Venous and arterial thrombosis associated with abemaciclib therapy for metastatic breast cancer

Efficacy and Safety of Abemaciclib in Combination With Endocrine Therapy for HR+/HER2- Advanced or Metastatic Breast Cancer: A Systematic Review and Meta-Analysis

OBJECTIVES

Breast cancer, particularly the hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) subtype, remains a major global health concern. Abemaciclib, a CDK4/6 inhibitor, has shown promising results in treating advanced cases. This study comprehensively assesses the efficacy and safety of abemaciclib in combination with endocrine therapy for HR+/HER2- advanced or metastatic breast cancer.

METHODS

Following PRISMA guidelines, a systematic review and meta-analysis was conducted. A thorough literature search was conducted on PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov til December 2023. Inclusion criteria encompassed randomized controlled trials and retrospective cohort studies reporting on abemaciclib in approved doses, either as monotherapy or in combination. Outcome assessments included progression-free survival (PFS), overall response rate (ORR), side effects/adverse effects (SE/AE), and overall survival (OS). Quality assessment utilized Cochrane's revised risk of bias tool and Newcastle-Ottawa scale.

RESULTS

Pooled results of 22 studies involving 14,010 patients revealed that abemaciclib significantly improved PFS (hazard ratio=0.53; 95% CI: 0.48-0.59; P=0.00; I2=0%), ORR (risk ratio=2.31; 95% CI: 1.93-2.75; P=0.00; I2=0%), and OS (risk ratio=0.76 (95% CI: 0.65-0.87; P=0.001; I2=0%). However, abemaciclib increased the risk of adverse events in the fulvestrant and nonsteroidal aromatase inhibitor (NSAI) combinations, respectively.

CONCLUSIONS

Abemaciclib, particularly in combination with fulvestrant, emerges as an effective therapeutic option for HR+/HER2- advanced or metastatic breast cancer, improving PFS and OS. The higher toxicity profile warrants cautious use, especially in treatment-naive patients.

Abemaciclib increases the risk of venous thromboembolism in breast cancer: Integrate meta-analysis, pharmacovigilance database analysis, and in vitro validation

BACKGROUND

Recently, cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have emerged as a novel treatment strategy for breast cancer. However, increasing reports of CDK4/6i-associated venous thromboembolism (VTE) have garnered attention. This study assessed CDK4/6i-associated VTE in breast cancer, and examined the effect of CDK4/6i on platelet/coagulation function for the first time in vitro.

METHODS

PubMed and Embase databases were searched for studies published from the establishment of the database to December 31, 2022 for randomized controlled trials (RCTs) and real-world studies of CDK4/6i in patients with breast cancer, and the data obtained from the included studies were used for meta-analysis. A disproportionality analysis by extracting adverse drug reaction signals of CDK4/6i-associated VTE from the FDA Adverse Event Reporting System (FAERS) database was also conducted. Additionally, the in vitro effect of CDK4/6i on platelet function was assessed based on platelet aggregation tests and flow cytometry, and coagulation function was assessed based on the blood clotting function test.

FINDINGS

A total of 16,903 patients in 13 RCTs and 6,490 patients in 9 real-world studies were included in the meta-analysis. In RCTs, VTE occurred in 193 (2.1 %) and 55 (0.7 %) patients in the CDK4/6i and control groups, respectively. In real-world studies, the aggregate incidence rate of VTE was 4.2 % (95 % CI: 2.1, 6.3). The meta-analysis of RCTs revealed that abemaciclib (Odds ratio [OR]: 4.40 [95 % CI: 2.74,7.05], p < 0.001) and palbociclib (OR: 2.35 [95 % CI: 1.34, 4.12], p < 0.01) significantly increased the risk of VTE in patients with breast cancer compared to placebo. FAERS database analysis revealed that abemaciclib (reporting odds ratio [ROR]: 1.63 [95 % CI: 1.36, 1.97]; IC025: 0.67) and ribociclib (ROR: 1.17 [95 % CI: 1.0, 1.39]; IC025: 0.18) demonstrated a significantly increased signal of VTE. Similarly, findings from in vitro experiments demonstrated that abemaciclib enhanced agonist-induced platelet activation, especially when collagen was used as the inducer, and this effect became more prominent with increasing its concentration.

INTERPRETATION

Use of abemaciclib may increase the risk of VTE in patients with breast cancer, which may be partially attributed to the effect of abemaciclib on platelet function. Close monitoring of VTE occurrence is highly recommended while using abemaciclib, especially in patients at a high risk of VTE.

Prophylaxis with abemaciclib delays tumorigenesis in dMMR mice by altering immune responses and reducing immunosuppressive extracellular vesicle secretion

BACKGROUND

The CDK4/6 inhibitor abemaciclib is an FDA-approved agent and induces T-cell-mediated immunity. Previously, we confirmed the therapeutic potential of abemaciclib on mismatch repair-deficient (dMMR) tumors in mice. Here, we applied a prophylactic administration/dosage setting using two preclinical mouse models of dMMR-driven cancer.

METHODS

Mlh1-/- and Msh2loxP/loxP mice received repeated prophylactic applications of abemaciclib mesylate (75 mg/kg bw, per oral) as monotherapy or were left untreated. Blood phenotyping and multiplex cytokine measurements were performed regularly. The tumor microenvironment was evaluated by immunofluorescence and Nanostring-based gene expression profiling. Numbers, size and immune composition and activity of extracellular vesicles (EVs) were studied at the endpoint.

FINDINGS

Prophylactic abemaciclib-administration delayed tumor development and significantly prolonged overall survival in both mouse strains (Mlh1-/-: 50.0 wks vs. control: 33.9 wks; Msh2loxP/loxP;TgTg(Vil1-cre: 58.4 wks vs. control 44.4 wks). In Mlh1-/- mice, pro-inflammatory cytokines (IL-2, IL-6) significantly increased, whereas IL-10 and IL-17A decreased. Circulating and splenic exhausted and regulatory T cell numbers were significantly lower in the abemaciclib groups. Deeper analysis of late-onset tumors revealed activation of the Hedgehog and Notch signaling in Mlh1-/- mice, and activation of the MAPK pathway in Msh2loxP/loxP;TgTg(Vil1-cre mice. Still, arising tumors had fewer infiltrating myeloid-derived suppressor cells (vs. control). Notably, prophylactic abemaciclib-administration prevented secretion of procoagulant EVs but triggered release of immunomodulatory EVs in Mlh1-/- mice.

INTERPRETATION

Prophylactic abemaciclib prolongs survival via global immunomodulation. Prophylactic use of abemaciclib should be considered further for individuals with inherited dMMR.

FUNDING

This work was supported by grants from the German research foundation [DFG grant number: MA5799/2-2] and the Brigitte und Dr. Konstanze Wegener-Stiftung to CM.

The CDK4/6 inhibitor revolution - a game-changing era for breast cancer treatment

Cyclin-dependent kinase (CDK) 4/6 inhibition in combination with endocrine therapy is the standard-of-care treatment for patients with advanced-stage hormone receptor-positive, HER2 non-amplified (HR+HER2-) breast cancer. These agents can also be administered as adjuvant therapy to patients with higher-risk early stage disease. Nonetheless, the clinical success of these agents has created several challenges, such as how to address acquired resistance, identifying which patients are most likely to benefit from therapy prior to treatment, and understanding the optimal timing of administration and sequencing of these agents. In this Review, we describe the rationale for targeting CDK4/6 in patients with breast cancer, including a summary of updated clinical evidence and how this should inform clinical practice. We also discuss ongoing research efforts that are attempting to address the various challenges created by the widespread implementation of these agents.

Open-label, phase II, multicenter study of lasofoxifene plus abemaciclib for treating women with metastatic ER+/HER2- breast cancer and an ESR1 mutation after disease progression on prior therapies: ELAINE 2

BACKGROUND

Acquired ESR1 mutations in estrogen receptor-positive (ER+) metastatic breast cancer (mBC) drive treatment resistance and tumor progression; new treatment strategies are needed. Lasofoxifene, a next-generation, oral, endocrine therapy and tissue-specific ER antagonist, provided preclinical antitumor activity, alone or combined with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) in ESR1-mutated mBC.

PATIENTS AND METHODS

In the open-label, phase II, ELAINE 2 trial (NCT04432454), women with ESR1-mutated, ER+/human epidermal growth factor receptor 2-negative (HER2-) mBC who progressed on prior therapies (including CDK4/6i) received lasofoxifene 5 mg/day and abemaciclib 150 mg b.i.d until disease progression/toxicity. The primary endpoint was safety/tolerability. Secondary endpoints included progression-free survival (PFS), clinical benefit rate (CBR), and objective response rate (ORR).

RESULTS

Twenty-nine women (median age 60 years) participated; all but one were previously treated with a CDK4/6i (median duration 2 years). The lasofoxifene-abemaciclib combination was well tolerated with primarily grade 1/2 treatment-emergent adverse events (TEAEs), most commonly diarrhea, nausea, fatigue, and vomiting. One patient (with no prior CDK4/6i) discontinued treatment due to grade 2 diarrhea. No deaths occurred during the study. Median PFS was 56.0 weeks [95% confidence interval (CI) 31.9 weeks-not estimable; ∼13 months]; PFS rates at 6, 12, and 18 months were 76.1%, 56.1%, and 38.8%, respectively. CBR at 24 weeks was 65.5% (95% CI 47.3% to 80.1%). In 18 patients with measurable lesions, ORR was 55.6% (95% CI 33.7% to 75.4%). ESR1-mutant circulating tumor DNA (ctDNA) allele fraction decreased from baseline to week 4 in 21/26 (80.8%) patients.

CONCLUSIONS

Lasofoxifene plus abemaciclib had an acceptable safety profile, was well tolerated, and exhibited meaningful antitumor activity in women with ESR1-mutated, ER+/HER2- mBC after disease progression on prior CDK4/6i. Observed decreases in ESR1-mutant ctDNA with lasofoxifene concordant with clinical response suggest target engagement. If the ELAINE 2 findings are confirmed in the initiated, phase III, ELAINE 3 trial, these data could be practice-changing and help address a critical unmet need.

[Venous thromboembolism and breast cancer]

Breast cancer is the most common cancer in women. Patients with breast cancer have a 4-fold increased risk of venous thromboembolism (VTE) compared to age- and sex-matched controls without cancer. VTE remains the second leading cause of death in cancer patients and an independent risk factor for mortality. In women with breast cancer, the main risk factors for developing VTE are increasing age, obesity, disease stage, central catheter placement and cancer treatments, including surgery, chemotherapy, hormonotherapy and cyclin-dependent kinase 4/6 inhibitors. In women receiving tamoxifen, the risk of VTE is particularly increased within the first 6 months after initiation of hormonotherapy, although some evidence suggests that this risk may persist through the first 2 years of treatment. The risk of VTE appears to be lower in patients receiving aromatase inhibitors. In breast cancer patients receiving cyclin-dependent kinase 4/6 inhibitors, the rate of VTE is approximately 6%. Current clinical practice guidelines for the treatment and prevention of VTE in patients with cancer suggest that thromboprophylaxis should not be used routinely in ambulatory cancer patients receiving chemotherapy or hormonotherapy. The risk-benefit ratio of thromboprophylaxis should be assessed on a case-by-case basis and be the subject of multidisciplinary discussion.

Thromboembolism profiles associated with cyclin-dependent kinase 4/6 inhibitors: a real-world pharmacovigilance study and a systematic review

BACKGROUND

Thrombosis is the second leading cause of mortality in cancer patients. This study aimed to investigate the association between cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) and thrombosis.

RESEARCH DESIGN AND METHODS

A retrospective pharmacovigilance analysis based on real-world data combined with a systematic review was used to explore the thrombotic risk profiles of CDK4/6i. The study has been registered with Prospero (CRD42021284218).

RESULT

In the pharmacovigilance analysis, CDK4/6i showed a higher rate of reported venous thromboembolism (VTE) (ROR = 2.78, 95% CI = 2.64-2.92), with the highest signal for trilaciclib (ROR = 27.55, 95% CI = 13.43-56.52) but only 9 cases, followed by abemaciclib (ROR = 3.73, 95% CI = 3.19-4.37). For arterial thromboembolism (ATE), only ribociclib increased the reporting rate (ROR = 2.14, 95% CI = 1.91-2.41). In the meta-analysis, palbociclib, abemaciclib, and trilaciclib all increased the risk of VTE (OR = 2.23, 3.17, and 3.90). In the subgroup analysis, only abemaciclib increased the risk of ATE (OR = 2.11, 95% CI = 1.12-3.99)    .

CONCLUSIONS

CDK4/6i had different profiles of thromboembolism. Palbociclib, abemaciclib, or trilaciclib increased the risk of VTE. Ribociclib and abemaciclib showed a weak association with the risk of ATE.

Identification of abemaciclib derivatives targeting cyclin-dependent kinase 4 and 6 using molecular dynamics, binding free energy calculation, synthesis, and pharmacological evaluation

CDK4/6 plays a crucial role in various cancers and is an effective anticancer drug target. However, the gap between clinical requirements and approved CDK4/6 drugs is unresolved. Thus, there is an urgent need to develop selective and oral CDK4/6 inhibitors, particularly for monotherapy. Here, we studied the interaction between abemaciclib and human CDK6 using molecular dynamics simulations, binding free energy calculations, and energy decomposition. V101 and H100 formed stable hydrogen bonds with the amine-pyrimidine group, and K43 interacted with the imidazole ring via an unstable hydrogen bond. Meanwhile, I19, V27, A41, and L152 interacted with abemaciclib through π-alkyl interactions. Based on the binding model, abemaciclib was divided into four regions. With one region modification, 43 compounds were designed and evaluated using molecular docking. From each region, three favorable groups were selected and combined with each other to obtain 81 compounds. Among them, C2231-A, which was obtained by removing the methylene group from C2231, showed better inhibition than C2231. Kinase profiling revealed that C2231-A showed inhibitory activity similar to that of abemaciclib; additionally, C2231-A inhibited the growth of MDA-MB-231 cells to a greater extent than did abemaciclib. Based on molecular dynamics simulation, C2231-A was identified as a promising candidate compound with considerable inhibitory effects on human breast cancer cell lines.

Cyclin-dependent kinase 4/6 inhibitor-associated thromboembolism: a critical evaluation of the current evidence

Cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors are an essential treatment modality for hormone receptor-positive breast cancer. As the rates of breast cancer continue to rise globally and the indications for CDK 4/6 inhibitors now extend beyond metastatic disease, more patients than ever are receiving these agents. Thrombosis is an emerging clinical concern with this class of agents, particularly venous thromboembolism. Although venous thromboembolism initially emerged as an adverse effect of interest in early trials, more recent studies have demonstrated even higher incidences of thrombosis in real-world clinical practice. In this review, we summarize the evidence to date that has informed the thrombosis risk for these agents both in clinical trials and real-world studies. We review data describing the venous and arterial thromboembolic risks in clinical trials of CDK 4/6 inhibitors as well as the now rather extensive real-world evidence available, including a comparison of risk for each of the 3 agents approved for use in breast cancer: palcociclib, ribociclib, and abemaciclib. As the role of prophylactic anticoagulation continues to remain unknown in women receiving CDK 4/6 inhibitors, future efforts directed at carefully investigating the risks and benefits of thromboprophylaxis may lead to improved outcomes in these patients.

Ovarian Vein Thrombosis: An Unusual Cause of Abdominal Pain in Breast Cancer

Ovarian vein thrombosis (OVT) is a rare but potentially life-threatening complication that is usually seen in the intrapartum or postpartum period but can also be seen in patients with risk factors for venous thromboembolism. When symptomatic, it usually presents with abdominal pain and other vague constitutional symptoms, hence it is important for healthcare professionals to be aware of this condition when evaluating patients with risk factors. We present a rare case of OVT in a patient with breast cancer. Due to a lack of clear guidelines regarding the treatment and duration of treatment in non-pregnancy-related OVT, we followed the guidelines for the treatment of venous thromboembolism and started the patient on rivaroxaban for a three-month duration with close outpatient follow-up.