Inclusion Criteria:

• Subjects previously started on and currently receiving ECP therapy for cGVHD.
• Subjects with a diagnosis of cGVHD manifesting at least as skin GVHD after stem cell or marrow transplant from a related or unrelated donor.
• Subjects with adequate renal, hepatic, pulmonary and cardiac function to enable the subject to tolerate the extracorporeal volume shifts associated with ECP, including ending procedure with a positive fluid balance (~> 650 mL of saline/anticoagulant infused), as determined by the investigator’s clinical judgment.
• Subjects with a white blood cell count ≥ 1,000/μ and platelet count ≥ 25,000/μL.
• Subjects with an estimated GFR from serum creatinine ≥ 30 mL/min/BSA and AST between 10-120 units/L.
• Physician evaluation of subjects’ pulmonary and cardiac function will be done by physical exam and evaluated against New York Heart Associate (NYHA) Classification for cardiac disease. Only subjects in Class I or Class II may participate in the study.
• Women of childbearing potential must agree to use a reliable method of birth control for the duration of the study.
• Subjects who weigh ≥ 50 kg (110 lb).
• Eligible male subjects will either be:
  • Surgically sterile (i.e., vasectomy), for at least 3 months prior to screening OR agree to use a condom with spermicide when sexually active with a female partner who is not using an acceptable method of birth control during the study and for 30 days after last study medication administration.
• Subjects with a systolic blood pressure ≥90 mmHg.
• Subjects must be between the ages of 18 – 80 years.
• Subjects must be able and willing to comply with all study procedures.
• Subjects who have provided a signed informed consent form prior to participating in any study procedures.
• Subjects with sufficient vascular access to accommodate the ECP procedure as determined by the medical staff responsible for obtaining intravenous access.

Exclusion Criteria:

• Subjects with a hypersensitivity and/or allergy to psoralen (methoxsalen).
• Subjects who are participating in another clinical trial for treatment of cGVHD within 7 days prior to enrollment.
• Subjects who are concurrently participating in another clinical trial, except observational studies.
• Subjects with active gastrointestinal bleeding.
• Subjects who have any overt signs of relapse of the underlying condition, related to allogeneic transplant.
• Subjects who have an uncontrolled viral, fungal, or bacterial infection.
• Subjects who have a Total bilirubin value ≥15 mg/dL.
• Subjects who have veno-occlusive liver disease.
• Subjects who have a life expectancy < 8 weeks.
• Subjects who require invasive ventilation or vasopressor support.
• Subjects who have a known human immunodeficiency virus (HIV) or hepatitis B or C virus infection.
• Subjects who have a known hypersensitivity or allergy to Anticoagulant Citrate Dextrose Formula-A (ACD-A).
• Females who are pregnant and/or lactating.
• Subjects with aphakia.
• Subjects with a history of a light-sensitive disease state including, but not limited to:
  • Lupus erythematosus;
  • Porphyria cutanea tarda;
  • Erythropoietic protoporphyria;
  • Variegate porphyria;
  • Xeroderma pigmentosum;
  • Albinism.
• Subjects who are receiving concomitant therapy with known photosensitizing agents, including but not limited to:
  • Anthralin;
  • Coal tar or coal tar derivatives;
  • Griseofulvin;
  • Phenothiazines;
  • Nalidixic acid;
  • Halogenated salicylanilides (bacteriostatic soaps);
  • Sulfonamides;
  • Tetracyclines;
  • Thiazides;
  • Certain organic staining dyes such as methylene blue, toluidine blue, rose bengal and methyl orange.