Milveterol Hydrochloride

Inhaled bronchodilators, including long-acting muscarinic receptor antagonists (LAMA) and long-acting β2-adrenoreceptor agonists (LABA), are the mainstay of pharmacological treatment of stable chronic obstructive pulmonary disease (COPD). Among approved LAMA, tiotropium bromide, glycopyrronium bromide, and umeclidinium bromide are administered once daily, whereas aclidinium bromide is administered every 12 h. New LAMA are under development for COPD. Among the approved LABA, indacaterol has a 24 h duration of action, whereas salmeterol and formoterol require twice-daily administration. New once-daily LABA, including vilanterol, olodaterol, milveterol, carmoterol, and abediterol, are in development. LAMA/LABA fixed dose combinations (FDCs) provide the convenience of two bronchodilators with different mechanism of action in a single inhaler. Indacaterol/glycopyrronium, umeclidinium/vilanterol, and olodaterol/tiotropium FDCs have been approved or are under approval and are likely to become a standard pharmacological strategy for COPD. Inhaled dual-pharmacology compounds, combining muscarinic antagonism and β2-agonism (MABA) in a single molecule, potentially provide additive or synergistic bronchodilation over either inhaled antimuscarinic or β2-agonist monotherapy.

A series of potent β2-adrenoceptor agonists incorporating a biarylamine secondary binding group was identified. The previously reported milveterol (5), identified by a multivalent approach and containing a typical β2-agonist primary binding group linked via a phenethylamine linker to a hydrophilic secondary binding group, served as an initiation point. A more hydrophobic set of secondary binding groups was explored, prepared rapidly from a common intermediate by Buchwald-Hartwig amination. TD-5471 (25), a potent and selective full agonist of the human β2-adrenoceptor, was identified as the most promising agent. It is potent, with slow onset in an in vitro guinea pig trachea model and shows a dose-dependent and long duration of action in an in vivo guinea pig model of bronchoprotection. TD-5471 is structurally differentiated from milveterol and its long duration of action is consistent with a correlation with hydrophobicity observed in other long-acting β2-agonist discovery programs.