A Study of CYP-001 for the Treatment of Steroid-Resistant Acute Graft Versus Host Disease

Inclusion Criteria: * Diagnosis using consensus grading with steroid-resistant Grade II-IV acute GvHD, after a haematopoietic stem cell transplant for a haematological disorder. * Life expectancy of at least one month. * Agree to have follow-up data collected for two years after their initial dose of CYP-001 (under a separate protocol). Exclusion Criteria: * Pregnant or breastfeeding or plan to become pregnant within three months of receiving their last dose of CYP-001. * Have received any investigational research agent within 30 days or five half-lives (whichever is longer) prior to the first dose of IMP. * Known or suspected current alcohol or substance abuse problem. * Progressive or relapsing haematological malignancy, a current solid tumour, or previous malignant solid tumour that is likely to recur during the period of the study (with the exception of a past history of basal or squamous cell carcinomas). * Heart failure (NYHA Functional Class II-IV) and/or pulmonary failure. * Haemodynamically unstable and/or at high risk of cardiovascular events. * Terminal organ failure. * Meningitis, pneumonia with hypoxemia, HIV or another severe or uncontrolled systemic infection, which in the opinion of the investigator is likely to impact on the ability of the patient to participate in the trial.