Cyclizing Painkillers: Development of Backbone-Cyclic TAPS Analogs

Abstract

Painkillers are commonly used medications. Native peptide painkillers suffer from various pharmacological disadvantages, while small molecule painkillers like morphine are highly addictive. We present a general approach aimed to use backbone-cyclization to develop a peptidomimetic painkiller. Backbone-cyclization was applied to transform the linear peptide Tyr-Arg-Phe-Sar (TAPS) into an active backbone-cyclic peptide with improved drug properties. We designed and synthesized a focused backbone-cyclic TAPS library with conformational diversity, in which the members of the library have the generic name TAPS c(n-m) where n and m represent the lengths of the alkyl chains on the nitrogens of Gly and Arg, respectively. We used a combined screening approach to evaluate the pharmacological properties and the potency of the TAPS c(n-m) library. We focused on an in vivo active compound, TAPS c(2-6) , which is metabolically stable and has the potential to become a peripheral painkiller being a full μ opioid receptor functional agonist. To prepare a large quantity of TAPS c(2-6) , we optimized the conditions of the on-resin reductive alkylation step to increase the efficiency of its SPPS. NMR was used to determine the solution conformation of the peptide lead TAPS c(2-6) .

Synthesis and Pharmacological Characterization of Visabron, a Backbone Cyclic Peptide Dual Antagonist of α4β1 (VLA-4)/α9β1 Integrin for Therapy of Multiple Sclerosis

“…Backbone cyclization (BC) was already proven a valuable tool in the methodological conversion of active regions of proteins to cyclic peptidomimetic drug leads. 15 , 16 The BC method is employed to introduce global constraints to peptides and active regions in proteins. It differs from other cyclization methods since it utilizes the amide bond nitrogen to anchor the cyclizing bridge, thus maintaining the active pharmacophore.…”

“…BC proved superior to other stabilization methods since the resultant peptides had defined structures that led to better selectivity 17 and improved pharmacological properties. 15 However, obtaining the desired active cyclic analogue based on a linear sequence is not a straightforward process and, therefore, requires selection from designed libraries with conformational diversity. 15 In this study, we describe the isolation of visabres disintegrin from viper venom, identification of the TMLD motif selective for α4β1/α4β7 integrin inhibition, and attempts for its cyclization to generate visabron, a backbone cyclic peptide dual antagonist of α4β1 (VLA-4)/ α9β1 integrin with druglike properties.…”

“… 15 However, obtaining the desired active cyclic analogue based on a linear sequence is not a straightforward process and, therefore, requires selection from designed libraries with conformational diversity. 15 In this study, we describe the isolation of visabres disintegrin from viper venom, identification of the TMLD motif selective for α4β1/α4β7 integrin inhibition, and attempts for its cyclization to generate visabron, a backbone cyclic peptide dual antagonist of α4β1 (VLA-4)/ α9β1 integrin with druglike properties. The pharmacological profile of visabron was achieved by in vitro functional cell adhesion and selectivity assays, characterizations of its pharmacokinetic, and safety properties and measurement of its therapeutic effect in vivo in a multiple sclerosis–experimental autoimmune encephalomyelitis mouse model.…”

“…BC proved superior to other stabilization methods since the resultant peptides had defined structures that led to better selectivity 17 and improved pharmacological properties. 15 However, obtaining the desired active cyclic analogue based on a linear sequence is not a straightforward process and, therefore, requires selection from designed libraries with conformational diversity. 15 In this The first step of the isolation of visabres was based on the preparative fractionation of the venom by FPLC gel filtration 18 into three protein fractions (Figure S1-A).…”

“…15 However, obtaining the desired active cyclic analogue based on a linear sequence is not a straightforward process and, therefore, requires selection from designed libraries with conformational diversity. 15 In this The first step of the isolation of visabres was based on the preparative fractionation of the venom by FPLC gel filtration 18 into three protein fractions (Figure S1-A). Fraction Vd-III, which was less toxic, not hemorrhagic, and less contaminated with protease and phospholipase A 2 activity but enriched in α4-inhibitory activity (Tables S1 and S2), was further separated by a consecutive step of reversed-phase HPLC using a linear gradient of increasing acetonitrile concentration (Figure S1-B).…”