title: Long-term regulation of genetically modified primary hematopoietic cells in dogs.
abstract: We report long-term results from a large animal model of in vivo selection. Nine years ago, we transplanted two dogs (E900 and E958) with autologous marrow CD34(+) cells that had been transduced with a gammaretrovirus vector encoding a conditionally activatable derivative of the thrombopoietin receptor. Receptor activation through administration of a chemical inducer of dimerization (CID) (AP20187 or AP1903) confers a growth advantage. We previously reported responses to two 30-day intravenous (i.v.) courses of AP20187 administered within the first 8 months post-transplantation. We now report responses to 5-day subcutaneous (s.c.) courses of AP20187 or AP1903 at months 14, 90, and 93 (E900), or month 18 (E958), after transplantation. Long-term monitoring showed no rise in transduced cells in the absence of drug. Retroviral insertion site analysis showed that 4 of 6 (E958) and 5 of 12 (E900) transduced hematopoietic cell clones persisted lifelong. Both dogs were euthanized for reasons unrelated to the gene therapy treatment at 8 years 11 months (E958) and 11 years 1 month (E900) of age. Three clones from E900 remained detectable in each of two secondary recipients, one of which was treated with, and responded to, AP1903. Our results demonstrate the feasibility of safely regulating genetically engineered hematopoietic cells over many years.
authors.affiliation: Department of Medicine and the Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington 98109, USA.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Okazuka
authors.forename: Brian C
authors.initials: BC
authors.lastname: Beard
authors.forename: David W
authors.initials: DW
authors.lastname: Emery
authors.forename: Kerstin
authors.initials: K
authors.lastname: Schwarzwaelder
authors.forename: Michele R
authors.initials: MR
authors.lastname: Spector
authors.forename: George E
authors.initials: GE
authors.lastname: Sale
authors.forename: Christof
authors.initials: C
authors.lastname: von Kalle
authors.forename: Beverly
authors.initials: B
authors.lastname: Torok-Storb
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Kiem
authors.forename: C Anthony
authors.initials: CA
authors.lastname: Blau
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004285:Dogs; D017988:Gammaretrovirus / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009930:Organic Chemicals / Q000494:pharmacology; D016559:Tacrolimus / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C463061:AP20187; D003432:Cross-Linking Reagents; D009930:Organic Chemicals; D049452:Green Fluorescent Proteins; C423866:AP 1903 reagent; D016559:Tacrolimus