title: Targeted delivery of a model immunomodulator to the lymphatic system: comparison of alkyl ester versus triglyceride mimetic lipid prodrug strategies.
abstract: A lipophilic prodrug approach has been used to promote the delivery of a model immunomodulator, mycophenolic acid (MPA), to the lymphatic system after oral administration. Lymphatic transport was employed to facilitate enhanced drug uptake into lymphocytes, as recent studies demonstrate that targeted drug delivery to lymph resident lymphocytes may enhance immunomodulatory effects. Two classes of lymph-directing prodrugs were synthesised. Alkyl chain derivatives (octyl mycophenolate, MPA-C8E; octadecyl mycophenolate, MPA-C18E; and octadecyl mycophenolamide, MPA-C18AM), to promote passive partitioning into lipids in lymphatic transport pathways, and a triglyceride mimetic prodrug (1,3-dipalmitoyl-2-mycophenoloyl glycerol, 2-MPA-TG) to facilitate metabolic integration into triglyceride deacylation-reacylation pathways. Lymphatic transport, lymphocyte uptake and plasma pharmacokinetics were assessed in mesenteric lymph and carotid artery cannulated rats following intraduodenal infusion of lipid-based formulations containing MPA or MPA prodrugs. Patterns of prodrug hydrolysis in rat digestive fluid, and cellular re-esterification in vivo, were evaluated to examine the mechanisms responsible for lymphatic transport. Poor enzyme stability and low absorption appeared to limit lymphatic transport of the alkyl derivatives, although two of the three alkyl chain prodrugs - MPA-C18AM (6-fold) and MPA-C18E (13-fold) still increased lymphatic drug transport when compared to MPA. In contrast, 2-MPA-TG markedly increased lymphatic drug transport (80-fold) and drug concentrations in lymphocytes (103-fold), and this was achieved via biochemical incorporation into triglyceride deacylation-reacylation pathways. The prodrug was hydrolysed rapidly to 2-mycophenoloyl glycerol (2-MPA-MG) in the presence of rat digestive fluid, and 2-MPA-MG was subsequently re-esterified in the enterocyte with oleic acid (most likely originating from the co-administered formulation) prior to accessing the lymphatics and lymphocytes. Importantly, after administration of 2-MPA-TG, the concentrations of free MPA in the mesenteric lymph nodes were significantly enhanced (up to 28 fold) when compared to animals administered equimolar quantities of MPA, suggesting the efficient conversion of the esterified prodrug back to the pharmacologically active parent drug. The data suggest that triglyceride mimetic prodrugs have potential as a means of enhancing immunotherapy via drug targeting to lymphocytes and lymph nodes.
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia.
authors.forename: Sifei
authors.initials: S
authors.lastname: Han
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia.
authors.forename: Tim
authors.initials: T
authors.lastname: Quach
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia.
authors.forename: Luojuan
authors.initials: L
authors.lastname: Hu
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia.
authors.forename: Anisa
authors.initials: A
authors.lastname: Wahab
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia.
authors.forename: William N
authors.initials: WN
authors.lastname: Charman
authors.affiliation: Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66047-1620, USA.
authors.forename: Valentino J
authors.initials: VJ
authors.lastname: Stella
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia.
authors.forename: Natalie L
authors.initials: NL
authors.lastname: Trevaskis
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia. Electronic address: Jamie.Simpson@monash.edu.
authors.forename: Jamie S
authors.initials: JS
authors.lastname: Simpson
authors.affiliation: Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia. Electronic address: Chris.Porter@monash.edu.
authors.forename: Christopher J H
authors.initials: CJ
authors.lastname: Porter
mesh_terms: D000818:Animals; D016503:Drug Delivery Systems; D004952:Esters / Q000737:chemistry; D007155:Immunologic Factors / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D008196:Lymph / Q000378:metabolism*; D008198:Lymph Nodes / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D009173:Mycophenolic Acid / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000737:chemistry / Q000493:pharmacokinetics; D011355:Prodrugs / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014280:Triglycerides / Q000008:administration & dosage* / Q000737:chemistry / Q000493:pharmacokinetics
chemical_list: C000603840:1,3-dipalmitoyl-2-mycophenoloyl glycerol; D004952:Esters; D007155:Immunologic Factors; D011355:Prodrugs; D014280:Triglycerides; D009173:Mycophenolic Acid
keywords: Immunomodulator; Lipid-based delivery; Lymph; Lymphatic transport; Mycophenolic acid; Prodrug