A Phase 1 Study of Oral OP-1250 in Combination With Palbociclib in HR+/HER2- Breast Cancer Patients

A Phase 1 Dose Escalation and Expansion Open-label, Multicenter, Study of OP-1250 in Combination With the CDK4/6 Inhibitor Palbociclib in Adult Subjects With Advanced or Metastatic HR-positive, HER2-negative Breast Cancer

Status

Active, not recruiting

Phases

Phase 1

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT05266105

Enrollment

Registered

2022-03-04

Start date

2021-12-10

Completion date

2026-03-31

Last updated

2025-11-24

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Breast Cancer

Brief summary

This is an open-label, Phase 1b dose escalation and expansion study to determine the maximum tolerated dose (MTD) of OP-1250 in combination with palbociclib (Ibrance®️, Pfizer Inc.). Purpose of study is to evaluate the safety and pharmacokinetic (PK) profile, and estimate the preliminary anti-tumor activity of the combination in adult subjects with hormone receptor-positive (ER+ / HER2-) advanced or metastatic breast cancer (MBC).

Interventions

DRUGPalazestrant

Complete Estrogen Receptor Antagonist

DRUGPalbociclib

Palbociclib is an approved CDK 4/6 Inhibitor drug

Study design

Allocation

NON_RANDOMIZED

Intervention model

SEQUENTIAL

Primary purpose

TREATMENT

Masking

NONE

Eligibility

Sex/Gender

ALL

Age

18 Years to No maximum

Healthy volunteers

Inclusion criteria

* Confirmed and evaluable locally advanced or metastatic breast cancer * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Must not have received prior oral endocrine or targeted therapy ≤ 2 weeks prior to first dose * Must not have received prior chemotherapy, antibody therapy, or investigational therapy ≤ 4 weeks prior to the first dose * Prior radiotherapy must have been completed 2 weeks prior to first dose * Adequate safety laboratory tests * Willingness to use effective contraception

Exclusion criteria

* Gastrointestinal disease * Significant hepatic disease * Significant cardiovascular disease * Significant ECG abnormalities * History of pulmonary embolism or high risk of thrombosis * Known HIV infection * Active infection (requiring antimicrobial therapy) * Pregnant

Design outcomes

Primary

Measure	Time frame
Incidence of Dose Limiting Toxicities	From Cycle 1 Day 1 through C1 Day 28
Characterization and Incidence in Adverse Events and Serious Adverse Events	From initial inform consent date through 30 days post last dose
Plasma levels of OP-1250 and Palbociclib	Up to 9 months

Countries

Australia

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: Feb 9, 2026