ECP has also been effective in treating solid organ transplant rejection and improving the course of various autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosis, and pemphigus vulgaris. Since the early 1990s, ECP has been investigated as a rescue immunotherapy for patients with steroid resistant acute and chronic GVHD. ECP is generally well tolerated and Phase II data have confirmed activity in more than 250 patients with steroid-refractory cGVHD.