Donor Alloantigen Reactive Tregs (darTregs) for Calcineurin Inhibitor (CNI) Reduction

A single intravenous infusion as described administered over a 20-30 minute interval with close monitoring prior to, during, and after the infusion.

Pre-medication for darTregs infusion. A dose of 15 mg/kg will be administered 30 to 60 minutes prior to the darTregs infusion.

Pre-medication for darTregs infusion. A dose of 1-2 mg/kg diphenhydramine will be administered 30 to 60 minutes prior to the darTregs infusion.

"Subjects:1.) who fulfill study eligibility criteria will withdraw IS 2.) enter the study on calcineurin inhibitor (CNI) monotherapy or a CNI-based regimen with either Prednisone or MMF as a second IS medication 3.) will proceed with changes in CNI dosing according to the protocol's CNI withdrawal algorithm.During the last 2 weeks of IS withdrawal (e.g., Step 2 in algorithm -CNI reduced 25%-pre darTregs), a single dose of darTregs will be infused IV. The subject will then, if eligible, proceed with IS withdrawal within 2 weeks after the infusion. Eligible subjects meeting the primary endpoint of 75% reduction in CNI from baseline after darTregs will be offered the opportunity to continue IS withdrawal until complete discontinuation of IS."

Blood draws (venipuncture); collection of peripheral blood mononuclear cells (PBMCs) by a procedure known as leukapheresis or venipuncture; buccal (cheek) swab for HLA typing; liver biopsies (per protocol and for cause).