Itacitinib and Tocilizumab for Steroid Refractory Acute Graft Versus Host Disease

The study's primary objective is designed to assess the safety and tolerability, and determine the maximum tolerated dose (MTD) of both itacitinib and tocilizumab when given in combination to patients with steroid-refractory acute graft versus host disease (SR-aGVHD). The study's secondary objectives are to: * Estimate the day 28 response rate (ORR) \[complete response (CR), very good partial response (VGPR), and partial response (PR)\] of the combination of itacitinib and tocilizumab for the treatment of SR-aGVHD * Estimate the time to response and duration of response * Estimate the incidence of primary disease relapse while on study treatment * Estimate the incidence of infections including viral reactivation, bacterial infections and fungal infections while on study treatment * Estimate the progression-free survival (PFS), overall survival (OS), non-relapse mortality, GVHD-related mortality of study subjects * Estimate the proportion of patients who successfully discontinue steroids by 6 months and 12 months after therapy initiation