Pembrolizumab and Lenvatinib in Mismatch Repair Proficient Recurrent Endometrial Cancer After Progression on or Following First-Line Immunotherapy Maintenance

Participants will receive Pembrolizumab in combination with Lenvatinib after failure of first-line therapy with a platinum-based doublet chemotherapy in combination with immunotherapy. Participants may receive treatment for a total of up to approximately 24 months, or until participants have progression of disease or experience a Grade 4 or higher severe adverse event (SAE).

Total participation duration is approximately 26 months.

Participants will receive 200mg of Pembrolizumab intravenously on Day 1 of every 21 day cycle, as per standard of care and as per institutional guidelines.

• Keytruda

Participants will self-administer Lenvatinib orally at a daily dose of 20mg or every 21 day cycle, as per standard of care and as per institutional guidelines.

• Lenvima

Clinical benefit rate (CBR) is defined as the proportion of participants achieving complete response (CR), partial response (PR) or sustained stable disease (SD), as the best response as assessed using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria.

Objective Response Rate (ORR) is defined as the proportion of participants achieving complete response (CR) or partial response (PR) as the best response assessed using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria.

Progression-Free Survival (PFS) is the elapsed time in months from date of treatment initiation until progression or death from any cause. Patients who are alive and without documented disease progression will be censored at the date of their last disease assessment.

Overall Survival (OS) is the elapsed time in months from date of treatment initiation until death from any cause. Alive patients will be censored at the last date known to be alive.

Duration of Response (DOR) is the elapsed time in months from date of first documentation of complete response (CR) or partial response (PR) until first documentation of progression or death from any cause for responders. Patients who are alive and without documented disease progression will be censored at the date of their last disease assessment.

The safety and tolerability of combination Pembrolizumab and Lenvatinib therapy will be reported as the number of participants experiencing treatment-related serious adverse events (SAEs). SAEs will be assessed using the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version 5.

The safety and tolerability of combination Pembrolizumab and Lenvatinib therapy will be reported as the number of participants experiencing treatment-related adverse events (AEs). AEs will be assessed using the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) version 5.

Participant quality of life will be assessed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire 17 (EORTC QLQ-17), a validated 17-item questionnaire measuring global health status and functional domains relevant to cancer patients. Items are scored using standardized Likert scales and converted to 0-100 domain scores according to EORTC scoring guidelines. Higher scores indicate better functioning and overall quality of life.

Social isolation will be measured using the 10-item short form of the Social Provisions Scale, a validated instrument assessing perceived social support and relational connectedness. Each item is rated on a 4-point Likert scale (1 = Strongly Disagree, 2 = Disagree, 3= Agree, 4 = Strongly Agree), yielding a total score ranging from 10 to 40, with higher scores indicating greater perceived social support (lower social isolation).

Unmet social needs will be assessed using the 10-item Health Leads Social Needs Screening Tool, a validated questionnaire identifying needs such as food insecurity, housing instability, transportation barriers, and utility challenges. Each item is coded as 1 (unmet need present) or 0 (no unmet need). Total scores represent the count of unmet social needs (range 0-10), with higher scores indicating greater social needs burden.