Recruiting

Phase 3

Mo-Rez & ImmunotherapyA Study to Investigate Mocertatug Rezetecan as Maintenance Treatment for Participants With MMRp Endometrial Cancer (BEHOLD-Endometrial02)

Sponsor:

GlaxoSmithKline

Code:

NCT07684599

Conditions

Neoplasms, Endometrial

Eligibility Criteria

Sex: Female

Age: 18+

Healthy Volunteers: Not accepted

Interventions

Mocertatug rezetecan

Dostarlimab

Pembrolizumab

Study Details

Brief summary:

The purpose of this study is to see how well mocertatug rezetecan (Mo-Rez) in combination with physician's choice of immunotherapy (dostarlimab or pembrolizumab) works as maintenance therapy in participants with advanced or recurrent endometrial cancer (EC) compared with the physician's choice of immunotherapy (dostarlimab or pembrolizumab) alone, which represents the current standard of care. The study will also assess whether the drug combination is safe and tolerated well by participants compared to standard of care and will help us better understand its impact on Health-Related Quality of Life of participants.

Conditions

Neoplasms, Endometrial

Study ID

NCT07684599

Start date

Sep 24, 2026

Status verified date

Oct, 2026

Completion date

Sep 18, 2031

Anticipated

Primary completion date

Jul 23, 2029

Anticipated

Eligibility Criteria

Sex: Female

Age: 18+

Healthy Volunteers: Not accepted

Inclusion Criteria:

Is at least 18 years of age and the legal age of consent in the jurisdiction in which the study is taking place at the time of signing the Informed consent form (ICF).
Has received 6 cycles of first-line therapy (i.e. induction therapy), consisting of platinum-based doublet chemotherapy (e.g., carboplatin/paclitaxel) with immune checkpoint inhibition as part of standard of care (either pembrolizumab or dostarlimab) or via trial Run-In (dostarlimab). Receipt of only 4 cycles of chemotherapy is permitted if chemotherapy was discontinued due to toxicity, provided that the participant received at least 12 weeks of immune checkpoint inhibitor therapy during the induction period.
Is able to commence C1D1 of study treatment within 3 - 9 weeks of the final dose of first-line therapy.
Is deemed suitable to continue with maintenance therapy with immune checkpoint inhibition (dostarlimab or pembrolizumab).
Demonstrates no clinical or radiographic progression of disease per investigator after the final dose of induction therapy. Final dose is defined as the last day that either platinum chemotherapy, taxane chemotherapy or immune checkpoint inhibition was given within the last cycle of induction therapy
Has histologically confirmed endometrial carcinoma including but not limited to endometrioid, serous, clear cell and endometrial carcinosarcoma. Mixed epithelial carcinomas are permitted.
Meets one of the following criteria:

Has newly diagnosed stage III disease \[2023 International Federation of Gynecology and Obstetrics (FIGO) staging\] with measurable residual disease >1 cm after primary debulking surgery (incomplete cytoreduction).
Has newly diagnosed stage III disease (2023 FIGO staging) that is not suitable for primary debulking surgery with measurable disease.
Has newly diagnosed stage IV disease (2023 FIGO staging) and any residual disease status (measurable or non-measurable) following debulking surgery. Participants not suitable for primary debulking surgery are also permitted.
Has recurrent disease and is naïve to systemic anticancer therapy and any disease status (measurable or non-measurable).
Has recurrent disease after receiving prior neo-adjuvant/adjuvant systemic anticancer therapy and had a recurrence >12 months after last dose of neo-adjuvant/adjuvant treatment. Participants with any disease status (measurable or non-measurable) are permitted.
Has a tumor demonstrating either Mismatch Repair proficient (MMRp) or Microsatellite stable (MSS).
Has provided a Formalin fixed, paraffin embedded (FFPE) tumor tissue sample sufficient for the central assessment of B7 homolog 4 protein (B7-H4) expression and MMR (if local MMRp/MSS test result(s) not available), with the result of B7-H4 expression testing available prior to date of randomization.
Is willing to use adequate contraception. Contraceptive use should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.
Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

Exclusion Criteria:

Mesenchymal tumors of the uterus (uterine sarcomas) and neuroendocrine uterine cancer.
Has a malignancy (except disease under study) that has progressed or required active treatment within 36 months prior to date of randomization except for basal cell or squamous cell carcinomas of the skin or in-situ carcinomas.
Any evidence of current Interstitial lung disease (ILD) or pneumonitis or a prior history of ILD or non-infectious pneumonitis.
Has experienced any of the following with prior immunotherapy: any imAE ≥ Grade 3, immune-mediated severe neurologic events of any grade (e.g., myasthenic syndrome/myasthenia gravis, encephalitis, Guillain-Barré Syndrome, or transverse myelitis), exfoliative dermatitis of any grade (Stevens-Johnson syndrome \[SJS\], Toxic Epidermal Necrolysis \[TEN\], or Drug Reaction with Eosinophilia and Systemic Symptoms \[DRESS\] syndrome, or myocarditis of any grade.
Has ongoing adverse reaction(s) from prior therapy that has(have) not recovered to ≤ Grade 1 or to the baseline status preceding prior therapy, excluding alopecia, hearing loss, vitiligo, endocrinopathy managed with replacement therapy, and Grade 2 neuropathy, or adverse reactions that the investigator, with the agreement of the sponsor, considers to be not clinically relevant for the tolerability of study intervention in the current clinical study.
Has had any major surgery within 28 days prior to date of C1D1 or received focal radiotherapy within 21 days prior to date of C1D1.
Has received treatment with an investigational agent within 30 days prior to C1D1.
Has received prior therapy with topoisomerase I inhibitors (e.g. irinotecan or topotecan) or Antibody-Drug Conjugate (ADC)with a topoisomerase I inhibitor warhead, B7-H4 targeted therapy, or immune checkpoint inhibitor.
Has received treatment with inhibitors of P-glycoprotein (P-gp) or Breast cancer resistant protein (BCRP), or OATP1B1/1B3 transporterswithin 7 days prior to the date of C1D1. Inducers of P-gp should be discontinued for at least 14 days prior to the date of C1D1.
Has received any transfusion of blood products (including platelets or red blood cells) or administration of colony-stimulating factors (including Granulocyte-Colony Stimulating Factor \[G-CSF\], Granulocyte-Macrophage Colony-Stimulating Factor \[GM-CSF\], or recombinant erythropoietin) within 14 days prior to C1D1.
Has an Alanine aminotransferase (ALT) value >2.5 × Upper limit of normal (ULN) or for participants with documented liver metastases/tumor infiltration has an ALT value >5 × ULN.
Has a total bilirubin value >1.5 × ULN.
Has cirrhosis or current unstable liver or biliary disease per investigator assessment defined by the presence of ascites, encephalopathy, coagulopathy, hypoalbuminemia, esophageal/gastric varices, or persistent jaundice. Participants who exhibit these signs or symptoms as a result of the malignancy under investigation and whose conditions are deemed adequately controlled by the investigator may be eligible for inclusion.
Has Corrected QT interval (QTc) >470 milliseconds (msec).
Has a history of symptomatic pericarditis of any cause within 6 months prior to screening or evidence of cardiac abnormalities within 12 months prior to screening such as serious, uncontrolled cardiac arrhythmia or clinically significant ECG abnormalities.
Has any active renal condition (e.g., infection, requirement for dialysis, or any other significant renal condition that could affect the participant's safety).

Study Design

Enrollment

610 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: Mocertatug rezetecan plus physician's choice of immunotherapy (dostarlimab or pembrolizumab)

Participants will receive Mocertatug rezetecan along with physician's choice of immunotherapy (Dostarlimab or Pembrolizumab)

active comparator: Physician's choice of immunotherapy (dostarlimab or pembrolizumab)

Participants will receive physician's choice of immunotherapy (Dostarlimab or Pembrolizumab alone)

Interventions

Mocertatug rezetecan

Mocertatug rezetecan will be administered

Dostarlimab

Dostarlimab will be administered

Pembrolizumab

Pembrolizumab will be administered

Primary outcome measure

Progression free survival (PFS) by BICR assessment [ Time Frame: Up to approximately 143 weeks ]

Central Contacts and Locations

Central contacts

US GSK Clinical Trials Call Center

877-379-3718 GSKClinicalSupportHD@gsk.com

EU GSK Clinical Trials Call Center

+44 (0) 20 89904466 GSKClinicalSupportHD@gsk.com

Locations

GSK Investigational Site

Recruiting

Toronto, Ontario, Canada, M5G 1X6

Contacts

US GSK Clinical Trials Call Center

877-379-3718 GSKClinicalSupportHD@gsk.com

EU GSK Clinical Trials Call Centre

+44 (0) 20 8990 4466 GSKClinicalSupportHD@gsk.com

Principal Investigator:

Stephanie Lheureux

GSK Investigational Site

Recruiting

Montreal, Quebec, Canada, H4A 0B1

Contacts

US GSK Clinical Trials Call Center

877-379-3718 GSKClinicalSupportHD@gsk.com

EU GSK Clinical Trials Call Centre

+44 (0) 20 8990 4466 GSKClinicalSupportHD@gsk.com

Principal Investigator:

Lucy Gilbert

More Information

Sponsor

GlaxoSmithKline

Last update posted

Nov 3, 2026

Last verified

Oct, 2026

Keywords

Mocertatug rezetecan
Mo-Rez
GSK5733584
Dostarlimab
Pembrolizumab
Endometrial Cancer
Antibody-Drug Conjugate
BEHOLD-Endometrial02

Trial information was received from ClinicalTrials.gov and was last updated on 2026-11-04. This information was provided to ClinicalTrials.gov by GlaxoSmithKline on 2026-11-03. Recruitment status is synced daily from ClinicalTrials.gov and may not reflect the sponsor's current status. Confirm during your call.