Background: Growth hormone (GH) treatment currently requires years of treatment. Maintaining full compliance with daily injections has been difficult. Teens have the highest rate of non-concordance (missing injections 1-2 per week). In adults the rate of low concordance (low IGFI) rises with each year of treatment. Improving compliance to GH therapy by less burdensome means of GH replacement can be achieved either by changing GH delivery frequency (weekly, monthly) or by changing injection device characteristics (minimal preparation, easy setting, minimal pain, automatic needle insertion, needle free devices). LONG ACTING FORMULATIONS: Long-acting forms of GH have been developed either as sustained-release preparations of GH (Nutropin-depot, which has been withdrawn in 2004 and LB 03002 once weekly GH, which has received a positive opinion by CHMP of EMA in early 2013) or as the conjugated analogues which prolong the half life of GH. Currently a variety of modified GH molecules which delay GH clearance (CTP modified GH, recombinant polypeptide XTEN, GH conjugated with albumin, GH linked to immunoglobulin) are studied and the ongoing studies are in different phases (from I-III). Each of these preparations has been tested in experimental animal models. EFFICACY AND SAFETY: Although different types of formulations have been studied, all are pharmacokinetically and pharmacodynamically effective in extending GH action and result in prolonged increase in IGF-I concentrations. Clinical data are available for once-weekly sustained-release GH treatment and the data show beneficial effects in adults with GH deficiency over a 12 month period and adequate growth rate in pre-pubertal children with GH deficiency over the period of three-years.
Conclusions: Clinical data are still very limited. Available short-term studies show that treatment with long-acting GH preparation is effective and safe in GH deficient children and adults. A different physiology underlies the long-acting GH and we still need to improve our knowledge about these formulations of GH. Long-term studies are needed to confirm the value and safety (greater exposure to GH) of these agents.