title: Individualizing combination of two antiproliferative immunosuppressants with pharmacodynamic modeling of stimulated lymphocyte responses.
abstract: BACKGROUND
  Unpredictable serious adverse events (SAE) of immunosuppression, e.g. nephrotoxicity, with the nephrotoxic immunosuppressants have fostered interest in alternative regimens, which contain two antiproliferative agents, and individualized therapy. However, titration of such combinations to individual needs is not understood.
  
  
  OBJECTIVE
  To determine concentration (C) mixtures of mycophenolate mofetil (MMF) and sirolimus (SRL), which produce half-maximal inhibitory effect (EC(50)) on human lymphocytes from individual subjects.
  
  
  METHODS
  Concentration mixtures of MMF (0-5 mug/ml) and SRL (0-30 ng/ml) were incubated with whole blood from each of five healthy human subjects. The intracellular cytokines IL-2, TNF-alpha, and IFN-gamma were measured in PMA-ionomycin-stimulated T-cells (CD4+), while CD54, CD95, CD86, CD25, CD69, and CD71 were measured in pokeweed mitogen-stimulated B-cells, by flow cytometry. Pharmacodynamic (PD) relationships were evaluated using Hill equations modified for single and multidrug regimens, and expressed as EC(50) for each target receptor.
  
  
  RESULTS
  No change was seen in the expression of the T-cell cytokines with either MMF or SRL. Each B-cell receptor was inhibited with increasing concentrations of either MMF or SRL. Each B-cell receptor was also inhibited half-maximally at lower concentrations of MMF in the presence of SRL, than with either agent alone, for the test population of five subjects together, and for each of five individual subjects. However, each subject showed distinctly different amounts of MMF and SRL that needed to be present together, in order to produce an identical inhibitory effect on lymphocyte function.
  
  
  CONCLUSIONS
  PD analysis of biological effect can potentially predict optimal concentration mixtures of two immunosuppressants for individual recipients, and enhance rejection prophylaxis and safety. While this holds promise for drug development efforts, clinical application must await correlation of lymphocyte markers with post-transplant clinical outcomes.
authors.affiliation: Division of Transplantation, Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15217, USA.
authors.forename: Vishal
authors.initials: V
authors.lastname: Berry
authors.forename: Amy
authors.initials: A
authors.lastname: Magill
authors.forename: Mary
authors.initials: M
authors.lastname: Yost
authors.forename: Janine
authors.initials: J
authors.lastname: Janosky
authors.forename: Rakesh
authors.initials: R
authors.lastname: Sindhi
mesh_terms: D015703:Antigens, CD / Q000032:analysis; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D015415:Biomarkers / Q000032:analysis; D016207:Cytokines / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005434:Flow Cytometry; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D009173:Mycophenolic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D020123:Sirolimus / Q000494:pharmacology* / Q000627:therapeutic use; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology
chemical_list: D015703:Antigens, CD; D015415:Biomarkers; D016207:Cytokines; D007166:Immunosuppressive Agents; D009173:Mycophenolic Acid; D020123:Sirolimus