N-Terminal Modification with Pseudo-Bifunctional PEG-Hexadecane Markedly Improves the Pharmacological Profile of Human Growth Hormone

Abstract

Human growth hormone (hGH) has been used to treat children with short stature, renal failure, and Turner's syndrome. However, clinical application of hGH suffers from its short plasma half-life and low bioavailability. PEGylation and albumin binding are two of the most effective approaches to prolong the plasma half-life of hGH. However, the steric shielding effects of polyethylene glycol (PEG) and albumin can drastically decrease the bioactivity of hGH, which is opposite to the increased pharmacokinetics (PK). In the present study, a long-acting hGH with markedly improved pharmacological profile was rationally designed and prepared by N-terminal modification of hGH with pseudo-bifunctional PEG-hexadecane by using PEG (3.5 kDa or 10 kDa) as the linker. PEGylation and albumin binding with hexadecane can increase the hydrodynamic volume and decrease the immunogenicity of hGH, which thereby markedly increases the PK of hGH. Since N-terminus is far from the bioactive domain of hGH, N-terminal modification of hGH can minimize the steric shielding effects on the bioactive domain of hGH. Hexadecane-bound albumin can be slowly released from hGH during the in vivo circulation, which can slowly restore the bioactivity of hGH. Thus, the high bioactivity of PEG-hexadecane modified hGH (hGH-PEG-HD) was synergistically achieved by N-terminal modification with pseudo-bifunctional PEG-hexadecane and slow-release of albumin. The high pharmacodynamics (PD) of hGH-PEG-HD was due to the synergistic effect of the high bioactivity and the overall increased PK.

Preparation and Characterization of Site-Specific Fatty Chain-Modified Recombinant Human Granulocyte Colony Stimulating Factor

“…However, it has a short in vivo half-life, resulting in frequent injection and low patient compliance ( Akizawa et al, 1995 ). To overcome these problems, the long-acting technologies such as polyethylene glycol modification (PEGylation) ( Wu et al, 2015 ), protein fusion ( Xu et al, 2015 ; Do et al, 2017 ), and new dosage forms technologies ( Kim and Park, 2004 ) have been used for the development of long-acting rhG-CSF. Among these technologies, PEGylation is one of the most successful methods, and several PEGylation rhG-CSF products (e.g., Pegfilgrastim ( Piedmonte and Treuheit, 2008 )) have been approved for clinical use.…”

Growth hormone receptor agonists and antagonists: From protein expression and purification to long‐acting formulations

“…Albumin has also been linked to hGH by N‐terminal modification with pseudo‐bifunctional PEG‐hexadecane (3.5 or 10 kDa PEG) as the linker (Wu et al, 2015 ). hGH‐PEG3.5 fused to albumin exhibited longer half‐life (19.2 ± 1.0 h) than hGH (1.9 ± 0.1 h) and hGH‐PEG3.5‐hexadecane (13.7 ± 0.3 h; Wu et al, 2013 ).…”