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NCT Number: NCT05169567

Abemaciclib (LY2835219) Plus Fulvestrant Compared to Placebo Plus Fulvestrant in Previously Treated Breast Cancer

This study will evaluate the effect of adding abemaciclib to fulvestrant for the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer that progressed or recurred after previous treatment with a type of drug known as a CDK4/6 inhibitor and endocrine therapy. Participation could last up to 5 years, depending on how you and your tumor respond.

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This study is active but is not currently recruiting participants.

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Key information

Conditions

Breast Neoplasm Breast Diseases Breast Neoplasms Neoplasm Metastasis Neoplasms Neoplasms by Site Neoplastic Processes Pathologic Processes Pathological Conditions, Signs and Symptoms Skin Diseases Skin and Connective Tissue Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 3

Primary location

Fundación Respirar, Buenos Aires, Buenos Air, Argentina

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Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Have a diagnosis of HR+, HER2- locally advanced or metastatic breast cancer
  • Have radiologic evidence of disease progression or recurrence either
  • On treatment with a CDK4/6 inhibitor with aromatase inhibitor (AI) as initial therapy for advanced disease, or
  • On/after treatment with a CDK4/6 inhibitor plus endocrine therapy (ET) administered as adjuvant therapy for early stage breast cancer
  • Must be deemed appropriate for treatment with ET
  • If female, have a postmenopausal status by natural or surgical means or by ovarian function suppression
  • Have Response Evaluable Criteria in Solid Tumors (RECIST) evaluable disease (measurable disease and/or nonmeasurable disease)
  • Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group scale (Oken et al. 1982)
  • Have adequate renal, hematologic, and hepatic organ function
  • Must be able to swallow capsules/tablets

Exclusion criteria

  • Have visceral crisis, lymphangitic spread, or leptomeningeal carcinomatosis
  • Have symptomatic or untreated central nervous system metastasis
  • Have received any systemic therapy between disease recurrence/progression and study screening
  • Have received more than 1 line of therapy for advanced or metastatic disease.
  • Have received prior chemotherapy for metastatic breast cancer (MBC)
  • Have received prior treatment with fulvestrant, any investigational estrogen receptor (ER)-directed therapy (including selective ER degraders [SERDs] and non-SERDs), any phosphatidylinositol 3-kinase (PI3K)-, mammalian target of rapamycin (mTOR)-, or protein kinase B (AKT)-inhibitor

Treatment and study plan

Abemaciclib

Drug

Administered orally.

Fulvestrant

Drug

Administered IM.

Placebo

Drug

Administered orally.

Primary outcomes

  1. Progression-Free Survival (PFS)

    Time frame: Randomization to the date of first documented progression of disease or death from any cause (Up to 21 Months)

    PFS defined as the time from the date of randomization to the first evidence of disease progression as defined by response evaluation criteria in solid tumors (RECIST) v1.1 or death from any cause. Progressive Disease (PD) was 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. If a participant does not have a complete baseline disease assessment, then the PFS time was censored at the date of randomization, regardless of whether or not objectively determined disease progression or death has been observed for the participant. If a participant was not known to have died or have objective progression as of the data inclusion cutoff date for the analysis, the PFS time was censored at the last adequate tumor assessment date.

Secondary outcomes

  1. Progression Free Survival (PFS) Determined by Blinded Independent Central Review (BICR)

    Time frame: Randomization to the date of first documented progression of disease or death from any cause (Up to 22 Months)

    PFS is defined as the time from the date of randomization to the earliest date of disease progression determined by blinded independent central review (BICR) or death from any cause, whichever occurs first.

  2. Objective Response Rate (ORR): Percentage of Participants Who Achieved a Best Overall Response (BOR) of Complete Response (CR) or Partial Response (PR)

    Time frame: Randomization until measured progressive disease (Up to 22 Months)

    ORR is the best overall tumor response of CR or PR as classified by the investigator according to the Response Evaluation Criteria In Solid Tumors (RECIST v1.1). CR is a disappearance of all target and non-target lesions and normalization of tumor marker level. PR is an at least 30% decrease in the sum of the diameters of target lesions (taking as reference the baseline sum diameter) without progression of non-target lesions or appearance of new lesions.

Sponsors and collaborators

Lead sponsor

Eli Lilly and Company

Industry

Registry information

Official study title

postMONARCH: A Randomized, Double Blind, Placebo-Controlled, Phase 3 Study to Compare the Efficacy of Abemaciclib Plus Fulvestrant to Placebo Plus Fulvestrant in Participants With HR+, HER2-, Advanced or Metastatic Breast Cancer Following Progression on a CDK4 & 6 Inhibitor and Endocrine Therapy

Acronym: postMONARCH

Important dates

Study start
2022
Primary completion
2024
Study completion
2027
First posted
Dec 27, 2021
Registry last updated
Jan 16, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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