Immunogenicity, toxicology, pharmacokinetics and pharmacodynamics of growth hormone ligand–receptor fusions

Abstract

A fundamental concern for all new biological therapeutics is the possibility of inducing an immune response. We have recently demonstrated that an LR-fusion (ligand-receptor fusion) of growth hormone generates a potent long-acting agonist; however, the immunogenicity and toxicity of these molecules have not been tested. To address these issues, we have designed molecules with low potential as immunogens and undertaken immunogenicity and toxicology studies in Macaca fascicularis and pharmacokinetic and pharmacodynamic studies in rats. Two variants of the LR-fusion, one with a flexible linker (GH-LRv2) and the other without (GH-LRv3), were tested. Comparison was made with native human GH (growth hormone). GH-LRv2 and GH-LRv3 demonstrated similar pharmacokinetics in rats, showing reduced clearance compared with native GH and potent agonist activity with respect to body weight gain in a hypophysectomized rat model. In M. fascicularis, a low level of antibodies to GH-LRv2 was found in one sample, but there was no other evidence of any immunogenic response to the other fusion protein. There were no toxic effects and specifically no changes in histology at injection sites after two repeated administrations. The pharmacokinetic profiles in monkeys confirmed long half-lives for both GH-LRv2 and GH-LRv3 representing exceptionally delayed clearance over rhGH (recombinant human GH). The results suggest that repeated administration of a GH LR-fusion is safe, non-toxic, and the pharmacokinetic profile suggests that two to three weekly administrations is a potential therapeutic regimen for humans.

Low-Intensity Pulsed Ultrasound Stimulation Facilitates Osteogenic Differentiation of Human Periodontal Ligament Cells

“…Most PDLCs in periodontal lesion tissues, however, require the inflammatory-free microenvironments and biological activity for periodontal wound healing. The addition of exogenous growth factors has been shown to improve osteogenic differentiation of PDLCs [11], but large-scale utilization of growth factors is clinically impracticable due to safety concern [12]. Therefore, it is of significance to develop new approaches to improve the osteogenic potential of PDLCs.…”

A long-acting GH receptor antagonist through fusion to GH binding protein

“…It appears that adding certain proteins to the C-terminus of GH such as albumen, CTP, Fc fragment and XTEN can delay clearance 17 . We previously undertook pharmacokinetic studies with our GHR agonist in non-human primates and based on allosteric modelling calculated that the fusion would only need to be administered once every 3 weeks 15 . Accepting that a GHR antagonist is required at higher concentration we can anticipate that GHA3 may only need to be administered once a week.…”

“…The pharmacokinetic characteristics suggested this fusion molecule could provide GH agonist therapy requiring injection every 21–28 days compared to daily GH administration. Thus, this technology clearly demonstrated that fusion to GH binding protein is an effective technology to delay clearance 15 . We have now tested whether a fusion of the GHR antagonist molecule to the GH binding protein could generate a long acting GHR antagonist and the hypothesis that introducing an amino acid change in the GH binding domain (W104A) would increase bioactivity.…”

Natural synthesis: Biologics, biosimilars and biobetters in protein hormone therapy

“…Furthermore, a single injection of GH-GHBP has bioactivity similar to a daily equimolar dose of GH when given to rats over a 10-day period 13 . The GH-GHBP fusion mimics the natural partnership of the separate GH and GHBP molecules and so was theorized to have low immunogenicity; in vivo immunogenicity studies confirmed this and also showed that GH-GHBP had low toxicity 14 . These initial results suggest that the GH-GHBP fusion could be administered weekly, or even less frequently, instead of the daily injections required for GH.…”