Development of a neuromedin U–human serum albumin conjugate as a long‐acting candidate for the treatment of obesity and diabetes. Comparison with the PEGylated peptide

Abstract

Neuromedin U (NMU) is an endogenous peptide implicated in the regulation of feeding, energy homeostasis, and glycemic control, which is being considered for the therapy of obesity and diabetes. A key liability of NMU as a therapeutic is its very short half-life in vivo. We show here that conjugation of NMU to human serum albumin (HSA) yields a compound with long circulatory half-life, which maintains full potency at both the peripheral and central NMU receptors. Initial attempts to conjugate NMU via the prevalent strategy of reacting a maleimide derivative of the peptide with the free thiol of Cys34 of HSA met with limited success, because the resulting conjugate was unstable in vivo. Use of a haloacetyl derivative of the peptide led instead to the formation of a metabolically stable conjugate. HSA-NMU displayed long-lasting, potent anorectic, and glucose-normalizing activity. When compared side by side with a previously described PEG conjugate, HSA-NMU proved superior on a molar basis. Collectively, our results reinforce the notion that NMU-based therapeutics are promising candidates for the treatment of obesity and diabetes.

Small lipidated anti-obesity compounds derived from neuromedin U

“…The double-lipidated analog, NM4-C 16 , did indeed have an extended plasma half-life (t 1/2 =28.2±1.0 h) compared to the single-lipidated NM4A (t 1/2 =24.0±1.0 h) although the effects of double-lipidation were limited (Figure 5). These results, as well as the relatively short plasma half-life of both, PEG- and HSA-NmU conjugates reported elsewhere [40,41] (t 1/2 ≈11–54 h, depending on species) suggested that a key factor for the in vivo activity of NmU analogs/derivatives may be their resistance to enzymatic proteolysis. Alternatively, loss of their activity may involve partial hydrolysis of the N-terminal N 7 -amide to α- or β-monocarboxylic acid residues (X-Asn-OH or X-Asp-NH 2 ) via an aminosuccinimide intermediate [22].…”

“…To test whether newly synthesized NmU analogs possess any in vivo anorectic activity, we compared NM4 and NM7 peptides in a diet-induced obese (DIO) mouse model using previously described protocols [39,41]. Initially we focused on single dose experiments comparing NM4 and NM7 at a dose of 5344 nmoles/kg body weight (Figure 3).…”

“…Notably, the chronic administration of NmU does not cause tachyphylaxis and significantly improves glucose tolerance in diet-induced obese (DIO) mice [39]. The unfavorable pharmacokinetic properties of NmU (the half-life of NmU after subcutaneous (s.c.) injection is less than 5 min [39]) were improved by conjugation with polyethylene glycol (PEG) [40] or human serum albumin (HSA) [41] showing in both cases long-lasting, potent anorectic, and blood glucose-normalizing activity. Although mentioned in a patent [31], full length lipid-conjugated (NMU24) and lipid/PEG40-bis-conjugated (NMU25) analogs of neuromedin U showed limited activity.…”

Neuromedin U: A Multifunctional Neuropeptide with Pleiotropic Roles

“…Polyethyleneglycol-and human serum albumin-conjugated NmU forms have recently been developed, which exert a potent anorexigenic effect and induce glucose tolerance in vivo with a much longer half-life compared to that of NmU (95,96 ). However, the effectiveness of this type of therapy in obese patients is under question, because chronic administration of NmU to rats showed no effect on food intake (74 ).…”

Discovery of Potent Hexapeptide Agonists to Human Neuromedin U Receptor 1 and Identification of Their Serum Metabolites

“…In addition, the observed relatively potent agonistic activity of hexapeptide 5d to NMUR2 would also be an important feature for the development of practical antiobesity drugs, which may require the engagement of both human NMU receptors to induce full anorexigenic activity from a peripheral administration of PEG-or HSA-conjugated hNMU. 8,9 Next, we examined the in vitro stability of derivative 5d in rat serum to understand its metabolic degradation profile. As comparators, we also examined the derivatives 1a, 1b, and 4d.…”