Metastatic Breast CancerPhase 1PHOEBENCT05900895
Estradiol Plus Olaparib for Breast Cancer (PHOEBE)
A Phase 1 study testing Olaparib and 17b-estradiol in people with Metastatic Breast Cancer, run by Mary D Chamberlin at 1 site in United States.
Trial summary
Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast cancer. Read more about this study
- Who is it for?
- Ages 18 years and older, women only
- Conditions the study is for
- Metastatic Breast Cancer
- What is being tested?
- Olaparib and 17b-estradiol
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 6 participants
- Where
- 1 siteUnited States
- Study dates
- 15 Jul 2024to Dec 2028
- 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
- Women only
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Post-menopausal women with ER+/HER2- breast cancer.
- Metastatic or locoregional recurrence not amenable to treatment with curative intent.
- Received ≥1 prior line of endocrine-based therapy in the advanced/metastatic setting.
Who cannot join
- During study treatment, no concurrent anti-cancer therapies are allowed with the following exceptions:
- o Anti-resorptive bone therapies (e.g., bisphosphonates, denosumab) permitted.
- Any investigational cancer therapy or systemic chemotherapy in the last 3 weeks.
- Any radiation therapy in the last 2 weeks.
- Known CNS disease, unless clinically stable for ≥ 3 months.
- Concomitant use of known strong or moderate CYP3A inhibitors.
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- Persistent toxicities (≥CTCAE grade 2) caused by previous cancer therapy.
- History of any of the following:
- Deep venous thrombosis
- Pulmonary embolism
- Stroke
- Acute myocardial infarction
- Congestive heart failure
- Previous malignancy not treated with curative intent, or with an estimated recurrence risk ≥30%
- Severe renal impairment (creatinine clearance ≤ 30 mL/min).
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Dartmouth Cancer Center
Lebanon, New Hampshire, 03756
Mary D Chamberlin, MD, 603-653-6181, mary.d.chamberlin@hitchcock.org
Ashley E Gaughan-Maher, MA, 603-653-0628, ashley.e.gaughan-maher@hitchcock.org
About this study
Official title: Phase 1b Study of Olaparib and Estradiol in Advanced ER+ Breast Cancer (PHOEBE)
Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast cancer.
Read the detailed description
Patients with endocrine-resistant ER+/HER2- breast cancer are eligible. Patients will be treated with the combination of 17b-estradiol and olaparib for 2 cycles, and then treated with single-agent 17b-estradiol until disease progression. Clinical benefit, progression-free survival, objective response, tumor metabolic response, and toxicity will be determined.
- Conditions
- Metastatic Breast Cancer
- Being tested
- Olaparib, 17b-estradiol
- Keywords
- metastatic, locally advanced, estradiol therapy, olaparib
- Medical subject headings
- Breast Neoplasms, Neoplasm Metastasis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
OlaparibDrug
Also called Lynparza
Participants will be treated with olaparib at the approved doses for the treatment of subtypes of breast cancer or at reduced dose/frequency for participants with moderate renal impairment.
17b-estradiolDrug
Also called Estrace
17b-estradiol will be taken orally three times per day.
| Study group | Role | What they receive |
|---|---|---|
| Treatment Arm | Experimental | Participants receive 2 cycles of olaparib in combination with 17b-estradiol and then continue to be treated with single-agent 17b-estradiol until disease progression. Receives: Drug: Olaparib; Drug: 17b-estradiol |
What is being measured
The primary outcome is the main question the study is designed to answer.
Determine the Phase II dose of olaparib in combination with 17b-estradiol
Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast cancer.
Measured: 8 weeks
Secondary outcomes (5)
Clinical benefit rate
The proportion of evaluable patients experiencing clinical benefit (stable disease at 24 weeks, complete or partial response per RECIST) will be measured.
Measured: 6 months
Objective response rate
The proportion of evaluable patients experiencing objective response (complete or partial response per RECIST) will be measured.
Measured: 6 months
Progression-free survival
Progression-free survival will be measured by measuring the length of time between the start of study treatment until the time of cancer progression or death from any cause.
Measured: 12 months
Plasma Olaparib concentration
The concentration of Olaparib in plasma will be measured over 6 hours.
Measured: 6 hours
Plasma 17b-Estradiol/Estrone concentration
The concentration of 17b-Estradiol/Estrone in plasma will be measured over 6 hours.
Measured: 6 hours
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 Jun 2023
- Study start15 Jul 2024
- Primary completionDec 2027 (estimated)
- Study completionDec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Metastatic 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
- Not applicable
- Intervention model
- Sequential
- Model description
- Single-arm, 3+3 design with a dose-expansion cohort.
- Masking
- None (open label)
- Enrolment
- 6 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Mary D Chamberlin
- Sponsor type
- University, hospital or other
- Collaborators
- Dartmouth-Hitchcock Medical Center
- Responsible party
- Sponsor-investigator, Mary D Chamberlin, Dartmouth-Hitchcock Medical Center
- Investigators
- Mary Chamberlin, MD, Principal investigator, Dartmouth-Hitchcock Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05900895
- Sponsor's protocol ID
- STUDY02002007
- Acronym
- PHOEBE
- Status last verified
- Oct 2025
- First submitted
- 24 May 2023
- Last updated
- 20 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 20 Nov 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Phase 1b Study of Olaparib and Estradiol in Advanced ER+ Breast Cancer (PHOEBE)
- ClinicalTrials.gov ID
- NCT05900895
- Acronym / sponsor ID
- PHOEBE / STUDY02002007
- Conditions
- Metastatic Breast Cancer
- Keywords
- metastatic, locally advanced, estradiol therapy, olaparib
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 6 participants (estimated)
- Lead sponsor
- Mary D ChamberlinUniversity, hospital or other
- Collaborators
- Dartmouth-Hitchcock Medical Center
- Study start
- 15 Jul 2024 (actual)
- Primary completion
- Dec 2027 (estimated)
- Study completion
- Dec 2028 (estimated)
- First posted
- 13 Jun 2023 (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.
Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast cancer.
Detailed description
Patients with endocrine-resistant ER+/HER2- breast cancer are eligible. Patients will be treated with the combination of 17b-estradiol and olaparib for 2 cycles, and then treated with single-agent 17b-estradiol until disease progression. Clinical benefit, progression-free survival, objective response, tumor metabolic response, and toxicity will be determined.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Sequential
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Single-arm, 3+3 design with a dose-expansion cohort.
| Arm | Type | Receives |
|---|---|---|
| Treatment Arm | Experimental | Drug: Olaparib, Drug: 17b-estradiolParticipants receive 2 cycles of olaparib in combination with 17b-estradiol and then continue to be treated with single-agent 17b-estradiol until disease progression. |
Who may qualify
- Ages
- 18 years and older
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Post-menopausal women with ER+/HER2- breast cancer.
- Metastatic or locoregional recurrence not amenable to treatment with curative intent.
- Received ≥1 prior line of endocrine-based therapy in the advanced/metastatic setting.
Key exclusion criteria (15 listed)
- During study treatment, no concurrent anti-cancer therapies are allowed with the following exceptions:
- o Anti-resorptive bone therapies (e.g., bisphosphonates, denosumab) permitted.
- Any investigational cancer therapy or systemic chemotherapy in the last 3 weeks.
- Any radiation therapy in the last 2 weeks.
- Known CNS disease, unless clinically stable for ≥ 3 months.
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 |
|---|---|---|
| OlaparibAlso: LynparzaParticipants will be treated with olaparib at the approved doses for the treatment of subtypes of breast cancer or at reduced dose/frequency for participants with moderate renal impairment. | Drug | Treatment Arm |
| 17b-estradiolAlso: Estrace17b-estradiol will be taken orally three times per day. | Drug | Treatment Arm |
Primary outcome
Determine the Phase II dose of olaparib in combination with 17b-estradiol
Time frame: 8 weeks
Determine the safety and recommended Phase II dose of olaparib in combination with 17b-estradiol in post-menopausal patients with advanced ER+/HER2- breast cancer.
5 secondary outcomes
Clinical benefit rate
Time frame: 6 months
Objective response rate
Time frame: 6 months
Progression-free survival
Time frame: 12 months
Plasma Olaparib concentration
Time frame: 6 hours
Plasma 17b-Estradiol/Estrone concentration
Time frame: 6 hours
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 20 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.
Mary Chamberlin, MD principal investigator
Dartmouth-Hitchcock Medical Center
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Olaparib and 17b-estradiol in people with Metastatic Breast Cancer, run by Mary D Chamberlin at 1 site in United States.
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 3 inclusion and 15 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: looking for participants now, as of the sponsor's last update on 20 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 1 site in United States. 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?
Contact Research Nurse (1-800-639-6918, Cancer.Research.Nurse@dartmouth.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Determine the Phase II dose of olaparib in combination with 17b-estradiol (time frame: 8 weeks). 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 20 Nov 2025.