TReatment for ImmUne Mediated PathopHysiology

Subjects in the high-dose methylprednisolone arm will receive an initial dose of methylprednisolone IV 10 mg/kg/day for 3 days and 5 mg/kg/day on Day 4. Normal saline will be used as placebo pre-medications and infusions given at the same volume and duration as the eATG infusions.

Subjects will receive eATG IV 40 mg/kg/day on Days 1- 4. Day 1 eATG infusion is run over 8 hours and Day 2-4 infusions are run over 4 hours.

"Subjects will receive prednisolone 1 mg/kg on Days 5-13 followed by a gradual taper with discontinuation at 42 Days as indicated below.~Days 5 - 13 Prednisolone PO 1 mg/kg/day (max 50 mg/day)~Days 14- 20 Prednisolone PO 0.5 mg/kg/day (max 25 mg/day)~Days 21 - 27 Prednisolone PO 0.3 mg/kg/day (max 15 mg/day)~Days 28 - 34 Prednisolone PO 0.1 mg/kg/day (max 5 mg/day)~Days 35 - 41 Prednisolone PO 0.1 mg/kg every OTHER day (max 5 mg every other day)~Day 42 Discontinue"

"Subjects will receive 1 mg/kg/day of oral placebo for prednisolone on days 5-13 followed by a gradual taper to discontinuation at 42 days as indicated below. Subjects receiving oral placebo will be given a solution that closely resembles the treatment drug.~Days 5 - 13 Placebo for Prednisolone PO 1 mg/kg/day (max 50 mg/day)~Days 14- 20 Placebo for Prednisolone PO 0.5 mg/kg/day (max 25 mg/day)~Days 21 - 27 Placebo for Prednisolone PO 0.3 mg/kg/day (max 15 mg/day)~Days 28 - 34 Placebo for Prednisolone PO 0.1 mg/kg/day (max 5 mg/day)~Days 35 - 41 Placebo for Prednisolone PO 0.1 mg/kg every OTHER day (max 5 mg every other day)~Day 42 Discontinue"

Subjects randomized to the supportive care alone arm will receive normal saline in place of all study treatments (skin test, premedication and IV infusions) on Days 1-4 given at the same volume and duration as the eATG infusions.

Subjects in the eATG arm will receive pre-treatment medication diphenhydramine IV 1 mg/kg prior to start of eATG infusion.

Subjects in the eATG arm will receive pre-treatment medication methylprednisolone IV 1 mg/kg prior to start of eATG infusion.