Preparation and characterization of albumin conjugates of a truncated peptide YY analogue for half-life extension.

Recombinant human serum albumin (HSA) conjugates of a 15-amino-acid truncated peptide YY (PYY) analogue were prepared using three heterobifunctional linkers [succinimidyl 4-[N-maleimidomethyl]cyclohexane-1-carboxylate (SMCC), 6-maleimidohexanoic acid N-hydroxysuccinimide ester (MHS), and N-[γ-maleimidobutyryloxy]sulfosuccinimide ester (GMBS)] in 2 synthetic steps involving (1) reaction of succinimidyl ester on linker with ε-amine of Lys2 on the peptide and (2) reaction of maleimide on peptide linker with free thiol of Cysteine 34 (Cys34) on albumin. In-process controls using ESI LC-MS were used to follow reactions and identify reaction products. Proteolytic digests of the conjugate revealed that peptide conjugation occurs at Cys34 on HSA. Conjugates were assayed in cell-based assays to determine potency at the human Y2-receptor, and selectivity at the human Y1-, Y4-, and Y5-receptors using a calcium flux assay. All three conjugates assayed were selective agonists of the Y2-receptor, and displayed nanomolar potencies. MCC and MH conjugates were selected for acute PK/PD studies in DIO mice. Significant reduction in food intake was observed with the MH conjugate, which lasted for 24 h at the 10 mg (or 4 µmol)/kg dose. While the MCC conjugate exhibited greater potency in vitro, it was slightly less effective than the MH conjugate in vivo with respect to reduction in food intake. Both conjugates were significantly less active than the peptide coupled to a 30 kDa PEG. The observed T1/2 (8-9 h) for both conjugates was significantly lower than that observed for the PEGylated peptide (∼25 h). These results suggest that, as compared with the unmodified and PEGylated peptide, the extended circulation half-life of albumin conjugates is mediated through uptake and recirculation by FcRn, and allometric scaling methods are necessary to account for interspecies variation in pharmacokinetic properties.