🏛️ Verified NIH Record • Updated 2026-07-21

Study of Pembrolizumab (MK-3475) Plus Chemotherapy Versus Placebo Plus Chemotherapy for HR+/HER2- Locally Recurrent Inoperable or Metastatic Breast Cancer (MK-3475-B49/KEYNOTE-B49) (NCT04895358)

A Randomized, Double-blind, Placebo-controlled, Phase 3 Study of Pembrolizumab Plus Chemotherapy Versus Placebo Plus Chemotherapy for the Treatment of Chemotherapy-Candidate Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative (HR+/HER2-) Locally Recurrent Inoperable or Metastatic Breast Cancer (KEYNOTE-B49)

🔵 Active, Not Recruiting Phase3 💊 Investigational Drug / Biologic Sponsor: Merck Sharp & Dohme LLC

🩺 Plain-English Summary (8th-Grade Level)

The safety and efficacy of pembrolizumab plus the investigator's choice of chemotherapy will be assessed compared to placebo plus the investigator's choice of chemotherapy in the treatment of chemotherapy-candidate hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) locally recurrent inoperable or metastatic breast cancer. The primary hypotheses are that the combination of pembrolizumab and chemotherapy is superior to placebo and chemotherapy in regards to Progression-Free Survival (PFS) in participants with programmed cell death-ligand 1 (PD-L1) combined positive score (CPS) ≥1. Prior to protocol amendment 7, participants who discontinued pembrolizumab/placebo with SD or better and subsequently experienced disease progression may have been eligible for up to 17 additional administrations of pembrolizumab if, upon unblinding, they were found to have received pembrolizumab, at the same dose and schedule used for the initial treatment period.

Who can join: To join this study, participants generally need to meet the listed inclusion criteria (19 items) and avoid the listed exclusions (27 items).

Location: University of Alabama at Birmingham-Medicine ( Site 0065) — Birmingham, Alabama

Age range: 18 Years

🧪 Interventions in This Study

📋 "Do I Qualify?" — 1-Minute Self Screener

Instant Checklist

Check every box below. If you can check all of them, you may meet the study's basic screening requirements (final eligibility is confirmed by the site team).

Usually NOT eligible if any of the following apply:

  • Exclusion Criteria:
  • Has breast cancer amenable to treatment with curative intent
  • Has a history or current evidence of any condition (e.g., transfusion-dependent anemia or thrombocytopenia), therapy, or laboratory abnormality that is specifically contraindicated per the current locally-approved labeling, that might confound the results of the study, interfere with the participant's involvement for the full duration of the study, or is not in the best interest of the participant to be involved, in the opinion of the treating investigator
  • Has significant cardiac disease, such as: history of myocardial infarction, acute coronary syndrome, coronary angioplasty/stenting/bypass within the last 6 months, congestive heart failure (CHF) New York Heart association (NYHA) Class II-IV, or history of CHF NYHA Class III or IV
  • Has advanced/metastatic, symptomatic visceral spread at risk of rapidly evolving into life-threatening complications, such as lymphangitic lung metastases, bone marrow replacement, carcinomatous meningitis, significant symptomatic liver metastases, shortness of breath requiring supplemental oxygen, symptomatic pleural effusion requiring supplemental oxygen, symptomatic pericardial effusion, symptomatic peritoneal carcinomatosis, or the need to achieve rapid symptom control
  • Has skin only disease
  • Has a known germline BRCA mutation (deleterious or suspected deleterious) and has not received previous treatment with PARP inhibition. either in the adjuvant or metastatic setting (where available and not medically contraindicated). Single-agent PARP inhibitor therapy does not count as a line of endocrine therapy.
  • Has received prior chemotherapy for locally recurrent inoperable or metastatic breast cancer
  • Has received prior therapy with an anti- programmed cell death 1 (PD-1), anti- programmed cell death ligand 1 (PD-L1), or anti- programmed cell death ligand 2 (PD-L2) agent or with an agent directed to another stimulatory or coinhibitory T-cell receptor (e.g., cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), OX-40, CD137)
  • Has received prior systemic anticancer therapy with other investigational agents within 4 weeks prior to randomization
  • Has received prior radiotherapy within 2 weeks of start of study intervention or radiation-related toxicities requiring corticosteroids.
  • Has received a live or live attenuated vaccine within 30 days prior to the first dose of study intervention

🔍 Extracted verbatim from the official NIH eligibility criteria. Always confirm with the study coordinator.

📍 All Participating Trial Locations (256 Sites)

Showing the first 25 of 256 sites.

  • University of Alabama at Birmingham-Medicine ( Site 0065) — Birmingham, Alabama
  • Arizona Oncology Associates-Arizona Oncology ( Site 0049) — Tucson, Arizona
  • Pacific Cancer Care ( Site 0023) — Monterey, California
  • UCSF Medical Center at Mission Bay ( Site 0043) — San Francisco, California
  • Georgetown University Medical Center-Department of Medicine and Oncology ( Site 0026) — Washington D.C., District of Columbia
  • MedStar Washington Hospital Center ( Site 0063) — Washington D.C., District of Columbia
  • Baptist MD Anderson Cancer Center ( Site 0013) — Jacksonville, Florida
  • Miami Cancer Institute at Baptist Health, Inc. ( Site 0070) — Miami, Florida
  • Miami Cancer Institute - Plantation ( Site 0076) — Plantation, Florida
  • University Cancer & Blood Center, LLC ( Site 0032) — Athens, Georgia
  • Northwest Georgia Oncology Centers, a Service of Wellstar Cobb Hospital-Research ( Site 0028) — Marietta, Georgia
  • University of Illinois at Chicago ( Site 0061) — Chicago, Illinois
  • Edward-Elmhurst Healthcare, Elmhurst Hospital-Nancy W. Knowles Cancer Center ( Site 0067) — Elmhurst, Illinois
  • Edward-Elmhurst Healthcare, Edward Hospital-Edward Cancer Center ( Site 0066) — Naperville, Illinois
  • Edward-Elmhurst Healthcare, Edward Hospital - Plainfield-Edward Cancer Center - Plainfield ( Site 00 — Plainfield, Illinois
  • Orchard Healthcare Research Inc. ( Site 0037) — Skokie, Illinois
  • Parkview Research Center at Parkview Regional Medical Center ( Site 0071) — Fort Wayne, Indiana
  • McFarland Clinic, PC ( Site 0041) — Ames, Iowa
  • Louisiana State University Health Sciences Shreveport ( Site 0072) — Shreveport, Louisiana
  • CHRISTUS Highland-Oncology Research ( Site 0073) — Shreveport, Louisiana
  • New England Cancer Specialists ( Site 0007) — Scarborough, Maine
  • Greater Baltimore Medical Center-Medical Oncology/Hematology ( Site 0062) — Baltimore, Maryland
  • MFSMC-HJWCI ( Site 0064) — Baltimore, Maryland
  • MedStar Good Samaritan Hospital-Oncology Research ( Site 0069) — Baltimore, Maryland
  • University of Massachusetts Medical School-Division of Hematology/Oncology ( Site 0052) — Worcester, Massachusetts

💰 Cost, Insurance & Patient Rights

  • 100% Free Items: The investigational treatment and protocol-required procedures are supplied at zero cost by the sponsor.
  • Routine Patient Care: Under federal law (ACA § 2709) and many state statutes, routine care costs are covered during participation.
  • Voluntary Participation: You may withdraw at any time without affecting your standard medical care.

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💡 How to Participate

  1. Check the checklist above to see if you may qualify.
  2. Review the official NIH record below to find the coordinating site.
  3. Ask about the visit schedule, what is covered at no cost, and any travel support.
  4. Confirm with your own doctor before making a decision.
🏛️ View Official NIH Record ↗