations to be potentially effective against breast cancer brain metastases or brain cancers. However, despite the modest BBB penetration, [18F]NT431 represents an important step towards the development and evaluation of a new generation of CDK4/6 inhibitors with superior BBB penetration for the treatment and visualization of CDK4/6 positive tumors in the CNS. Also, [18F]NT431 may have potential application in peripheral tumors such as breast cancer and other CDK4/6 positive tumors.

Synergistic Enhancement of Antitumor Effects by Combining Abemaciclib with Desipramine.

Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors, including abemaciclib, have been approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced, and metastatic breast cancer. Despite the high therapeutic efficacy of CDK4/6 inhibitors, they are associated with various adverse effects, including potentially fatal interstitial lung disease. Therefore, a combination of CDK4/6 inhibitors with letrozole or fulvestrant has been attempted but has demonstrated limitations in reducing adverse effects, highlighting the need to develop new combination therapies. This study proposes a combination strategy using CDK4/6 inhibitors and tricyclic antidepressants to enhance the therapeutic outcomes of these inhibitors while reducing their side effects. The therapeutic efficacies of abemaciclib and desipramine were tested in different cancer cell lines (H460, MCF7, and HCT-116). The antitumor effects of the combined abemaciclib and desipramine treatment were evaluated in a xenograft colon tumor model. In vitro cell studies have shown the synergistic anticancer effects of combination therapy in the HCT-116 cell line. The combination treatment significantly reduced tumor size compared with control or single treatment without causing apparent toxicity to normal tissues. Although additional in vivo studies are necessary, this study suggests that the combination therapy of abemaciclib and desipramine may represent a novel therapeutic approach for treating solid tumors.

HER4 Affects Sensitivity to Tamoxifen and Abemaciclib in Luminal Breast Cancer Cells and Restricts Tumor Growth in MCF-7-Based Humanized Tumor Mice.

The impact of the HER4 receptor on the growth and treatment of estrogen receptor-positive breast cancer is widely uncertain. Using CRISPR/Cas9 technology, we generated stable HER4 knockout variants derived from the HER4-positive MCF-7, T-47D, and ZR-75-1 breast cancer cell lines. We investigated tumor cell proliferation as well as the cellular and molecular mechanisms of tamoxifen, abemaciclib, AMG232, and NRG1 treatments as a function of HER4 in vitro. HER4 differentially affects the cellular response to tamoxifen and abemaciclib treatment. Most conspicuous is the increased sensitivity of MCF-7 in vitro upon HER4 knockout and the inhibition of cell proliferation by NRG1. Additionally, we assessed tumor growth and immunological effects as responses to tamoxifen and abemaciclib therapy in humanized tumor mice (HTM) based on MCF-7 HER4-wildtype and the corresponding HER4-knockout cells. Without any treatment, the enhanced MCF-7 tumor growth in HTM upon HER4 knockout suggests a tumor-suppressive effect of HER4 under preclinical but human-like conditions. This phenomenon is associated with an increased HER2 expression in MCF-7 in vivo. Independent of HER4, abemaciclib and tamoxifen treatment considerably inhibited tumor growth in these mice. However, abemaciclib-treated hormone receptor-positive breast cancer patients with tumor-associated mdm2 gene copy gains or pronounced HER4 expression showed a reduced event-free survival. Evidently, the presence of HER4 affects the efficacy of tamoxifen and abemaciclib treatment in different estrogen receptor-positive breast cancer cells, even to different extents, and is associated with unfavorable outcomes in abemaciclib-treated patients.

Case report: A case of pseudo-acute kidney injury due to cyclin-dependent kinase inhibitor.

Various classes of targeted therapies have emerged in the last few years, which have revolutionized cancer treatment, and improved the prognosis and survival of cancer patients. Unfortunately, these agents have serious toxic effects on the kidneys. Some of the toxic effects are hypertension, acute kidney injury (AKI), and proteinuria. One interesting phenomenon that has emerged recently is pseudo-acute kidney injury due to the interference with the tubular secretion of creatinine by some of the targeted therapeutic agents. Understanding this physiology is needed to avoid unnecessary investigation and withholding of lifesaving chemo regimen. Alternative methods to assess renal function such as cystatin C-based estimated glomerular filtration rate (eGFR) can differentiate true AKI from pseudo-AKI. Here, we describe one such case of pseudo-AKI from cyclin-dependent kinase (CDK) 4/6 inhibitor, abemaciclib, which inhibits tubular secretion of creatinine. Using cystatin-C-based eGFR revealed pseudo-AKI in this case.

Targeting Tyro3, Axl, and MerTK Receptor Tyrosine Kinases Significantly Sensitizes Triple-Negative Breast Cancer to CDK4/6 Inhibition.

Triple-negative breast cancer (TNBC) is the most aggressive subtype with high metastasis and mortality rates. Given the lack of actionable targets such as ER and HER2, TNBC still remains an unmet therapeutic challenge. Despite harboring high CDK4/6 expression levels, the efficacy of CDK4/6 inhibition in TNBC has been limited due to the emergence of resistance. The resistance to CDK4/6 inhibition is mainly mediated by RB1 inactivation. Since our aim is to overcome resistance to CDK4/6 inhibition, in this study, we primarily used the cell lines that do not express RB1. Following a screening for activated receptor tyrosine kinases (RTKs) upon CDK4/6 inhibition, we identified the TAM (Tyro3, Axl, and MerTK) RTKs as a crucial therapeutic vulnerability in TNBC. We show that targeting the TAM receptors with a novel inhibitor, sitravatinib, significantly sensitizes TNBC to CDK4/6 inhibitors. Upon prolonged HER2 inhibitor treatment, HER2+ breast cancers suppress HER2 expression, physiologically transforming into TNBC-like cells. We further show that the combined treatment is highly effective against drug-resistant HER2+ breast cancer as well. Following quantitative proteomics and RNA-seq data analysis, we extended our study into the immunophenotyping of TNBC. Given the roles of the TAM receptors in promoting the creation of an immunosuppressive tumor microenvironment (TME), we further demonstrate that the combination of CDK4/6 inhibitor abemaciclib and sitravatinib modifies the immune landscape of TNBC to favor immune checkpoint blockade. Overall, our study offers a novel and highly effective combination therapy against TNBC and potentially treatment-resistant HER2+ breast cancer that can be rapidly moved to the clinic.

Concurrent Use of Abemaciclib and Radiotherapy in Metastatic Breast Cancer Patients: A Single-Center Experience.

INTRODUCTION: There is little evidence regarding the safety and efficacy of the combination of abemaciclib plus radiotherapy (RT). The majority of studies investigated the combination of RT with palbociclib or ribociclib reporting that hematological toxicity is common. Given the unique toxicity profile of abemaciclib with greater gastrointestinal toxicity compared to hematological toxicity, we wanted to evaluate the toxicity of the combination with RT in metastatic breast cancer (BC) patients. METHODS: Patients with histologically proven metastatic or locally advanced BC treated with RT and concurrent abemaciclib were selected. Toxicity was assessed according to the NCI-CTCAE V4.0. RESULTS: Thirty-two metastatic sites were treated in 19 patients and analyzed. All patients received abemaciclib during the RT course. A total of 68% of patients received a full dose of abemaciclib during RT. Also, 71.9% of patients received a palliative intent (median dose = 30 Gy, range = 8-30 Gy), and 26.3% were treated for 9 oligo-metastatic or oligo-progressive sites of disease with stereotactic body RT (median dose = 30 Gy, range 21-30 Gy, given in 3-5 fractions). Overall, the rate of G3 toxicity was 15.7%. The rate of G3 hematological toxicity was 10.6% (2/19 patients, one G3 neutropenia and one G3 anemia). No patient presented diarrhea, including those treated for RT sites close to the bowel. One patient developed G3 skin toxicity. Pain significantly improved after RT (mean value NRS pre-RT = 3.9, SD = 3.07; mean value NRS after RT = 0.9, SD = 0.46; p < 0.0001). CONCLUSION: Abemaciclib and concomitant RT seem well tolerated showing acceptable toxicity.

Tailoring advanced breast cancer treatment after cyclin-dependent kinase 4/6 inhibitors progression - real-world data analysis.

Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) represent the gold standard of the hormone receptor positive human epidermal growth factor receptor 2 (HER-2) negative advanced breast cancer. However, optimal treatment after disease progression is a matter of debate. We aimed to assess predictive and prognostic factors associated with the treatment outcome following CDK4/6i progression. Methods: We retrospectively analyzed patients who progressed on CDK4/6i treatment between 2018 and 2024. Treatment based on molecular findings (PIK3CA mutation), genetic findings (BRCA1/2 germline mutation), or adapted to the change in the tumor phenotype in rebiopsy (anti-HER2 therapy in the transformation to HER-2-positive disease) was grouped into tailored treatment and compared to the endocrine-based therapy and chemotherapy alone. Results: Five hundred twelve patients were treated with CDK4/6i. Two hundred patients with disease progression were enrolled in the study. Duration of response to CDK4/6i was not predictive of the response to subsequent treatment, whereas the progression in the central nervous system was the worst prognostic factor. Thirty patients were ineligible for subsequent treatment. Survival after CDK4/6i progression was significantly longer in patients eligible for tailored treatment. The median PFS in patients with tailored treatment (n=19) was 13.5 months vs. 4.9 months in patients with non-tailored therapy (n=151; p=0.045). 12-month PFS was 54.1% with tailored treatment [95% CI 24.1-76.7%] compared to 18.5% with non-tailored therapy [95% CI 11.6-26.6%]. The median OS for patients treated with a tailored approach was not reached compared to 11.5 months with non-tailored treatment (p=0.016). The 24-month OS for patients treated with a tailored approach was 80.2% [95% CI 40.3-94.8%] compared to 21.1% [95% CI 12.2-31.7%] for patients with non-tailored treatment. Conclusions: Tailoring of subsequent treatment strategy seems to be essential for achieving long-term benefit. Further studies are required, as the prognosis after CDK4/6i progression remains dismal, especially in cases affecting the central nervous system.

Real-world data on patients with early breast cancer who were prescribed abemaciclib adjuvant therapy in Japan.

Aim: To understand the real-world use of abemaciclib in Japanese patients with early breast cancer (EBC). Methods: This retrospective observational study was conducted using a Japanese administrative claims database in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative EBC who received abemaciclib adjuvant therapy from December 2021-March 2023. Patient characteristics and treatment patterns were summarized. Results: Among 374 patients, 38.2, 51.6 and 63.4% patients received neoadjuvant chemotherapy, adjuvant chemotherapy and radiotherapy, respectively; 13.1% were chemotherapy naive. Tamoxifen (37.7%), letrozole (35.6%), anastrozole (24.3%) were the commonly prescribed concomitant adjuvant endocrine therapies. Abemaciclib dose reductions were observed in 42.0% patients. Conclusion: Use of abemaciclib for treatment of high-risk EBC was described, which could help inform patient selection and treatment patterns.

Abemaciclib (150 mg twice daily) is prescribed with hormonal therapy for the treatment of early breast cancer (EBC) with high risk of recurrence. We used a big database from Japan that has anonymized information about 44 million patients from 480 hospitals. We aim to describe the characteristics of patients with EBC who receive abemaciclib and their treatment patterns in Japan.We included 374 patients with EBC who had breast cancer surgery and were prescribed abemaciclib with hormonal therapy between December 2021 and March 2023. The median age of patients is 54 years, almost all (99.2%) are female. The most commonly prescribed hormonal therapy with abemaciclib is tamoxifen (37.7%), letrozole (35.6%) and anastrozole (24.3%).Of the 374 patients who were prescribed abemaciclib, 38.2% patients received chemotherapy before surgery, 51.6% received chemotherapy after surgery and 63.4% received radiation therapy after surgery; whereas, 13.1% received no perioperative chemotherapy before abemaciclib therapy. Around 42% of patients reduced their dose from starting dose of abemaciclib. Higher proportion of older patients and patients with low body weight, had dose reduction. Majority of the patients are prescribed either an antidiarrheal agent or probiotic within a day of starting abemaciclib.This is the first study describing patient characteristics and treatment patterns of Japanese patients who are prescribed abemaciclib in the clinical practice. The results will help understand who can benefit from abemaciclib, and to choose the most appropriate patients to receive abemaciclib for the treatment of EBC.

CDK4/6 inhibitor abemaciclib combined with low-dose radiotherapy enhances the anti-tumor immune response to PD-1 blockade by inflaming the tumor microenvironment in Rb-deficient small cell lung cancer.

Background: Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors have shown significant activity against several solid tumors by reducing the phosphorylation of the canonical CDK4/6 substrate retinoblastoma (Rb) protein, while the anti-tumor effect of CDK4/6 inhibitors on Rb-deficient tumors is not clear. Most small cell lung cancers (SCLCs) are Rb-deficient and show very modest response to immune checkpoint blockade (ICB) despite recent advances in the use of immunotherapy. Here, we aimed to investigate the direct effect of CDK4/6 inhibition on SCLC cells and determine its efficacy in combination therapy for SCLC. Methods: The immediate impact of CDK4/6 inhibitor abemaciclib on cell cycle, cell viability and apoptosis in four SCLC cell lines was initially checked. To explore the effect of abemaciclib on double-strand DNA (ds-DNA) damage induction and the combination impact of abemaciclib coupled with radiotherapy (RT), western blot, immunofluorescence (IF) and quantitative real-time polymerase chain reaction (qRT-PCR) were performed. An Rb-deficient immunocompetent murine SCLC model was established to evaluate efficacy of abemaciclib in combination therapy. Histological staining, flow cytometry analysis and RNA sequencing were performed to analyze alteration of infiltrating immune cells in tumor microenvironment (TME). Results: Here, we demonstrated that abemaciclib induced increased ds-DNA damage in Rb-deficient SCLC cells. Combination of abemaciclib and RT induced more cytosolic ds-DNA, and activated the STING pathway synergistically. We further showed that combining low doses of abemaciclib with low-dose RT (LDRT) plus anti-programmed cell death protein-1 (anti-PD-1) antibody substantially potentiated CD8+ T cell infiltration and significantly inhibited tumor growth and prolonged survival in an Rb-deficient immunocompetent murine SCLC model. Conclusions: Our results define previously uncertain DNA damage-inducing properties of CDK4/6 inhibitor abemaciclib in Rb-deficient SCLCs, and demonstrate that low doses of abemaciclib combined with LDRT inflame the TME and enhance the efficacy of anti-PD-1 immunotherapy in SCLC model, which represents a potential novel therapeutic strategy for SCLC.

Abemaciclib-Associated Skin, Hair, and Nail Toxicities: A Case Report.

Abemaciclib is a cyclin-dependent kinase 4/6 inhibitor that is utilized to manage hormone-sensitive human epidermal growth factor receptor-2 positive metastatic breast cancer. Palbociclib and ribociclib are types of other orally administered CDK4/6i that share similar safety and tolerability compared with Abemaciclib. Reported side effects include reversible neutropenia of a lower grade, gastrointestinal toxicity, and anemia. CDK4/6i could induce dermatological side effects. Although less frequent, cutaneous adverse effects of CDK4/6i account for 25% of medication discontinuation. Frequent cutaneous adverse events are rash and pruritus; nonetheless, hair loss, nail changes, vitiligo, and photosensitivity reactions, were also reported to a lesser extent. Herein, we report a case of hair, nail, and pigmentary disorder that occurred 10 months after initiating abemaciclib treatment.

Abemaciclib-induced epithelial-mesenchymal transition mediated by cyclin-dependent kinase 4/6 independent of cell cycle arrest pathway.

Abemaciclib (ABM), a cyclin-dependent kinase 4/6 inhibitor, shows pharmacological effects in cell cycle arrest. Epithelial-mesenchymal transition is an important cellular event associated with pathophysiological states such as organ fibrosis and cancer progression. In the present study, we evaluated the contribution of factors associated with cell cycle arrest to ABM-induced epithelial-mesenchymal transition. Treatment with 0.6 µM ABM induced both cell cycle arrest and epithelial-mesenchymal transition-related phenotypic changes. Interestingly, the knockdown of cyclin-dependent kinase 4/6, pharmacological targets of ABM or cyclin D1, which forms complexes with cyclin-dependent kinase 4/6, resulted in cell cycle arrest at the G1-phase and induction of epithelial-mesenchymal transition, indicating that downregulation of cyclin-dependent kinase 4/6-cyclin D1 complexes would mimic ABM. In contrast, knockdown of the Rb protein, which is phosphorylated by cyclin-dependent kinase 4/6, had no effect on the expression level of α-smooth muscle actin, an epithelial-mesenchymal transition marker. Furthermore, ABM-induced epithelial-mesenchymal transition was not affected by Rb knockdown, suggesting that Rb is not involved in the transition process. Our study is the first to suggest that cyclin-dependent kinase 4/6-cyclin D1 complexes, as pharmacological targets of ABM, may contribute to ABM-induced epithelial-mesenchymal transition, followed by clinical disorders such as organ fibrosis and cancer progression. This study suggests that blocking epithelial-mesenchymal transition might be a promising way to prevent negative side effects caused by a medication (ABM) without affecting its ability to treat the disease.

Abemaciclib plus a nonsteroidal aromatase inhibitor as initial therapy for HR+, HER2- advanced breast cancer: final overall survival results of MONARCH 3.

BACKGROUND: In MONARCH 2, the addition of abemaciclib to fulvestrant significantly improved both progression-free survival (PFS) and overall survival (OS) in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC) with disease progression on prior endocrine therapy. In MONARCH 3, the addition of abemaciclib to a nonsteroidal aromatase inhibitor (NSAI) as initial therapy for HR+, HER2- ABC significantly improved PFS. Here, we present the prespecified final OS results for MONARCH 3. PATIENTS AND METHODS: MONARCH 3 is a randomized, double-blind, phase III study of abemaciclib plus NSAI (anastrozole or letrozole) versus placebo plus NSAI in postmenopausal women with HR+, HER2- ABC without prior systemic therapy in the advanced setting. The primary objective was investigator-assessed PFS; OS was a gated secondary endpoint, and chemotherapy-free survival was an exploratory endpoint. RESULTS: A total of 493 women were randomized 2 : 1 to receive abemaciclib plus NSAI (n = 328) or placebo plus NSAI (n = 165). After a median follow-up of 8.1 years, there were 198 OS events (60.4%) in the abemaciclib arm and 116 (70.3%) in the placebo arm (hazard ratio, 0.804; 95% confidence interval 0.637-1.015; P = 0.0664, non-significant). Median OS was 66.8 versus 53.7 months for abemaciclib versus placebo. In the subgroup with visceral disease, there were 113 OS events (65.3%) in the abemaciclib arm and 65 (72.2%) in the placebo arm (hazard ratio, 0.758; 95% confidence interval 0.558-1.030; P = 0.0757, non-significant). Median OS was 63.7 months versus 48.8 months for abemaciclib versus placebo. The previously demonstrated PFS benefit was sustained, and chemotherapy-free survival numerically improved with the addition of abemaciclib. No new safety signals were observed. CONCLUSIONS: Abemaciclib combined with an NSAI resulted in clinically meaningful improvement in median OS (intent-to-treat population: 13.1 months; subgroup with visceral disease: 14.9 months) in patients with HR+ HER2- ABC; however, statistical significance was not reached.

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.

Abemaciclib and Vacuolin-1 decrease aggregate-prone TDP-43 accumulation by accelerating autophagic flux.

(Macro)autophagy is a cellular degradation system for unnecessary materials, such as aggregate-prone TDP-43, a central molecule in neurodegenerative diseases including amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Abemaciclib (Abe) and vacuolin-1 (Vac) treatments are known to induce vacuoles characterized by an autophagosome and a lysosome component, suggesting that they facilitate autophagosome-lysosome fusion. However, it remains unknown whether Abe and Vac suppress the accumulation of aggregate-prone TDP-43 by accelerating autophagic flux. In the present study, the Abe and Vac treatment dose-dependently reduced the GFP/RFP ratio in SH-SY5Y neuroblastoma cells stably expressing the autophagic flux marker GFP-LC3-RFP-LC3ΔG. Abe and Vac also increased the omegasome marker GFP-ATG13 signal and the autophagosome marker mCherry-LC3 localized to the lysosome marker LAMP1-GFP. The Abe and Vac treatment decreased the intracellular level of the lysosome marker LAMP1-GFP in SH-SY5Y cells stably expressing LAMP1-GFP, but did not increase the levels of LAMP1-GFP, the autophagosome marker LC3-II, or the multivesicular body marker TSG101 in the extracellular vesicle-enriched fraction. Moreover, Abe and Vac treatment autophagy-dependently inhibited GFP-tagged aggregate-prone TDP-43 accumulation. The results of a PI(3)P reporter assay using the fluorescent protein tagged-2 × FYVE and LAMP1-GFP indicated that Abe and Vac increased the intensity of the PI(3)P signal on lysosomes. A treatment with the VPS34 inhibitor wortmannin (WM) suppressed Abe-/Vac-facilitated autophagic flux and the degradation of GFP-tagged aggregate-prone TDP-43. Collectively, these results suggest that Abe and Vac degrade aggregate-prone TDP-43 by accelerating autophagosome formation and autophagosome-lysosome fusion through the formation of PI(3)P.

Abemaciclib pharmacology and interactions in the treatment of HR+/HER2- breast cancer: a critical review.

Abemaciclib (ABE) in combination with endocrine therapy represents the mainstay treatment for either endocrine-resistant metastatic or high-risk early-stage HR+/HER2- breast cancer patients. Hence, an adequate knowledge of this agent pharmacodynamic, pharmacokinetic, and of its drug-drug interactions (DDIs) is crucial for an optimal patients management. Additionally, ABE interference with food and complementary/alternative medicines should be taken into account in the clinical practice. Several online tools allow to freely check DDIs and can be easily consulted before prescribing ABE. According to one of this instruments, ABE display the lowest number of interactions among the available cyclin-dependent kinase 4/6 inhibitors. Still, clinicians should be aware that online tools cannot replace the technical datasheet of the drug as well as a comprehensive clinical assessment for each patient. Here we critically review the main pharmacological features of ABE, then focusing on its potential interactions with drugs, food, and alternative medicine, in order to provide a guide for its optimal use in the treatment of HR+/HER2- breast cancer patients.

Pharmacological features and drug interactions of abemaciclib Why was the review done? Abemaciclib, paired with hormone therapy, is a key treatment for breast cancer patients whose cancer cells respond to hormones but not to a protein called HER2. Understanding how this medication functions in the body, how it interacts with other drugs, and how the body processes it is crucial for providing optimal care. What did the authors do? The authors looked for published evidence about the way abemaciclib works into the body and about how it interacts with other drugs (including alternative medicines) or food. Then they summarized these findings. What did the authors find? Abemaciclib absorption, distribution, metabolism and excretion is well known and it is here described. What people eat and any alternative medications they take can affect how abemaciclib works. Online tools are available for doctors to check potential interactions between abemaciclib and other drugs a patient might be using. It's advisable for doctors to consult abemaciclib data sheet and use online tools before prescribing the drug. Notably, compared to similar treatments, abemaciclib has fewer interactions with other drugs. What does the review mean? This review delves into how abemaciclib works in the body and explore its potential interactions with other drugs, food, and alternative medicines. This information will aid doctors in using abemaciclib effectively for treating breast cancer patients.

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

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

Association between CDK4/6 inhibitors and drug-related osteonecrosis of the jaw: A pharmacoepidemiological study using the FDA Adverse Events Reporting System.

The most common toxicities associated with cyclin-dependent kinase (CDK) 4/6 inhibitor therapy include decreased leukopenia and neutropenia due to the inhibition of CDK6 of leukocyte and neutrophil precursors in bone marrow. These hematological toxicities are more commonly observed with palbociclib administration than with abemaciclib administration, which is approximately 13 times more selective against CDK4 than CDK6. Thus, even though both successfully inhibit CDK4/6, the side effects of palbociclib and abemaciclib differ due to differences in selectivity. Recent reports have suggested an association between palbociclib and medication-related osteonecrosis of the jaw; however, reports on this association are inconsistent. This study investigated the potential association of palbociclib and abemaciclib with MRONJ using the FAERS. Signals of "Osteonecrosis of jaw" were detected only in females using palbociclib (cROR025: 2.08). Other signals detected included stomatitis-related adverse events with abemaciclib and intraoral soft tissue damage and infection with palbociclib. As previous exploratory studies have reported MRONJ signals for bisphosphonates and denosumab, we calculated the aROR for palbociclib-induced osteonecrosis of the jaw using concomitant bisphosphonates and denosumab as covariates. A signal was detected even after adjusting for sex, age, and concomitant medications as covariates (aROR0025: 5.74). A proper understanding of the differences in CDK selectivity is necessary for the appropriate use of CDK4/6 inhibitors. To the best of our knowledge, this is the first report on CDK4/6 inhibitors and drug-related osteonecrosis of the jaw. We believe that these results will offer new insights into adverse events related to the use of CDK4/6 inhibitors, and may aid in the proper use of CDK4/6 inhibitors.