EndometriosisPhase 2APPOSENCT04002141
Assessment and Prevention of Pain During Ovarian Stimulation in Patients With Endometriosis
A Phase 2 study testing Letrozole in people with Endometriosis and Ovarian Hyperstimulation, run by University of California, San Francisco at 1 site in United States.
Trial summary
Randomized double blinded placebo-controlled trial to evaluate the impact of ovarian hyperstimulation on endometriosis-related symptoms and to evaluate the impact of letrozole use during ovarian hyperstimulation with respect to endometriosis-related symptoms, embryo/egg quality and quantity, and pregnancy rates. Read more about this study
- Who is it for?
- Ages 18 to 42 years, women onlyHealthy volunteers can take part
- Conditions the study is for
- Endometriosis, Ovarian Hyperstimulation
- What is being tested?
- Letrozole
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 60 participants
- Where
- 1 siteUnited States
- Study dates
- 17 Sep 2019to 1 Jan 2025
- Phase
- Phase 2
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
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 to 42 years
- Women only
- Healthy volunteers accepted
- Adult
Who may be able to join
- Age 18-42 years
- Planning to undergo controlled ovarian hyperstimulation
- Prior diagnosis of endometriosis by one of the following: (1) surgical diagnosis (2) endometrioma on pelvic ultrasound
- Planning to freeze all retrieved oocytes/embryos prior to transfer
Who cannot join
- Hypersensitivity to letrozole
- Any significant concurrent disease, illness, or psychiatric disorder that would compromise patient safety or compliance, interfere with consent, study participation, follow-up, or interpretation of study results
Trial locations and contacts
1 site in 1 country.
United States1 site
UCSF Center for Reproductive Health
San Francisco, California, 94158
About this study
Randomized double blinded placebo-controlled trial to evaluate the impact of ovarian hyperstimulation on endometriosis-related symptoms and to evaluate the impact of letrozole use during ovarian hyperstimulation with respect to endometriosis-related symptoms, embryo/egg quality and quantity, and pregnancy rates.
Read the detailed description
Randomized double blinded placebo-controlled trial to evaluate: (1) the impact of letrozole use during ovarian hyperstimulation with respect to endometriosis-related symptoms, embryo/egg quality and quantity, and pregnancy rates, (2) the impact of ovarian hyperstimulation on endometriosis-related symptoms.
There will be a total of 60 participants, 20 participants with endometriosis randomized to the placebo group, 20 participants with endometriosis randomized to the letrozole group and 20 control patients with no history of endometriosis. Letrozole and placebo medication will be started on the first day of gonadotropin injections and continued until the day of trigger shot. Medication will be restarted the night of egg retrieval and continued for 2 weeks post retrieval. Endometriosis associated symptoms will be evaluated using a survey modeled after the clinical survey developed by the World Endometriosis Research Foundation Endometriosis Phenome and Biobanking Harmonisation Project. Surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval.
- Conditions
- Endometriosis, Ovarian Hyperstimulation
- Being tested
- Placebo oral tablet, Letrozole
- Keywords
- Endometriosis, Letrozole
- Medical subject headings
- Endometriosis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Placebo oral tabletDrug
1 tablet oral daily
LetrozoleDrug
5mg oral daily
| Study group | Role | What they receive |
|---|---|---|
| Endometriosis Letrozole | Experimental | Participants will be asked to take 5mg letrozole daily throughout their ovarian stimulation and for 2 weeks following retrieval. Participants will be blinded to their randomization to letrozole. Participants will be asked to complete surveys during their stimulation and up to 12 weeks following retrieval to evaluate endometriosis associated symptoms. Specifically, surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval. There will be a total of 20 participants in this arm. Receives: Drug: Letrozole |
| Endometriosis Placebo | Placebo comparator | Participants will be asked to take one tablet placebo daily throughout their ovarian stimulation and for 2 weeks following retrieval. Participants will be blinded to their randomization to placebo. Participants will be asked to complete surveys during their stimulation and up to 12 weeks following retrieval to evaluate endometriosis associated symptoms. Specifically, surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval. There will be a total of 20 participants in this arm. Receives: Drug: Placebo oral tablet |
| No Endometriosis Control | No intervention | Participants will be asked to complete surveys during their ovarian stimulation and up to 12 weeks following retrieval to evaluate symptoms of pelvic pain. Specifically, surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval. There will be a total of 20 participants in this arm. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Average Delta in Endometriosis Pain Score Pre and Post Stimulation With and Without Use Of Letrozole
To evaluate how letrozole impacts pain scores throughout controlled ovarian hyperstimulation in patients with endometriosis. Pain scores will be evaluated using a 0-10 visual acuity scale, where 0 is no pain and 10 is the worst imaginable pain. The average delta between pre-stimulation pain score and day of trigger shot pain score will be compared between patients with endometriosis receiving placebo and with endometriosis receiving letrozole.
Measured: Baseline ultrasound (day 2 of menstrual cycle) and day 12 (average day of trigger shot).
Secondary outcomes (7)
Average Delta in Endometriosis Pain Score Pre and Post Stimulation of Patients Receiving Placebo Compared to No Endometriosis
To evaluate the impact of endometriosis on pain scores throughout controlled ovarian hyperstimulation. Pain scores will be evaluated using a 0-10 visual acuity scale, where 0 is no pain and 10 is the worst imaginable pain. The average delta between pre-stimulation pain score and day of trigger shot will be compared between patients with endometriosis receiving placebo and patients without endometriosis.
Measured: Baseline ultrasound (day 2 of menstrual cycle) and day 12 (average day of trigger shot).
Comparative Trends in Endometriosis Pain Score Pre and Post Stimulation of Patients With Endometriosis Receiving Either Placebo or Letrozole and Patients Without Endometriosis
To evaluate the impact of letrozole on endometriosis pain scores throughout controlled ovarian hyperstimulation. Pain scores will be evaluated using a 0-10 visual acuity scale, where 0 is no pain and 10 is the worst imaginable pain. The calculated change in pain scores from pre-stimulation through 12 weeks post retrieval will be compared between patients with endometriosis receiving placebo, patients with endometriosis receiving letrozole and patients without endometriosis.
Measured: Pre-stimulation through 12 weeks post retrieval. This time span varies per each patient's course of treatment but is typically 14 weeks in tota
Does Letrozole Impact Egg Quantity in Endometriosis Patients
To describe the impact of letrozole on egg quantity in patients with endometriosis receiving letrozole and those with endometriosis not receiving letrozole and those without endometriosis during controlled ovarian stimulation. The total arm aggregate number of MII eggs retrieved per baseline arm aggregate Antral Follicle Count will be compared between the three groups.
Measured: Baseline ultrasound (day 2 of menstrual cycle) and day 14 (average day of egg retrieval).
Follicular Fluid
To compare follicular fluid average estradiol levels between placebo, letrozole and control groups.
Measured: Baseline ultrasound (day 2 of menstrual cycle) and day 14 (average day of egg retrieval).
Pregnancy Outcomes
To compare pregnancy rates in the placebo, letrozole and control groups. Pregnancy will be defined as positive serum hCG after transfer of embryo. The rate will determined by positive hCG per transfer.
Measured: Up to 2 years.
Egg Maturity
To describe the impact of letrozole on egg maturity. Measured by number of MII eggs per total number eggs retrieved in patients with endometriosis receiving letrozole and those with endometriosis not receiving letrozole during controlled ovarian stimulation.
Measured: Baseline ultrasound to time of cryopreservation of eggs/embryos, which occurs within 7 days of retrieval..
Embryo Grade
To describe the impact of letrozole on embryo quality. Measured by the average total number of freezable quality embryos (6c or greater, grades 1-2 for symmetry and fragmentation) in patients with endometriosis receiving letrozole and those with endometriosis not receiving letrozole and those without endometriosis during controlled ovarian stimulation.
Measured: 2 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted28 Jun 2019
- Study start17 Sep 2019
- Primary completion1 Oct 2023
- Study completion1 Jan 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for EndometriosisStudies of the same condition, open and under way.
- More trials run by University of California, San FranciscoThe sponsor's other registered studies.
- 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 2
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 60 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of California, San Francisco
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Marcelle I Cedars, Principal investigator, University of California, San Francisco
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04002141
- Sponsor's protocol ID
- 18-26544
- Acronym
- APPOSE
- Status last verified
- Jan 2026
- First submitted
- 28 May 2019
- Last updated
- 28 Jan 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- 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 28 Jan 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Assessment and Prevention of Pain During Ovarian Stimulation in Patients With Endometriosis
- ClinicalTrials.gov ID
- NCT04002141
- Acronym / sponsor ID
- APPOSE / 18-26544
- Conditions
- Endometriosis, Ovarian Hyperstimulation
- Keywords
- Endometriosis, Letrozole
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 60 participants (actual)
- Lead sponsor
- University of California, San FranciscoUniversity, hospital or other
- Study start
- 17 Sep 2019 (actual)
- Primary completion
- 1 Oct 2023 (actual)
- Study completion
- 1 Jan 2025 (actual)
- First posted
- 28 Jun 2019 (actual)
- Results
- Posted 28 Jan 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Randomized double blinded placebo-controlled trial to evaluate the impact of ovarian hyperstimulation on endometriosis-related symptoms and to evaluate the impact of letrozole use during ovarian hyperstimulation with respect to endometriosis-related symptoms, embryo/egg quality and quantity, and pregnancy rates.
Detailed description
Randomized double blinded placebo-controlled trial to evaluate: (1) the impact of letrozole use during ovarian hyperstimulation with respect to endometriosis-related symptoms, embryo/egg quality and quantity, and pregnancy rates, (2) the impact of ovarian hyperstimulation on endometriosis-related symptoms.
There will be a total of 60 participants, 20 participants with endometriosis randomized to the placebo group, 20 participants with endometriosis randomized to the letrozole group and 20 control patients with no history of endometriosis. Letrozole and placebo medication will be started on the first day of gonadotropin injections and continued until the day of trigger shot. Medication will be restarted the night of egg retrieval and continued for 2 weeks post retrieval. Endometriosis associated symptoms will be evaluated using a survey modeled after the clinical survey developed by the World Endometriosis Research Foundation Endometriosis Phenome and Biobanking Harmonisation Project. Surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (participant)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Endometriosis Letrozole | Experimental | Drug: LetrozoleParticipants will be asked to take 5mg letrozole daily throughout their ovarian stimulation and for 2 weeks following retrieval. Participants will be blinded to their randomization to letrozole. Participants will be asked to complete surveys during their stimulation and up to 12 weeks following retrieval to evaluate endometriosis associated symptoms. Specifically, surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval. There will be a total of 20 participants in this arm. |
| Endometriosis Placebo | Placebo comparator | Drug: Placebo oral tabletParticipants will be asked to take one tablet placebo daily throughout their ovarian stimulation and for 2 weeks following retrieval. Participants will be blinded to their randomization to placebo. Participants will be asked to complete surveys during their stimulation and up to 12 weeks following retrieval to evaluate endometriosis associated symptoms. Specifically, surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval. There will be a total of 20 participants in this arm. |
| No Endometriosis Control | No intervention | –Participants will be asked to complete surveys during their ovarian stimulation and up to 12 weeks following retrieval to evaluate symptoms of pelvic pain. Specifically, surveys will be administered at baseline ultrasound appointment for controlled ovarian hyperstimulation cycle, the day of trigger shot, 3 weeks following egg retrieval, 6 weeks following egg retrieval and 12 weeks following egg retrieval. There will be a total of 20 participants in this arm. |
Who may qualify
- Ages
- 18 to 42 years
- Sex
- Female only
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Age 18-42 years
- Planning to undergo controlled ovarian hyperstimulation
- Prior diagnosis of endometriosis by one of the following: (1) surgical diagnosis (2) endometrioma on pelvic ultrasound
- Planning to freeze all retrieved oocytes/embryos prior to transfer
Key exclusion criteria (2 listed)
- Hypersensitivity to letrozole
- Any significant concurrent disease, illness, or psychiatric disorder that would compromise patient safety or compliance, interfere with consent, study participation, follow-up, or interpretation of study results
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 |
|---|---|---|
| Placebo oral tablet1 tablet oral daily | Drug | Endometriosis Placebo |
| Letrozole5mg oral daily | Drug | Endometriosis Letrozole |
Primary outcome
Average Delta in Endometriosis Pain Score Pre and Post Stimulation With and Without Use Of Letrozole
Time frame: Baseline ultrasound (day 2 of menstrual cycle) and day 12 (average day of trigger shot).
To evaluate how letrozole impacts pain scores throughout controlled ovarian hyperstimulation in patients with endometriosis. Pain scores will be evaluated using a 0-10 visual acuity scale, where 0 is no pain and 10 is the worst imaginable pain. The average delta between pre-stimulation pain score and day of trigger shot pain score will be compared between patients with endometriosis receiving placebo and with endometriosis receiving letrozole.
7 secondary outcomes
Average Delta in Endometriosis Pain Score Pre and Post Stimulation of Patients Receiving Placebo Compared to No Endometriosis
Time frame: Baseline ultrasound (day 2 of menstrual cycle) and day 12 (average day of trigger shot).
Comparative Trends in Endometriosis Pain Score Pre and Post Stimulation of Patients With Endometriosis Receiving Either Placebo or Letrozole and Patients Without Endometriosis
Time frame: Pre-stimulation through 12 weeks post retrieval. This time span varies per each patient's course of treatment but is typically 14 weeks in tota
Does Letrozole Impact Egg Quantity in Endometriosis Patients
Time frame: Baseline ultrasound (day 2 of menstrual cycle) and day 14 (average day of egg retrieval).
Follicular Fluid
Time frame: Baseline ultrasound (day 2 of menstrual cycle) and day 14 (average day of egg retrieval).
Pregnancy Outcomes
Time frame: Up to 2 years.
Egg Maturity
Time frame: Baseline ultrasound to time of cryopreservation of eggs/embryos, which occurs within 7 days of retrieval..
Embryo Grade
Time frame: 2 weeks
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 28 Jan 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- 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.
Marcelle I Cedars principal investigator
University of California, San Francisco
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing Letrozole in people with Endometriosis and Ovarian Hyperstimulation, run by University of California, San Francisco 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 4 inclusion and 2 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: finished, as of the sponsor's last update on 28 Jan 2026. 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. Some participants in this study may receive a placebo. 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 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 28 Jan 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
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?
Average Delta in Endometriosis Pain Score Pre and Post Stimulation With and Without Use Of Letrozole (time frame: Baseline ultrasound (day 2 of menstrual cycle) and day 12 (average day of trigger shot).). 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 28 Jan 2026.