Safety and Efficacy of Targeting PP2A in Ovarian Clear Cell Carcinoma Using Dostarlimab and LB-100

Inclusion criteria

Inclusion criteria will be assessed within 28 days of starting study treatment: 1. Ability to provide signed informed consent 2. Age 18-75 years at time of study entry 3. Willingness and ability to comply with the protocol for the duration of the study including undergoing treatment and scheduled visits and examinations including follow up 4. Histology showing recurrent clear cell ovarian, peritoneal, or fallopian tube cancer (mixed histology with predominant clear cell component is acceptable). 5. Receipt of at least one prior line of therapy for recurrent disease or development of platinum resistant or refractory disease, defined by progression of disease on a platinum-containing regimen or recurrence of disease within 180 days of previous platinum treatment 6. Available somatic mutation testing results (CLIA source) that reveal no PPP2R1A mutations 7. Measurable disease based on modified RECIST v1.1. For the purposes of this study measurable disease is defined at least one "target lesion" that can be accurately measured in at least one dimension (longest dimension to be recorded). Each target lesion must be \>20 mm when measured by conventional techniques, including palpation, plain x-ray, computed tomography (CT), and magnetic resonance imaging (MRI), or \>10 mm when measured by spiral CT. The target lesion must be distinct from other tumor areas selected for pre-treatment biopsies. Second lesion selected for pre-treatment biopsy must be biopsy accessible. 8. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. See Section 14. 9. Life expectantly of ≥12 weeks 10. Adequate normal organ and bone marrow function as defined below. 1. Hemoglobin ≥8.0 g/ dL 2. Absolute neutrophil count (ANC) ≥ 1000/mm3 3. Platelet count ≥100 x 109/L (\>100,000/mm3) 4. Serum bilirubin ≤1.5 x ULN. This will not apply to patients with confirmed Gilbert's syndrome (persistent or recurrent hyperbilirubinemia that is predominantly unconjugated in the absence of hemolysis or hepatic pathology), who will be allowed only in consultation with their physician. 5. AST (SGOT)/ALT (SGPT) ≤2.5 x ULN unless liver metastases are present, in which case it must be ≤5 x ULN 6. Measured creatinine clearance (CL) ≥ 50 mL/min or Calculated creatinine CL ≥ 50 mL/min by the Cockcroft-Gault formula (Cockcroft and Gault 1976) or by 24-hour urine collection for determination of creatinine clearance: Creatinine CL (mL/min) = Weight (kg) x (140 - Age) x 0.85 72 x serum creatinine (mg/dL) 11. Evidence of post-menopausal status or negative serum pregnancy test for female pre-menopausal patients. The effects of dostarlimab and LB-100 on the developing human fetus are unknown. For this reason, women of child-bearing potential must agree to use adequate contraception (See Section 5.6.2). 12. Women will be considered post-menopausal if they have been amenorrheic for 12 months without an alternative medical cause. The following age-specific requirements apply: 1. Women \<50 years of age would be considered post-menopausal if they have been amenorrheic for 12 months or more following cessation of exogenous hormonal treatments and if they have luteinizing and follicle-stimulating hormone levels in the post-menopausal range for the institution or underwent surgical sterilization (bilateral oophorectomy or hysterectomy) 2. Women ≥50 years of age would be considered post-menopausal if they have been amenorrheic for 12 months or more following cessation of all exogenous hormonal treatments, had radiation-induced menopause with last menses \>1 year ago, had chemotherapy-induced menopause with last menses \>1 year ago, or underwent surgical sterilization (bilateral oophorectomy, bilateral salpingectomy, or hysterectomy)