A Phase 3 interventional study of PF-08634404 and Pembrolizumab in Endometrial Neoplasms and Endometrial Cancer, sponsored by Pfizer. Recruiting at 54 sites in 5 countries. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-30.
Sponsored by Pfizer · Phase 3, Interventional, and Treatment
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Among 13 studies in Endometrial Neoplasms by Pfizer — 2 open to participants now, 3 under way, 1 of them phase 3. Endometrial Neoplasms · Pfizer.
Among the 13 studies in Endometrial Neoplasms by Pfizer, this one is the 2nd largest by planned enrollment, is the only one that started in 2026, is the only one in phase 3, and was the 13th registered.
1,426 studies on the registry are indexed under Endometrial Neoplasms; 471 are open to participants now.
Browse Endometrial Neoplasms studies →2 of the 13 studies in Endometrial Neoplasms by Pfizer are open now, in 12 countries. Recruiting first, the newest first:
Seagen, a wholly owned subsidiary of Pfizer · Sites in United States, Belgium, Canada and 8 more countries
Ages 18+
By country, each count listing its studies:
Of the 357 Endometrial Neoplasms studies recruiting now, 267 (75%) set no upper age limit and 54 (15%) stop at 75 or younger; 26 take children under 18; 23 take healthy volunteers.
This study: 18 Years and older · female · no healthy volunteers.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
13 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 9 · Phase 2 5 · Phase 3 1
First in 2012; this study’s year is marked. 1 started in 2026.
By drug class, each counting the studies that test any of its medicines:
This study's planned enrollment of 600 is above the median of 71 across 1,027 interventional studies indexed under Endometrial Neoplasms.
Median enrollment 88 across the 13 interventional studies. Of the 10 that completed or were terminated, 5 (50%) have results posted.
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Pfizer is the lead sponsor of 3,337 studies on the registry; 150 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 392 (65%) have results posted.
None of the studies under way reaches primary completion within a year.
Among the 13 studies in Endometrial Neoplasms by Pfizer, from their registry updates:
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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:
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.
Exclusion Criteria:
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.
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.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
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.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
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.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
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.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
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.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
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.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
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.
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.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
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.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Washout period
A planned gap after a treatment, so that its effects can lessen before the study treatment or a study assessment. Ask the study team and the doctor who prescribed it before changing any medicine.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
Data sharing details ↗ · www.pfizer.com
Start is estimated for Oct 2026; primary completion for Jun 2029, 31 months later.
Of 44 phase 3 interventional studies under Endometrial Neoplasms, half reached primary completion within 53 months of starting (the median), counting those still running; a quarter within 45 and three quarters within 126. This study's planned 31 months is below that.
How these figures are worked out, and which studies are left out of them.
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 ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
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Studies of the drug tested here: Anti-PD-1/Anti-VEGF Bispecific Antibody PF-08634404