title: Netarsudil Increases Outflow Facility in Human Eyes Through Multiple Mechanisms.
abstract: OBJECTIVE
  Netarsudil is a Rho kinase/norepinephrine transporter inhibitor currently in phase 3 clinical development for glaucoma treatment. We investigated the effects of its active metabolite, netarsudil-M1, on outflow facility (C), outflow hydrodynamics, and morphology of the conventional outflow pathway in enucleated human eyes.
  
  
  METHODS
  Paired human eyes (n = 5) were perfused with either 0.3 μM netarsudil-M1 or vehicle solution at constant pressure (15 mm Hg). After 3 hours, fluorescent microspheres were added to perfusion media to trace the outflow patterns before perfusion-fixation. The percentage effective filtration length (PEFL) was calculated from the measured lengths of tracer distribution in the trabecular meshwork (TM), episcleral veins (ESVs), and along the inner wall (IW) of Schlemm's canal after global and confocal imaging. Morphologic changes along the trabecular outflow pathway were investigated by confocal, light, and electron microscopy.
  
  
  RESULTS
  Perfusion with netarsudil-M1 significantly increased C when compared to baseline (51%, P < 0.01) and to paired controls (102%, P < 0.01), as well as significantly increased PEFL in both IW (P < 0.05) and ESVs (P < 0.01). In treated eyes, PEFL was significantly higher in ESVs than in the IW (P < 0.01) and was associated with increased cross-sectional area of ESVs (P < 0.01). Percentage effective filtration length in ESVs positively correlated with the percentage change in C (R2 = 0.58, P = 0.01). A significant increase in juxtacanalicular connective tissue (JCT) thickness (P < 0.05) was found in treated eyes compared to controls.
  
  
  CONCLUSIONS
  Netarsudil acutely increased C by expansion of the JCT and dilating the ESVs, which led to redistribution of aqueous outflow through a larger area of the IW and ESVs.
authors.affiliation: Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States 2Department of Anatomoy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts, United States.
authors.forename: Ruiyi
authors.initials: R
authors.lastname: Ren
authors.affiliation: Department of Ophthalmology, Duke University, Durham, North Carolina, United States.
authors.forename: Guorong
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States.
authors.forename: Thuy Duong
authors.initials: TD
authors.lastname: Le
authors.affiliation: Aerie Pharmaceuticals, Inc., Durham, North Carolina, United States.
authors.forename: Casey
authors.initials: C
authors.lastname: Kopczynski
authors.affiliation: Department of Ophthalmology, Duke University, Durham, North Carolina, United States.
authors.forename: W Daniel
authors.initials: WD
authors.lastname: Stamer
authors.affiliation: Department of Ophthalmology, Boston University School of Medicine, Boston, Massachusetts, United States 2Department of Anatomoy and Neurobiology, Boston University School of Medicine, Boston, Massachusetts, United States.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Gong
mesh_terms: D000328:Adult; D000368:Aged; D001082:Aqueous Humor / Q000187:drug effects / Q000378:metabolism*; D002102:Cadaver; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008875:Middle Aged; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors; D010477:Perfusion / Q000379:methods*; D014129:Trabecular Meshwork / Q000378:metabolism* / Q000648:ultrastructure; D054460:rho-Associated Kinases / Q000494:pharmacology*
chemical_list: D050484:Norepinephrine Plasma Membrane Transport Proteins; C493227:SLC6A2 protein, human; D054460:rho-Associated Kinases