A Study of Abemaciclib (LY2835219) in Participants With Breast Cancer (MONARCH plus)

A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study to Compare NSAI (Anastrozole or Letrozole) Plus Abemaciclib, a CDK4 and CDK6 Inhibitor, or Plus Placebo, and to Compare Fulvestrant Plus Abemaciclib or Plus Placebo in Postmenopausal Women With Hormone Receptor-Positive, HER2-Negative Locoregionally Recurrent or Metastatic Breast Cancer

The main purpose of this study is to evaluate the efficacy of the study drug abemaciclib in postmenopausal women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) locoregionally recurrent or metastatic breast cancer.

Study Overview

• Status: Active, not recruiting
• Conditions: Breast Cancer
• Intervention / Treatment: Drug: Placebo; Drug: Abemaciclib; Drug: Fulvestrant; Drug: Anastrozole; Drug: Letrozole

• Study Type: Interventional
• Enrollment (Actual): 463
• Phase: Phase 3

Contacts and Locations

Study Locations

• Brazil
  • São Paulo, Brazil, 01246-000
    • Icesp - Instituto Do Câncer Do Estado de São Paulo
  • São Paulo, Brazil, 01317-000
    • Clínica de Pesquisa e Centro de Estudos em Ginecologia Oncológica e Mamária LTDA
  • Rio Grande do Sul
    • Ijuí, Rio Grande do Sul, Brazil, 98700 000
      • ONCOSITE - Centro de Pesquisa Clinica em Oncologia
    • Porto Alegre, Rio Grande do Sul, Brazil, 90110-270
      • Centro Gaucho Integrado De Oncologia, Hematologia, Ensino E Pesquisa
  • São Paulo
    • Barretos, São Paulo, Brazil, 14784-400
      • Fundacao Pio Xii - Hospital De Cancer De Barretos
    • São José do Rio Preto, São Paulo, Brazil, 15091-000
      • Hospital de Base de Sao Jose do Rio Preto
• China
  • Anhui
    • Bengbu, Anhui, China, 233004
      • Afflilated Hospital of Bengbu Medical College
  • Beijing Municipality
    • Beijing, Beijing Municipality, China, 100142
      • Beijing Cancer Hospital
    • Beijing, Beijing Municipality, China, 100071
      • The Fifth Medical Center of PLA General Hospital
  • Fujian
    • Fuzhou, Fujian, China, 350025
      • Fuzhou General hospital of Nanjing Military Command
    • Fuzhou, Fujian, China, 350014
      • Fujian Provincial Cancer Hospital
  • Guangdong
    • Guangzhou, Guangdong, China, 510120
      • Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University
    • Guangzhou, Guangdong, China, 510080
      • Guangdong Province People's Hospital
  • Guangxi
    • Nanning, Guangxi, China, 530021
      • Guangxi Medical University Affiliated Tumor Hospital
  • Hebei
    • Shijiazhuang, Hebei, China, 50035
      • The Fourth Hospital of Hebei Medical University
  • Heilongjiang
    • Harbin, Heilongjiang, China, 150081
      • Harbin Medical University Caner Hospital
  • Henan
    • Zhengzhou, Henan, China, 450008
      • Henan Cancer Hospital
  • Hubei
    • Wuhan, Hubei, China, 430079
      • Hubei Cancer Hospital
    • Wuhan, Hubei, China, 430022
      • Wuhan Union Hospital Cancer Center
    • Wuhan, Hubei, China, 430030
      • Tongji Hospital Tongji Medical, Science & Technology
  • Hunan
    • Changsha, Hunan, China, 410013
      • Hunan Cancer Hospital
  • Jiangsu
    • Nanjing, Jiangsu, China, 210029
      • Jiangsu Province Hospital
    • Nanjing, Jiangsu, China, 210009
      • Jiangsu Cancer Hospital
    • Nanjing, Jiangsu, China, 210000
      • Nanjing Drum Tower Hospital The Affiliated Hospital of Nanjing University Medical School
  • Jilin
    • Changchun, Jilin, China, 130012
      • Jilin Province Tumor Hospital
  • Liaoning
    • Dalian, Liaoning, China, 116023
      • The 2nd Affiliated Hospital of Dalian Medical University
    • Shenyang, Liaoning, China, 110001
      • The First Affiliated Hospital of China Medical University
    • Shenyang, Liaoning, China, 100042
      • Liaoning Cancer Hospital&Institute
  • Shaanxi
    • Xi'an, Shaanxi, China, 710061
      • The First Affiliated Hospital of Xi'an Jiaotong University
  • Shanghai Municipality
    • Shanghai, Shanghai Municipality, China, 200080
      • Shanghai General Hospital
    • Shanghai, Shanghai Municipality, China, 200032
      • Fudan University Shanghai Cancer Center
  • Tianjin Municipality
    • Tianjin, Tianjin Municipality, China
      • Tianjin Medical University Cancer Institute & Hospital
  • Zhejiang
    • Hangzhou, Zhejiang, China, 310022
      • Zhejiang Cancer Hospital
    • Hangzhou, Zhejiang, China, 310052
      • The Second Affiliate Hospital of Zhejiang University School of medicine
• India
  • Gujarat
    • Ahmedabad, Gujarat, India, 380016
      • The Gujarat Cancer & Research Institute (GCRI)
  • Karnataka
    • Bangalore, Karnataka, India, 560027
      • Healthcare Global Enterprises Limited (HCG)
    • Bangalore, Karnataka, India, 560054
      • M S Ramaiah Medical College Hospitals
  • Maharashtra
    • Mumbai, Maharashtra, India, 400 012
      • Tata Memorial Hospital
    • Pune, Maharashtra, India, 411001
      • Jehangir Hospital
  • National Capital Territory of Delhi
    • New Delhi, National Capital Territory of Delhi, India, 110005
      • Dr. B. L. Kapur Memorial Hospital
  • Tamil Nadu
    • Ranipet, Tamil Nadu, India, 632513
      • Christian Medical College Vellore
  • West Bengal
    • Kolkata, West Bengal, India, 700099
      • Medica Superspecialty Hospital
• South Africa
  • Johannesburg, South Africa, 2196
    • Sandton Oncology Centre
  • Gauteng
    • Johannesburg, Gauteng, South Africa, 2196
      • The Medical Oncology Centre of Rosebank
    • Pretoria, Gauteng, South Africa, 0081
      • Eastleigh Breast Care Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Have a diagnosis of HR+, HER2- breast cancer. Although not required as a protocol procedure, metastatic disease should be considered for biopsy whenever possible to reassess hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status if clinically indicated.

  • To fulfill the requirement for HR+ disease, a breast cancer must express, by immunohistochemistry (IHC), at least 1 of the HRs (estrogen receptor [ER], progesterone receptor [PgR]) as defined in the relevant American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines.
  • To fulfill the requirement of HER2- disease, a breast cancer must not demonstrate, at initial diagnosis or upon subsequent biopsy, overexpression of HER2 by either IHC or in-situ hybridization as defined in the relevant ASCO/CAP guidelines.
• Meet either Inclusion Criterion (2a) or Inclusion Criterion (2b). Participants meeting Inclusion Criterion 2a will be enrolled in Cohort A and participants meeting Inclusion Criterion 2b will be enrolled in Cohort B.

• (2a) Have locoregionally recurrent disease not amenable to resection or radiation therapy with curative intent or metastatic disease.

  • Relapsed with radiologic evidence of progression more than 1 year from completion of adjuvant endocrine therapy and have received no prior endocrine therapy for locoregionally recurrent or metastatic disease (Note: prior adjuvant endocrine therapy for localized disease may have included, but is not limited to, anti-estrogens or aromatase inhibitors. In addition, a participant may be enrolled if she has received ≤2 weeks of NSAI in this disease setting immediately preceding screening and agrees to discontinue NSAI until study treatment initiation.) OR
  • Presented with de novo metastatic breast cancer (mBC) and not received any prior endocrine therapy. OR
• Relapsed with radiologic evidence of progression less than 1 year from completion of or while receiving adjuvant endocrine therapy (except for letrozole or anastrozole) and have received no prior endocrine therapy for locoregionally recurrent or metastatic disease.

• (2b) Have locoregionally recurrent disease not amenable to resection or radiation therapy with curative intent or metastatic disease.

  • Relapsed with radiologic evidence of progression while receiving neoadjuvant or adjuvant endocrine therapy, with no subsequent endocrine therapy received following progression OR
  • Relapsed with radiologic evidence of progression within 1 year from completion of adjuvant endocrine therapy, with no subsequent endocrine therapy received following progression OR
  • Relapsed with radiologic evidence of progression more than 1 year from completion of adjuvant endocrine therapy and then subsequently relapsed with radiologic evidence of progression after receiving treatment with either an antiestrogen or an aromatase inhibitor as firstline endocrine therapy for metastatic disease. Participants may not have received more than 1 line of endocrine therapy or any prior chemotherapy for metastatic disease OR
  • Presented with de novo metastatic disease and then relapsed with radiologic evidence of progression after receiving treatment with either an antiestrogen or an aromatase inhibitor as first-line endocrine therapy for metastatic disease. Participants may not have received more than 1 line of endocrine therapy or any prior chemotherapy for metastatic disease.

• Have postmenopausal status defined as meeting at least 1 of the following:

  • Prior bilateral oophorectomy
  • Age ≥60 years
  • Age <60 years and amenorrheic for at least 12 months (in the absence of chemotherapy, tamoxifen, toremifene, or ovarian suppression) and follicle-stimulating hormone (FSH) and estradiol levels in the postmenopausal range.

• Have 1 of the following, as defined by the Response Evaluation Criteria in Solid Tumors (RECIST) v1.1:

  • Measurable disease
  • Nonmeasurable bone-only disease. Nonmeasurable bone-only disease may include any of the following: blastic bone lesions, lytic bone lesions without a measurable soft tissue component, or mixed lytic-blastic bone lesions without a measurable soft tissue component.
• Have a performance status (PS) of ≤1 on the Eastern Cooperative Oncology (ECOG) scale.

• Have adequate organ function, including:

  • Hematologic: absolute neutrophil count (ANC) ≥1.5 × 109/Liter (L), platelets

    ≥100 × 109/L, and hemoglobin ≥8 g/deciliter (dL). Participants may receive erythrocyte transfusions to achieve this hemoglobin level at the discretion of the investigator; however, initial study drug treatment must not begin earlier than the day after the erythrocyte transfusion.

  • Hepatic: Total bilirubin ≤1.5 times the upper limit of normal (ULN) and alanine aminotransferase (ALT) and aspartate aminotransferase (AST)

    ≤3.0 times ULN (or ALT and AST ≤5 times ULN if liver metastases are present).

  • Renal: serum creatinine ≤1.5 times ULN.
• Have discontinued previous localized radiotherapy for palliative purposes or for lytic lesions at risk of fracture at least 2 weeks prior to randomization and recovered from the acute effects of therapy (until the toxicity resolves to either baseline or at least Grade 1) except for residual alopecia or peripheral neuropathy.
• Are able to swallow capsules.
• Are reliable, willing to be available for the duration of the study, and willing to follow study procedures.

Exclusion Criteria:

• Have visceral crisis, lymphangitic spread, or leptomeningeal carcinomatosis. Visceral crisis is not the mere presence of visceral metastases, but implies severe organ dysfunction as assessed by symptoms and signs, laboratory studies, and rapid progression of the disease.
• Have inflammatory breast cancer.
• Have clinical evidence or a history of central nervous system (CNS) metastasis. Screening test is not required for enrollment.
• Are currently receiving or have previously received chemotherapy for locoregionally recurrent or metastatic breast cancer. (Note: Participants may be enrolled if they received prior [neo]adjuvant chemotherapy for localized disease.)
• Have received prior treatment with everolimus or fulvestrant (for Cohort B only).
• Have received prior treatment with any cyclin-dependent kinases 4 and 6 (CDK4 and CDK6) inhibitor (or participated in any CDK4 and CDK6 inhibitor clinical trial for which treatment assignment is still blinded).
• Have initiated bisphosphonates or approved Receptor activator of nuclear factor kappa-B ligand (RANK-L) targeted agents <7 days prior to randomization.
• Are currently enrolled in a clinical trial involving an investigational product (IP) or non-approved use of a drug or device (other than the IP/device used in this study), or concurrently enrolled in any other type of medical research judged not to be scientifically or medically compatible with this study. If a participant is currently enrolled in a clinical trial involving non-approved use of a device, then agreement with the investigator and Eli Lilly and Company (Lilly) clinical research physician (CRP) is required to establish eligibility.
• Have received treatment with a drug that has not received regulatory approval for any indication within 14 or 21 days of randomization for a nonmyelosuppressive or myelosuppressive agent, respectively.
• Have had major surgery within 14 days prior to randomization to allow for post-operative healing of the surgical wound and site(s).
• Have received recent (within 28 days prior to randomization) live attenuated vaccines such as yellow fever vaccine.
• Have serious preexisting medical conditions that, in the judgment of the investigator, would preclude participation in this study (eg, history of major surgical resection involving the stomach or small bowel, or preexisting Crohn's disease or ulcerative colitis).
• Have a personal history within the last 12 months of any of the following conditions: syncope of cardiovascular etiology, ventricular tachycardia, ventricular fibrillation, or sudden cardiac arrest.
• Have a history of any other cancer (except nonmelanoma skin cancer or carcinoma in-situ of the cervix), unless in complete remission with no therapy for a minimum of 3 years.
• Have received an autologous or allogeneic stem-cell transplant.
• Have clinical evidence of active bacterial or fungal infection or active viral infection that, in the judgment of the investigator, would preclude participation in this study (eg, human immunodeficiency virus [HIV] or viral hepatitis). Screening test is not required for enrollment.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Abemaciclib + Nonsteroidal Aromatase Inhibitor (NSAI); Abemaciclib given orally every 12 hours (Q12H) plus anastrozole or letrozole given orally every 24 hours (Q24H) on days 1 to 28 of a 28 day cycle. Participants receiving benefit may continue until disease progression.	Drug: Abemaciclib; Administered orally; Other Names: LY2835219; Drug: Anastrozole; Administered orally; Drug: Letrozole; Administered orally
Experimental: Placebo + NSAI; Placebo given orally Q12H plus anastrozole or letrozole given orally Q24H on days 1 to 28 of a 28 day cycle. Participants receiving benefit may continue until disease progression.	Drug: Placebo; Administered orally; Drug: Anastrozole; Administered orally; Drug: Letrozole; Administered orally
Experimental: Abemaciclib + Fulvestrant; Abemaciclib given orally Q12H on days 1 to 28 of a 28 day cycle plus fulvestrant intramuscularly (IM) on days 1 and 15 of cycle 1, then on day 1 of cycle 2 and beyond. Participants receiving benefit may continue until disease progression.	Drug: Abemaciclib; Administered orally; Other Names: LY2835219; Drug: Fulvestrant; Administered intramuscularly
Experimental: Placebo + Fulvestrant; Placebo given orally Q12H on days 1 to 28 of a 28 day cycle plus fulvestrant IM on days 1 and 15 of cycle 1, then on day 1 of cycle 2 and beyond. Participants receiving benefit may continue until disease progression.	Drug: Placebo; Administered orally; Drug: Fulvestrant; Administered intramuscularly

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Progression Free Survival (PFS) (Abemaciclib + NSAI & Placebo NSAI)	Progression-free survival time was measured from randomization until the date of objective progression as defined by Response Evaluation Criteria in Solid Tumors v1.1 (RECIST v1.1), or death from any cause. PD is defined as at least a 20% increase in the sum of the diameters of target lesions, with reference being the smallest sum on study and an absolute increase of at least 5 mm, or unequivocal progression of non-target lesions, or 1 or more new lesions. Patients who have neither progressed nor died were censored at the day of their last radiographic tumor assessment, if available, or date of randomization if no post-baseline radiographic assessment is available.	Randomization to Measured Progressive Disease or Death (up to 26 Months)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Progression Free Survival (PFS) (Abemaciclib + Fulvestrant and Placebo + Fulvestrant Arms)	Progression-free survival time was measured from randomization until the date of objective progression as defined by Response Evaluation Criteria in Solid Tumors v1.1 (RECIST v1.1), or death from any cause. PD is defined as at least a 20% increase in the sum of the diameters of target lesions, with reference being the smallest sum on study and an absolute increase of at least 5 mm, or unequivocal progression of non-target lesions, or 1 or more new lesions. Patients who have neither progressed nor died were censored at the day of their last radiographic tumor assessment, if available, or date of randomization if no post-baseline radiographic assessment is available.	Randomization to Measured Progressive Disease or Death (up to 26 Months)
Overall Survival (OS)		Randomization to Date of Death from Any Cause (Estimated up to 38 Months)
Percentage of Participants With Best Overall Response (BOR) of Complete Response (CR) or Partial Response (PR) [Objective Response Rate (ORR)]	Objective response rate is the percentage of participants with a BOR of CR or PR as defined by RECIST v1.1. CR is defined as the disappearance of all target and non-target lesions and no appearance of new lesions. PR is defined as at least a 30% decrease in the sum of the LD of target lesions (taking as reference the baseline sum LD), no progression of non-target lesions, and no appearance of new lesions.	Randomization to Measured Progressive Disease (up to 26 Months)
Duration of Response (DoR)		Date of CR or PR to Date of Objective Disease Progression or Death Due to Any Cause (Estimated up to 38 Months)
Percentage of Participants Who Exhibit Stable Disease (SD) or CR or PR [Disease Control Rate (DCR)]	Disease control rate (DCR) is the percentage of participants with a best overall response of CR, PR or SD as defined by RECIST v1.1. CR is defined as the disappearance of all target and non-target lesions and no appearance of new lesions. PR is defined as at least a 30% decrease in the sum of the longest diameter (LD) of target lesions (taking as reference the baseline sum LD), no progression of non-target lesions, and no appearance of new lesions. SD is neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for progressive disease (PD) for target lesions, no progression of non-target lesions, and no appearance of new lesions. PD is defined as at least a 20% increase in the sum of the diameters of target lesions, with reference being the smallest sum on study and an absolute increase of at least 5 mm, or unequivocal progression of non-target lesions, or 1 or more new lesions.	Randomization to Measured Progressive Disease (up to 26 Months)
Percentage of Participants With Best Overall Response of CR, PR, or SD With Duration of SD for at Least 6 Months [Clinical Benefit Rate (CBR)]	Clinical benefit rate (CBR) is the percentage of participants with a BOR of CR or PR, or SD for at least 6 months. CR is defined as the disappearance of all target and non-target lesions & no appearance of new lesions. PR is defined as at least a 30% decrease in the sum of the LD of target lesions (taking as reference the baseline sum LD), no progression of non-target lesions, and no appearance of new lesions. SD is neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for PD for target lesions, no progression of non-target lesions, and no appearance of new lesions. PD is defined as at least a 20% increase in the sum of the diameters of target lesions, with reference being the smallest sum on study and an absolute increase of at least 5 mm, or unequivocal progression of non-target lesions, or 1 or more new lesions.	Randomization to Measured Progressive Disease (up to 26 Months)
Change From Randomization in Symptom Burden on the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-C30 (EORTC QLQ-C30)	consists of 30 items covered by 1 of 3 dimensions: Global health status/quality of life (2 items) with scores ranging from 1 (Very Poor) to 7 (Excellent).; Functional scales (15 total items addressing either physical, role, emotional, cognitive, or social functioning), each item scores ranging from 1 (not at all) to 4 (very much); Symptom scales (13 total items addressing either fatigue, nausea/vomiting, pain, dyspnea, insomnia, appetite loss, constipation, diarrhea, or financial impact), each item scores ranging from 1 (not at all) to 4 (very much). Raw scores are linearly converted to a 0-100 scale with higher scores reflecting higher levels of function/QOL or higher levels of symptom burden.	Baseline through 19 Months
Pharmacokinetics (PK): Area Under the Concentration Curve of Abemaciclib, Its Metabolites (M2 & M20)	Pharmacokinetics (PK): Area Under the Concentration Curve of Abemaciclib and its Metabolites LSN2839567 (M2) & LSN3106726 (M20) was reported. C=Cycle, D=day;	C1D1 post dose, C2D1 post dose, C3D1 predose, C4D1 predose

Collaborators and Investigators

• Sponsor: Eli Lilly and Company
• Investigators: Study Director: Call 1-877-CTLILLY (1-877-285-4559) or 1-317-615-4559 Mon - Fri 9 AM - 5 PM Eastern time (UTC/GMT - 5 hours, EST), Eli Lilly and Company

Publications and helpful links

General Publications

• Zhang QY, Sun T, Yin YM, Li HP, Yan M, Tong ZS, Oppermann CP, Liu YP, Costa R, Li M, Cheng Y, Ouyang QC, Chen X, Liao N, Wu XH, Wang XJ, Feng JF, Hegg R, Kanakasetty GB, Coccia-Portugal MA, Han RB, Lu Y, Chi HD, Jiang ZF, Hu XC. MONARCH plus: abemaciclib plus endocrine therapy in women with HR+/HER2- advanced breast cancer: the multinational randomized phase III study. Ther Adv Med Oncol. 2020 Oct 22;12:1758835920963925. doi: 10.1177/1758835920963925. eCollection 2020.
• Hu X, Zhang Q, Sun T, Yin Y, Li H, Yan M, Tong Z, Li M, Teng Y, Oppermann CP, Kanakasetty GB, Portugal MC, Yang L, Zhang W, Jiang Z. Abemaciclib plus non-steroidal aromatase inhibitor or fulvestrant in women with HR+/HER2- advanced breast cancer: Final results of the randomized phase III MONARCH plus trial. Chin Med J (Engl). 2025 Jun 20;138(12):1477-1486. doi: 10.1097/CM9.0000000000003151. Epub 2024 Oct 10.

Helpful Links

• A Study of Abemaciclib (LY2835219) in Participants With Breast Cancer

Study record dates

Study Major Dates

• Study Start (Actual): December 5, 2016
• Primary Completion (Actual): March 29, 2019
• Study Completion (Estimated): March 1, 2028

Study Registration Dates

• First Submitted: May 4, 2016
• First Submitted That Met QC Criteria: May 4, 2016
• First Posted (Estimated): May 5, 2016

Study Record Updates

• Last Update Posted (Actual): February 5, 2026
• Last Update Submitted That Met QC Criteria: January 19, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: HER2-Negative; CDK4; CDK6; Hormone Receptor-Positive
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Skin Diseases; Breast Diseases; Skin and Connective Tissue Diseases; Breast Neoplasms; Hormones; Hormones, Hormone Substitutes, and Hormone Antagonists; Organic Chemicals; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Azoles; Polycyclic Compounds; Steroids; Fused-Ring Compounds; Nitriles; Estradiol; Estrenes; Estranes; Estradiol Congeners; Gonadal Steroid Hormones; Gonadal Hormones; Triazoles; Letrozole; Fulvestrant; Anastrozole; abemaciclib
• Other Study ID Numbers: 15530; I3Y-CR-JPBQ (Other Identifier: Eli Lilly and Company)