Long-term effects of continuous subcutaneous infusion versus daily subcutaneous injections of growth hormone (GH) on the insulin-like growth factor system, insulin sensitivity, body composition, and bone and lipoprotein metabolism in GH-deficient adults

Long-term effectiveness and safety of long-acting growth hormone preparation in children with growth hormone deficiency

OBJECTIVES

To evaluate the long-term effectiveness of weekly vs. daily growth hormone (GH) administration in children with GH deficiency.

METHODS

This study, part of the "LG Growth Study", included a total of 996 children with GH deficiency (773 receiving daily GH and 193 receiving weekly GH). Anthropometric data were collected at baseline and every 12 months; clinical and laboratory data were collected at baseline and throughout the study.

RESULTS

At baseline, the weekly GH group was older, shorter in mid-parental height (MPH), and had more pubertal boys compared to the daily GH group (age: 8.46 ± 3.44 vs. 7.46 ± 2.89 years, p<0.001; MPH: -0.88 ± 0.73 SD vs. -1.02 ± 0.84 SD, p=0.044; pubertal boys: 34.0 vs. 16.9 %, p=0.006). Height velocity and change in height SDS during the first 12 months were higher in the daily GH group (height velocity: 9.06 ± 1.72 vs. 8.67 ± 1.98 cm/year, p=0.028; height SDS change: 0.78 ± 0.39 vs. 0.61 ± 0.41, p<0.001). However, height SDS at 24 and 48 months were similar between groups. No significant differences in overall height velocity, annualized treatment continuation rate, and safety profile were observed over 48 months.

CONCLUSIONS

Weekly GH therapy appears to be an effective and safe alternative to daily GH treatment in children with GH deficiency over a 4-year period. Further research with larger sample sizes and longer follow-up is needed to confirm these findings and assess the extended safety and effectiveness of LAGH.

Long acting growth hormone (LAGH), an update

In 1957, Maurice Raben at Yale was able to isolate and purify growth hormone from cadaveric pituitary glands. Pituitary growth hormone was the only way to treat children with growth hormone (GH) deficiency, until 1985 when recombinant GH became available for daily subcutaneous injection. For many years, the pediatric endocrine community longed for a long-acting recombinant GH formulation that would decrease the inconvenience of daily injections. Several mechanisms were employed to develop a GH that is rapidly absorbed into the blood stream after subcutaneous injection, but provides slow removal from the circulatory system to potentially optimize patient adherence to GH therapy. Four long-acting growth hormones are currently available in the world, or are close to regulatory approval. They are: (1) Pegylated formulations, (2) Prodrug formulations which are converted into active drug, (3) Nonvalent transient albumin binding GH compounds and (4) GH fusion proteins where a protein si fused with GH. All four formulations have undergone detailed phase 3 studies and were found to show non-inferiority in these clinical studies. All four demonstrate a safety and tolerability profile that is comparable to that of daily somatropin with an excellent adherence profile.

Long-acting growth hormone in 2022

After the isolation of pituitary growth hormone (GH) in 1957, this form of GH, always in limited supply, was the only drug available for the treatment of GH deficiency. In 1985, recombinant GH became available, and the modalities of GH therapies changed dramatically as the supply was unlimited. New indications for GH in pediatrics and adult medicine were developed. Treatment was daily. Now in 2021 long-acting GH (LAGH) became available the world over making GH therapy more patient-friendly and even showing slightly greater efficacy than daily GH therapy. We are now entering a new era of LAGH therapy for pediatric and adult use with new formulations of GH, which will predictably be the preferred form of GH therapy for years to come increasing adherence to GH therapy and possibly even efficacy, that is, better growth rate. The continued availability of new safety data will further solidify the use of LAGH in clinical medicine.

Effect of Weekly Long-Acting Growth Hormone Replacement Therapy Compared to Daily Growth Hormone on Children With Short Stature: A Meta-Analysis

Background

We performed a meta-analysis to evaluate the efficacy and safety of weekly long-acting growth hormone replacement therapy compared to daily growth hormone in children with short stature.

Methods

A systematic literature search up to April 2021 was performed and 11 studies included 1,232 children with short stature treated with growth hormone replacement therapy at the start of the study; 737 of them were using weekly long-acting growth hormone replacement therapy and 495 were using daily growth hormone. They were reporting relationships between the efficacy and safety of long-acting growth hormone replacement therapy and daily growth hormone in children with short stature. We calculated the odds ratio (OR), and mean difference (MD) with 95% confidence intervals (CIs) to assess the efficacy and safety of weekly long-acting growth hormone replacement therapy compared to daily growth hormone in children with short stature using the dichotomous or continuous method with a random or fixed-effect model.

Results

Long-acting growth hormone replacement therapy had significantly lower height standard deviation scores chronological age (MD, -0.10; 95% CI, -0.13 to -0.08, p <0.001), and insulin-like growth factor binding protein-3 (MD, -0.69; 95% CI, -1.09 to -0.30, p <0.001) compared to daily growth hormone in children with short stature.However, growth hormone replacement therapy had no significantly difference in height velocity (MD, -0.09; 95% CI, -0.69-0.5, p = 0.76), height standard deviation scores bone age (MD, -0.04; 95% CI, -0.10-0.02, p = 0.16), insulin-like growth factor 1 standard deviation scores (MD, 0.26; 95% CI, -0.26-0.79, p = 0.33), and incidence of adverse events (OR, 1.16; 95% CI, 0.90-1.50, p = 0.25) compared to daily growth hormone in children with short stature.

Conclusions

Long-acting growth hormone replacement therapy had significantly lower height standard deviation scores chronological age, and insulin-like growth factor binding protein-3 compared to daily growth hormone in children with short stature. However, growth hormone replacement therapy had no significant difference in height velocity, height standard deviation scores bone age, insulin-like growth factor 1 standard deviation scores, and incidence of adverse events compared to daily growth hormone in children with short stature. Further studies are required to validate these findings.

Population Pharmacokinetics and Pharmacodynamics of Once-Daily Growth Hormone Norditropin® in Children and Adults

Background and Objective

Once-daily injectable recombinant human growth hormone (GH) formulations (e.g. Norditropin^®; Novo Nordisk A/S) are used to treat GH deficiency in children and adults, with much of the therapeutic effect mediated via the insulin-like growth factor-I (IGF-I) response. Despite a long history of use, there are few data on the pharmacokinetics and pharmacodynamics (serum IGF-I response) of this therapy, or of potential differences in the relationship of GH pharmacokinetic/pharmacodynamic (PK/PD) effects between children and adults. This study aimed to characterise the GH pharmacokinetics and IGF-I profile following daily subcutaneous GH in adults and children with GH deficiency.

Methods

A model was developed based on a population PK/PD modelling meta-analysis of data from three phase I clinical trials (two using Norditropin^® as a comparator with somapacitan, and one as a comparator with a pegylated GH product). Sequential model building was performed, first developing a model that could describe GH pharmacokinetics. A PD model of IGF-I data was then developed using PK and PD data, and where all PK parameters were kept fixed to those estimated in the PK model.

Results

The model developed accurately describes and predicts GH pharmacokinetics and IGF-I response. Body weight was shown to have an important inversely correlated influence on GH exposure (and IGF-I standard deviation score), and this largely explained differences between adults and children.

Conclusions

The pharmacokinetics/pharmacodynamics developed here can inform expectations about the PD effects of different doses of GH in patients with GH deficiency of different body weights, regardless of their age.

Clinical Trial Registration

Pooled modelling analysis of data from ClinicalTrials.gov identifiers NCT01973244, NCT00936403 and NCT01706783.

Dates of registration

NCT01973244: 22 October, 2013; NCT00936403: 9 July, 2009; NCT01706783: 11 October, 2012.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01011-3.

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.

Physician' attitudes to growth hormone replacement therapy in adults following pituitary surgery: Results of an online survey

OBJECTIVE

The aim of this study was to evaluate physician attitudes and practices in the management of adult growth hormone deficiency (GHD) following pituitary surgery.

MATERIALS AND METHODS

An online questionnaire survey was sent to a sample group of physicians.

RESULTS

A total of 131 respondents provided usable responses. More than three quarters were senior physicians, with most practicing in tertiary care centers (73%). Four-fifths of the respondents see at least 1 to 5 patients with GHD following pituitary surgery per year. Seventy-four percent acknowledge the benefit in principle of growth hormone replacement therapy (GHRT) for patients with GHD after pituitary surgery. Most respondents (84%) would only consider GHRT for symptomatic patients. However, 16% stated that patients with GHD after pituitary surgery generally suffer from the side effects of GHRT. Forty-four percent said that the serum insulin-like growth factor-1 (IGF-1) level is the best screening test for assessing GHD after pituitary surgery but 57% of the respondents would use IGF-I levels, and 29% the insulin tolerance test (ITT), in patients with a documented deficiency in three pituitary axes. The main barriers to long-term GHRT use were that it requires injections (67%), and is costly with limited supply (61%). Other reasons not to use GHRT include an absence of GHD symptoms and apparent GHT ineffectiveness (44%), physician lack of familiarity with the medication (40%), and lack of adherence to available guidelines (38%).

CONCLUSION

This survey addressed physician attitudes and practices in recognizing and treating GHD in adult's post-pituitary surgery. Regional guidelines must be developed to help address/tackle these issues and assist physicians in understanding and treating this condition.

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.

Once-weekly Somapacitan is Effective and Well Tolerated in Adults with GH Deficiency: A Randomized Phase 3 Trial

CONTEXT

Growth hormone (GH) replacement requires daily GH injections, which is burdensome for some adult patients with GH deficiency (AGHD).

OBJECTIVE

To demonstrate efficacy and safety of somapacitan, a once-weekly reversible albumin-binding GH derivative, versus placebo in AGHD.

DESIGN

Randomized, parallel-group, placebo-controlled (double-blind) and active-controlled (open-label) phase 3 trial, REAL 1 (NCT02229851).

SETTING

Clinics in 17 countries.

PATIENTS

Treatment-naïve patients with AGHD (n = 301 main study period, 272 extension period); 257 patients completed the trial.

INTERVENTIONS

Patients were randomized 2:2:1 to once-weekly somapacitan, daily GH, or once-weekly placebo for 34 weeks (main period). During the 52-week extension period, patients continued treatment with somapacitan or daily GH.

MAIN OUTCOME MEASURES

Body composition measured using dual-energy x-ray absorptiometry (DXA). The primary endpoint was change in truncal fat percentage to week 34. Insulin-like growth factor 1 (IGF-I) standard deviation score (SDS) values were used to dose titrate.

RESULTS

At 34 weeks, somapacitan significantly reduced truncal fat percentage (estimated difference: -1.53% [-2.68; -0.38]; P = 0.0090), demonstrating superiority compared with placebo, and it improved other body composition parameters (including visceral fat and lean body mass) and IGF-I SDS. At 86 weeks, improvements were maintained with both somapacitan and daily GH. Somapacitan was well tolerated, with similar adverse events (including injection-site reactions) compared with daily GH.

CONCLUSIONS

In AGHD patients, somapacitan administered once weekly demonstrated superiority over placebo, and the overall treatment effects and safety of somapacitan were in accordance with known effects and safety of GH replacement for up to 86 weeks of treatment. Somapacitan may provide an effective alternative to daily GH in AGHD. A short visual summary of our work is available (1).

Perspectives on long-acting growth hormone therapy in children and adults

Growth hormone therapy with daily injections of recombinant human growth hormone has been available since 1985, and is shown to be safe and effective treatment for short stature in children and for adult growth hormone deficiency. In an effort to produce a product that would improve patient adherence, there has been a strong effort from industry to create a long acting form of growth hormone to ease the burden of use. Technologies used to increase half-life include depot formulations, PEGylated formulations, pro-drug formulations, non-covalent albumin binding growth hormone and growth hormone fusion proteins. At present, two long acting formulations are on the market in China and South Korea, and several more promising agents are under clinical investigation at various stages of development throughout the world. Arch Endocrinol Metab. 2019;63(6):601-7.

Efficacy and safety of long-acting growth hormone in children with short stature: a systematic review and meta-analysis

PURPOSE

Long-acting growth hormone (GH) has been developed to address the noncompliance and decreased efficacy associated with daily GH injections. We aimed to evaluate the efficacy and safety of long-acting GH replacement therapy in children with short stature.

METHODS

Randomized controlled trials (RCTs) that investigated the efficacy and safety of long-acting GH therapy in children with short stature in comparison with daily GH injections were searched in Medline, Embase, and the Cochrane Central Register of Controlled Trials. A random-effect model was used to pool data using mean difference and odds ratios (OR). (PROSPERO registration number: CRD42018111105).

RESULTS

Seven relevant studies were finally included. Meta-analysis found there was no significant difference between high-dose long-acting GH and daily GH in terms of height velocity (HV) (mean difference (MD) = -0.10, 95% CI, -0.79 to 0.60, P = 0.79). Moreover, no significant difference was observed in height standard deviation scores (Ht SDS) between high-dose long-acting GH and daily GH (MD = -0.07, 95% CI, -0.18 to 0.03, P = 0.17). Treatment with high-dose long-acting GH significantly increased IGF-1 SDS when compared with daily GH (MD = 0.31, 95% CI, 0.06-0.56, P = 0.02). In safety assessment, no significant difference was observed in the incidence of adverse events between high-dose long-acting GH and daily GH (OR 1.42, 95% CI, 0.65-3.11, P = 0.38).

CONCLUSIONS

There is no evidence to support differences in the effects of long-acting GH compared with those of daily GH. More RCTs that focus on the safety of high-dose long-acting GH treatment, especially the detection of adverse events caused by elevated levels of serum IGF-1, are needed in the future.

Long-Acting Growth Hormone Preparations in the Treatment of Children

Human growth hormone (hGH), which had been in use since 1958, was supplanted by recombinant human growth hormone (rhGH) in 1985 for those with growth hormone deficiency (GHD). Adherence to daily subcutaneous growth hormone is challenging for patients. Thus, several companies have pursued the creation of long acting rhGH. These agents can be divided broadly into depot formulations, PEGylated formulations, pro-drug formulations, non-covalent albumin binding GH and GH fusion proteins. Nutropin Depot is the only long acting rhGH ever approved by the U.S. Food and Drug Administration, and it was removed from the market in 2004. Of the approximately seventeen candidate drugs, only a handful remain under active clinical investigation or are commercially available.

Effects of growth hormone on hepatic insulin sensitivity and glucose effectiveness in healthy older adults

PURPOSE

Growth hormone (GH) replacement decreases insulin sensitivity in healthy individuals. However, the effects of GH on organ-specific insulin sensitivity and glucose effectiveness are not well characterized. The purpose of this study was to evaluate the effects of GH administration for 26 weeks on muscle and hepatic insulin sensitivity and glucose effectiveness in healthy older individuals.

METHODS

This report is from a 26-week randomized, double-blind, placebo-controlled parallel-group trial in healthy, ambulatory, community-dwelling older women and men. We compared surrogate indices of insulin sensitivity [quantitative insulin-sensitivity check index (QUICKI), muscle insulin sensitivity index (MISI), hepatic insulin resistance index (HIRI)] and glucose effectiveness [oral glucose effectiveness index (oGE)] derived from oral glucose tolerance tests (OGTTs) in subjects before and after 26 weeks of administration of GH (n = 17) or placebo (n = 15) as an exploratory outcome.

RESULTS

GH administration for 26 weeks significantly increased fasting insulin concentrations and HIRI but did not significantly change MISI or oGE compared to placebo.

CONCLUSIONS

GH administration for 26 weeks in healthy older subjects impairs insulin sensitivity in the liver but not skeletal muscle and does not alter glucose effectiveness.

The rationale and design of TransCon Growth Hormone for the treatment of growth hormone deficiency

The fundamental challenge of developing a long-acting growth hormone (LAGH) is to create a more convenient growth hormone (GH) dosing profile while retaining the excellent safety, efficacy and tolerability of daily GH. With GH receptors on virtually all cells, replacement therapy should achieve the same tissue distribution and effects of daily (and endogenous) GH while maintaining levels of GH and resulting IGF-1 within the physiologic range. To date, only two LAGHs have gained the approval of either the Food and Drug Administration (FDA) or the European Medicines Agency (EMA); both released unmodified GH, thus presumably replicating distribution and pharmacological actions of daily GH. Other technologies have been applied to create LAGHs, including modifying GH (for example, protein enlargement or albumin binding) such that the resulting analogues possess a longer half-life. Based on these approaches, nearly 20 LAGHs have reached various stages of clinical development. Although most have failed, lessons learned have guided the development of a novel LAGH. TransCon GH is a LAGH prodrug in which GH is transiently bound to an inert methoxy polyethylene glycol (mPEG) carrier. It was designed to achieve the same safety, efficacy and tolerability as daily GH but with more convenient weekly dosing. In phase 2 trials of children and adults with growth hormone deficiency (GHD), similar safety, efficacy and tolerability to daily GH was shown as well as GH and IGF-1 levels within the physiologic range. These promising results support further development of TransCon GH.

MOD-4023, a long-acting carboxy-terminal peptide-modified human growth hormone: results of a Phase 2 study in growth hormone-deficient adults

OBJECTIVE

Growth hormone (GH) replacement therapy currently requires daily injections, which may cause distress and low compliance. C-terminal peptide (CTP)-modified growth hormone (MOD-4023) is being developed as a once-weekly dosing regimen in patients with GH deficiency (GHD). This study's objective is to evaluate the safety, pharmacokinetics (PK), pharmacodynamics (PD) and efficacy of MOD-4023 administered once-weekly in GHD adults.

DESIGN

54 adults with GHD currently treated with daily GH were normalized and randomized into 4 weekly dosing cohorts of MOD-4023 at 18.5%, 37%, 55.5% or 123.4% of individual cumulative weekly molar hGH dose. The study included 2 stages: Stage A assessed the effectiveness and PK/PD profiles of the 4 dosing regimens of MOD-4023. Stage B was an extension period of once-weekly MOD-4023 administration (61.7% molar hGH content) to collect further safety data and confirm the results from Stage A.

RESULTS

Dose-dependent response was observed for both PK and PD data of weekly MOD-4023 treatment. Insulin-like growth factor I (IGF-I) SDS levels were maintained within normal range. The 18.5% cohort was discontinued due to low efficacy. MOD-4023 was well tolerated and exhibited favorable safety profile in all dose cohorts. The reported adverse events were consistent with known GH-related side effects.

CONCLUSIONS

Once-weekly MOD-4023 administration in GHD adults was found to be clinically effective while maintaining a favorable safety profile and may obviate the need for daily injections. Weekly GH injections may improve compliance and overall outcome. The promising results achieved in this Phase 2 study led to a pivotal Phase 3 trial, which is currently ongoing.

Comparison of pulsatile vs. continuous administration of human placental growth hormone in female C57BL/6J mice

Exogenous growth hormone has different actions depending on the method of administration. However, the effects of different modes of administration of the placental variant of growth hormone on growth, body composition and glucose metabolism have not been investigated. In this study, we examined the effect of pulsatile vs. continuous administration of recombinant variant of growth hormone in a normal mouse model. Female C57BL/6J mice were randomized to receive vehicle or variant of growth hormone (2 or 5 mg/kg per day) by daily subcutaneous injection (pulsatile) or osmotic pump for 6 days. Pulsatile treatment with 2 and 5 mg/kg per day significantly increased body weight. There was also an increase in liver, kidney and spleen weight via pulsatile treatment, whereas continuous treatment did not affect body weight or organ size. Pulsatile treatment with 5 mg/kg per day significantly increased fasting plasma insulin concentration, whereas with continuous treatment, fasting insulin concentration was not significantly different from the vehicle-treated control. However, a dose-dependent increase in fasting insulin concentration and decrease in insulin sensitivity, as assessed by HOMA, was observed with both modes of treatment. At 5 mg/kg per day, hepatic growth hormone receptor expression was increased compared to vehicle-treated animals, by both modes of administration. Pulsatile variant of growth hormone did not alter the plasma insulin-like growth factor-1 concentration, whereas a slight decrease was observed with continuous variant of growth hormone treatment. Neither pulsatile nor continuous treatment affected hepatic insulin-like growth factor-1 mRNA expression. Our findings suggest that pulsatile variant of growth hormone treatment was more effective in stimulating growth but caused marked hyperinsulinemia in mice.

Growth Hormone Research Society perspective on the development of long-acting growth hormone preparations

OBJECTIVE

The Growth Hormone (GH) Research Society (GRS) convened a workshop to address important issues regarding trial design, efficacy, and safety of long-acting growth hormone preparations (LAGH).

PARTICIPANTS

A closed meeting of 55 international scientists with expertise in GH, including pediatric and adult endocrinologists, basic scientists, regulatory scientists, and participants from the pharmaceutical industry.

EVIDENCE

Current literature was reviewed for gaps in knowledge. Expert opinion was used to suggest studies required to address potential safety and efficacy issues.

CONSENSUS PROCESS

Following plenary presentations summarizing the literature, breakout groups discussed questions framed by the planning committee. Attendees reconvened after each breakout session to share group reports. A writing team compiled the breakout session reports into a draft document that was discussed and revised in an open forum on the concluding day. This was edited further and then circulated to attendees from academic institutions for review after the meeting. Participants from pharmaceutical companies did not participate in the planning, writing, or in the discussions and text revision on the final day of the workshop. Scientists from industry and regulatory agencies reviewed the manuscript to identify any factual errors.

CONCLUSIONS

LAGH compounds may represent an advance over daily GH injections because of increased convenience and differing phamacodynamic properties, providing the potential for improved adherence and outcomes. Better methods to assess adherence must be developed and validated. Long-term surveillance registries that include assessment of efficacy, cost-benefit, disease burden, quality of life, and safety are essential for understanding the impact of sustained exposure to LAGH preparations.

Comparative pharmacokinetics and pharmacodynamics of a PEGylated recombinant human growth hormone and daily recombinant human growth hormone in growth hormone-deficient children

Objective

Recombinant human growth hormone (rhGH) replacement therapy in children generally requires daily subcutaneous (sc) injections, which may be inconvenient for patients. Jintrolong^® is a PEGylated rhGH with the purpose of weekly sc injections. The aim of the current study was to examine the pharmacokinetics, pharmacodynamics, safety, and tolerability of multiple sc doses of Jintrolong^® vs daily doses of rhGH.

Design and methods

Twelve children with growth hormone deficiency participated in this single-center, open-label, crossover Phase I trial. All subjects received daily sc injections of rhGH at 0.0286 mg/kg/d for 7 days, followed by a 4-week washout period and six weekly doses of Jintrolong^® at 0.2 mg/kg/w.

Results

In comparison with rhGH, sc injection of Jintrolong^® produced a noticeably higher C_max, significantly longer half-life (t_1/2), and slower plasma clearance, signifying a profile suitable for long-term treatment. The ratio of the area under the concentration vs time curve (AUC) after the seventh and first injections (AUC_(0–∞)7th/AUC_(0–∞)1st) of rhGH was 1.02, while the AUC_(0–∞)6th/AUC_(0–∞)1st of Jintrolong ^® was 1.03, indicating no accumulation of circulating growth hormone. There was no significant difference in the change in insulin-like growth factor-1 expression produced by 7 days of sc rhGH and weekly Jintrolong^® injections. There were no severe adverse events during the trial.

Conclusion

The elimination rate of Jintrolong^® was slower than that of sc rhGH. No progressive serum accumulation of Jintrolong^® was found. The changes in insulin-like growth factor-1 expression produced by rhGH and Jintrolong^® were comparable, indicating similar pharmacodynamics. Our results demonstrate that Jintrolong^® is suitable for long-term growth hormone treatment in children with growth hormone deficiency.

Functional human antibody CDR fusions as long-acting therapeutic endocrine agonists

On the basis of the 3D structure of a bovine antibody with a well-folded, ultralong complementarity-determining region (CDR), we have developed a versatile approach for generating human or humanized antibody agonists with excellent pharmacological properties. Using human growth hormone (hGH) and human leptin (hLeptin) as model proteins, we have demonstrated that functional human antibody CDR fusions can be efficiently engineered by grafting the native hormones into different CDRs of the humanized antibody Herceptin. The resulting Herceptin CDR fusion proteins were expressed in good yields in mammalian cells and retain comparable in vitro biological activity to the native hormones. Pharmacological studies in rodents indicated a 20- to 100-fold increase in plasma circulating half-life for these antibody agonists and significantly extended in vivo activities in the GH-deficient rat model and leptin-deficient obese mouse model for the hGH and hLeptin antibody fusions, respectively. These results illustrate the utility of antibody CDR fusions as a general and versatile strategy for generating long-acting protein therapeutics.

Exercise-Induced growth hormone during acute sleep deprivation

The effect of acute (24‐h) sleep deprivation on exercise‐induced growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) was examined. Ten men (20.6 ± 1.4 years) completed two randomized 24‐h sessions including a brief, high‐intensity exercise bout following either a night of sleep (SLEEP) or (24‐h) sleep deprivation (SLD). Anaerobic performance (mean power [MP], peak power [PP], minimum power [MinP], time to peak power [TTPP], fatigue index, [FI]) and total work per sprint [TWPS]) was determined from four maximal 30‐sec Wingate sprints on a cycle ergometer. Self‐reported sleep 7 days prior to each session was similar between SLEEP and SLD sessions (7.92 ± 0.33 vs. 7.98 ± 0.39 h, P =0.656, respectively) and during the actual SLEEP session in the lab, the total amount of sleep was similar to the 7 days leading up to the lab session (7.72 ± 0.14 h vs. 7.92 ± 0.33 h, respectively) (P =0.166). No differences existed in MP, PP, MinP, TTPP, FI, TWPS, resting GH concentrations, time to reach exercise‐induced peak GH concentration (TTP), or free IGF‐1 between sessions. GH area under the curve (AUC) (825.0 ± 199.8 vs. 2212.9 ± 441.9 μg/L*min, P <0.01), exercise‐induced peak GH concentration (17.8 ± 3.7 vs. 39.6 ± 7.1 μg/L, P <0.01) and ΔGH (peak GH – resting GH) (17.2 ± 3.7 vs. 38.2 ± 7.3 μg/L, P <0.01) were significantly lower during the SLEEP versus SLD session. Our results indicate that the exercise‐induced GH response was significantly augmented in sleep‐deprived individuals.

Human growth hormone release is heavily influenced by sleep and exercise. Our study shows that sleep deprivation dramatically augments the exercise‐induced human growth hormone response.

Developments in human growth hormone preparations: sustained-release, prolonged half-life, novel injection devices, and alternative delivery routes

Since the availability of recombinant human growth hormone (rhGH) enabled the application of human growth hormone both in clinical and research use in the 1980s, millions of patients were prescribed a daily injection of rhGH, but noncompliance rates were high. To address the problem of noncompliance, numerous studies have been carried out, involving: sustained-release preparations, prolonged half-life derivatives, new injectors that cause less pain, and other noninvasive delivery methods such as intranasal, pulmonary and transdermal deliveries. Some accomplishments have been made and launched already, such as the Nutropin Depot^® microsphere and injectors (Zomajet^®, Serojet^®, and NordiFlex^®). Here, we provide a review of the different technologies and illustrate the key points of these studies to achieve an improved rhGH product.

Insulin and IGF-I inhibit GH synthesis and release in vitro and in vivo by separate mechanisms

IGF-I is considered a primary inhibitor of GH secretion. Insulin may also play an important role in regulating GH levels because insulin, like IGF-I, can suppress GH synthesis and release in primary pituitary cell cultures and insulin is negatively correlated with GH levels in vivo. However, understanding the relative contribution insulin and IGF-I exert on controlling GH secretion has been hampered by the fact that circulating insulin and IGF-I are regulated in parallel and insulin (INSR) and IGF-I (IGFIR) receptors are structurally/functionally related and ubiquitously expressed. To evaluate the separate roles of insulin and IGF-I in directly regulating GH secretion, we used the Cre/loxP system to knock down the INSR and IGFIR in primary mouse pituitary cell cultures and found insulin-mediated suppression of GH is independent of the IGFIR. In addition, pharmacological blockade of intracellular signals in both mouse and baboon cultures revealed insulin requires different pathways from IGF-I to exert a maximal inhibitory effect on GH expression/release. In vivo, somatotrope-specific knockout of INSR (SIRKO) or IGFIR (SIGFRKO) increased GH levels. However, comparison of the pattern of GH release, GH expression, somatotrope morphometry, and pituitary explant sensitivity to acute GHRH challenge in lean SIRKO and SIGFRKO mice strongly suggests the primary role of insulin in vivo is to suppress GH release, whereas IGF-I serves to regulate GH synthesis. Finally, SIRKO and/or SIGFRKO could not prevent high-fat, diet-induced suppression of pituitary GH expression, indicating other factors/tissues are involved in the decline of GH observed with weight gain.

Adult growth hormone deficiency - benefits, side effects, and risks of growth hormone replacement

Deficiency of growth hormone (GH) in adults results in a syndrome characterized by decreased muscle mass and exercise capacity, increased visceral fat, impaired quality of life, unfavorable alterations in lipid profile and markers of cardiovascular risk, decrease in bone mass and integrity, and increased mortality. When dosed appropriately, GH replacement therapy (GHRT) is well tolerated, with a low incidence of side effects, and improves most of the alterations observed in GH deficiency (GHD); beneficial effects on mortality, cardiovascular events, and fracture rates, however, remain to be conclusively demonstrated. The potential of GH to act as a mitogen has resulted in concern over the possibility of increased de novo tumors or recurrence of pre-existing malignancies in individuals treated with GH. Though studies of adults who received GHRT in childhood have produced conflicting reports in this regard, long-term surveillance of adult GHRT has not demonstrated increased cancer risk or mortality.

A novel long-acting human growth hormone fusion protein (VRS-317): enhanced in vivo potency and half-life

A novel recombinant human growth hormone (rhGH) fusion protein (VRS-317) was designed to minimize receptor-mediated clearance through a reduction in receptor binding without mutations to rhGH by genetically fusing with XTEN amino acid sequences to the N-terminus and the C-terminus of the native hGH sequence. Although in vitro potency of VRS-317 was reduced approximately 12-fold compared with rhGH, in vivo potency was increased because of the greatly prolonged exposure to the target tissues and organs. VRS-317 was threefold more potent than daily rhGH in hypophysectomized rats and fivefold more potent than daily rhGH in juvenile monkeys. In juvenile monkeys, a monthly dose of 1.4 mg/kg VRS-317 (equivalent to 0.26 mg/kg rhGH) caused a sustained pharmacodynamic response for 1 month equivalent to 0.05 mg/kg/day rhGH (1.4 mg/kg rhGH total over 28 days). In monkeys, VRS-317, having a terminal elimination half-life of approximately 110 h, was rapidly and near-completely absorbed, and was well tolerated with no observed adverse effects after every alternate week subcutaneous dosing for 14 weeks. VRS-317 also did not cause lipoatrophy in pig and monkey studies. VRS-317 is currently being studied in GH-deficient patients to confirm the observations in these animal studies.

Rapid suppression of growth hormone concentration by overeating: potential mediation by hyperinsulinemia

CONTEXT

The very low GH concentration in obesity is commonly attributed to high body fat mass; however, the influence of overeating on GH secretion is not clear.

OBJECTIVE

The aim of the study was to examine the effects of 2 wk of overeating on changes in GH secretion.

SETTING

Subjects were admitted to the hospital and stayed within the Michigan Clinical Research Unit throughout the entire 2-wk overeating period.

PARTICIPANTS

We studied seven healthy, nonobese men (body mass index, 24 ± 1 kg/m(2); age, 25 ± 1 yr).

INTERVENTION

Subjects ate standardized meals containing 70 kcal/kg fat free mass/d (∼4000 kcal/d) for 2 wk.

MAIN OUTCOME MEASURES

Twenty-four-hour plasma concentrations of GH (every 20 min) and insulin (every 2 h) were measured before overeating (baseline), on d 3, and after 2 wk of overeating.

RESULTS

Compared with baseline, average 24-h plasma GH concentration declined nearly 80% by d 3 of overeating (1.30 ± 0.18 vs. 0.36 ± 0.09 ng/ml; P = 0.01). This marked suppression of GH secretion occurred in the absence of an increase in body weight (77.0 ± 2.2 vs. 76.4 ± 2.4 kg). At the same time, average 24-h insulin concentration doubled (16.6 ± 2.1 vs. 31.7 ± 5.8 μU/ml; P = 0.009). After 2 wk, body weight significantly increased (79.0 ± 2.1 kg; P < 0.001), and body fat increased by more than 10% (P = 0.002). However, this did not induce a further suppression in plasma GH concentration (0.33 ± 0.08 ng/ml).

CONCLUSION

Only a few days of overeating markedly suppressed GH secretion before any measurable weight gain and was accompanied by chronic hyperinsulinemia. Increased body weight and body fat by 2 wk of overeating did not further suppress GH secretion.

Microneedle-based intradermal delivery enables rapid lymphatic uptake and distribution of protein drugs

PURPOSE

The purpose of this research was to examine the pharmacokinetics (PK) of drug uptake for microneedle-based intradermal (ID) delivery of several classes of protein drugs compared to standard subcutaneous (SC) administration.

METHODS

Systemic absorption kinetics of various proteins were analyzed following microneedle-based ID delivery and standard injection methods in the swine model. Comparative PK data were determined using standard non-compartmental techniques based on blood serum levels.

RESULTS

Delivery of proteins using microneedles resulted in faster systemic availability, measured via t(max,) and increased maximal drug concentration, C(max,) over SC delivery for all proteins tested. Some agents also exhibited increased bioavailability for the ID route. Imaging studies using reporter dyes showed rapid lymphatic-mediated uptake.

CONCLUSIONS

Microneedle delivery is applicable to a wide variety of protein drugs and is capable of effective parenteral administration of therapeutic drug dosages. This delivery route alters absorption kinetics via targeting a tissue bed better perfused with lymphatic and blood vessels than the SC space. Microneedle delivery may afford various advantages, including a robust method to increase the absorption rate and bioavailability of proteins that have been challenging to deliver at therapeutic levels or with physiologically relevant profiles.

The behavioral and biochemical effects of BDNF containing polymers implanted in the hippocampus of rats

Brain-derived neurotrophic factor (BDNF) is closely linked with neuronal survival and plasticity in psychiatric disorders. In this work, we engineered degradable, injectable alginate microspheres and non-degradable, implantable poly(ethylene vinyl acetate) matrices to continuously deliver BDNF to the dorsal hippocampus of rats for two days or more than a week, respectively. The antidepressant-like behavioral effects of BDNF delivery were examined in the Porsolt forced swim test. Rats were sacrificed 10days after surgery and tissue samples were analyzed by western blot. A small dose of BDNF delivered in a single infusion, or from a two-day sustained-release alginate implant, produced an antidepressant-like behavior, whereas the same dose delivered over a longer period of time to a larger tissue region did not produce antidepressant-like effects. Prolonged delivery of BDNF resulted in a dysregulation of plasticity-related functions: increased dose and duration of BDNF delivery produced increased levels of TrkB, ERK, CREB, and phosphorylated ERK, while also producing decreased phosphorylated CREB. It is evident from this work that both duration and magnitude of BDNF dosing are of critical importance in achieving functional outcome.

The pattern of growth hormone delivery to peripheral tissues determines insulin-like growth factor-1 and lipolytic responses in obese subjects

CONTEXT

It is unclear whether the pattern of GH delivery to peripheral tissues has important effects.

OBJECTIVE

The aim of the study was to compare the effects of pulsatile vs. continuous administration of GH upon metabolic and IGF-I parameters in obese subjects.

SETTING

The study was conducted at the General Clinical Research Center at the University of Michigan Medical Center.

PARTICIPANTS

Four men and five women with abdominal obesity (body mass index, 33 +/- 3 kg/m(2); body fat, 40 +/- 3%) participated in the study.

INTERVENTION

GH (0.5 mg/m(2) . d) was given iv for 3 d as: 1) continuous infusion (C); and 2) pulsatile boluses (P) (15% of the dose at 0700, 1300, and 1800 h and 55% at 2400 h). These trials were preceded by a basal period (B) when subjects received normal saline.

MAIN OUTCOME MEASURES

Rate of lipolysis and hepatic glucose production were evaluated using stable isotope tracer techniques. The composite index of insulin sensitivity (Matsuda index) was assessed using oral glucose tolerance test.

RESULTS

The increase in plasma IGF-I concentrations was greater (P < 0.05) with continuous GH infusion (211 +/- 31, 423 +/- 38, and 309 +/- 34 microg/liter for B, C, and P, respectively). Muscle IGF-I mRNA was significantly increased (P < 0.05) only after the continuous GH infusion (1.2 +/- 0.4, 4.4 +/- 1.3, and 2.3 +/- 0.6 arbitrary units, for B, C, and P, respectively). Only pulsatile GH augmented the rate of lipolysis (4.1 +/- 0.3, 4.8 +/- 0.7, and 7.1 +/- 1.1 mumol/kg . min for B, C, and P, respectively). GH had no effect on hepatic glucose production, but both modes of GH administration were equally effective in impairing insulin sensitivity.

CONCLUSION

These findings indicate that, in obese subjects, discrete components of GH secretory pattern may differentially affect IGF-I generation and lipolytic responses.