title: Pharmacokinetics of CAMPATH-1H in BMT patients.
abstract: BACKGROUND
  CAMPATH-1 (CD52)Abs are used in stem-cell transplantation for prevention of GvHD and rejection. The humanized Ab CAMPATH1H has recently replaced the rat Ab CAMPATH-1G. There was a concern whether it might have a longer half-life in vivo and, possibly, cause prolonged immunosuppression post-transplant.
  
  
  METHODS
  Serum samples were collected pre- and post-transplant from patients receiving CAMPATH-1H at 10 mg/day according to two protocols: (A) from Day -5 to Day +4 (total dose, 100 mg), (B) from Day -10 to Day -6 (total dose, 50 mg). The Ab concentrations were measured using an immunofluorescence assay.
  
  
  RESULTS
  Lymphocytes were substantially depleted by the second day of treatment and were below 0.1 x 10(9)/L by the day of transplant and for at least 1 month post-transplant. By Day 90 there was a greater recovery in Group B, to a median of 0.32 x 10(9)/L compared with 0.25 x 10(9)/L in Group A. By Day 180, both groups had recovered to approx 0.52 x 10(9)/L. Serum concentrations of CAMPATH-1H on the day of transplant were well above the level necessary for opsonization of lymphocytes. The peak Ab concentration was 6.1 micro g/mL in Group A and 2.5 micro g/mL in Group B. CAMPATH-1H could be detected in Group A for 23 days post-transplant, significantly longer than in Group B (11 days). The terminal half-life in the two groups was similar (range 15-21 days) and contrasts with the half-life of < 1 day previously estimated for CAMPATH-1G. There were no cases of graft failure and the incidence of GvHD was similar in the two groups.
  
  
  CONCLUSIONS
  The humanized Ab CAMPATH-1H appears to persist in the circulation for longer than the original rat Ab CAMPATH-1G. This might contribute to delayed lymphocyte recovery and prohibit the use of early donor-lymphocyte infusions. A short course of treatment given early pre-transplant is likely to be preferable to the extended course given both pre- and post-transplant.
authors.affiliation: Sir William Dunn School of Pathology, University of Oxford, UK.
authors.forename: P
authors.initials: P
authors.lastname: Rebello
authors.forename: K
authors.initials: K
authors.lastname: Cwynarski
authors.forename: M
authors.initials: M
authors.lastname: Varughese
authors.forename: A
authors.initials: A
authors.lastname: Eades
authors.forename: J F
authors.initials: JF
authors.lastname: Apperley
authors.forename: G
authors.initials: G
authors.lastname: Hale
mesh_terms: D000328:Adult; D000074323:Alemtuzumab; D000911:Antibodies, Monoclonal / Q000097:blood / Q000493:pharmacokinetics*; D061067:Antibodies, Monoclonal, Humanized; D000912:Antibodies, Neoplasm / Q000097:blood; D015703:Antigens, CD / Q000276:immunology; D000951:Antigens, Neoplasm; D016465:Bone Marrow Purging / Q000379:methods*; D016026:Bone Marrow Transplantation / Q000276:immunology*; D000074301:CD52 Antigen; D002452:Cell Count; D004334:Drug Administration Schedule; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000379:methods; D006023:Glycoproteins / Q000037:antagonists & inhibitors* / Q000276:immunology; D006086:Graft vs Host Disease / Q000188:drug therapy* / Q000276:immunology / Q000517:prevention & control*; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods*; D006801:Humans; D007165:Immunosuppression Therapy / Q000379:methods*; D008212:Lymphocyte Depletion / Q000379:methods*; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009026:Mortality; D020127:Recovery of Function / Q000187:drug effects / Q000276:immunology; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000912:Antibodies, Neoplasm; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D000074301:CD52 Antigen; C000613862:CD52 protein, human; C000613864:Cd52 protein, rat; D006023:Glycoproteins; D000074323:Alemtuzumab