Efficacy and tolerability of folate-aminopterin therapy in a rat focal model of multiple sclerosis

Petri Elo, Xiang Guo Li, Heidi Liljenbäck, Maria Gardberg, Olli Moisio, Maxwell Miner, Jenni Virta, Antti Saraste, Madduri Srinivasarao, Michael Pugh, Philip S. Low, Juhani Knuuti, Sirpa Jalkanen, Laura Airas, Yingjuan June Lu, Anne Roivainen*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)
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Background: Activated macrophages in the experimental model of multiple sclerosis (MS) express folate receptor-β (FR-β), representing a promising target for the treatment of MS. Here, we both evaluated the efficacy of a novel folate-aminopterin construct (EC2319) in a rat focal model of multiple sclerosis (MS) and investigated the utility of 68Ga-labeled 1,4,7-triazacyclononane-1,4,7-triacetic acid-conjugated folate (68Ga-FOL) for assessing inflammatory lesions. In addition, we investigated whether FR-β is expressed in the brain of patients with MS. Methods: Focal delayed-type hypersensitivity experimental autoimmune encephalomyelitis (fDTH-EAE) was induced in 40 Lewis rats; 20 healthy Lewis rats were used as controls. Rats were divided into six groups according to the duration of disease (control, acute, or chronic) and intervention (vehicle versus EC2319). 68Ga-FOL analyses, histology, and immunofluorescence of the brain were performed to evaluate the efficacy of subcutaneously administered EC2319 on lesion development. Immunofluorescence was used to assess FR-β expression in postmortem brain samples from 5 patients with MS and 5 healthy controls. Results: Immunofluorescence and histological analyses revealed significant reductions in FR-β expression (P < 0.05) and lesion size (P < 0.01), as well as improved inducible nitric oxide synthase/mannose receptor C type 1 ratios (P < 0.01) in macrophages and microglia during the chronic but not acute phase of fDTH-EAE in EC2319-treated rats. The uptake of IV-injected 68Ga-FOL in the brain was low and did not differ between the groups, but the in vitro binding of 68Ga-FOL was significantly lower in EC2319-treated rats (P < 0.01). FR-β positivity was observed in chronically active lesions and in normal-appearing white matter in MS brain samples. Conclusions: EC2319 was well tolerated and attenuated inflammation and lesion development in a rat model of a chronic progressive form of MS. Human MS patients have FR-β-positive cells in chronically active plaques, which suggests that these results may have translational relevance.

Original languageEnglish
Article number30
JournalJournal of Neuroinflammation
Issue number1
Publication statusPublished - Dec 2021
MoE publication typeA1 Journal article-refereed


  • Aminopterin
  • Experimental autoimmune encephalomyelitis
  • Folate receptor
  • Inflammation
  • Macrophages
  • Multiple sclerosis
  • Positron emission tomography


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