Ovarian NeoplasmsPhase 1NCT07870278

A Clinical Trial of MK-6255 to Treat Endometrial and Ovarian Cancer (MK-6255-001)

A Phase 1 study testing MK-6255, CD8 PET Tracer and Acetaminophen in people with Ovarian Neoplasms and Endometrial Neoplasms, run by Merck Sharp & Dohme LLC.

Not yet recruiting

Opening soon. The study is approved but enrolment has not started yet. Sites may already take enquiries.

Official record

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Trial summary

Researchers are looking for new ways to treat advanced and recurrent endometrial cancer (EC) and ovarian cancer (OC). Advanced means the cancer has spread to other parts of the body and cannot be removed with surgery. Recurrent means the cancer came back after treatment. Read more about this study

Who is it for?: Ages 18 years and older, women only
Conditions the study is for: Ovarian Neoplasms, Endometrial Neoplasms
What is being tested?: MK-6255, CD8 PET Tracer and Acetaminophen
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 80 participants
Where: No sites listed yet
Study dates: 13 Nov 2026to 7 Jul 2031
Phase: Phase 1

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

The main inclusion criteria include but are not limited to the following:
Has one of the following diagnoses:
Recurrent, pathologically documented epithelial OC, primary peritoneal cancer, or fallopian tube cancer that is either (1) platinum resistant or (2) platinum sensitive, with progression during prior treatment with poly-adenosine diphosphate (ADP) ribose polymerase inhibitor (PARPi)
Histologically confirmed well, moderately, or poorly differentiated (ie, Grade 1 to Grade 3) serous or endometrioid EC that has progressed after at least 1 line of platinum-based therapy in any setting
Has received all protocol-required and available standard of care (SOC) therapies, unless ineligible for or intolerant to the therapies
Has provided archival tumor tissue or a recently obtained biopsy before treatment start

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If living with human immunodeficiency virus (HIV), has well-controlled HIV on antiretroviral therapy (ART)
If hepatitis B surface antigen (HBsAg)-positive, has undetectable hepatitis B virus (HBV) viral load and has received HBV antiviral - therapy for at least 4 weeks
If history of hepatitis C virus (HCV) infection, has undetectable HCV viral load
Has adequate organ function

Who cannot join

The main exclusion criteria include but are not limited to the following:
Has a diagnosis of any 1 of the following: Primary platinum-refractory OC; neuroendocrine tumors or endometrial sarcoma, including stromal sarcoma, leiomyosarcoma, adenosarcoma, or other types of pure sarcomas; carcinosarcoma; EC that is amenable to curative-intent surgery or curative-intent radiotherapy; or EC that requires recurrent drainage of effusions
Has a history of serious cardiovascular and cerebrovascular diseases
Has a history or presence of clinically relevant central nervous system (CNS) diseases
Has received prior systemic anticancer therapy within 4 weeks or 5 half-lives (whichever is shorter) before start of study intervention
Has received prior radiotherapy within 2 weeks of start of study intervention

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Has known additional malignancy that is progressing or has required active treatment within the past 3 years
Has known active CNS metastases and/or carcinomatous meningitis
Has active autoimmune disease that has required systemic treatment in the past 2 years
Is living with HIV and has a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease
Has a history of stem cell/solid organ transplant
Has not adequately recovered from major surgery or has ongoing surgical complications

About this study

Official title: A Phase 1 Open-label Study to Evaluate the Safety and Efficacy of MK-6255 Monotherapy in Advanced Solid Tumors

MK-6255 is a trial medicine designed to treat advanced and recurrent EC and OC. This trial is the first time that researchers will give MK-6255 to people.

The goals of this trial are to learn about:

The safety of MK-6255 and if participants tolerate it. Tolerate means participants will receive the trial medicine unless they need to stop it due to health problems.
What happens to different dose levels (amounts) of MK-6255 in the body over time.

Conditions: Ovarian Neoplasms, Endometrial Neoplasms
Being tested: MK-6255, CD8 PET Tracer, Acetaminophen, Diphenhydramine, Dexamethasone
Medical subject headings: Ovarian Neoplasms, Endometrial Neoplasms

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

MK-6255Biological
During initial dose escalation, participants will receive MK-6255 one weekly (QW). During Dose Interval Extension, participants will receive target doses every 3 weeks (Q3W).
CD8 PET TracerOther
Also called GEH200520, GEH200521 (18F)
Participants may receive an optional CD8 PET tracer for exploratory imaging assessments.
AcetaminophenDrug
Participants will receive acetaminophen (or similar antipyretic) as premedication.
DiphenhydramineDrug
Participants will receive diphenhydramine (or similar antihistamine) as premedication.
DexamethasoneDrug
Participants will receive dexamethasone as premedication.
TocilizumabBiological
Participants will receive this rescue medication at the investigator's discretion for treatment of cytokine release syndrome (CRS) after MK-6255 administration.
Tocilizumab biosimilarBiological
Also called Avtozma®, Tyenne®
Participants will receive this rescue medication at the investigator's discretion for treatment of cytokine release syndrome (CRS) after MK-6255 administration.
SiltuximabBiological
Participants will receive this rescue medication at the investigator's discretion for treatment of cytokine release syndrome (CRS) after MK-6255 administration.

Study groups in NCT07870278
Study group	Role	What they receive
Dose Escalation	Experimental	Participants receive MK-6255 once every week (QW). Receives: Biological: MK-6255; Other: CD8 PET Tracer; Drug: Acetaminophen; Drug: Diphenhydramine; Drug: Dexamethasone; Biological: Tocilizumab; Biological: Tocilizumab biosimilar; Biological: Siltuximab
Dose Interval Extension	Experimental	Participants receive MK-6255 at extended interval dosing. Receives: Biological: MK-6255; Other: CD8 PET Tracer; Drug: Acetaminophen; Drug: Diphenhydramine; Drug: Dexamethasone; Biological: Tocilizumab; Biological: Tocilizumab biosimilar; Biological: Siltuximab

What is being measured

The primary outcome is the main question the study is designed to answer.

Number of Participants Who Experience a Dose-limiting Toxicity (DLT) as Assessed Using National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), Version 6.0
A DLT is defined as any drug-related AE observed during the DLT evaluation period that meet criteria specified in the protocol. DLTs will be evaluated until 21 days after the first fixed dose during fixed-dose escalation and until 21 days after the first target dose during step-up dose escalation and dose interval extension.
Measured: Up to 21 days at each dose level
Number of participants who experience one or more adverse events (AEs)
An AE is 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. The number of participants that experience AEs will be reported.
Measured: Up to approximately 56 months
Number of participants who discontinue study intervention due to an adverse event (AE)
An AE is 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. The number of participants that discontinue study intervention due to an AE will be reported.
Measured: Up to approximately 56 months

Secondary outcomes (4)

Area Under the Serum Concentration-Time Curve (AUC) of MK-6255
AUC is defined as the measure of overall drug exposure over time after administration. Blood samples will be collected to determine the AUC of MK-6255.
Measured: At designated timepoints (up to approximately 2 weeks postdose)
Minimum Serum Concentration (Cmin) of MK-6255
Cmin is defined as the lowest observed concentration of a drug after administration. Blood samples will be collected to determine the Cmin of MK-6255.
Measured: At designated timepoints (up to approximately 2 weeks postdose)
Maximum Serum Concentration (Cmax) of MK-6255
Cmax is defined as the highest observed concentration of a drug after administration. Blood samples will be collected to determine the Cmax of MK-6255.
Measured: At designated timepoints (up to approximately 2 weeks postdose)
Time to Maximum Serum Concentration (Tmax) of MK-6255
Tmax is defined as the time at which the maximum observed concentration of a drug occurs after administration. Blood samples will be collected to determine the Tmax of MK-6255.
Measured: At designated timepoints (up to approximately 2 weeks postdose)

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

13 Nov 20267 Jul 2031

First posted13 Oct 2026
Study start13 Nov 2026 (estimated)
Primary completion5 Jul 2031 (estimated)
Study completion7 Jul 2031 (estimated)

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Other trials for Ovarian NeoplasmsStudies of the same condition, open and under way.
More trials run by Merck Sharp & Dohme LLCThe 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 1
Primary purpose: Treatment
Allocation: Non-randomised
Intervention model: Sequential
Masking: None (open label)
Enrolment: 80 participants (estimated)

IDs, dates and publications

ClinicalTrials.gov ID: NCT07870278
Sponsor's protocol ID: 6255-001
Other IDs: MK-6255-001
Status last verified: Oct 2026
First submitted: 6 Oct 2026
Last updated: 13 Oct 2026
Results posted: No
Data monitoring committee: No
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf

Interested in taking part?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

Official record

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