title: Single-dose, subcutaneous recombinant phenylalanine ammonia lyase conjugated with polyethylene glycol in adult patients with phenylketonuria: an open-label, multicentre, phase 1 dose-escalation trial.
abstract: BACKGROUND
  Phenylketonuria is an inherited disease caused by impaired activity of phenylalanine hydroxylase, the enzyme that converts phenylalanine to tyrosine, leading to accumulation of phenylalanine and subsequent neurocognitive dysfunction. Phenylalanine ammonia lyase is a prokaryotic enzyme that converts phenylalanine to ammonia and trans-cinnamic acid. We aimed to assess the safety, tolerability, pharmacokinetic characteristics, and efficacy of recombinant Anabaena variabilis phenylalanine ammonia lyase (produced in Escherichia coli) conjugated with polyethylene glycol (rAvPAL-PEG) in reducing phenylalanine concentrations in adult patients with phenylketonuria.
  
  
  METHODS
  In this open-label, phase 1, multicentre trial, single subcutaneous injections of rAvPAL-PEG were given in escalating doses (0·001, 0·003, 0·010, 0·030, and 0·100 mg/kg) to adults with phenylketonuria. Participants aged 18 years or older with blood phenylalanine concentrations of 600 μmol/L or higher were recruited from among patients attending metabolic disease clinics in the USA. The primary endpoints were safety and tolerability of rAvPAL-PEG. Secondary endpoints were the pharmacokinetic characteristics of the drug and its effect on concentrations of phenylalanine. Participants and investigators were not masked to assigned dose group. This study is registered with ClinicalTrials.gov, number NCT00925054.
  
  
  RESULTS
  25 participants were recruited from seven centres between May 6, 2008, and April 15, 2009, with five participants assigned to each escalating dose group. All participants were included in the safety population. The most frequently reported adverse events were injection-site reactions and dizziness, which were self-limited and without sequelae. Two participants had serious adverse reactions to intramuscular medroxyprogesterone acetate, a drug that contains polyethylene glycol as an excipient. Three of five participants given the highest dose of rAvPAL-PEG (0·100 mg/kg) developed a generalised skin rash. By the end of the study, all participants had developed antibodies against polyethylene glycol, and some against phenylalanine ammonia lyase as well. Drug concentrations peaked about 89-106 h after administration of the highest dose. Treatment seemed to be effective at reducing blood phenylalanine in all five participants who received the highest dose (mean reduction of 54·2% from baseline), with a nadir about 6 days after injection and an inverse correlation between drug and phenylalanine concentrations in plasma. Phenylalanine returned to near-baseline concentrations about 21 days after the injection.
  
  
  CONCLUSIONS
  Subcutaneous administration of rAvPAL-PEG in a single dose of up to 0·100 mg/kg was fairly safe and well tolerated in adult patients with phenylketonuria. At the highest dose tested, rAvPAL-PEG reduced blood phenylalanine concentrations. In view of the development of antibodies against polyethylene glycol (and in some cases against phenylalanine ammonia lyase), future studies are needed to assess the effect of repeat dosing.
  
  
  BACKGROUND
  BioMarin Pharmaceutical.
authors.affiliation: University of Utah, Salt Lake City, UT, USA. Electronic address: nicola.longo@hsc.utah.edu.
authors.forename: Nicola
authors.initials: N
authors.lastname: Longo
authors.affiliation: Oregon Health & Sciences University, Portland, OR, USA.
authors.forename: Cary O
authors.initials: CO
authors.lastname: Harding
authors.affiliation: Ann and Robert H Lurie Children's Hospital and Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Barbara K
authors.initials: BK
authors.lastname: Burton
authors.affiliation: Washington University School of Medicine, St Louis, MO, USA.
authors.forename: Dorothy K
authors.initials: DK
authors.lastname: Grange
authors.affiliation: University of Pittsburgh School of Medicine, PA, USA.
authors.forename: Jerry
authors.initials: J
authors.lastname: Vockley
authors.affiliation: Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Wasserstein
authors.affiliation: University of Wisconsin, Madison, WI, USA.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Rice
authors.affiliation: BioMarin Pharmaceutical, Novato, CA, USA.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Dorenbaum
authors.affiliation: BioMarin Pharmaceutical, Novato, CA, USA.
authors.forename: Jutta K
authors.initials: JK
authors.lastname: Neuenburg
authors.affiliation: BioMarin Pharmaceutical, Novato, CA, USA.
authors.forename: Donald G
authors.initials: DG
authors.lastname: Musson
authors.affiliation: BioMarin Pharmaceutical, Novato, CA, USA.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Gu
authors.affiliation: BioMarin Pharmaceutical, Novato, CA, USA.
authors.forename: Saba
authors.initials: S
authors.lastname: Sile
mesh_terms: D000328:Adult; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D010649:Phenylalanine / Q000097:blood*; D010650:Phenylalanine Ammonia-Lyase / Q000008:administration & dosage* / Q000276:immunology / Q000494:pharmacology*; D010661:Phenylketonurias / Q000097:blood / Q000188:drug therapy*; D011092:Polyethylene Glycols / Q000008:administration & dosage*; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States
chemical_list: D011092:Polyethylene Glycols; D010649:Phenylalanine; D010650:Phenylalanine Ammonia-Lyase
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