Inclusion:
* Patients with an active autoimmune disease requiring systemic treatment within the past 3 months, or a syndrome that requires systemic steroids greater than dexamethasone 2 mg daily (or equivalent) or immunosuppressive agents within the past 3 months will be ineligible. Patients with a documented history of severe autoimmune disease but have been off of steroids and immunosuppressive agents for greater than 3 months, or only require intermittent steroid bursts may be eligible following discussion and approval from the Principal Investigator. Subjects with vitiligo or resolved childhood asthma/atopy would be an exception to this rule. Subjects who require intermittent use of inhaled steroids or local steroid injections would not be excluded from the study. Subjects with hypothyroidism stable on hormone replacement, or psoriasis not requiring systemic therapy (within the past 3 years) or Type 1 diabetes on stable insulin will not be excluded from the study
* Histologically or cytologically documented Extensive Stage Small Cell Lung Cancer with documented disease progression after at least one prior systemic regimen, including one platinum-based regimen, with progression of disease on or after their most recent therapy. Patients previously diagnosed with limited stage Small Cell Lung Cancer treated with concurrent chemoradiation with a platinum doublet now diagnosed with recurrent extensive disease are eligible.
* ECOG performance status of 0 to 2
* Measurable disease with at least one tumor site amenable to biopsy
* Patients may have untreated asymptomatic Central Nervous System (CNS) metastases or treated CNS metastases if they are not currently receiving corticosteroids greater than dexamethasone 2 mg daily or equivalent for 7 days prior to the first dose of study drug. Patients should have completed stereotactic radiation or whole-brain radiation at least 2 weeks prior to Cycle 1, Day 1
Exclusion:
* Patients with an active autoimmune disease requiring systemic treatment within the past 3 months or a documented history of clinically severe autoimmune disease, or a syndrome that requires systemic steroids \> dexamethasone 2 mg daily (or equivalent dose of other corticosteroids) or other immunosuppressive agents.
* Treatment with systemic immunosuppressive medications including but not limited to, dexamethasone at doses \> 2 mg or equivalent dose of other corticosteroids, cyclophosphamide, tacrolimus, sirolimus, azathioprine, methotrexate, thalidomide, and antitumor necrosis factor (anti-TNF) agents within 2 weeks prior to initiation of trial therapy. Inhaled or topically applied steroids, and acute and chronic standard-dose NSAIDs are permitted. Replacement steroids are also permitted.
* Prior treatment with anti-CTLA4 antibodies. Prior anti-PD1 or anti-PDL1 therapy is allowed.
* Symptomatic untreated CNS metastases. Patients with asymptomatic CNS metastases are eligible. Patients with symptomatic brain metastases are eligible, provided they meet all of the following criteria:
* Completed stereotactic radiosurgery or whole- brain radiation at least 2 weeks prior to Cycle 1, Day 1.
* No evidence of interim progression between the completion of CNS-directed therapy and the start of trial therapy.
* No ongoing requirement for steroids greater than dexamethasone 2 mg daily (or equivalent dose of other corticosteroids) as therapy for CNS disease; anticonvulsants at a stable dose are allowed.
* History of leptomeningeal carcinomatosis.
* Interstitial lung disease that is symptomatic or may interfere with the detection or management of suspected drug-related pulmonary toxicity.
* Any systemic anti-cancer chemotherapy, within 21 days prior to initiation of study treatment.
* Treatment with any other investigational agent or participation in another clinical trial with therapeutic intent within 21 days prior to enrollment.
* Uncontrolled intercurrent illness including, but not limited to, symptomatic congestive heart failure, unstable angina pectoris, or psychiatric illness/social situations that would limit compliance with study requirements.
* Major surgery or traumatic injury within 4 weeks of starting study drug.
* \- Women who are pregnant or lactating.
* \- Known infection with HIV, HBV or HCV. Patients with prior exposure to hepatitis, but no evidence of active or chronic infection, may be eligible.
* \- Evidence of end-organ damage as defined by the following laboratory results obtained within 14 days prior to the first study treatment:
* ANC \<1,000 cells/µL (without granulocyte colony-stimulating factor support within 2 weeks prior to Cycle 1, Day 1).
* Platelet count \<75,000/µL (without transfusion within 2 weeks prior to Cycle 1, Day 1).
* Hemoglobin \<8.0 g/dL (Patients may be transfused to meet this criterion).
* AST and ALT ≥2.5 x ULN, with the following exceptions: Patients with documented liver metastases: AST and/or ALT≥5 x ULN. o Serum bilirubin ≥1.5 x ULN (Patients with known Gilbert disease who have serum bilirubin level ≤ 3 x ULN may be enrolled).
* INR and aPTT ≥1.5 x ULN (This applies only to patients who are not receiving therapeutic anticoagulation; patients receiving therapeutic anticoagulation should be on a stable dose).
