Breast CancerPhase 1NCT05266105
A Phase 1 Study of Oral OP-1250 in Combination With Palbociclib in HR+/HER2- Breast Cancer Patients
A Phase 1 study testing Palazestrant and Palbociclib in people with Breast Cancer, run by Olema Pharmaceuticals, Inc. at 8 sites in Australia.
Trial 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.). Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Breast Cancer
- What is being tested?
- Palazestrant and Palbociclib
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 60 participants
- Where
- 8 sitesAustralia
- Study dates
- 10 Dec 2021to Mar 2026
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- 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
Trial locations and contacts
8 sites in 1 country.
8 sites in 1 country
Australia8 sites
Clinical Trial Site
Clayton, Victoria, 3168
Clinical Trial Site
Frankston, Victoria, 3199
Clinical Trial Site
Geelong, Victoria, 3220
Clinical Trial Site
Nedlands, Western Australia, 6009
Clinical Trial Site
South Brisbane, Queensland, 4101
Clinical Trial Site
Southport, Queensland, 4215
Clinical Trial Site
Waratah, New South Wales, 2298
Clinical Trial Site
Westmead, New South Wales, 2145
About this study
Official title: 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
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).
- Conditions
- Breast Cancer
- Being tested
- Palazestrant, Palbociclib
- Medical subject headings
- Breast Neoplasms
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
PalazestrantDrug
Also called OP-1250
Complete Estrogen Receptor Antagonist
PalbociclibDrug
Also called Ibrance®️
Palbociclib is an approved CDK 4/6 Inhibitor drug
| Study group | Role | What they receive |
|---|---|---|
| Dose Escalation | Experimental | This portion of the study will evaluate the safety and pharmacology of a range of OP-1250 doses administered daily with Palbociclib in subjects with advanced and/or metastatic hormone receptor (HR)-positive, HER2-negative breast cancer Receives: Drug: Palazestrant; Drug: Palbociclib |
| Dose Expansion | Experimental | This portion of the study further explores the clinical activity, safety and pharmacology of OP-1250 in combination with Palbociclib and estimates preliminary data of anti-tumor efficacy Receives: Drug: Palazestrant; Drug: Palbociclib |
What is being measured
The primary outcome is the main question the study is designed to answer.
Incidence of Dose Limiting Toxicities
Measured: From Cycle 1 Day 1 through C1 Day 28
Characterization and Incidence in Adverse Events and Serious Adverse Events
Measured: From initial inform consent date through 30 days post last dose
Plasma levels of OP-1250 and Palbociclib
Measured: Up to 9 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted4 Mar 2022
- Study start10 Dec 2021
- Primary completionMar 2026 (estimated)
- Study completionMar 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Breast CancerStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Enrolment
- 60 participants (actual)
Sponsor and investigators
- Lead sponsor
- Olema Pharmaceuticals, Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Collaborators
- Pfizer
- Responsible party
- Sponsor
- Investigators
- Sue Johnson, Study director, Olema Pharmaceuticals, Inc.
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05266105
- Sponsor's protocol ID
- OP-1250-002
- Status last verified
- Nov 2025
- First submitted
- 11 Feb 2022
- Last updated
- 24 Nov 2025
- Results posted
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 24 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- 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
- ClinicalTrials.gov ID
- NCT05266105
- Acronym / sponsor ID
- OP-1250-002
- Conditions
- Breast Cancer
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 60 participants (actual)
- Lead sponsor
- Olema Pharmaceuticals, Inc.Industry (pharma, biotech, devices)
- Collaborators
- Pfizer
- Study start
- 10 Dec 2021 (actual)
- Primary completion
- Mar 2026 (estimated)
- Study completion
- Mar 2026 (estimated)
- First posted
- 4 Mar 2022 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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).
Study design
- Primary purpose
- Treatment
- Allocation
- Non-randomised
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Dose Escalation | Experimental | Drug: Palazestrant, Drug: PalbociclibThis portion of the study will evaluate the safety and pharmacology of a range of OP-1250 doses administered daily with Palbociclib in subjects with advanced and/or metastatic hormone receptor (HR)-positive, HER2-negative breast cancer |
| Dose Expansion | Experimental | Drug: Palazestrant, Drug: PalbociclibThis portion of the study further explores the clinical activity, safety and pharmacology of OP-1250 in combination with Palbociclib and estimates preliminary data of anti-tumor efficacy |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- 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
Key exclusion criteria (8 listed)
- Gastrointestinal disease
- Significant hepatic disease
- Significant cardiovascular disease
- Significant ECG abnormalities
- History of pulmonary embolism or high risk of thrombosis
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| PalazestrantAlso: OP-1250Complete Estrogen Receptor Antagonist | Drug | Dose Escalation, Dose Expansion |
| PalbociclibAlso: Ibrance®️Palbociclib is an approved CDK 4/6 Inhibitor drug | Drug | Dose Escalation, Dose Expansion |
Primary outcome
Incidence of Dose Limiting Toxicities
Time frame: From Cycle 1 Day 1 through C1 Day 28
Characterization and Incidence in Adverse Events and Serious Adverse Events
Time frame: From initial inform consent date through 30 days post last dose
Plasma levels of OP-1250 and Palbociclib
Time frame: Up to 9 months
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Nov 2025.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Sue Johnson study director
Olema Pharmaceuticals, Inc.
8 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Palazestrant and Palbociclib in people with Breast Cancer, run by Olema Pharmaceuticals, Inc. at 8 sites in Australia.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 24 Nov 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 8 sites in Australia. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Incidence of Dose Limiting Toxicities (time frame: From Cycle 1 Day 1 through C1 Day 28). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Nov 2025.