NCT04735367 is a clinical trial of palbociclib plus letrozole in Breast Cancer, sponsored by Pfizer.

Who is sponsoring NCT04735367?

NCT04735367 is sponsored by Pfizer.

What drugs are being tested in NCT04735367?

Interventions in NCT04735367: palbociclib plus letrozole.

What condition does NCT04735367 study?

NCT04735367 studies Breast Cancer.

Is NCT04735367 still recruiting?

NCT04735367 is currently completed. Last updated 9 December 2025.

Are results published for NCT04735367?

Yes — primary outcome results have been posted to ClinicalTrials.gov. See the outcomes section above for details.

Last reviewed 2025-12-09 · How we verify

NCT04735367

Name: Drug Landscape Pharmaceutical Database
Creator: Drug Landscape
Published: 2026-01-01
License: https://creativecommons.org/licenses/by/4.0/

Study to Evaluate Overall Survival in Japanese Patients With HR+/HER2- Advanced Breast Cancer Treated With Palbociclib Plus Letrozole

Completed Results posted Last updated 9 December 2025

What this trial tests

trial testing palbociclib plus letrozole in Breast Cancer in 42 participants. Completed in 29 September 2023.

Timeline

3 February 2021

Primary endpoint
29 September 2023

29 September 2023

Quick facts

Lead sponsor	Pfizer
Status	Completed
Study type	OBSERVATIONAL
Enrollment	42
Start date	3 February 2021
Primary completion	29 September 2023
Estimated completion	29 September 2023
Sites	13 locations across Japan

Drugs / interventions tested

palbociclib plus letrozole (palbociclib-plus-letrozole) — full drug profile →

Conditions studied

Breast Cancer — all drugs for Breast Cancer →

Sponsor

Pfizer — full company profile →

Who can join

20 and older, female only, with Breast Cancer. Patients with the condition only — healthy volunteers not accepted.

Sponsor's own description

This is a retrospective, multicenter, observational study in Japan. The primary objective is to evaluate overall survival (OS) in Japanese patients with HR+/HER2- advanced breast cancer who have been treated with palbociclib plus letrozole. This observational study was planned as follow-up study of Japanese phase 2 study of palbociclib (NCT01684215, phase 2 portion of A5481010 study).

Publications & conference data

2 peer-reviewed publications reference this trial (live from Europe PMC):

Overall survival in Japanese patients with ER+/HER2- advanced breast cancer treated with first-line palbociclib plus letrozole.
Takahashi M, Osako T, Yasojima H, Inoue K, et al · · 2024 · cited 4× · PMID 37882974 · DOI 10.1007/s12282-023-01511-z
Overall survival and subsequent therapy patterns in Japanese patients with ER+/HER2- advanced breast cancer treated with palbociclib plus letrozole in the first-line setting: a final analysis.
Takahashi M, Yasojima H, Osako T, Inoue K, et al · · 2025 · PMID 40841781 · DOI 10.1007/s12282-025-01760-0

Verify or expand the search:

Other recruiting trials for Breast Cancer

Currently open trials in the same condition.

NCT06148038 — CBD for Breast Cancer Primary Tumors · Phase 1 · recruiting
NCT07405801 — A Phase II Study Evaluating the Efficacy and Safety of Inavolisib Plus Ribociclib Plus Fulvestrant Versus Placebo Plus R · Phase 2 · recruiting
NCT07285993 — Detection and Outcomes in Metastatic Invasive Lobular Breast Cancer Through Novel F-18 FAP PET · Phase 2 · recruiting
NCT07510698 — Same-Day Awake Mastectomy With Immediate Breast Reconstruction for Patients With Breast Cancer · NA · recruiting
NCT06768931 — Biolosion Combined Standard Neoadjuvant Therapy to Treat Triple-negative Breast Cancer · Phase 2 · recruiting

Other Pfizer trials

Trials by the same sponsor.

NCT04982848 — Korea Post Marketing Surveillance (PMS) Study of Talzenna® · not yet recruiting
NCT06873191 — A Study to Learn More About Tukysa Once it is Out in the Korean Market · not yet recruiting
NCT07497854 — A Study to Learn About the Study Medicine NURTEC® ODT 75 mg After it is Released Into the Markets in Korea · not yet recruiting
NCT06507904 — A Study to Learn How Different Preparations of Osivelotor Taste and Enter the Blood With Food or Liquids or With an Anta · Phase 1 · not yet recruiting
NCT06864585 — A Study to Learn About the Study Medicine - Zavicefta in Patients With Sepsis or Loss of Kidney Function in Japan · not yet recruiting

Verify against primary sources

ClinicalTrials.gov — authoritative US registry record
WHO ICTRP — international registry index
EU Clinical Trials Register
Sponsor press releases (Google)

Data sources for this page

Trial protocol + status: ClinicalTrials.gov NCT04735367 (US National Library of Medicine, public domain)
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Pfizer
Last refreshed: 9 December 2025

Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT04735367.

Primary sources · FDA · ClinicalTrials.gov · EMA · SEC EDGAR · ChEMBL · Wikidata · full sourcing