# KEYNOTE-B49: HCP commentary report

> 74 verified statements (27 from clinicians verified by NPI or staff page) from 40 commentary sources · 8 findings · updated Oct 31, 2026

## Report

- Trial: 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)
- NCT ID: NCT04895358
- Registry: https://clinicaltrials.gov/study/NCT04895358
- Sponsor: Merck Sharp & Dohme LLC
- Phase: Phase 3
- Status: Active, not recruiting
- Drugs tested: pembrolizumab
- Indication: HR+/HER2- locally recurrent inoperable or metastatic breast cancer
- Version: v1.0.0, edition 1
- Accepted: 2026-10-31
- Last checked: 2026-10-31
- Release hash: cf3fed2cda20b0f0deaf9ad2a08a6373fbbf6ff537bdc9ef9bf53c6b4256a845

## Counts

- HCP commentary sources screened: 101
- Sources cited by verified statements: 42
- Verified statements: 74
- From speakers with a confirmed clinical role (verified by the NPI registry or their own institution's staff page): 27
- Findings: 8
- Named people in screened sources (unnamed speakers and accounts not counted): 29
- Voices cited: 28
- Cited voices identity-verified: 23
- Organisational or shared accounts (not counted as people): 4

Counts describe the retained sources. They do not estimate how many HCPs hold a view.

## Abstract

Clinician commentary on KEYNOTE-B49 in the sources reviewed for this edition leads to one open question: Which biomarker-defined patients, if any, have a sufficiently credible durable-benefit signal to justify added toxicity and treatment burden against contemporary alternatives? Its leading findings: (1) statistical positivity does not settle the case for broad adoption. (2) late benefit and higher CPS sustain selective interest, with important evidentiary limits. (3) toxicity, administration burden and cost are part of the benefit assessment. 5 more findings follow. 101 sources screened, 42 cited; not all HCPs or all public discussion.

## Open Medical Affairs question

Which biomarker-defined patients, if any, have a sufficiently credible durable-benefit signal to justify added toxicity and treatment burden against contemporary alternatives?

Raised by the leading finding. The report shows what clinicians said and the sources behind it; it does not settle the question.

## Findings (titles)

- F1. Statistical positivity does not settle the case for broad adoption
- F2. Late benefit and higher CPS sustain selective interest, with important evidentiary limits
- F3. Toxicity, administration burden and cost are part of the benefit assessment
- F4. The ADC-era comparator and sequencing question changes perceived relevance
- F5. Better selection is both a biological question and a testing-feasibility problem
- F6. The biological rationale remains contested, with earlier evidence kept separate from metastatic results
- F7. Conference interest is not equivalent to local treatment availability
- F8. Scientific value, public reception and consensus are different questions

## What sits behind each finding

Counts describe what the report retained, not how many clinicians hold a view. A statement can support more than one finding.

| Finding | Statements | Passages | Sources | Named voices | Counterview | Limitations |
| --- | ---: | ---: | ---: | ---: | --- | ---: |
| F1 | 10 | 10 | 10 | 9 | recorded | 2 |
| F2 | 10 | 9 | 8 | 7 | recorded | 4 |
| F3 | 7 | 8 | 6 | 6 | recorded | 3 |
| F4 | 7 | 7 | 6 | 4 | none recorded | 3 |
| F5 | 9 | 9 | 8 | 8 | recorded | 3 |
| F6 | 10 | 8 | 7 | 3 | recorded | 3 |
| F7 | 4 | 3 | 1 | 0 | none recorded | 3 |
| F8 | 11 | 15 | 9 | 7 | recorded | 4 |

### What the statements are

| Finding | Views | Questions and uncertainty | Clinical experience | Comparisons | Restated results and context | Passages supporting | Passages giving context | Sources by kind | Feeds the Medical Affairs question |
| --- | ---: | ---: | ---: | ---: | ---: | ---: | ---: | --- | --- |
| F1 | 9 | 1 | 0 | 0 | 0 | 11 | 0 | 10 posts and articles | yes |
| F2 | 7 | 0 | 0 | 0 | 3 | 10 | 1 | 7 posts and articles, 1 podcast or video | yes |
| F3 | 4 | 1 | 1 | 0 | 1 | 7 | 1 | 5 posts and articles, 1 podcast or video | yes |
| F4 | 4 | 1 | 0 | 2 | 0 | 7 | 1 | 5 posts and articles, 1 podcast or video | yes |
| F5 | 8 | 0 | 0 | 0 | 1 | 10 | 0 | 7 posts and articles, 1 publication | yes |
| F6 | 4 | 3 | 0 | 1 | 2 | 14 | 1 | 6 posts and articles, 1 podcast or video | yes |
| F7 | 1 | 1 | 0 | 0 | 2 | 7 | 0 | 1 podcast or video | yes |
| F8 | 5 | 0 | 0 | 2 | 4 | 13 | 7 | 8 posts and articles, 1 podcast or video | no |

### Trial dimensions

- Primary endpoint: 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: F1 (8 shared claims), F2 (6 shared claims), F3 (2 shared claims), F4 (1 shared claims), F5 (1 shared claims), F8 (2 shared claims)
- Secondary endpoints: F1 (5 shared claims), F2 (9 shared claims), F3 (2 shared claims), F4 (2 shared claims), F5 (1 shared claims), F8 (1 shared claims)
- Population and setting: F1 (4 shared claims), F2 (1 shared claims), F4 (1 shared claims), F5 (8 shared claims), F6 (7 shared claims), F7 (1 shared claims), F8 (2 shared claims)
- The comparison: F3 (1 shared claims), F4 (1 shared claims), F7 (1 shared claims), F8 (1 shared claims)
- Safety and tolerability: F2 (3 shared claims), F3 (4 shared claims)
- Design and conduct: F1 (1 shared claims), F2 (1 shared claims), F5 (2 shared claims), F8 (1 shared claims)

## Sample findings

Paraphrased; the full report links each statement to its source.

## What's inside

| Section | Items | Access |
| --- | ---: | --- |
| Findings with interpretation, counterviews and limits | 8 | Titles free |
| Detailed analysis | 9 sections | Paid |
| Verified statements with short source quotes and links | 74 | Paid |
| Trial aspects mapped | 12 | Free |
| Sources with links | 42 | Counts free |
| Speaker attribution for cited voices | 28 | Paid |

## Trial aspects

12 discussed · 0 no commentary found · 0 assessment incomplete.

| Aspect | Coverage | Statements | Sources |
| --- | --- | ---: | ---: |
| Primary endpoint: 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 | discussed | 21 | 18 |
| Secondary endpoints | discussed | 21 | 18 |
| Population and setting | discussed | 22 | 19 |
| The comparison | discussed | 7 | 5 |
| Safety and tolerability | discussed | 5 | 5 |
| Design and conduct | discussed | 3 | 3 |
| Contemporary alternatives, ADC partners and sequencing | discussed | 8 | 6 |
| Patient burden, cost and individualized value | discussed | 6 | 5 |
| Biomarker work-up, tissue adequacy and translational research | discussed | 14 | 10 |
| Biological rationale and prior evidence relevant to the metastatic decision | discussed | 11 | 8 |
| Local access and patient-facing treatment discussion | discussed | 5 | 2 |
| Scientific contribution, reception and limits of consensus inference | discussed | 10 | 8 |

An aspect marked incomplete is a question the public commentary did not let us answer. We show it rather than hide it.

## Sources

| Channel | Screened | Cited |
| --- | ---: | ---: |
| X threads | 92 | 35 |
| YouTube | 4 | 2 |
| LinkedIn posts | 2 | 2 |
| Bluesky threads | 2 | 0 |
| Podcasts | 1 | 1 |
| Publications (primary source, cited for context) | not screened | 1 |
| Registry (primary source, cited for context) | not screened | 1 |

- Screened window: 2021-05-20 to 2026-10-30
- Cited window: 2023-07-05 to 2026-10-30
- Retrieved: 2026-10-31

Screened sources were retrieved for this trial. Cited sources back at least one verified statement and include primary sources used for context.

## The trial

From ClinicalTrials.gov.

- Title: 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)
- Registry: NCT04895358 (https://clinicaltrials.gov/study/NCT04895358)
- Study IDs: 3475-B49 · MK-3475-B49 (MSD) · KEYNOTE-B49 (MSD) · 2023-506752-24-00 (EU CT) · U1111-1294-3354 (UTN) · jRCT2051210049 (Japan Registry of Clinical Trials (jRCT)) · PHRR210721-003751 (Philippine Health Research Registry (PHRR)) · 2020-005407-38
- Sponsor: Merck Sharp & Dohme LLC
- Design: Phase 3 · interventional, randomized, parallel, phase3
- Status: Active, not recruiting
- Enrollment: 342 (actual)
- Start: 2021-06-18 (actual)
- Primary completion: 2026-04-24 (actual)
- Primary endpoint: 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 (Up to approximately 50 months)
- Intervention: pembrolizumab (biological)
- Intervention: paclitaxel (drug)
- Intervention: nab-paclitaxel (drug)
- Intervention: liposomal doxorubicin (drug)
- Intervention: capecitabine (drug)
- Intervention: normal saline (drug)
- Intervention: dextrose (drug)

## Scope and limits

This report does not judge efficacy, estimate HCP prevalence or consensus or give treatment advice.

- Discussion that does not name the trial may be missing from this edition.
- Not yet captured in this edition: a view on overall survival, CPS-specific progression-free survival and chemotherapy distribution with pembrolizumab plus chemotherapy.
- Some clinician views in the sources used in this report are not yet captured as evidence in this edition.
- Some passages in the sources used in this report were not fully assessed for clinician views, so a view there may be missing from this edition.
- 70 statements in the sources reviewed for this edition are about other patients or topics, or only mention the trial, and are not counted.
- Further source limits: discussion that describes the trial without naming it may be incomplete; some discussion that describes the trial without naming it may be missing; sources about other trials are not included.
- The sources reviewed for this edition are not a representative sample of HCP opinion. Reposts, quotations and repeated posts cannot be counted as additional independent speakers.
- Some passages and organizational commentary were not fully assessed, so additional interpretations or qualifications may be absent.
- Some speakers' identities or clinical roles are not established in the sources used in this report; each statement is attributed only as far as its source shows.
- A full study protocol was not available for assessment, limiting independent evaluation of amendments and planned analyses.
- Drug-label review was incomplete, including no exact nab-paclitaxel label. The Japan approval statement applies to October 2026 and cannot establish current or international availability.
- The publication excerpt supports methods. Efficacy and safety figures in this report are attributed to the commentators who reported them, not independently reconstructed from results tables.
- Higher-CPS observations include small numbers and secondary-endpoint qualifications. CPS greater than ten and CPS ≥10 are preserved as stated, and a speaker's subgroup label rendered as 19 remains uncertain.
- Late-tail percentages and terminology differ across authors and have not been harmonized. A speaker's remaining-on wording is not assumed to be a specified PFS rate.
- OS maturity is described differently by two speakers. The sources do not justify silently reconciling pending mature OS with final OS.
- The interview's three deaths during the study lack arm and causality information and must not be equated with a reported treatment-related fatal-event rate.
- Earlier-stage I-SPY 2 evidence, prior metastatic studies and personal treatment experience explain views but are not KEYNOTE-B49 outcomes.

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## Editions and corrections

- v1.0.0, accepted 2026-10-31: current edition

Last checked for new commentary 2026-10-31. No corrections. Versions follow semver: a new or changed finding is a minor version, more evidence without a material change is a patch.

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## Cite

Erudio Health. KEYNOTE-B49 (NCT04895358): HCP commentary report. Edition 1, v1.0.0. Accepted Oct 31, 2026. https://www.erudio.com/reports/keynote-b49-nct04895358

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