Efficacy and safety of palbociclib plus endocrine therapy in North American women with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer

Reporting of older subgroups in registration breast cancer trials 2012-2021

INTRODUCTION

Adequate reporting of data specific to older populations enrolled to breast cancer trials is critical, given the high incidence of the disease among this demographic. This study aimed to examine the completeness of reporting of older subgroups among patients recruited to registration clinical trials investigating systemic treatments for breast cancer.

METHODS

Clinical trials leading to a US food and drug administration (FDA) approval in breast cancer between 2012 and 2021 were included. Primary study reports and and all available secondary publications were systematically and objectively assessed with regard to the availability of data regarding efficacy, baseline characteristics, safety, and health-related quality of life (HRQOL) outcomes among older subgroups.

RESULTS

27 trials and 216 publications were assessed. 20.3% of patients were aged ≥65. 70.0% of patients had an eastern cooperative oncology group (ECOG) performance status of 0. Although complete reporting of primary endpoints was adequate (72.7%), most protocol-defined primary endpoints were surrogate endpoints (84.8%). Overall survival data among older populations was unavailable in 50.0% of studies. Reporting was poor for secondary efficacy endpoints (81.8% unreported), baseline characteristics (70.4% unreported), toxicity (55.6% unreported), and health-related quality of life outcomes (87.5% unreported).

CONCLUSION

The findings underline significant deficits in the reporting of age-specific data in breast cancer registration trials. The underreporting of key efficacy, safety, and HRQOL outcomes highlights the need for mandatory reporting standards and a dedicated emphasis on older populations' priorities and needs in the reporting of registration clinical trials.

Palbociclib in combination with sunitinib exerts a synergistic anti-cancer effect in patient-derived xenograft models of various human cancers types

The efficacy/safety of combining palbociclib (a CDK4/6 inhibitor) and sunitinib (a multi-targeted receptor tyrosine kinase inhibitor) was evaluated, using patient-derived xenograft (PDX) models. Twenty-three PDX mice models were developed from patients with various solid tumors. The mice were randomized to 4 groups (5-6 mice in each): control/palbociclib (100 mg/kg)/sunitinib (50 mg/kg)/combination. Drugs were administered orally, 5 days/week. In 17/23 PDX models (74%), the combination demonstrated a synergistic inhibitory effect vs the monotherapies ("responder" models) with no unexpected toxicities. In 13/17 responder models, where standard-of-care (SOC) was an additional comparator, the combination was more effective than SOC in 7 models, as effective in 4, and less effective in 2. The mean ± SEM experiment duration in 15/17 responder models (2/17 were excluded due to technical issues) was 86 ± 12 and 31 ± 5 days for the combination and control groups, respectively (p = 0.0002). The effect of the combination was dose-dependent. Cell-viability experiments in A549/MDA-MB-231/HT-29 cell lines and experiments using tumor-derived primary cell spheroids supported the PDX findings. In conclusion, combination of palbociclib and sunitinib exerts a synergistic anti-tumor effect without adding unexpected toxicity. A clinical trial assessing this combination is underway.

Breast cancer liver metastasis: current and future treatment approaches

Nearly all fatalities arising from breast tumors are attributable to distant metastases. Breast cancer liver metastasis (BCLM) is associated with poor prognoses, with the median survival time being 2 to 3 years. Tumor intrinsic subtype directs preferential metastasis to specific organs, with HER2-enriched tumors demonstrating the highest rates of metastasis to the liver, though all subtypes can grow in the liver. There is no singular established standard-of-care for BCLM; therapeutic selection is driven by histologic and molecular hallmarks of the primary tumor or biopsied metastasis samples. Given the poor prognosis of patients with hepatic spread, pre-clinical studies are necessary to identify and evaluate promising new treatment strategies. It is critical that these laboratory studies accurately recapitulate the BCLM disease process, standard progression, and histological attributes. In this review, we summarize the histologic and molecular characteristics of BCLM, evaluate the efficacy of existing surgical and medical treatment strategies, and discuss future approaches to preclinical study of BCLM.

CDK4/6 inhibitor palbociclib reduces inflammation in lupus-prone mice

Lupus is an autoimmune inflammatory disease that affects multiple organs. Cyclin-dependent kinases (CDKs) have been associated with inflammation. The objective of this study was to explore the effects of palbociclib (a CDK4/6 inhibitor) on inflammation in a lupus-prone MRL-lpr mouse model. Twenty mice (10 females and 10 males) were randomized into control group (n=10, treated with vehicle) and treatment group (n=10, treated with 3 cycles of palbociclib at a dose of 120 mg/kg/day for 2 weeks on and 10 weeks off, through oral gavage). Animals were euthanized after the third cycle of treatment. We found that facial skin lesions developed later and smaller in the female mice treated with palbociclib than the female mice in the control group. The lymph node number was less and the lymph node weight was lighter in the female treatment group compared to the female control group. The inflammatory lesions in the kidneys of male mice treated with palbociclib were significantly reduced compared to the male mice in the control group. Our findings suggest that palbociclib treatment reduces inflammation in lupus-prone mice in a gender-specific manner, targeting the facial skin and lymph nodes in the female mice and the kidneys in the male mice.

Clinical Challenges in the Management of Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer: A Literature Review

Endocrine therapy (ET) is integral to the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) metastatic breast cancer (MBC). Aromatase inhibitors (AIs; e.g., anastrozole, letrozole, exemestane), selective estrogen receptor modulators (e.g., tamoxifen), and the selective estrogen receptor degrader, fulvestrant, inhibit tumor cell proliferation by targeting ER signaling. However, the efficacy of ET could be limited by intrinsic and acquired resistance mechanisms, which has prompted the development of targeted agents and combination strategies. In recent years, the treatment landscape for HR+, HER2− MBC has evolved rapidly. AIs, historically the first-line treatment for postmenopausal patients with HR+, HER2− MBC, have been challenged by more effective ET, such as fulvestrant alone or in combination with an AI, and the cyclin-dependent kinase (CDK)4/6 inhibitors, which have increasingly become the new standard of care. For endocrine-resistant disease (≥ second-line), clinical trials demonstrated that the mammalian target of rapamycin inhibitor, everolimus, enhanced the efficacy of exemestane or fulvestrant after progression on an AI. CDK4/6 inhibitors in combination with fulvestrant have demonstrated superior progression-free survival and overall survival versus fulvestrant alone. Recently, the combination of fulvestrant with alpelisib in phosphatidylinositol-4,5-bisphosphate 3-kinase (PIK3CA) mutated HR+, HER2− MBC following progression on or after ET was approved, based on the SOLAR-1 study. However, the optimal sequencing of treatments is unknown, especially following disease progression on a CDK4/6 inhibitor. This review aims to provide practical guidance for the management of HR+, HER2− MBC based on available data and the utility of genomic biomarkers, including germline breast cancer genes 1 and 2 (BRCA1/2) mutations, and somatic estrogen receptor alpha gene (ESR1), HER2, and PIK3CA mutations.

Arctigenin inhibits proliferation of ER-positive breast cancer cells through cell cycle arrest mediated by GSK3-dependent cyclin D1 degradation

Estrogen receptor (ER) positive accounts for a large proportion of breast cancer. Although there are many targeted therapeutic drugs, the emergence of drug resistance urgently requires the development of new drugs. Arctigenin (Arc), a lignan found in certain plants of the Asteraceae, has the effect on inhibiting breast cancer, but its molecular mechanism has not been clear.

AIMS

To this end, the current study focuses on understanding the mechanism of Arc on ER-positive breast cancer cells.

MAIN METHODS

Colony formation experiments and sulforhodamine B methods were used to determine the growth-inhibitory effect of Arc. The cell cycle and apoptosis were analyzed by flow cytometry. Alterations of signaling proteins were measured by Western blotting. Protein degradation was determined by comparing protein half-lives and inhibiting proteasome.

KEY FINDINGS

The experimental results show that Arc did not induce apoptosis in ER-positive breast cancer cell, rather caused G1 cycle arrest by decreasing cyclin D1 levels without effect on altering CDK4/6 levels. Moreover, we have demonstrated that Arc decreases cyclin D1 levels through prompting Akt/GSK3β-mediated degradation.

SIGNIFICANCE

These findings warrant the potential of Arc as a candidate treatment for ER-positive breast cancer.

Efficacy and safety of palbociclib plus endocrine therapy in North American women with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer

Palbociclib is a cyclin-dependent kinase 4/6 inhibitor indicated for treatment of hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer in combination with endocrine therapy. We investigated the efficacy and safety of palbociclib in patients enrolled in North America during two-phase 3 trials: PALOMA-2 (n = 267, data cutoff: May 31, 2017) and PALOMA-3 (n = 240, data cutoffs: April 13, 2018, for overall survival, October 23, 2015, for all other outcomes). In PALOMA-2, treatment-naïve postmenopausal patients with advanced breast cancer were randomized 2:1 to palbociclib (125 mg/d; 3 weeks on/1 week off [3/1]) plus letrozole (2.5 mg/d, continuous) or placebo plus letrozole. In PALOMA-3, patients who progressed on prior endocrine therapy were randomized 2:1 to palbociclib (125 mg/d; 3/1) plus fulvestrant (500 mg, per standard of care) or placebo plus fulvestrant; pre/perimenopausal patients received ovarian suppression with goserelin. Palbociclib plus endocrine therapy prolonged median progression-free survival vs placebo plus endocrine therapy in North American patients (PALOMA-2: 25.4 vs 13.7 months, hazard ratio, 0.54 [95% CI, 0.40-0.74], P < .0001; PALOMA-3: 9.9 vs 3.5 months, hazard ratio, 0.52 [95% CI, 0.38-0.72], P < .0001). Objective response and clinical benefit response rates were greater with palbociclib vs placebo in North American patients in both trials. While overall survival data are not yet mature for PALOMA-2, median overall survival was increased in PALOMA-3 (32.0 vs 24.7 months, hazard ratio, 0.75 [95% CI, 0.53-1.04]), though this did not reach statistical significance (P = .0869). Safety profiles in North American patients were similar to those of the overall populations; neutropenia was the most common treatment-emergent adverse event. No new safety signals were observed. In summary, palbociclib plus endocrine therapy is an effective treatment option for North American women with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer.