title: A long-acting, mono-PEGylated human growth hormone analog is a potent stimulator of weight gain and bone growth in hypophysectomized rats.
abstract: Recombinant human GH is used to treat GH deficiency in children and adults and wasting in AIDS patients. GH has a circulating half-life of only a few hours in humans and must be administered to patients by daily injection for maximum effectiveness. Previous studies showed that longer-acting forms of GH could be created by modification of GH with multiple 5-kDa amine-reactive polyethylene glycols (PEGs). Eight of nine lysine residues and the N-terminal amino acid were modified to varying extents by amine PEGylation of GH. The amine-PEGylated GH product comprised a complex mixture of multiple PEGylated species that differed from one another in mass, in vitro bioactivity, and in vivo potency. In vitro bioactivity of GH was reduced 100- to 1000-fold by extensive amine PEGylation of the protein. Here we describe a homogeneously modified, mono-PEGylated GH protein that possesses near complete in vitro bioactivity, a long half-life, and increased potency in vivo. The mono-PEGylated GH was created by substituting cysteine for threonine-3 (T3C) of GH, followed by modification of the added cysteine residue with a single 20-kDa cysteine-reactive PEG. The PEG-T3C protein has an approximate 8-fold longer half-life than GH after sc administration to rats. Every other day or every third day administration of PEG-T3C stimulates increases in body weight and tibial epiphysis growth comparable with that produced by daily administration of GH in hypophysectomized rats. Long-acting, mono-PEGylated GH analogs such as PEG-T3C are promising candidates for future testing in humans.
authors.affiliation: Bolder BioTechnology, Inc., 2945 Wilderness Place, Boulder, Colorado 80301, USA. jcox@bolderbio.com
authors.forename: George N
authors.initials: GN
authors.lastname: Cox
authors.forename: Mary S
authors.initials: MS
authors.lastname: Rosendahl
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Chlipala
authors.forename: Darin J
authors.initials: DJ
authors.lastname: Smith
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Carlson
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Doherty
mesh_terms: D000818:Animals; D001846:Bone Development / Q000187:drug effects*; D003692:Delayed-Action Preparations; D004353:Drug Evaluation, Preclinical; D006207:Half-Life; D019382:Human Growth Hormone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics*; D007016:Hypophysectomy; D008297:Male; D011092:Polyethylene Glycols / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000187:drug effects; D016896:Treatment Outcome; D015430:Weight Gain / Q000187:drug effects*
chemical_list: D003692:Delayed-Action Preparations; D019382:Human Growth Hormone; D011092:Polyethylene Glycols