The ultimate goal of the study is to identify potential biomarkers, immune gene expression signatures, and co-stimulatory pathways that may be used to understand the effect of immune checkpoint inhibitors on gynecologic cancers.

Epithelial gynecologic malignancies are tumors of müllerian origin, which include ovarian, endometrial, fallopian tube, and primary peritoneal cancers, and account for >70,000 new diagnoses and >22,000 deaths per year in the United States alone. Treatment typically consists of a thorough cytoreductive and staging surgery in combination with platinum/taxane chemotherapy. Newer approaches adding anti-angiogenic therapies to chemotherapy have resulted in moderate improvements in recurrence free survival. However, despite these aggressive treatments, the majority of women with advanced stage at diagnosis will experience relapse. Unfortunately, relapsed disease is incurable and women ultimately die of their disease despite maximal efforts at cancer control using subsequent chemotherapy or targeted agents. There has been significant interest in incorporating immune checkpoint therapies in the treatment of gynecologic malignancies, especially given the durable remissions associated with these therapies in the treatment of melanoma and early indications of durable responses in recurrent ovarian cancer. At this time, little is known about whether or how to combine chemotherapy, anti-angiogenic therapies, and immunologic therapies for maximal benefit. Understanding the tumor microenvironment, particularly immune and angiogenic factors that contribute to tumor survival, as well as the changes that occur in response to immunotherapy is critical to identify favorable biomarker profiles which could lead to improved prognostic outcomes and inform the development and sequencing of therapies to maximize benefit.

Inclusion Criteria:

1. Have histologically or cytologically confirmed gynecologic tumor of müllerian origin, specifically epithelial ovarian, fallopian tube, primary peritoneal, or uterine endometrial cancer.
2. Have disease amenable to surgical resection.
3. Be willing and able to provide written informed consent for the trial.
4. Be at least 18 years of age on day of signing informed consent.
5. Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion. Subjects for whom newly-obtained samples cannot be provided (e.g. inaccessible or subject safety concern) may submit an archived specimen only upon agreement of the investigator.
6. Have a performance status of 0 or 1 on the ECOG Performance Scale.
7. Demonstrate adequate organ function as defined below. All screening labs should be performed within 10 days of study drug administration:

7a. ANC ≥ 1,500/mcL

7b. Platelets ≥ 100,000/mcL

7c. Hemoglobin ≥ 9 g/dL or ≥ 5.6 mmol/L without transfusion or EPO dependency (within 7 days of assessment)

7d. Serum creatinine ≤ 1.5 times the upper limit of normal or calculated creatinine clearance ≥ 60 mL/min for subject with creatinine levels > 1.5 times institutional upper limit of normal

7e. Serum total bilirubin ≤ 1.5 times the upper limit of normal or direct bilirubin ≤ the upper limit of normal with total bilirubin levels > 1.5 times upper limit of normal

7f. AST and ALT ≤ 2.5 times the upper limit of normal or ≤ 5 times the upper limit of normal for subjects with liver metastases

7g. Albumin > 2.5 mg/dL

7h. International Normalized Ratio (INR) or Prothrombin Time (PT) ≤ 1.5 times the upper limit of normal unless subject is receiving anticoagulant therapy as long as PT or PTT is within therapeutic range of intended use of anticoagulants

7i. Activated Partial Thromboplastin Time (aPTT) ≤ 1.5 times the upper limit of normal unless subject is receiving anticoagulant therapy as long as PT or PTT is within therapeutic range of intended use of anticoagulants

8. Female subjects of childbearing potential should have a negative urine or serum pregnancy within 72 hours prior to receiving the first dose of study medication. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required.

9. Female subjects of childbearing potential should be willing to use 2 methods of birth control or be surgically sterile, or abstain from heterosexual activity until planned hysterectomy/oophorectomy. Subjects of childbearing potential are those who have not been surgically sterilized or have not been free from menses for > 1 year.

Exclusion Criteria:

1. Is currently participating and receiving a study therapy or has participated in a study of an investigational agent and received study therapy or used an investigational device within 4 weeks of the study drug administration.

2. Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior to study drug administration.

3. Has a known history of active TB (Bacillus Tuberculosis)

4. Hypersensitivity to pembrolizumab or any of its excipients.

5. Has had a prior anti-cancer monoclonal antibody (mAb) within 4 weeks prior to study Day 1 or who has not recovered (i.e., ≤ Grade 1 or at baseline) from adverse events due to agents administered more than 4 weeks earlier.

6. Has received prior chemotherapy, targeted small molecule therapy, or radiation therapy for the current gynecologic malignancy.

   NOTE: Subjects who have received treatment for a prior unrelated malignancy must have recovered (i.e., ≤ Grade 1 or at baseline) from adverse events due to a previously administered agent.

   NOTE: If subject received major surgery, they must have recovered adequately from the toxicity and/or complications from the intervention prior to starting therapy.

7. Has a known additional malignancy that is progressing or requires active treatment. Exceptions include basal cell carcinoma of the skin, squamous cell carcinoma of the skin that has undergone potentially curative therapy, or in situ cervical cancer.

8. Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis. Subjects with previously treated brain metastases may participate provided they are stable (without evidence of progression by imaging for at least four weeks prior to study drug administration and any neurologic symptoms have returned to baseline), have no evidence of new or enlarging brain metastases, and are not using steroids for at least 7 days prior to study drug administration. This exception does not include carcinomatous meningitis which is excluded regardless of clinical stability.

9. Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs). Replacement therapy (eg., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment.

10. Has known history of, or any evidence of active, non-infectious pneumonitis.

11. Has an active infection requiring systemic therapy.

12. Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the subject to participate, in the opinion of the treating investigator.

13. Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.

14. Is pregnant or breastfeeding.

15. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent.

16. Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies).

17. Has known active Hepatitis B (e.g., HBsAg reactive) or Hepatitis C (e.g., HCV RNA [qualitative] is detected).

18. Has received a live vaccine within 30 days of planned start of study therapy. NOTE: Seasonal influenza vaccines for injection are generally inactivated flu vaccines and are allowed; however intranasal influenza vaccines (e.g., Flu-Mist®) are live attenuated vaccines, and are not allowed.

Analysis was conducted only on subjects who completed the study.

The study collected AEs and SAEs from the time of informed consent to 30 days after the first Pembrolizumab infusion, an average of 1 month. AEs and SAEs were also collected during the Pembrolizumab maintenance phase. They were not collected while subjects were receiving standard of care chemotherapy.