Treatment of Experimental Allergic Encephalomyelitis (EAE) by a Rationally Designed Cyclic Analogue of Myelin Basic Protein (MBP) Epitope 72±85 Theodore Tselios, a Ioanna Daliani, a,b,d Spyros Deraos, a Soteria Thymianou, e Elisabeth Matsoukas, a Anastasios Troganis, c Ioannis Gerothanassis, c Athanasia Mouzaki, e Thomas Mavromoustakos, d Lesley Probert b and John Matsoukas a, * a Department of Chemistry, University of Patras, 26500 Patras, Greece b Department of Molecular Genetics, Hellenic Pasteur Institute, 11521 Athens, Greece c Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece d National Hellenic Research Foundation, Institute of Organic and Pharmaceutical Chemistry, 11635 Athens, Greece e Laboratory of Experimental Haematology and Transfusion Medicine, Medical School, University of Patras, 26110 Patras, Greece Received 23 June 2000; revised 5 September 2000; accepted 21 September 2000 AbstractÐIn this report the rational design, synthesis and pharmacological properties of an amide-linked cyclic antagonist anal- ogue of the guinea pig myelin basic protein epitope MBP 72 85 are described. Design of the potent cyclic analogue was based on 2D NOESY nuclear magnetic resonance and molecular dynamics studies carried out in the linear antagonist Ala 81 MBP 72 85 . The cyclic antagonist completely prevented the induction of experimental allergic/autoimmune encephalomyelitis when coinjected with linear and cyclic agonist analogues MBP 72 85 and cyclo(2±9)MBP 72 85 . # 2000 Elsevier Science Ltd. All rights reserved. Experimental autoimmune encephalomyelitis (EAE) is one of the best studied experimental animal models of multiple sclerosis (MS). 1 3 It is a useful in vivo system for the therapeutic management of disease characterized by tissue damage and mediated by autoimmune T-cells. In Lewis rats immunized with guinea pig MBP protein, encephalitogenic T cells recognize the MBP 72 85 epitope dominating the immune response. 4 The linear analogue Gln 1 -Lys 2 -Ser 3 -Gln 4 -Arg 5 -Ser 6 - Gln 7 -Asp 8 -Glu 9 -Asn 10 -Pro 11 -Val 12 (MBP 72 85 ) has been found to induce EAE, while substitution of the Asp residue at position 8 with Ala resulted in an analogue ([Ala 81 ]MBP 72 85 ) that prevented the induction of EAE by its parent peptide. 5,6 Such peptides may interfere with the formation of the trimolecular complex MHC±peptide±TCR and therefore can actively inhibit disease. 7,8 One approach in the development of more stable mol- ecules is the synthesis of cyclic analogues. 9,10 Cycliza- tion is known to restrict the number of possible conformations, allowing the possibility to diminish the unfavored conformations from approaching the recep- tor site. Furthermore, cyclization of peptide sequences results in increased metabolic stability, potency, recep- tor selectivity and bioavailability, all of them re¯ecting a better pharmacological pro®le. 11,12 In particular cyclic peptides have been used in several cases as synthetic immunogens, 13 potent vaccines for diabetes, 14 antigens for herpes simplex virus, 15 transmembrane ion chan- nels, 16 inhibitors of HIV-1 Tat-TAR interactions in human cells, 17 of a-amylase, 18 pancreatic trypsin 19 and as protein stabilizers. 20 The appropriate design of cyclic ana- logue by connecting the two least important residues for activity without causing drastic changes in the conforma- tion of active peptide results in a rigid geometry of the cyclic peptide enhancing the binding anity compared to the linear counterpart. The engineering of stable peptides is of great technological and economic importance, since the limited stability of peptides often severely restricts their medical and industrial application. 0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0960-894X(00)00556-4 Bioorganic & Medicinal Chemistry Letters 10 (2000) 2713±2717 *Corresponding author. Tel.: 30-61-997-180; fax: 30-61-997-118; e- mail: johnmatsoukas@hotmail.com