The main purpose of this study is to evaluate the effects of the interleukin-2 given in combination with pembrolizumab.

Interleukin-2 (IL-2) is also called aldesleukin, or Proleukin™.

Pembrolizumab is also called Keytruda™, or anti-PD-1 antibody.

The treatment is organized into blocks of 9 weeks, with pembrolizumab treatment planned for weeks 1, 4 and 7. On the second and third blocks, interleukin-2 is added, for 5 doses at a time, one dose every 8 hours, on a weekly schedule on the two weeks after the week 1 and the week 4 pembrolizumab doses.

There is no dose escalation portion: The dose and schedule of IL-2 is fixed, 600,000 IU/kg/dose, with a cap of 66 mIU/dose. Doses may be omitted for safety. The dose of pembrolizumab is fixed, flat dose 200 mg/dose.

Inclusion Criteria:

• Diagnosis/Condition for Entry into the Trial: Metastatic kidney cancer. Clear cell histology component from primary or metastatic lesion.
• Willing and able to provide written informed consent for the trial.
• Age over 18 on day of signing informed consent.
• Have measurable disease based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1.
• Willing to provide tissue from a newly obtained or archival tissue, if available.
• Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance Scale.
• Demonstrate adequate organ function, as outlined in Table 1 of study protocol document.
• Females of childbearing potential must 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.
• Females of childbearing potential must agree to use 2 methods of birth control or be surgically sterile, or abstain from heterosexual activity for the course of the study through 120 days after the last dose of study medication.
• Males must agree to use an adequate method of contraception starting with the first dose of study therapy through 120 days after the last dose of study therapy.
• Cardiac testing with either exercise stress test or thallium stress test, within 3 months of start of the first treatment day. Atrial fibrillation that is rate controlled is allowed. Note - the first treatment day is about 9 weeks before the first IL-2 treatment day. If a cardiologist's evaluation determines that this is superfluous based on other assessments, then this may be omitted.
• Pulmonary function test is required, within 3 months of start.

Exclusion Criteria:

• Is currently participating and receiving 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 first dose of treatment.
• Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior to the first dose of trial treatment.
• Has a known history of active Bacillus Tuberculosis (TB).
• Has hypersensitivity to pembrolizumab or any of its excipients.
• The number of prior therapies is restricted as follows: (a) Zero or one prior therapies during the preceding one year. This serves to limit the treatment cohort to patients with either only slowly progressive disease, or up to one prior therapy. (b) No prior PD-1 or PD-L1 antibody therapies are allowed. (c) Prior IL-2 is allowed, if it finished more than 1 year prior. (d) The following are not counted as medical therapies: nephrectomy, radiation therapy, other energy-ablative techniques, or metastasectomy.
• 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.
• Has had prior chemotherapy, targeted small molecule therapy, or radiation therapy within 2 weeks prior to study Day 1 or who has not recovered (i.e., ≤ Grade 1 or at baseline) from adverse events due to a previously administered agent. - Note: Subjects with ≤ Grade 2 neuropathy are an exception to this criterion and may qualify for the study. - Note: If subject received major surgery, they must have recovered adequately from the toxicity and/or complications from the intervention prior to starting therapy.
• Has a known additional malignancy that is progressing or requires active treatment. Exceptions include basal cell carcinoma of the skin or squamous cell carcinoma of the skin that has undergone potentially curative therapy or in situ cervical cancer.
• Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis. Potential participants with previously treated brain metastases may participate provided they are stable (without evidence of progression by imaging for at least four weeks prior to the first dose of trial treatment 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 trial treatment. This exception does not include carcinomatous meningitis which is excluded regardless of clinical stability.
• 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 (e.g., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment that would be exclusionary.
• Has known history of, or any evidence of active, non-infectious pneumonitis.
• Has an active infection requiring systemic therapy.
• Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with participation for the full duration of the trial, or is not in the best interest of the patient to participate, in the opinion of the treating investigator.
• Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial.
• Is pregnant or breastfeeding, or expecting to conceive or father children within the projected duration of the trial, starting with the pre-screening or screening visit through 120 days after the last dose of trial treatment.
• Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent.
• Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies).
• Has known active Hepatitis B (e.g., HBsAg reactive) or Hepatitis C (e.g., hepatitis C virus (HCV) RNA [qualitative] is detected).
• 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.
• Myocardial infarction, stroke, coronary artery bypass surgery, coronary stent, or unstable angina within one year.

Adverse events recorded from Cycle 1 day 1 through 30 days after cessation of treatment