title: Feasibility of tissue plasminogen activator formulated for pulmonary delivery.
abstract: OBJECTIVE
  This study was conducted to assess the feasibility of a pulmonary formulation of tissue plasminogen activator (tPA) for nebulization into the airway by measuring protein stability, biologic activity, particle size, and estimating human lung distribution.
  
  
  METHODS
  Formulations were derived by varying the surfactant and protein concentrations. Protein stability and recovery of each nebulized tPA formulation were assessed by ultraviolet spectroscopy. Formulations that met protein stability feasibility criteria were assessed for biologic and fibrinolytic activities. Biologic activity was determined by their ability to inhibit superoxide anion production by human neutrophils. Fibrinolytic activity was assessed by the cleavage of plasminogen to plasmin. Aerodynamic properties were assessed using a cascade impactor, and an estimation of human airway deposition was made via a human lung replica.
  
  
  RESULTS
  Twenty-seven tPA formulations were initially assessed, 15 of which met protein stability criteria. Subsequently, three of these formulations maintained biologic and fibrinolytic activities. These formulations exhibited particle sizes of 2.4-3.1 microm, and had respirable doses > or =65%. A formulation of 1mg mL(-1) tPA and 0.1% Tween 80 exhibited a 45% deposition in the lower airways of a human lung replica.
  
  
  CONCLUSIONS
  A suitable pulmonary tPA formulation was identified that, following nebulization, maintained protein stability as well as biologic and fibrinolytic activities, and resulted in an optimal respirable dose and human airway deposition. This formulation may be applicable in the treatment of lung diseases, such as acute respiratory distress syndrome by permitting targeted pulmonary delivery of a therapeutic protein to the lungs.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Dunn
authors.forename: Rajiv
authors.initials: R
authors.lastname: Nayar
authors.forename: Jackie
authors.initials: J
authors.lastname: Campos
authors.forename: Brooks M
authors.initials: BM
authors.lastname: Hybertson
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhou
authors.forename: Mark Cornell
authors.initials: MC
authors.lastname: Manning
authors.forename: John E
authors.initials: JE
authors.lastname: Repine
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Stringer
mesh_terms: D002626:Chemistry, Pharmaceutical; D016503:Drug Delivery Systems; D004795:Enzyme Stability; D005240:Feasibility Studies; D005343:Fibrinolytic Agents / Q000008:administration & dosage / Q000378:metabolism; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D011652:Pulmonary Circulation; D012123:Pulmonary Ventilation; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism*
chemical_list: D005343:Fibrinolytic Agents; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator