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)

Conditions

• Breast Neoplasms

Eligibility Criteria

Sex

ALL

Age

18 Years - N/A

Healthy Volunteers

Not accepted

Interventions

• pembrolizumab — BIOLOGICAL
  Intravenous (IV) infusion
• paclitaxel — DRUG
  IV infusion
• nab-paclitaxel — DRUG
  IV infusion
• liposomal doxorubicin — DRUG
  IV infusion
• capecitabine — DRUG
  oral administration
• normal saline — DRUG
  IV infusion
• dextrose — DRUG
  IV infusion

Study Details

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.

Key Dates

First listed

May 20, 2021

Start date

Jun 18, 2021

Status verified

Jul 2026

Primary completion

Apr 24, 2026

Completion

Dec 18, 2027

Study Design

Enrollment

342 participants (actual)

Allocation

RANDOMIZED

Intervention model

PARALLEL

Primary purpose

TREATMENT

Arms

• Experimental: Pembrolizumab + Chemotherapy
  Participants receive pembrolizumab 200 mg administered by intravenous infusion (IV) on Day 1 of each 21-day cycle (Q3W) PLUS one of four chemotherapy regimens: 1) paclitaxel 90 mg/m\^2 IV on Days 1, 8, and 15 of each 28-day cycle (Q4W), 2) nab-paclitaxel 100 mg/m\^2 IV on Days 1, 8, and 15 Q4W, 3) liposomal doxorubicin 50 mg/m\^2 IV on Day 1 Q4W, OR 4) capecitabine 1000 mg/m\^2 by oral administration (PO) twice a day (BID) on Days 1-14 Q3W for up to 35 administrations.
• Active Comparator: Placebo + Chemotherapy
  Participants receive placebo (normal saline or dextrose) IV on Day 1 Q3W PLUS one of four chemotherapy regimens: 1) paclitaxel 90 mg/m\^2 IV on Days 1, 8, and 15 Q4W, 2) nab-paclitaxel 100 mg/m\^2 IV on Days 1, 8, and 15 Q4W, 3) liposomal doxorubicin 50 mg/m\^2 IV on Day 1 Q4W, OR 4) capecitabine 1000 mg/m\^2 PO BID on Days 1-14 Q3W for up to 35 administrations.

Primary Outcome Measure

Progression-free Survival (PFS) per Response Evaluation Criteria in Solid Tumors 1.1 (RECIST 1.1) by Blinded Independent Central Review (BICR) in Participants With Combined Positive Score (CPS) ≥1 [ Time Frame: Up to approximately 50 months ]

Locations (41)

Related coverage on Hipa.ai

• Pembrolizumab Phase 3 Trial in HR+/HER2- Breast Cancer Reaches Primary…
  Pembrolizumab · Apr 24, 2026 · ClinicalTrials.gov

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