A Phase 3 interventional study of PF-08634404 and Pembrolizumab in Endometrial Neoplasms and Endometrial Cancer, sponsored by Pfizer. Not yet recruiting at 39 sites in 2 countries. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-28.
Sponsored by Pfizer · Phase 3, Interventional, and Treatment
This study is being conducted to assess whether the study medicine PF 08634404, given in combination with chemotherapy, improves outcomes compared with another medicine called pembrolizumab plus chemotherapy. Chemotherapy is a type of cancer treatment that uses medicines to destroy cancer cells or stop them from growing.
Our bodies have a built-in DNA "spell-checker," called the mismatch repair (MMR) system, that fixes genetic mistakes. In most endometrial cancers, this system works normally, and these cancers are called MMR-proficient (pMMR). However, pMMR tumors are harder for the immune system to recognize and attack. When endometrial cancer has spread beyond the uterus or comes back after previous treatment, it is called advanced or recurrent endometrial cancer. This study is for adults with mismatch repair-pMMR advanced or recurrent endometrial cancer.
Participants must meet key criteria, including:
Experimental Group will receive new study medicine called PF-08634404 plus chemotherapy. It will be followed by PF 08634404 alone for up to 2 years (35 cycles).
Control Group will receive an approved medicine called pembrolizumab plus chemotherapy. It will be followed by pembrolizumab alone for up to 2 years (20 cycles).
The study will include regular visits for:
Exclusion Criteria:
PF-08634404 plus Chemotherapy, followed by PF-08634404 maintenance therapy
Biological: PF-08634404 · Drug: Standard of Care Chemotherapy
Pembrolizumab plus Chemotherapy, followed by Pembrolizumab maintenance therapy
Biological: Pembrolizumab · Drug: Standard of Care Chemotherapy
Solution for IV infusion
Solution for IV infusion
Also known as: keytruda
Solution for IV infusion
Progression-Free Survival (PFS) using RECIST v1.1 as assessed by Blinded Independent Central Review (BICR)
PFS by BICR is defined as the time from the date of randomization to the date of first documented disease progression per RECIST v1.1 as assessed by BICR, or death due to any cause, whichever occurs first.
Time frame: Approximately 36 months
Overall Survival (OS)
OS is defined as the time from the date of randomization to the date of death due to any cause.
Time frame: Approximately 56 months
PFS using RECIST v1.1 as assessed by investigator
PFS by investigator is defined as the time from the date of randomization to the date of first documented disease progression per RECIST v1.1 as assessed by investigator, or death due to any cause, whichever occurs first. PFS by investigator will be analyzed with the same methodology as for PFS by BICR.
Time frame: Approximately 36 months
Objective Response Rate (ORR) as assessed by BICR and investigator
Proportion of participants with confirmed Complete Response (CR) or Partial Response (PR) per RECIST v1.1, assessed by BICR and by investigator
Time frame: Approximately 56 months
Duration of Response (DoR) as assessed by BICR and investigator
Time from first documented CR or PR to disease progression or death, per RECIST v1.1, assessed by BICR and by investigator
Time frame: Approximately 56 months
Number of participants with treatment-emergent adverse events
AEs as characterized by type, frequency, intensity as graded by NCI CTCAE version 5.0, timing, seriousness, and relationship to study intervention(s)
Time frame: Through end of the study and up to approximately 56 months
Number of participants with laboratory abnormalities
Laboratory abnormalities as characterized by type, frequency, severity (as graded by NCI CTCAE version 5.0), and timing. For laboratory tests without CTCAE grade definitions, results will be categorized as normal, high, low, or not done and be listed.
Time frame: Through end of the study and up to approximately 56 months
Serum concentrations of PF-08634404
Pre-dose and post-dose serum concentrations of PF-08634404
Time frame: Through end of the study and up to approximately 56 months
Incidence of ADA against PF-08634404
Incidence of anti-drug antibodies (ADA) to PF-08634404
Time frame: Through end of the study and up to approximately 56 months
Change from baseline in the global health status/quality of life (QoL) and physical functioning scale of the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30)
The EORTC QLQ-C30 is a questionnaire for quantitative measure of health-related quality of life pertinent to participants with a broad range of cancers who are participating in international clinical trials. The core instrument is a 30-item questionnaire consisting of the following: * 5 Functional scales (physical, role, cognitive, emotional, social) * 3 Symptom scales (fatigue, pain, nausea, and vomiting, shortness of breath, loss of appetite, sleep disturbance, constipation, diarrhea) and financial impact of the disease * 2 Global items (global health status, overall HRQoL) All of the scales and single-item measures range in score from 0 to 100. High scale score represents a higher response level.
Time frame: Baseline, up to approximately 56 months
Change from baseline in the back pain/pelvis pain, GI symptoms, and urological symptoms scales of the EORTC QLQ EN24
The Endometrial Cancer Module (EORTC QLQ-EN24) is a disease-specific measure that is supplemental to the EORTC QLQ-C30 to capture patient's experiences with endometrial cancer-specific symptoms and impacts. The recall period is the past week. The 24-item questionnaire consists of the following: * Symptom scales/items (Lymphoedema, urological symptoms, gastrointestinal symptoms, poor body image, and sexual/vaginal problems, pain in back and pelvis, tingling/numbness, muscular pain, hair loss, and taste change) * Functional scales (sexual interest, sexual activity, and sexual enjoyment) Higher scores for functional scales represent high level of functioning, while higher scores for symptoms scales represent higher levels of symptoms/problems.
Time frame: Baseline, up to approximately 56 months
Time to definitive deterioration in the global health status/QoL and physical functioning scale of the EORTC QLQ-C30.
The European Organisation for Research and Treatment of Cancer Quality of Life-Core 30 Questionnaire (EORTC QLQ-C30), is a validated 30-item self-administered core questionnaire designed to assess HRQoL, functioning, and symptoms in all cancer patients or survivors. Time to deterioration is defined as time from baseline (defined as day 1 of cycle 1 before first application of maintenance therapy) to the date of the first clinically meaningful deterioration i.e. a decrease by ≥10 points for the functional scales and an increase by ≥ 10 points for the symptom scales or death in: * Physical functioning score * Role functioning score
Time frame: Approximately 56 months
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.
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