A Phase 2 interventional study of Opevesostat and Fludrocortisone/ Fludrocortisone acetate in Malignant Neoplasm, sponsored by Merck Sharp & Dohme LLC. Recruiting at 60 sites in 13 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-06.
Sponsored by Merck Sharp & Dohme LLC (part of Merck & Co., Inc) · Phase 2, Interventional, and Treatment
Researchers want to learn if MK-5684 (the study medicine) can treat breast cancer, ovarian cancer, and endometrial cancer. MK-5684, the study medicine, is designed to treat cancer by blocking the body from making steroid hormones.
Researchers will compare MK-5684 to the standard treatments for each cancer type in this study.
The goal of this study is to learn if people who receive MK-5684 live longer without the cancer growing or spreading compared to people who receive a standard treatment.
10,818 studies on the registry are indexed under Neoplasms; 2,324 are open to participants now.
This study's planned enrollment of 250 is above the median of 60 across 7,703 interventional studies indexed under Neoplasms.
Browse Neoplasms studies →Merck Sharp & Dohme LLC is the lead sponsor of 2,166 studies on the registry; 132 are open to participants now.
Of its 501 completed or terminated interventional studies of FDA-regulated products, 370 (74%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
The main inclusion criteria include but are not limited to the following:
Cohort A:
Cohort B:
Cohort C:
All Cohorts :
Exclusion Criteria:
The main exclusion criteria include but are not limited to the following:
Cohort A:
Cohort B:
Cohort C:
All Cohorts:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adjuvant and neoadjuvant
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Relapsed and refractory
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Live vaccines
Vaccines made with a weakened form of the germ, such as measles–mumps–rubella (MMR), chickenpox and yellow fever. They can be risky when the immune system is weakened. Flu injections are not live; the nasal flu spray is.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants with breast cancer, ovarian cancer, or endometrial cancer will receive 5 mg of MK-5684 orally twice daily. Participants will also receive fludrocortisone/fludrocortisone acetate starting at 0.1 mg orally, and dexamethasone/dexamethasone acetate starting at 1 mg orally; both will be adjusted individually during the study. Participants will receive treatment until one of the conditions for discontinuation of study intervention is met.
Drug: Opevesostat · Drug: Fludrocortisone/ Fludrocortisone acetate · Drug: Dexamethasone/Dexamethasone acetate · Drug: Rescue Medications
Participants with breast cancer receive endocrine therapy of the physician's choice: either 500 mg of fulvestrant on Day 1 and Day 15 of Cycle 1 and Day 1 of every cycle thereafter (cycles are 28 days in length) or 25 mg of exemestane once daily (QD). Participants will receive treatment until one of the conditions for discontinuation of study intervention is met.
Drug: Fulvestrant · Drug: Exemestane
Participants with ovarian cancer will be observed but will receive no treatment for the duration of the study.
Participants with endometrial cancer will receive the physician's choice of either 80 mg megestrol acetate/medroxyprogesterone acetate twice daily, or alternating between 80 mg megestrol acetate twice daily for three weeks and 20 mg tamoxifen twice daily for three weeks, or 2.5 mg letrozole once daily. Participants will receive treatment until one of the conditions for discontinuation of study intervention is met.
Drug: Megestrol acetate/Medroxyprogesterone acetate · Drug: Tamoxifen · Drug: Letrozole
Tablet for oral administration.
Also known as: MK-5684
Drug page: Fludrocortisone acetate
Tablet for oral administration.
Drug page: Dexamethasone acetate
Tablet for oral administration.
Hydrocortisone or hydrocortisone/hydrocortisone acetate administered via intramuscular injection as rescue medication.
Administered via intramuscular injection.
Tablet for oral administration.
Drug pages: Megestrol Acetate · Medroxyprogesterone Acetate
Tablet for oral administration.
Tablet for oral administration.
Tablet for oral administration.
Progression-Free Survival (PFS) - All Cohorts
For all cohorts, PFS is defined as the time from randomization to the first documented progressive disease (PD) or death due to any cause, whichever occurs first as assessed by Response Criteria in Solid Tumors Version 1.1 (RECIST 1.1). PD is defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also demonstrate an absolute increase of ≥5 mm. The appearance of one or more new lesions is also considered PD. PFS as assessed by blinded independent central review (BICR) will be presented.
Time frame: Up to approximately 2 years
Overall Survival (OS) - All Cohorts
For all cohorts, OS is defined the time from randomization to death due to any cause.
Time frame: Up to approximately 2 years
Clinical Benefit Rate (CBR) - Cohort A
For cohort A (participants with breast cancer), CBR is defined as the percentage of participants who have complete response (CR): disappearance of all target lesions; partial response (PR): At least a 30% decrease in the sum of diameters of target lesions; or stable disease (SD): Neither sufficient decrease to qualify for PR nor sufficient increase to qualify for progressive disease (PD), with reference to the smallest sum diameters while on study) for ≥24 weeks per RECIST 1.1 as assessed by BICR.
Time frame: Up to approximately 2 years
Objective Response Rate (ORR) - All Cohorts
For all cohorts, ORR is defined as the percentage of participants who have achieved confirmed Complete Response (CR: disappearance of all target lesions) or a Partial Response (PR: at least a 30% decrease in the sum of diameters of target lesions) per RECIST 1.1 as assessed by BICR.
Time frame: Up to approximately 2 years
Duration of Response (DOR) - All Cohorts
For all cohorts, for participants who demonstrate CR or PR, DOR is defined as the time from the first documented evidence of CR or PR until disease progression or death due to any cause, whichever occurs first.
Time frame: Up to approximately 2 years
Number of Participants who Discontinue Study Intervention Due to an Adverse Event (AE) - All Cohorts
An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE could therefore have been any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.
Time frame: Up to approximately 8 months
Number of Participants who Experience One or More Adverse Events (AEs) - All Cohorts
An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. An AE could therefore have been any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention.
Time frame: Up to approximately 11 months
Plan to share: Yes — https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
Data sharing details ↗ · externaldatasharing-msd.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drugs tested here: Opevesostat · Megestrol Acetate · Medroxyprogesterone Acetate · Tamoxifen · Letrozole