title: APLP1 as a cerebrospinal fluid biomarker for γ-secretase modulator treatment.
abstract: BACKGROUND
  Alzheimer's disease brains are characterized by extracellular plaques containing the aggregated amyloid β42 (Aβ42) peptide and intraneuronal tangles containing hyperphosphorylated tau. Aβ42 is produced by sequential processing of the amyloid precursor protein (APP) by β-secretase followed by γ-secretase. Substantial efforts have been put into developing pharmaceuticals preventing the production or increasing the clearance of Aβ42. However, treatments inhibiting γ-secretase have proven disappointing due to off-target effects. To circumvent these effects, γ-secretase modulators (GSMs) have been developed, which rather than inhibiting γ-secretase shift its preference into producing less aggregation-prone shorter Aβ peptides. Belonging to the same family of proteins as APP, amyloid-like protein 1 (APLP1) is also a substrate for γ-secretase. Herein we investigated whether the GSM E2012 affects APLP1 processing in the central nervous system by measuring APLP1 peptide levels in cerebrospinal fluid (CSF) before and after E2012 treatment in dogs.
  
  
  METHODS
  An in-house monoclonal APLP1 antibody, AP1, was produced and utilized for immunopurification of APLP1 from human and dog CSF in a hybrid immuno-affinity mass spectrometric method. Seven dogs received a single dose of 20 or 80 mg/kg of E2012 in a randomized cross-over design and CSF was collected prior to and 4, 8 and 24 hours after dosing.
  
  
  RESULTS
  We have identified 14 CSF APLP1 peptides in humans and 12 CSF APLP1 peptides in dogs. Of these, seven were reproducibly detectable in dogs who received E2012. We found a dose-dependent relative increase of the CSF peptides APLP1β17, 1β18 and 1β28 accompanied with a decrease of 1β25 and 1β27 in response to E2012 treatment. All peptides reverted to baseline over the time of sample collection.
  
  
  CONCLUSIONS
  We show an in vivo effect of the GSM E2012 on the processing of APLP1 which is measurable in CSF. These data suggest that APLP1 peptides may be used as biomarkers to monitor drug effects of GSMs on γ-secretase processing in clinical trials. However, this requires further investigation in larger cohorts, including studies in man.
authors.affiliation: Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Mölndal, S-431 80, Sweden. simon.sjodin@neuro.gu.se.
authors.forename: Simon
authors.initials: S
authors.lastname: Sjödin
authors.affiliation: Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Mölndal, S-431 80, Sweden. kerstin.ka.andersson@vgregion.se.
authors.forename: Kerstin K A
authors.initials: KK
authors.lastname: Andersson
authors.affiliation: Janssen Research and Development, Beerse, Belgium. mmercken@its.jnj.com.
authors.forename: Marc
authors.initials: M
authors.lastname: Mercken
authors.affiliation: Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Mölndal, S-431 80, Sweden. henrik.zetterberg@clinchem.gu.se.|UCL Institute of Neurology, University College London, London, UK. henrik.zetterberg@clinchem.gu.se.
authors.forename: Henrik
authors.initials: H
authors.lastname: Zetterberg
authors.affiliation: Janssen Research and Development, Beerse, Belgium. hborghys@its.jnj.com.
authors.forename: Herman
authors.initials: H
authors.lastname: Borghys
authors.affiliation: Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Mölndal, S-431 80, Sweden. kaj.blennow@neuro.gu.se.
authors.forename: Kaj
authors.initials: K
authors.lastname: Blennow
authors.affiliation: Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Mölndal, S-431 80, Sweden. erik.portelius@neuro.gu.se.
authors.forename: Erik
authors.initials: E
authors.lastname: Portelius
mesh_terms: D000595:Amino Acid Sequence; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000134:cerebrospinal fluid* / Q000235:genetics / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000302:isolation & purification; D054316:Biomarkers, Pharmacological / Q000134:cerebrospinal fluid; D018592:Cross-Over Studies; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D047468:Immunoprecipitation; D008807:Mice, Inbred BALB C; D010880:Piperidines / Q000494:pharmacology*; D011897:Random Allocation; D053719:Tandem Mass Spectrometry
chemical_list: C555019:1-(1-(4-fluorophenyl)ethyl)-3-((3-methoxy-4-(4-methyl-1H-imidazol-1-yl)phenyl)methylene)-2-piperidinone; C489697:APLP1 protein, human; D016564:Amyloid beta-Protein Precursor; D000911:Antibodies, Monoclonal; D054316:Biomarkers, Pharmacological; D007093:Imidazoles; D010880:Piperidines; D053829:Amyloid Precursor Protein Secretases