Study of Pregnyl as Adjunct Therapy for High-Risk or Refractory Acute GVHD

Inclusion Criteria: * Acute graft versus host disease (GVHD) fitting one of the following categories: * High-Risk aGVHD (ARM 1): Pediatric or adult (ages 12-76 years) HCT recipients with high-risk acute GVHD, as determined by the refined MN acute GVHD risk score: http://z.umn.edu/MNAcuteGVHDRiskScore OR high risk on the basis of blood biomarkers (Ann Arbor Score 3 or amphiregulin ≥ 33 pg/ml) or * Steroid-Refractory aGVHD (ARM 2): Pediatric or adult (ages 12-76 years) HCT recipient with grade II-IV steroid refractory or steroid-dependent acute GVHD, defined as any one of the following: * No response of acute GVHD after at least 4 days of systemic corticosteroids of at least 2 mg/kg prednisone or equivalent * Progression of acute GVHD within 3 days of systemic corticosteroids of at least 2 mg/kg prednisone or equivalent * Failure to improve to at least grade II acute GVHD after 14 days of systemic corticosteroids, with initial doses of at least 2 mg/kg prednisone or equivalent * Flare of acute GVHD of at least grade II/IV severity despite tapering dose of steroids being \> 0.5 mg/kg/day. * Adequate organ function at study enrollment defined as: * Renal: 1.73m2Serum creatinine ≤2.5x upper limit of normal (ULN) * Cardiac: Left ventricular ejection fraction (LVEF) ≥ 35% * Voluntary written consent (adult or parent/guardian with minor assent for 12 through 17 year olds) Exclusion Criteria: * Progressive malignancy * Diagnosis of a hormone responsive malignancy * Uncontrolled infection at initiation of protocol treatment * Current thromboembolic disease requiring full-dose anticoagulation - patients receiving pharmacologic prophylaxis for thromboembolic disease will be eligible * Active or recent (within prior 3 months) thrombus, irrespective of anticoagulation status * Pregnancy as assessed on baseline blood hCG level * Unwilling or unable to stop supplemental sex hormone therapy (estrogen, progesterone, and/or testosterone preparations) * Women or men of childbearing potential unwilling to take adequate precautions to avoid pregnancy from the start of protocol treatment through 28 days after the last treatment Screening Inclusion Criteria: * Pediatric or adult (ages 0-76 years) HCT recipients * Suspected high risk GVHD * Voluntary written consent (adult or parent/guardian with minor assent for 12 through 17 year olds)