Design and Development of a Cyclic Decapeptide Scaffold with Suitable Properties for Bioavailability and Oral Exposure

Abstract

Permeability and oral bioavailability of macrocyclic peptides still represent difficult challenges in drug discovery. Despite the recognized potential of macrocyclic peptides as therapeutics, their use is still restricted to extracellular targets and intravenous administration. Indeed, macrocyclic peptides generally suffer from limited proteolytic stability, high clearance, and poor membrane permeability, and this leads to the absence of systemic exposure after oral administration. To overcome these limitations, we started to investigate the development of a general cyclic decapeptide scaffold that possesses ideal features for cell permeability and oral exposure. On the basis of a rigid hairpin structure, the scaffold design aimed to decrease the overall polarity of the compound, thereby limiting the energetic cost of NH desolvation and the entropy penalty during cell penetration. The results of this study also demonstrate the importance of rigidity for the β-turn design regarding clearance. To stabilize the scaffold in the desired β-hairpin conformation, the introduction of d-proline at the i+1 turn position proved to be beneficial for both permeability and clearance. As a result, cyclopeptide decamers with unprecedented high values for oral bioavailability and exposure are reported herein. NMR spectroscopy conformation and dynamic analysis confirmed, for selected examples, the rigidity of the scaffold and the presence of transannular hydrogen bonds in polar and apolar environments. Furthermore, we showed, for one compound, that its transition from a polar environment to an apolar one was accompanied by an increased molecular motion, revealing an entropy contribution to membrane permeation.

Pharmacokinetic Studies around the Mono‐ and Difunctionalization of a Bioavailable Cyclic Decapeptide Scaffold

“…[3] We recently developed ageneric decapeptides caffold that displays favorable properties, including high permeabilitya nd low clearance. [4] From this scaffold, we reported 1 and 2 as decapeptidesw ith unprecedentedb ioavailability and oral exposure for this class of cyclic peptides ( Table 1). The generic scaffold based on a b-hairpin conforma-tion was designed to minimize its polar surface area and the energetic cost of desolvationu pon membrane permeation thanks to ac onformation that favored the formationo ft ransannular hydrogen bonds and as pecific N-methylated amide pattern.…”

“…Alternatively, this additional intramolecular hydrogen bond could indeed have been presentb ut also be responsible for disrupting the geometryo ft he turn and, consequently,c hanging the whole conformation of the cyclic peptide;t his would lead to the observed loss of permeability andm etabolic stability.However,N MR spectroscopy analysis of 3 showeda ll four transannular hydrogen bonds were present with aboutt he same stability,a sw as the case for the compounds described in our previouss tudy. [4,7] Therefore, we believe that the overall decrease in the lipophilicity of the decapeptidee xplainst he loss of permeability.2 -Pyridylalanine is also known to form an intramolecular hydrogen bond between itsp yridine moiety and the hydrogen atom of its amide group;t his should circumvent the need fori ts N-methylation and, therefore, increases the chance for good solubility without impairing permeability properties. [8] However,i no ur case, this intramolecular hydrogen-bond formation could not be confirmed, as 5 (Table 2, Ta ble 3) exhibited low in vitro permeability [P app (A!B) = 0.783 10 À6 cm s À1 ]c oupled with high in vivo clearance (CL = 87 mL min À1 kg À1 ).…”

Understanding and designing head‐to‐tail cyclic peptides

“…In general, cyclization of small peptides tends to result in increased bioavailability, which can be further improved upon by incorporating N ‐methylated residue(s), as demonstrated in the cases of somatostatin and the melanocortin family . To shed more light on how N ‐methylation affects CP conformation and bioavailability, libraries of N ‐methylated CPs were synthesized and characterized . For example, Beck and co‐workers characterized 54 N ‐methylated derivatives of cyclo‐(aAAAAA) to understand how N ‐methylation affected the CP's membrane permeability as well as its conformational preferences .…”

Neue Methoden und Designprinzipien für zellgängige Peptide

“…[75] Weitere Arbeiten zeigten, dass ein chiraler Kohlenwasserstoff-Linker eine helikale Windung in einem Pentapeptid auslçsen kann, wodurch die passive Zellpenetration gefçrdert wird. [77][78][79][80][81] Alle diese Beispiele bieten unabhängige Ansätze,u mi ntramolekulare Wasserstoffbrückennetzwerke so zu organisieren, dass die Zahl der lçsungsmittelexponierten Rückgratamide reduziert wird, wodurch die passive Zellpenetration von Peptiden im Grçßenbereich von Tetrameren bis Heptameren ermçglicht wird. [77][78][79][80][81] Alle diese Beispiele bieten unabhängige Ansätze,u mi ntramolekulare Wasserstoffbrückennetzwerke so zu organisieren, dass die Zahl der lçsungsmittelexponierten Rückgratamide reduziert wird, wodurch die passive Zellpenetration von Peptiden im Grçßenbereich von Tetrameren bis Heptameren ermçglicht wird.…”

“…[76] Ferner verwendeten verschiedene Arbeitsgruppen NMR-Strukturanalysen als Grundlage fürd as Design interner Wasserstoffbrückennetzwerke zur Verbesserung der passiven Zellpenetration. [77][78][79][80][81] Alle diese Beispiele bieten unabhängige Ansätze,u mi ntramolekulare Wasserstoffbrückennetzwerke so zu organisieren, dass die Zahl der lçsungsmittelexponierten Rückgratamide reduziert wird, wodurch die passive Zellpenetration von Peptiden im Grçßenbereich von Tetrameren bis Heptameren ermçglicht wird.…”