title: Chemoproteomic profiling reveals that cathepsin D off-target activity drives ocular toxicity of β-secretase inhibitors.
abstract: Inhibition of β-secretase BACE1 is considered one of the most promising approaches for treating Alzheimer's disease. Several structurally distinct BACE1 inhibitors have been withdrawn from development after inducing ocular toxicity in animal models, but the target mediating this toxicity has not been identified. Here we use a clickable photoaffinity probe to identify cathepsin D (CatD) as a principal off-target of BACE1 inhibitors in human cells. We find that several BACE1 inhibitors blocked CatD activity in cells with much greater potency than that displayed in cell-free assays with purified protein. Through a series of exploratory toxicology studies, we show that quantifying CatD target engagement in cells with the probe is predictive of ocular toxicity in vivo. Taken together, our findings designate off-target inhibition of CatD as a principal driver of ocular toxicity for BACE1 inhibitors and more generally underscore the power of chemical proteomics for discerning mechanisms of drug action.
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Zuhl
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Neuroscience Research Unit.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Nolan
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Brodney
authors.affiliation: Worldwide Medicinal Chemistry.|Pfizer Worldwide Research and Development, San Diego, California 92121, USA.
authors.forename: Sherry
authors.initials: S
authors.lastname: Niessen
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Neuroscience Research Unit.
authors.forename: Kevin
authors.initials: K
authors.lastname: Atchison
authors.affiliation: Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.|Drug Safety Research and Development.
authors.forename: Christopher
authors.initials: C
authors.lastname: Houle
authors.affiliation: Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.|Drug Safety Research and Development.
authors.forename: David A
authors.initials: DA
authors.lastname: Karanian
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Neuroscience Research Unit.
authors.forename: Claude
authors.initials: C
authors.lastname: Ambroise
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Brulet
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Beck
authors.affiliation: Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.|Pharmacokinetics, Dynamics and Metabolism.
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Doran
authors.affiliation: Worldwide Medicinal Chemistry.|Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: O'Neill
authors.affiliation: Worldwide Medicinal Chemistry.|Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Am Ende
authors.affiliation: Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.|Pharmacokinetics, Dynamics and Metabolism.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chang
authors.affiliation: Worldwide Medicinal Chemistry.|Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.|Structural Biology and Biophysics Group.
authors.forename: Kieran F
authors.initials: KF
authors.lastname: Geoghegan
authors.affiliation: Worldwide Medicinal Chemistry.|Pfizer Worldwide Research and Development, Groton, Connecticut 06340, USA.|Structural Biology and Biophysics Group.
authors.forename: Graham M
authors.initials: GM
authors.lastname: West
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Judkins
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Xinjun
authors.initials: X
authors.lastname: Hou
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Neuroscience Research Unit.
authors.forename: David R
authors.initials: DR
authors.lastname: Riddell
authors.affiliation: Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139, USA.|Worldwide Medicinal Chemistry.
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Johnson
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D002402:Cathepsin D / Q000378:metabolism*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology / Q000633:toxicity*; D005123:Eye / Q000187:drug effects / Q000473:pathology*; D006801:Humans; D020128:Inhibitory Concentration 50; D013058:Mass Spectrometry; D018345:Mice, Knockout; D015335:Molecular Probes / Q000138:chemical synthesis / Q000737:chemistry; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D040901:Proteomics / Q000379:methods*; D017208:Rats, Wistar; D055213:Retinal Pigment Epithelium / Q000187:drug effects / Q000473:pathology; D013194:Staining and Labeling; D018675:Toxicity Tests
chemical_list: D004791:Enzyme Inhibitors; D015335:Molecular Probes; D010455:Peptides; D053829:Amyloid Precursor Protein Secretases; D002402:Cathepsin D