title: Treatment of experimental adjuvant arthritis with a novel folate receptor-targeted folic acid-aminopterin conjugate.
abstract: BACKGROUND
  Folate receptor (FR)-expressing macrophages have been shown to accumulate at sites of inflammation, where they promote development of inflammatory symptoms. To target such a macrophage population, we designed and evaluated the biologic activity of EC0746, a novel folic acid conjugate of the highly potent antifolate, aminopterin.
  
  
  METHODS
  Using a FR-positive subclone of murine macrophage-derived RAW264.7 cells and rat thioglycollate-elicited macrophages, we studied the effect of EC0746 on dihydrofolate reductase activity, cell proliferation, and cellular response towards bacterial lipopolysaccharide as well as IFNγ activation. The EC0746 anti-inflammatory activity, pharmacokinetics, and toxicity were also evaluated in normal rats or in rats with adjuvant-induced arthritis; that is, a FR-positive macrophage model that closely resembles rheumatoid arthritis in humans.
  
  
  RESULTS
  EC0746 suppresses the proliferation of RAW264.7 cells and prevents the ability of nonproliferating rat macrophages to respond to inflammatory stimuli. In the macrophage-rich rat arthritis model, brief treatment with subcutaneously administered EC0746 is shown to mediate an FR-specific anti-inflammatory response that is more potent than either orally administered methotrexate or subcutaneously delivered etanercept. More importantly, EC0746 therapy is also shown to be ~40-fold less toxic than unmodified aminopterin, with fewer bone marrow and gastrointestinal problems.
  
  
  CONCLUSIONS
  EC0746 is the first high FR-binding dihydrofolate reductase inhibitor that demonstrates FR-specific anti-inflammatory activities both in vitro and in vivo. Our data reveal that a relatively toxic anti-inflammatory drug, such as aminopterin, can be targeted with folic acid to inflammatory macrophages and thereby relieve inflammatory symptoms with greatly reduced toxicity.
authors.affiliation: Endocyte, Inc., 3000 Kent Avenue, West Lafayette, IN 47906, USA.
authors.forename: Yingjuan
authors.initials: Y
authors.lastname: Lu
authors.forename: Torian W
authors.initials: TW
authors.lastname: Stinnette
authors.forename: Elaine
authors.initials: E
authors.lastname: Westrick
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Klein
authors.forename: Mark A
authors.initials: MA
authors.lastname: Gehrke
authors.forename: Vicky A
authors.initials: VA
authors.lastname: Cross
authors.forename: Iontcho R
authors.initials: IR
authors.lastname: Vlahov
authors.forename: Philip S
authors.initials: PS
authors.lastname: Low
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Leamon
mesh_terms: D000630:Aminopterin / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000494:pharmacology*; D001169:Arthritis, Experimental / Q000188:drug therapy*; D005260:Female; D058973:Folate Receptors, GPI-Anchored / Q000187:drug effects; D005492:Folic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000494:pharmacology*; D005493:Folic Acid Antagonists / Q000138:chemical synthesis / Q000493:pharmacokinetics / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects; D051379:Mice; D051381:Rats; D011917:Rats, Inbred Lew
chemical_list: D000893:Anti-Inflammatory Agents; C570294:EC 0746; D058973:Folate Receptors, GPI-Anchored; D005493:Folic Acid Antagonists; D005492:Folic Acid; D000630:Aminopterin