Table 1 Key Eligibility Criteria

1. Adult subjects at least 18 years old with treatment-naïve primary or locally recurrent DDLPS of the retroperitoneum or UPS of the trunk/extremity

1. Active, known, or suspected autoimmune disease

2. Disease determined to be surgically resectable and are candidates for upfront surgery as agreed upon by multidisciplinary consensus

2. Known history of testing positive for human immunodeficiency virus or known acquired immunodeficiency syndrome

3. Recent imaging within 4 weeks of trial enrollment, demonstrating measure disease as defined by RECIST 1.1

3. Any positive test results for hepatitis B or C virus indicating acute or chronic infection

4. Must have at least 1 tumor amenable to serial biopsy in clinic or be willing to undergo serial biopsies through image-guided procedures during the neoadjuvant phase of the trial

4. Condition requiring systemic treatment with corticosteroids (> 10 mg daily prednisone equivalents) or other immunosuppressive medications within 14 days of study drug administration.

5. Must be medically fit to undergo surgery

5. Prior intraabdominal surgery within 4 weeks of trial enrollment

6. Must be immunotherapy-naïve

6. Prior chemotherapy for treatment of the sarcoma under consideration for resection or radiation therapy for sarcoma in the same area

7. Patients who have received prior conventional chemotherapy for another malignancy are eligible after a 28 day wash-out period

7. Active concurrent second malignancy

8. Patients must have organ/marrow function as defined below:

8. Current use of anticoagulants at therapeutic levels

 a. WBC > 3 K/uL, ANC > 1 K/uL

 b. hemoglobin > 9 g/dL

 c. platelets > 1000 K/mm³

 d. serum creatinine < 2 mg/dL or creatinine clearance > 50 mL/min

 e. AST < 1.5 x upper limit of normal, ALT < 1.5 x upper limit of normal, bilirubin < 1.5 x upper limit of normal