The purpose of this study is to find out how much of Modigraf is absorbed and used in the body and how fast it leaves the body (Pharmacokinetics). The results will then help to decide how much Modigraf in future can be given safely to children and young people following transplantation.

The primary objective of this study is to determine the pharmacokinetics (PK) of tacrolimus following oral administration of Modigraf, after the first oral dose and at steady state in paediatric subjects undergoing de novo allograft transplantation.

Inclusion Criteria:

• The subject is the recipient of a solid organ (liver, kidney or heart) transplant. Multiorgan transplants are acceptable as long as one of the organs transplanted is liver, kidney or heart

Exclusion Criteria:

• The subject has previously received another organ transplant (including liver, kidney or heart re-transplantation)
• Subject has a high immunological risk, defined as a Panel Reactive Antibody (PRA) score >50% in the previous 6 months (only applicable for renal transplant recipients)
• Cold ischemia time of the donor kidney greater than 30 hours (only applicable for renal transplant recipients)
• Subject receives an AB0 incompatible donor organ
• Subject has significant renal impairment, defined as having serum creatinine ≥230 μmol/l (≥2.6 mg/dl) pre-transplantation (not applicable for renal transplant recipients)
• Subject has significant liver disease, defined as having elevated Alanine Aminotransferase (ALT) and/or Asparate Aminotransferase (AST) and/or Total Bilirubin levels 3 times the upper value of the normal range during the 28 days prior to transplantation (not applicable for liver transplant recipients)
• Subject with pulmonary vascular resistance greater than 4 Wood units which is unresponsive to treatment
• Subjects with malignancies or a history of malignancy within the last 5 years
• Subject has a significant, uncontrolled systemic infection and/or severe diarrhea, vomiting, active upper gastrointestinal disorder that may affect the absorption of tacrolimus or has an active peptic ulcer
• Subject requires systemic immunosuppressive medication for any indication other than transplantation
• Recipient or donor known to be HIV, HCV or HBV positive
• Known allergy or intolerance to steroids, macrolide antibiotics, basiliximab or tacrolimus
• Subject is currently participating in another clinical trial and/or has been taking an investigational drug in the 3 months prior to transplantation
• Subject is unlikely to comply with the visits scheduled in the protocol
• Subjects taking or requiring to be treated with medication or substances prohibited by this protocol

Access to anonymized individual participant level data collected during the study, in addition to study-related supporting documentation, is planned for studies conducted with approved product indications and formulations, as well as products terminated during development. Studies conducted with product indications or formulations that remain active in development are assessed after study completion to determine if Individual Participant Data can be shared. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.

Access to participant level data is offered to researchers after publication of the primary manuscript (if applicable) and is available as long as Astellas has legal authority to provide the data.

Researchers must submit a proposal to conduct a scientifically relevant analysis of the study data. The research proposal is reviewed by an Independent Research Panel. If the proposal is approved, access to the study data is provided in a secure data sharing environment after receipt of a signed Data Sharing Agreement.