As Stephen doesn't show much in visible symptoms, I can only go on labwork as well. Bloodwork taken just before Stephen's 3rd loading dose already showed his CRP had dropped from 6.5 (before starting) to 0.3, it also showed his HGB had risen (124 to 135). Blood taken at the next infusion (so, two months later, 4th infusion), showed CRP had dropped to 0.2 and HGB risen to 137.
He is scheduled for an MRE on Aug 2 - I'm not sure how long before mucosal healing should be apparent, I'm expecting MRE to provide an answer.