A Study of Pembrolizumab in Patients With Advanced Gynaecological Clear Cell Cancer

Main Inclusion Criteria: 1. Histological diagnosis of advanced clear cell ovarian (including primary peritoneal and fallopian tube), endometrial, vaginal, vulval or cervical cancer. 2. Have measurable disease based on RECIST 1.1. 3. Evidence of radiological disease progression. 4. Patient is willing to provide tissue from a newly obtained core or excisional biopsy of a tumour lesion at baseline, 6-8 weeks after start of treatment and at the time of progression. 5. ECOG Performance Status 0 or 1. 6. Patient has a life expectancy of at least 3 months from consent. 7. Received ≥ 1 line of prior chemotherapy . Main Exclusion Criteria: 1. Has a known diagnosis of immunodeficiency or is receiving systemic steroid therapy at doses \> 10mg prednisolone daily or equivalent or any other form of immunosuppressive therapy within 7 days prior to the first dose of trial treatment. 2. Has a known history of active TB (Bacillus Tuberculosis), Hepatitis B (e.g., HBsAg reactive), Hepatitis C or a known history of Human Immunodeficiency Virus (HIV). 3. Has symptomatic central nervous system (CNS) metastases and/or carcinomatous meningitis. 4. Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids (at a dose \>10mg predisolone daily or equivalent) or immunosuppressive drugs). 5. Has known history or evidence of active, non-infectious pneumonitis. 6. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent. 7. Has received a live vaccine within 30 days prior to the planned start of trial treatment.