rhGH safety and efficacy update

Average IGF-1 Prediction for Once-Weekly Lonapegsomatropin in Children With Growth Hormone Deficiency

CONTEXT

Serum insulin-like growth factor 1 (IGF-1) levels are relatively constant in somatropin-treated children with growth hormone deficiency (GHD), and guide dose adjustments for clinical efficacy and long-term safety. IGF-1 levels following treatment with long-acting growth hormones such as lonapegsomatropin (lonapegsomatropin-tcgd, TransCon hGH), a once-weekly somatropin prodrug, exhibit a characteristic profile over the dosing interval.

OBJECTIVE

This study aimed to develop a method to predict average IGF-1 in lonapegsomatropin-treated GHD children to interpret IGF-1 data based on a single sample obtained any time at steady state.

METHODS

A population nonlinear mixed-effect pharmacodynamic model for IGF-1 was developed based on 2 randomized, open-label trials of TransCon hGh in GHD children and used to develop a linear mixed model with Taylor series to fit simulated IGF-1 profiles of lonapegsomatropin-treated children.

A TOTAL OF

49 896 IGF-1 sample data simulated from 105 lonapegsomatropin-treated GHD children were utilized for the final prediction model. The dosage range of TransCon hGh was 0.14 to 0.30 hGH mg/kg/week, and weekly average IGF-1 was calculated using IGF-1 profiles simulated from the nonlinear pharmacodynamic model. Predicted average IGF-1 was obtained by linear mixed model with Taylor series.

RESULTS

The nonlinear mixed-effect model provided satisfactory model fit. The linear mixed model with Taylor series fit simulated IGF-1 data well, with a relatively straightforward prediction formula. IGF-1 values sampled at ~4.5 days post-dose coincided with weekly average IGF-1 at steady state.

CONCLUSION

A formula to predict average IGF-1 from a single sample of IGF-1 at steady state was established to aid clinicians in interpreting IGF-1 levels in GHD children administered lonapegsomatropin.

Long-Acting Growth Hormone Preparations - Current Status and Future Considerations

CONTEXT

Long-acting GH (LAGH) preparations are currently being developed in an attempt to improve adherence. The profile of GH action following administration of LAGH raises practical questions about clinical monitoring and long-term safety and efficacy of these new therapeutic agents.

METHODS

Recent literature and meeting proceedings regarding LAGH preparations are reviewed.

RESULTS

Multiple LAGH preparations are currently at various stages of development, allowing for decreased GH injection frequency from daily to weekly, biweekly, or monthly. Following administration of LAGH, the serum peak and trough GH and IGF-I levels vary depending upon the mechanism used to prolong GH action. Randomized, controlled clinical trials of some LAGH preparations have reported non-inferiority compared with daily recombinant human GH (rhGH) for improved growth velocity and body composition in children and adults with GH deficiency (GHD), respectively. No significant LAGH-related adverse events have been reported during short-term therapy.

CONCLUSION

Multiple LAGH preparations are proceeding through clinical development with some showing promising evidence of short-term clinical efficacy and safety in children and adults with GHD. The relationship of transient elevations of GH and IGF-I following administration of LAGH to efficacy and safety remain to be elucidated. For LAGH to replace daily rhGH in the treatment of individuals with GHD, a number of practical questions need to be addressed including methods of dose adjustment, timing of monitoring of IGF-I, safety, efficacy, and cost-effectiveness. Long-term surveillance of efficacy and safety of LAGH preparations will be needed to answer these clinically relevant questions.

Attaining genetic height potential: Analysis of height outcomes from the ANSWER Program in children treated with growth hormone over 5 years

OBJECTIVE

This study aimed to assess attainment of genetic height potential after long-term growth hormone (GH) treatment in GH-naïve children diagnosed with isolated growth hormone deficiency (IGHD), multiple pituitary hormone deficiency (MPHD), born small for gestational age (SGA), or idiopathic short stature (ISS) enrolled in the American Norditropin®

STUDIES

Web-enabled Research (ANSWER) Program.

DESIGN

Children with IGHD (n=2884), MPHD (n=200), SGA (n=481), or ISS (n=733) with baseline height standard deviation score (HSDS)≤-2 were assessed over 5 years of GH treatment for mean HSDS, change in HSDS (ΔHSDS), and corrected HSDS (HSDS-target HSDS).

RESULTS

Mean HSDS and corrected HSDS significantly increased to close to target height across all diagnostic groups after 5 years of GH treatment (P<0.0001). ∆HSDS at year 5 increased for all groups (IGHD: 1.8; MPHD: 2.1; SGA: 1.8; ISS: 1.6). Among patients who continued GH for 5 years, mean insulin-like growth factor-I (IGF-I) SDS increased to within normal range across all groups. Body mass index (BMI) SDS remained relatively stable in all diagnostic groups. Bone age (BA) increased, and the mean BA to chronological age (BA/CA) ratio reached or approached 1 across diagnostic groups over 5 years of GH treatment.

CONCLUSIONS

Long-term GH therapy resulted in a significant increase in mean HSDS and corrected HSDS from baseline values in all diagnostic groups. The observed increase in mean corrected HSDS is consistent with growth that approached the patients' genetic height potential, although complete height gains will be evaluated at the attainment of final height.

Efficacy and safety of Samtropin™ recombinant human growth hormone; a double-blind randomized clinical trial

Background

Recombinant human growth hormone (rhGH) can increase the growth rate in growth hormone deficient children (GHD). In this randomized clinical trial, we compared the efficacy and side effects of an Iranian brand; Samtropin with Norditropin.

Methods

The GHD children were randomly treated either with standard dose of Samtropin or Norditropin rhGH for one year. Upstanding height, height standard deviation score (HSDS), growth velocity (GV), serum levels of insulin like growth factor-1 (IGF-1), and bone age (BA) were determined before and during one year treatment concomitant side effects of treatment.

Results

We evaluated 22 subjects; 12 on Samtropin and, 10 on Norditropin. In each group, mean age was 12 yr and 50% of them were male. The mean differences in height, HSDS, IGF-1 and BA by Norditropin before and after 12 months were 8.8 cm, 0.5, 49 ng/ml and 2.8 yr, respectively. These measures by Samtropin were 9.1 cm, 0.6, 133 ng/ml, and 1.7 yr, respectively without any significant difference. The mean of GV by Samtropin was 9.1 vs. 8.8 cm by Norditropin without significant difference. Since the efficacy of Samtropin was found to be similar to Norditropin after 12 months; we switched to use only Samtropin for the next 12 months. The mean differences in height, HSDS, GV and BA in 20 children between months 12 and 24 were 7.0 cm, 1.6, 2.1 cm/yr and 1.0 yr, respectively (P < 0.001). We also found a non-significant decrease in IGF-1 levels. No side effects were observed.

Conclusions

We need to conduct a post marketing surveillance with a large sample size in order to confirm our findings.

Trial registration

Registration code number in the Iranian Registry of Clinical Trials (IRCT): IRCT1138901181414N11.

Debate: idiopathic short stature should be treated with growth hormone

In this paper we outline the case for and against the treatment of idiopathic short stature with growth hormone. Drs Ambler and Fairchild argue that many of those with 'idiopathic' short stature are not 'short, normal children' and will ultimately receive molecular diagnoses. They also argue that there is a subset of children who suffer negative psychosocial consequences of their stature for whom growth hormone therapy is effective. Growth hormone has a very good safety record and is likely to be as cost-effective in idiopathic short-stature as in some other conditions that are currently funded. Dr Wilkinson counters that short stature is not associated with physical or psychological illness, and that there is no evidence that growth hormone improves psychological or physical wellbeing. Moreover, growth hormone for idiopathic short stature represents a form of enhancement rather than treatment, and is not a fair use of resources. Socially mediated disadvantage should be treated by attention to prejudice and not by hormone treatment.