Biological Significance of Anti-GH Antibodies in Children Treated with rhGH

Comparing treatment with daily and long-acting growth hormone formulations in adults with growth hormone deficiency: Challenging issues, benefits, and risks

Daily administration of growth hormone (GH) treatment has been in clinical use for treatment for GH deficiency (GHD) in adults for more than 30 years. Numerous studies have demonstrated evidence that GH treatment improves body composition, cardiovascular risk factors and quality of life with few side effects. Less frequent GH injections are hypothesized to improve adherence and several long-acting GH (LAGH) formulations have been developed and a few have been approved and marketed. Different pharmacological modifications have been applied and the pharmacokinetics and pharmacodynamics of LAGH are different to each other and to those of daily injections and require different dosing and monitoring specific for each LAGH. Studies have shown improved adherence with LAGH, and short-term efficacy and side effects are comparable between daily GH injections and LAGHs. Long-term treatment with daily GH injections is effective and safe, while long-term studies for LAGHs are awaited. In this review challenges, benefits, and risks of treatment with daily and long-acting GH preparations will be compared.

Response to growth hormone treatment in patients with sufficient secretion

BACKGROUND

There are situations of short stature, with a normal stimulus test for GH, but decreased nocturnal secretion in which there could be a benefit with GH treatment.

OBJETIVES

To assess adult height and height gain in patients with neurosecretory dysfunction diagnosis treated with growth hormone.

MATERIAL Y METHODS

Longitudinal, retrospective and observational study including 61 patients treated with growth hormone after diagnosis of neurosecretory dysfunction who have already reached adult height. Variables such as adult height gain, growth rate, growth prognosis variation and IGF-I and IGFBP-3 were evaluated. Variables related to a good response in the first year have also been calculated, using the Index of responsiveness (IoR).

RESULTS

GH treatment produces an improvement in growth rate and height, observing an increase in adult height with respect to initial height of 1.15±0.60 SD, height with respect to genetic height of -0.015±0.62 SD and adult height with respect to the initial growth prognosis 0,74±1,13 DE. The IoR in the first year is associated with a greater increase in height in the first year (p=0.000), with a greater adult height (p=0.000) and with a greater gain in adult height compared to its initial height (p=0.039).

CONCLUSIONS

Patients with growth delay due to neurosecretory dysfunction of GH show a good response to treatment with rhGH, observing a significant height gain in their genetic size and improving their initial growth prognosis.

Detection of methionine- and alanine-recombinant bovine somatotropins and their induced antibodies in serum and milk of cows suggests blood-milk barrier specificity for these compounds

The elimination of recombinant bovine somatotropin (rbST) and its induced antibodies through milk of 2 formulations is studied to propose a control strategy for its use or abuse. Two dairy cows were treated with alanine-rbST (Ala-rbST), which is identical to endogenous bovine somatotropin, and ten dairy cows were treated with methionine-rbST (Met-rbST), which differs by 1 amino acid from endogenous bovine somatotropin. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method able to measure rbST at a decision limit (CCα) of 0.8 ng/mL and 2.3 ng/mL for serum and milk, respectively. The results show that the administered Ala-rbST is transferred from blood to milk but that this is not the case for Met-rbST. This suggests a blood-milk barrier-related specificity for these compounds. In addition, rbST-induced antibodies were formed in animals treated with Ala-rbST and those treated with Met-rbST. In both treatments, the rbST-induced antibodies were transferred from blood to milk, showing no blood-milk barrier specificity for these antibodies. These elimination patterns show that, for enforcement purposes, the detection of rbST-induced antibodies in tank milk can serve to screen for rbST administration, and subsequent confirmatory serum analysis by LC-MS/MS is needed to identify whether Ala-rbST or Met-rbST has been used.

Usefulness and Potential Pitfalls of Long-Acting Growth Hormone Analogs

Daily recombinant human GH (rhGH) is currently approved for use in children and adults with GH deficiency (GHD) in many countries with relatively few side-effects. Nevertheless, daily injections can be painful and distressing for some patients, often resulting in non-adherence and reduction of treatment outcomes. This has prompted the development of numerous long-acting GH (LAGH) analogs that allow for decreased injection frequency, ranging from weekly, bi-weekly to monthly. These LAGH analogs are attractive as they may theoretically offer increased patient acceptance, tolerability, and therapeutic flexibility. Conversely, there may also be pitfalls to these LAGH analogs, including an unphysiological GH profile and differing molecular structures that pose potential clinical issues in terms of dose initiation, therapeutic monitoring, incidence and duration of side-effects, and long-term safety. Furthermore, fluctuations of peak and trough serum GH and IGF-I levels and variations in therapeutic efficacy may depend on the technology used to prolong GH action. Previous studies of some LAGH analogs have demonstrated non-inferiority compared to daily rhGH in terms of increased growth velocity and improved body composition in children and adults with GHD, respectively, with no significant unanticipated adverse events. Currently, two LAGH analogs are marketed in Asia, one recently approved in the United States, another previously approved but not marketed in Europe, and several others proceeding through various stages of clinical development. Nevertheless, several practical questions still remain, including possible differences in dose initiation between naïve and switch-over patients, methodology of dose adjustment/s, timing of measuring serum IGF-I levels, safety, durability of efficacy and cost-effectiveness. Long-term surveillance of safety and efficacy of LAGH analogs are needed to answer these important questions.

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.