A Phase 1 interventional study of MK-6255 and CD8 PET Tracer in Ovarian Neoplasms and Endometrial Neoplasms, sponsored by Merck Sharp & Dohme LLC. Not yet recruiting. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-13.
Sponsored by Merck Sharp & Dohme LLC (part of Merck & Co., Inc) · Phase 1, Interventional, and Treatment
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.
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:
2,757 studies on the registry are indexed under Ovarian Neoplasms; 735 are open to participants now.
This study's planned enrollment of 80 is above the median of 59 across 2,075 interventional studies indexed under Ovarian Neoplasms.
Browse Ovarian Neoplasms studies →Merck Sharp & Dohme LLC is the lead sponsor of 2,159 studies on the registry; 133 are open to participants now.
Of its 497 completed or terminated interventional studies of FDA-regulated products, 369 (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:
Has one of the following diagnoses:
Exclusion Criteria:
The main exclusion criteria include but are not limited to the following:
Participants receive MK-6255 once every week (QW).
Biological: MK-6255 · Other: CD8 PET Tracer · Drug: Acetaminophen · Drug: Diphenhydramine · Drug: Dexamethasone · Biological: Tocilizumab · Biological: Tocilizumab biosimilar · Biological: Siltuximab
Participants receive MK-6255 at extended interval dosing.
Biological: MK-6255 · Other: CD8 PET Tracer · Drug: Acetaminophen · Drug: Diphenhydramine · Drug: Dexamethasone · Biological: Tocilizumab · Biological: Tocilizumab biosimilar · Biological: Siltuximab
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).
Participants may receive an optional CD8 PET tracer for exploratory imaging assessments.
Also known as: GEH200520, GEH200521 (18F)
Participants will receive acetaminophen (or similar antipyretic) as premedication.
Participants will receive diphenhydramine (or similar antihistamine) as premedication.
Participants will receive dexamethasone as premedication.
Participants will receive this rescue medication at the investigator's discretion for treatment of cytokine release syndrome (CRS) after MK-6255 administration.
Participants will receive this rescue medication at the investigator's discretion for treatment of cytokine release syndrome (CRS) after MK-6255 administration.
Also known as: Avtozma®, Tyenne®
Participants will receive this rescue medication at the investigator's discretion for treatment of cytokine release syndrome (CRS) after MK-6255 administration.
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.
Time frame: 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.
Time frame: 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.
Time frame: Up to approximately 56 months
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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: At designated timepoints (up to approximately 2 weeks postdose)
No study locations are listed for this record.
Plan to share: Yes — https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf
Data sharing details ↗ · externaldatasharing-msd.com
No publications or documents are linked to this record.
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 ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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