The pharmacokinetic and pharmacodynamic characteristics of a long-acting growth hormone (GH) preparation (nutropin depot) in GH-deficient adults

Long-acting microneedle formulations

The minimally-invasive and painless nature of microneedle (MN) application has enabled the technology to obviate many issues with injectable drug delivery. MNs not only administer therapeutics directly into the dermal and ocular space, but they can also control the release profile of the active compound over a desired period. To enable prolonged delivery of payloads, various MN types have been proposed and evaluated, including dissolving MNs, polymeric MNs loaded or coated with nanoparticles, fast-separable MNs hollow MNs, and hydrogel MNs. These intricate yet intelligent delivery platforms provide an attractive approach to decrease side effects and administration frequency, thus offer the potential to increase patient compliance. In this review, MN formulations that are loaded with various therapeutics for long-acting delivery to address the clinical needs of a myriad of diseases are discussed. We also highlight the design aspects, such as polymer selection and MN geometry, in addition to computational and mathematical modeling of MNs that are necessary to help streamline and develop MNs with high translational value and clinical impact. Finally, up-scale manufacturing and regulatory hurdles along with potential avenues that require further research to bring MN technology to the market are carefully considered. It is hoped that this review will provide insight to formulators and clinicians that the judicious selection of materials in tandem with refined design may offer an elegant approach to achieve sustained delivery of payloads through the simple and painless application of a MN patch.

Growth hormone receptor agonists and antagonists: From protein expression and purification to long-acting formulations

Recombinant human growth hormone (rhGH) and GH receptor antagonists (GHAs) are used clinically to treat a range of disorders associated with GH deficiency or hypersecretion, respectively. However, these biotherapeutics can be difficult and expensive to manufacture with multiple challenges from recombinant protein generation through to the development of long-acting formulations required to improve the circulating half-life of the drug. In this review, we summarize methodologies and approaches used for making and purifying recombinant GH and GHA proteins, and strategies to improve pharmacokinetic and pharmacodynamic properties, including PEGylation and fusion proteins. Therapeutics that are in clinical use or are currently under development are also discussed.

Vasculometabolic effects in patients with congenital growth hormone deficiency with and without GH replacement therapy during adulthood

PURPOSE

To evaluated the metabolic profiles and vascular properties in congenital growth hormone (GH) deficiency (GHD) and its replacement in adults.

PATIENTS AND METHODS

Cross-sectional study conducted in a single tertiary center for pituitary diseases. Eighty-one adult subjects were divided into three groups: (1) 29 GHD patients with daily subcutaneous GH replacement therapy (GHRT) during adulthood; (2) 20 GHD patients without GHRT during adulthood and (3) 32 controls. Only patients with adequate adherence to others pituitary hormone deficiencies were included. Anthropometric parameters, body composition by dual-energy X-ray absorptiometry, metabolic profiles and vascular properties (carotid intima media thickness, pulse wave velocity and flow-mediated dilation) were compared among the groups.

RESULTS

Waist-to-height ratio (WHR), body fat percentages and fat mass index (FMI) were lower in patients with GHRT than patients without GHRT during adulthood (0.49 ± 0.06 vs. 0.53 ± 0.06 p = 0.026, 30 ± 10 vs. 40 ± 11 p = 0.003 and 7.3 ± 4 vs. 10 ± 3.5 p = 0.041, respectively). In addition, association between longer GHRT and lower body fat percentage was observed (r =  - 0.326, p = 0.04). We found higher triglyceride (113.5 ± 62 vs. 78 ± 36, p = 0.025) and lower HDL cholesterol (51 ± 17 vs. 66 ± 23, p = 0.029) levels in patients without GHRT during adulthood in comparison to controls. No statistical differences were observed for vascular properties among the groups.

CONCLUSIONS

No differences in vascular properties were observed in congenital GHD adult patients with or without GHRT despite patients without GHRT had an unfavorable body composition. GHRT currently remains an individualized decision in adults with GHD and these findings bring new insight into the treatment and follow-up of these patients.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Current strategies in extending half-lives of therapeutic proteins

Macromolecular protein and peptide therapeutics have been proven to be effective in treating critical human diseases precisely. Thanks to biotechnological advancement, a huge number of proteins and peptide therapeutics were made their way to pharmaceutical market in past few decades. However, one of the biggest challenges to be addressed for protein therapeutics during clinical application is their fast degradation in serum and quick elimination owing to enzymatic degradation, renal clearance, liver metabolism and immunogenicity, attributing to the short half-lives. Size and hydrophobicity of protein molecules make them prone to kidney filtration and liver metabolism. On the other hand, proteasomes responsible for protein destruction possess the capability of specifically recognizing almost all kinds of foreign proteins while avoiding any unwanted destruction of cellular components. At present almost all protein-based drug formulations available in market are administered intravenously (IV) or subcutaneously (SC) with high dosing at frequent interval, eventually creating dose-fluctuation-related complications and reducing patient compliance vastly. Therefore, artificially increasing the therapeutic half-life of a protein by attaching to it a molecule that increases the overall size (eg, PEG) or helps with receptor mediated recycling (eg, albumin), or manipulating amino acid chain in a way that makes it more prone towards aggregate formation, are some of the revolutionary approaches to avoid the fast degradation in vivo. Half-life extension technologies that are capable of dramatically enhancing half-lives of proteins in circulation (2-100 folds) and thus improving their overall pharmacokinetic (PK) parameters have been successfully applied on a wide range of protein therapeutics from hormones and enzymes, growth factor, clotting factor to interferon. The focus of the review is to assess the technological advancements made so far in enhancing circulatory half-lives and improving therapeutic potency of proteins.

Antimicrobial peptide encapsulation and sustained release from polymer network particles prepared in supercritical carbon dioxide

Antimicrobial peptide loaded poly(2-hydroxyethyl methacrylate) particles were synthesized in supercritical carbon dioxide via one-pot free-radical dispersion polymerisation of 2-hydroxyethyl methacrylate and a cross-linker. Discrete particles with a well-defined spherical morphology and a diameter as low as 450 nm have been obtained in mild conditions. The encapsulation and release of the peptide were confirmed by antimicrobial tests that demonstrated for the first time a sustained release of the peptide from poly(2-hydroxyethyl methacrylate) microgels prepared by one-pot dispersion polymerization in supercritical carbon dioxide and then dispersed in water.

Stabilized single-injection inactivated polio vaccine elicits a strong neutralizing immune response

Vaccination in the developing world is hampered by limited patient access, which prevents individuals from receiving the multiple injections necessary for protective immunity. Here, we developed an injectable microparticle formulation of the inactivated polio vaccine (IPV) that releases multiple pulses of stable antigen over time. To accomplish this, we established an IPV stabilization strategy using cationic polymers for pH modulation to enhance traditional small-molecule-based stabilization methods. We investigated the mechanism of this strategy and showed that it was broadly applicable to all three antigens in IPV. Our lead formulations released two bursts of IPV 1 month apart, mimicking a typical vaccination schedule in the developing world. One injection of the controlled-release formulations elicited a similar or better neutralizing response in rats, considered the correlate of protection in humans, than multiple injections of liquid vaccine. This single-administration vaccine strategy has the potential to improve vaccine coverage in the developing world.

Mild synthesis of poly(HEMA)-networks as well-defined nanoparticles in supercritical carbon dioxide

Free-radical dispersion polymerisation of 2-hydroxyethyl methacrylate was carried out in supercritical carbon dioxide (scCO₂) in the presence of stabilisers based on polyethylene oxide (PEO) and poly(heptadecafluorodecyl acrylate) (PFDA). Different architectures of copolymers (random, palm-tree and diblock) were tested for their surface tension, cloud point and as a stabilising agent. The diblock architecture was found to be the best candidate resulting in poly(HEMA) spherical particles with a size of 316 nm. Furthermore, the effect of the CO₂-phobic block (PEO) in the diblock architecture was investigated by using three different chain lengths (1000, 2000, 5000 g mol^-1). By optimizing the stabiliser composition and structure, mild reaction conditions have been identified allowing us to obtain well-defined spherical cross-linked poly(HEMA) particles with a mean diameter of unprecedented low size (216 nm) at a temperature as low as 35 °C.

Injectable formulations of poly(lactic acid) and its copolymers in clinical use

Poly(lactic acid) and its copolymers have revolutionized the field of drug delivery due to their excellent biocompatibility and tunable physico-chemical properties. These copolymers have served the healthcare sector by contributing many products to combat various diseases and for biomedical applications. This article provides a comprehensive overview of clinically used products of poly(lactic acid) and its copolymers. Multi-dimension information covering product approval, formulation aspects and clinical status is described to provide a panoramic overview of each product. Moreover, leading patented technologies and various clinical trials on these products for different applications are included. This review focuses on marketed injectable formulations of PLA and its copolymers.

Safety and PK/PD correlation of TV-1106, a recombinant fused human albumin-growth hormone, following repeat dose administration to monkeys

PURPOSE

TV-1106 is a recombinant human albumin genetically fused to growth hormone which is intended to reduce the frequency of injections for GH therapy users. We report the safety, tolerability, pharmacokinetics and pharmacodynamics of repeated subcutaneous injections of TV-1106 in Cynomolgus monkeys.

METHOD

Cynomolgus monkeys received four weekly subcutaneous injections of 0, 5, 10 or 20mg/kg TV-1106 and were monitored for safety signals throughout the study. Serum levels of TV-1106 and insulin-like growth factor 1 (IGF-1) were assayed.

RESULTS

Treated animals showed no adverse effects or histopathological changes. TV-1106 serum concentrations showed sustained exposure to the drug. Exposure increased in a dose-dependent manner with peak concentrations at approximately 24h post-dosing and elimination half-lives in the range of 12 to 24h. IGF-1 serum concentrations were elevated throughout the entire study duration, indicative of the pharmacological response. There was a clear correlation between change in IGF-1 levels and dose or exposure to TV-1106.

CONCLUSIONS

The safety, pharmacokinetic and pharmacodynamic findings support the further development of TV-1106 as a once-weekly administered treatment for patients with GHD.

Status of long-acting-growth hormone preparations--2015

Growth hormone (GH) treatment has been an established therapy for GH deficiency (GHD) in children and adults for more than three decades. Numerous studies have shown that GH treatment improves height, body composition, bone density, cardiovascular risk factors, physical fitness and quality of life and that the treatment has few side effects. Initially GH was given as intramuscular injections three times per week, but daily subcutaneous injections were shown to be more effective and less inconvenient and the daily administration has been used since its introduction in the 1980s. However, despite ongoing improvements in injection device design, daily subcutaneous injections remain inconvenient, painful and distressing for many patients, leading to noncompliance, reduced efficacy and increased health care costs. To address these issues a variety of long-acting formulations of GH have been developed. In this review we present the current status of long-acting GH preparations and discuss the specific issues related to their development.

12-month effects of once-weekly sustained-release growth hormone treatment in adults with GH deficiency

The weekly sustained-release recombinant human GH formulation LB03002, showed beneficial effects in GH-deficient (GHD) adults in a previous 26-week double-blind study. Prior studies of long-acting GH preparations in adults have only been conducted for 6 or 8 months, so the effects of longer-term use are unknown; this is important to address, as replacement is given for many years in GHD adults. This open-label, 26-week study extension evaluated longer-term safety and efficacy of LB03002 over 52 weeks in adults with GHD who had previously been randomized to GH, and provides additional safety and efficacy data over 26 weeks in the cohort who had previously been randomized to placebo. Of 147 adults with GHD who completed a preceding study, 136 patients continued in this open-label study to receive LB03002 over an additional 26 weeks. This represented a continuation of long-acting GH for 26 weeks in the cohort who took this medication in the prior study (LB03002 Throughout group), and describes the first use of long-acting GH in the cohort that was randomized to placebo in the prior study (Switched to LB03002 group). The LB03002 dose was adjusted according to serum insulin-like growth factor-I (IGF-I) levels. LB03002 treatment demonstrated mean significant decreases from baseline in fat mass (FM) for both 26 (Switched group, P = 0.001) and 52 weeks (Throughout group, P = 0.002) of 1.11 (1.95) kg and 1.06 (3.16) kg, respectively. Prolonged GH treatment was effective in sustaining the increase in lean body mass (LBM), serum IGF-I and IGFBP-3 levels achieved during the first 26 weeks. Long-term treatment with the sustained-release weekly GH preparation over both 26 and 52 weeks in adults with GHD demonstrated a sustained reduction of FM with a favorable safety profile. This study extends prior knowledge about long-acting GH because it reports the most prolonged treatment of adults with any long-acting GH preparation, thereby confirming the value and safety of such agents for long-term GH replacement.

Developing long-acting growth hormone formulations

Daily recombinant growth hormone (GH) restores normal growth and body composition in GH-deficient children and adults; however, daily injections are inconvenient and can be distressing for some children. On top of this compliance is a problem in up to 75% of children. Developing long-acting GH formulations has proved challenging, and questions remain regarding safety and efficacy. In this review, we focus on the rationale for generating long-acting GH agonists and the technologies being developed to deliver prolonged exposure to GH.

A long-acting human growth hormone with delayed clearance (VRS-317): results of a double-blind, placebo-controlled, single ascending dose study in growth hormone-deficient adults

BACKGROUND

Administration of daily recombinant human GH (rhGH) poses a considerable challenge to patient compliance. Reduced dosing frequency may improve treatment adherence and potentially overall treatment outcomes.

OBJECTIVES

This study assessed the safety and tolerability and the potential for achieving IGF-I levels within the target range in adults with GH deficiency after a single dose of the long-acting rhGH analog, VRS-317.

DESIGN

This was a randomized, double-blind, placebo-controlled, single ascending dose study.

PATIENTS

Fifty adults with growth hormone deficiency (mean age, 45 years) were studied in 5 treatment groups of 10 subjects each (8 active drug and 2 placebo).

SETTING

The study was conducted in 17 adult endocrinology centers in North America and Europe.

MAIN OUTCOME MEASURES

Adverse events, laboratory safety assessments, and VRS-317 pharmacokinetics and pharmacodynamics (IGF-I and IGF binding protein-3) were analyzed.

RESULTS

At 0.80 mg/kg, VRS-317 had a mean terminal elimination half-life of 131 hours. Single VRS-317 doses of 0.05, 0.10, 0.20, 0.40, and 0.80 mg/kg (approximately equivalent to daily rhGH doses of 0.3-5.0 μg/kg over 30 d) safely increased the amplitude and duration of IGF-I responses in a dose-dependent manner. After a single 0.80 mg/kg dose, serum IGF-I was maintained in the normal range between -1.5 and 1.5 SD values for a mean of 3 weeks. No unexpected or serious adverse events were observed.

CONCLUSIONS

The elimination half-life for VRS-317 is 30- to 60-fold longer and stimulates more durable IGF-I responses than previously studied rhGH products. Prolonged IGF-I responses do not come at the expense of overexposure to high IGF-I levels. The pharmacokinetics and pharmacodynamics combined with the observed safety profile indicate the potential for safe and effective monthly dosing.

Arrest of atherosclerosis progression after interruption of GH replacement in adults with congenital isolated GH deficiency

OBJECTIVE

GH replacement therapy (GHRT) in adult-onset GH deficiency (AOGHD) reduces carotid intima-media thickness (IMT) and increases myocardial mass, with improvement of systolic and diastolic function. These observations have reinforced the use of GHRT on AOGHD. Conversely, we have previously reported that in adults with lifetime congenital and severe isolated GH deficiency (IGHD) due to a mutation in GHRH receptor gene (GHRHR), a 6-month treatment with depot GH increased carotid IMT, caused the development of atherosclerotic plaques, and an increase in left ventricular mass index (LVMI), posterior wall, and septal thickness and ejection fraction. Such effects persisted 12 months after treatment (12-month washout - 12 mo).

METHODS

We have studied the cardiovascular status (by echocardiography and carotid ultrasonography) of these subjects 60 months after completion of therapy (60-month washout - 60 mo).

RESULTS

Carotid IMT reduced significantly from 12 to 60 mo, returning to baseline (pre-therapy) value. The number of individuals with plaques was similar at 12 and 60 mo, remaining higher than pre-therapy. LVMI, relative posterior wall thickness, and septum thickness did not change between 12 and 60 mo, but absolute posterior wall increased from 12 to 60 mo. Systolic function, evaluated by ejection fraction and shortening fraction, was reduced at 60 mo in comparison with 12 mo returning to baseline levels. The E/A wave ratio (expression of diastolic function) decreased at 60 mo compared with both 12 mo and baseline.

CONCLUSIONS

In adults with lifetime congenital IGHD, the increase in carotid IMT elicited by GHRT was transitory and returned to baseline 5 years after therapy discontinuation. Despite this, the number of subjects with plaques remained stable at 60 mo and higher than at baseline.

Effects of depot growth hormone replacement on thyroid function and volume in adults with congenital isolated growth hormone deficiency

BACKGROUND

Conflicting data exist on the effects of GH replacement therapy (GHRT) on thyroid function and thyroid volume (TV) in GH-deficient (GHD) patients.

AIM

The aim of this study was to assess the effects of GHRT on thyroid function and TV in adults with congenital lifetime isolated GHD (IGHD).

SUBJECTS AND METHODS

We studied 20 GH-naïve adults with IGHD due to a homozygous mutation of the GHRH-receptor gene at baseline, after 6-month depot- GH replacement therapy (pGH), and 6-month washout (6mo). Total T(3), free T(4) (FT(4)), reverse T(3) (rT(3)), TSH, IGF-I, SHBG, and TV were measured; body surface area-corrected TV (CTV) was calculated.

RESULTS

IGF-I and T(3) increased pGH. T(3) levels remained elevated at 6mo. GHRT did not significantly change FT(4), rT(3), TSH, and SHBG. TV and CTV increased pGH and remained elevated at 6mo.

CONCLUSIONS

GHRT in IGHD adults caused an increase in serum T(3) levels and TV, suggesting an important role of the GH-IGF-I axis in thyroid function.

Effects on metabolic variables after 12-month treatment with a new once-a-week sustained-release recombinant growth hormone (GH: LB03002) in patients with GH deficiency

INTRODUCTION

GH substitution in GH deficiency (GHD) must be subcutaneously administered daily. A new sustained-release formulation of GH (LB03002) has been developed, which has to be injected once a week. As a substudy to the phase III study, we performed this prospective study to evaluate the influence of LB03002 on metabolic variables and hormones.

METHODS

Eleven patients with GHD [four women/seven men, 58 years (29-69 years)] without GH therapy were included in the study. Eight patients were treated with LB03002 for 12 months and three patients received placebo for 6 months followed by LB03002 for 6 months. A 3-h oral glucose tolerance test (OGTT) was performed at study entry and at study end. Additionally, IGF-I, cholesterol, LDL, HDL, triglycerides, leptin, ghrelin, HbA1c and C-peptide were measured. Body composition was evaluated by dual-energy X-ray absorptiometry (DXA), and waist/hip ratio (WHR) and waist/height (WHtR) ratio were measured by tape and scale.

RESULTS

Multiple of upper limit of normal (xULN) of IGF-I (0·23 (0·09-0·4) vs 0·71 (0·4-1·04), P < 0·01), WHR (0·98 (0·86-1·04) vs 1·01 (0·86-1·05), P < 0·05) and ghrelin levels [119·8 ng/l (67·7-266·6) vs 137 ng/l (67-289·5), P < 0·05] were significantly higher, whereas fat mass (FM) [34·7% (20·4-49·2) vs 32·4% (16·7-48·5), P < 0·05] and leptin [11·2 μg/l (3·3-55·7) vs 7·05 μg/l (2·4-54·3), P < 0·05] were significantly lower at study end. Glucose, insulin, HOMA-IR, ISI, HOMA-β, C-peptide and HbA1c during OGTT were not significantly different before and after GH substitution, neither were BMI, WHtR, bone mineral density and lipid variables.

CONCLUSION

Substitution with LB03002 showed statistically significant reduction in FM, which reduces leptin levels and increases ghrelin levels but does not seem to influence glucose and lipid metabolism.

Sustained-release delivery of octreotide from biodegradable polymeric microspheres

The study reports on the drug release behavior of a potent synthetic somatostatin analogue, octreotide acetate, from biocompatible and biodegradable microspheres composed of poly-lactic-co-glycolic acid (PLGA) following a single intramuscular depot injection. The serum octreotide levels of three Oakwood Laboratories formulations and one Sandostatin LAR(®) formulation were compared. Three formulations of octreotide acetate-loaded PLGA microspheres were prepared by a solvent extraction and evaporation procedure using PLGA polymers with different molecular weights. The in vivo drug release study was conducted in male Sprague-Dawley rats. Blood samples were taken at predetermined time points for up to 70 days. Drug serum concentrations were quantified using a radioimmunoassay procedure consisting of radiolabeled octreotide. The three octreotide PLGA microsphere formulations and Sandostatin LAR(®) all showed a two-phase drug release profile (i.e., bimodal). The peak serum drug concentration of octreotide was reached in 30 min for all formulations followed by a decline after 6 h. Following this initial burst and decline, a second-release phase occurred after 3 days. This second-release phase exhibited sustained-release behavior, as the drug serum levels were discernible between days 7 and 42. Using pharmacokinetic computer simulations, it was estimated that the steady-state octreotide serum drug levels would be predicted to fall in the range of 40-130 pg/10 μL and 20-100 pg/10 μL following repeat dosing of the Oakwood formulations and Sandostatin LAR(®) every 28 days and every 42 days at a dose of 3 mg/rat, respectively.

Multiple doses of pegylated long-acting growth hormone are well tolerated in healthy male volunteers and possess a potential once-weekly treatment profile

OBJECTIVES

Recombinant human growth hormone (rhGH) replacement therapy in children and adults currently requires daily subcutaneous injections for several years or lifelong. The current study examined safety, tolerability, pharmacokinetic and pharmacodynamic response parameters after single and multiple doses of a long-acting rhGH preparation (NNC126-0083).

DESIGN

Randomized, double-blinded, placebo-controlled, multiple-dose, dose-escalating (0·02, 0·04, 0·08 and 0·16 mg protein/kg), sequential dose group trial.

SUBJECTS

Forty adult Japanese healthy male volunteers (aged 20-45; body mass index: 18·0-27·0 kg/m(2)). Five groups (n = 8) were randomized to receive multiple doses of NNC126-0083 (n = 6) or placebo (n = 2).

METHODS

Primary outcome was safety, and tolerability of multiple doses of NNC126-0083 compared with placebo. Blood samples for the assessment of pharmacokinetics (PK) and pharmacodynamics response [insulin-like growth factor I (IGF-I) and IGF binding protein 3 (IGFBP-3)] were taken after multiple ascending doses.

RESULTS

NNC126-0083 was well tolerated and not associated with any local injection-site reactions or lipoatrophy. Following administration, NNC126-0083 levels increased rapidly and remained elevated for several days, returning to baseline before each weekly injection. Steady-state PK was achieved after the third dosing. A more than dose-proportional exposure was observed at the highest NNC126-0083 dose (0·16 mg protein/kg). A strong dose-dependent pharmacodynamic response in circulating concentrations of both IGF-I and IGFBP-3 compared with placebo (P < 0·0001) was observed during the administration of all doses.

CONCLUSIONS

Multiple administration of NNC126-0083 in healthy male volunteers indicates that NNC126-0083 has the potential for an efficacious, well-tolerated, once-weekly rhGH compound in the treatment of GH deficiency.

Genetic causes and treatment of isolated growth hormone deficiency-an update

Isolated growth hormone deficiency is the most common pituitary hormone deficiency and can result from congenital or acquired causes, although the majority of cases are idiopathic with no identifiable etiology. Known genes involved in the genetic etiology of isolated growth hormone deficiency include those that encode growth hormone (GH1), growth-hormone-releasing hormone receptor (GHRHR) and transcription factor SOX3. However, mutations are identified in a relatively small percentage of patients, which suggests that other, yet unidentified, genetic factors are involved. Among the known factors, heterozygous mutations in GH1 remain the most frequent cause of isolated growth hormone deficiency. The identification of mutations has clinical implications for the management of patients with this condition, as individuals with heterozygous GH1 mutations vary in phenotype and can, in some cases, develop additional pituitary hormone deficiencies. Lifelong follow-up of these patients is, therefore, recommended. Further studies in the genetic etiology of isolated growth hormone deficiency will help to elucidate mechanisms implicated in the control of growth and may influence future treatment options. Advances in pharmacogenomics will also optimize the treatment of isolated growth hormone deficiency and other conditions associated with short stature, for which recombinant human growth hormone is a licensed therapy.

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

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.

Quality of life in congenital, untreated, lifetime isolated growth hormone deficiency

Impaired quality of life (QoL) is commonly described as being associated with growth hormone (GH) deficiency (GHD), and beneficial effects of GH replacement therapy on QoL have been reported. However, most studies examined heterogeneous cohorts of patients GHD of varying etiologies, severities and age of onset. Most of these patients miss other pituitary hormones, whose replacement can also influence QoL. We studied the QoL of a homogeneous cohort of 20 adults with isolated GH deficiency (IGHD) due to the same mutation in the GH-releasing hormone receptor gene (IGHD, 10 men) using the Life Satisfaction Hypopituitarism Module (QLS-H), and compared them with 20 matched controls residing in the same community (CO, 10 men). Additionally, the IGHD group was evaluated after 6 months of treatment with bi-monthly depot GH, and after 12 months from its interruption. There was no difference in the total score of QoL (TSQoL) or in any of the nine categories that composes the questionnaire between IGHD and CO. Similar results were obtained when data were analyzed by sex. GH treatment only increased satisfaction with physical endurance, but did not cause an increase in the TSQoL. We conclude that in this unique population congenital, untreated, lifetime IGHD does not reduce QoL, and treatment with GH for 6 months only causes improvement in satisfaction with physical resistance.

Growth hormone receptor modulators

Growth hormone (GH) regulates somatic growth, substrate metabolism and body composition. Its actions are elaborated through the GH receptor (GHR). GHR signalling involves the role of at least three major pathways, STATs, MAPK, and PI3-kinase/Akt. GH receptor function can be modulated by changes to the ligand, to the receptor or by factors regulating signal transduction. Insights on the physico-chemical basis of the binding of GH to its receptor and the stoichiometry required for activation of the GH receptor-dimer has led to the development of novel GH agonists and antagonists. Owing to the fact that GH has short half-life, several approaches have been taken to create long-acting GHR agonists. This includes the pegylation, sustained release formulations, and ligand-receptor fusion proteins. Pegylation of a GH analogue (pegvisomant) which binds but not activate signal transduction forms the basis of a new successful approach to the treatment of acromegaly. GH receptors can be regulated at a number of levels, by modifying receptor expression, surface availability and signalling. Insulin, thyroid hormones and sex hormones are among hormones that modulate GHR through some of these mechanisms. Estrogens inhibit GH signalling by stimulating the expression of SOCS proteins which are negative regulators of cytokine receptor signalling. This review of GHR modulators will cover the effects of ligand modification, and of factors regulating receptor expression and signalling.

Pharmacokinetic and pharmacodynamic profile of a new sustained-release GH formulation, LB03002, in children with GH deficiency

OBJECTIVE

LB03002 is a novel, sustained-release recombinant human GH, developed for once-a-week s.c. injection. To evaluate the suitability for long-term GH replacement therapy in children with GH deficiency (GHD), the present study assessed the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of LB03002 at three doses.

STUDY DESIGN AND PATIENTS

The randomised, comparator-controlled, assessor-blinded, phase II study assessed 37 (24 boys, 13 girls) pre-pubertal, GH-naïve children with GHD, in 11 European centres, for PK and PD analyses. GH, IGF1 and IGFBP3 concentrations were measured following the last daily GH dose and the first and 13th once-a-week administration of LB03002 at doses of 0.2, 0.5 or 0.7 mg/kg.

RESULTS

GH C(max) values after the three doses of LB03002 were increased up to fourfold, with a clear dose proportionality. For each LB03002 dose, GH area under the concentration versus time curve did not increase from the first to 13th (month 3) administration, indicating no accumulation of circulating GH. IGF1 C(max) showed a progressive increase during LB03002 administration. Conversely, IGFBP3 showed a rapid increase in C(max). IGF1 SDS were fully normalised after 3 months of treatment, whereas IGFBP3 SDS were already in the normal range for all the three LB03002 dosages after 1 week.

CONCLUSIONS

At the doses used, LB03002 has a suitable profile for long-term treatment to promote growth in children with GHD. The quantitative changes in IGF1 and IGFBP3 indicate adequate stimulation of the IGF system by LB03002 and the pattern of increase is comparable with that seen in GHD children in a standard IGF1 generation test using daily GH.

Pereira F, Oliveira CRP, Pereira RMC, Farias CT, Vicente TAR, Salvatori R. Consequences of lifetime isolated growth hormone (GH) deficiency and effects of short-term GH treatment on bone in adults with a mutation in the GHRH-receptor gene

OBJECTIVE

Growth hormone (GH) influences bone mass maintenance. However, the consequences of lifetime isolated GH deficiency (IGHD) on bone are not well established. We assessed the bone status and the effect of 6 months of GH replacement in GH-naive adults with IGHD due to a homozygous mutation of the GH-releasing hormone (GHRH)-receptor gene (GHRHR).

PATIENTS AND METHODS

We studied 20 individuals (10 men) with IGHD at baseline, after 6 months of depot GH treatment, and 6 and 12 months after discontinuation of GH. Quantitative ultrasound (QUS) of the heel was performed and serum osteocalcin (OC) and C-terminal cross-linking telopeptide of type I collagen (ICTP) were measured. QUS was also performed at baseline and 12 months later in a group of 20 normal control individuals (CO), who did not receive GH treatment.

RESULTS

At baseline, the IGHD group had a lower T-score on QUS than CO (-1.15 +/- 0.9 vs.-0.07 +/- 0.9, P < 0.001). GH treatment improved this parameter, with improvement persisting for 12 months post-treatment (T-score for IGHD = -0.59 +/- 0.9, P < 0.05). GH also caused an increase in serum OC (baseline vs. pGH, P < 0.001) and ICTP (baseline vs. pGH, P < 0.01). The increase in OC was more marked during treatment and its reduction was slower after GH discontinuation than in ICTP.

CONCLUSIONS

These data suggest that lifetime severe IGHD is associated with significant reduction in QUS parameters, which are partially reversed by short-term depot GH treatment. The treatment induces a biochemical pattern of bone anabolism that persists for at least 6 months after treatment discontinuation.

[News options and preparations in growth hormone therapy]

In the last twenty years, recombinant human Growth hormone (hrGH) has been available for the treatment of Growth Hormone Deficiency (GHD) in children and more recently in adults. However, the necessity of daily injections compromises the patient's compliance. Attempts to improve this compliance includes the use of pens and needle free devices, once the infusion pumps, not always physiologic, are of restricted use. When growth is the purpose of treatment, daily subcutaneous hrGH is still the most indicated. Nevertheless the expansion of GH replacement to new uses and especially in adults will need new preparations. Nowadays, the oral secretagogues have not proved efficacy to be used in clinical practice and the slow- release preparations of GH and GH releasing hormone that could improve the patient's compliance will need to be studied considering long term efficacy and safety.

Congenital growth hormone (GH) deficiency and atherosclerosis: effects of GH replacement in GH-naive adults

BACKGROUND

GH deficiency (GHD) in adults is associated with increased abdominal adiposity and systolic blood pressure, total and low-density lipoprotein cholesterol, and C-reactive protein.

METHODS

We have studied the effects of 6-month GH replacement therapy in 20 adult members of a large Brazilian kindred with lifelong severe and isolated GHD due to a homozygous mutation in GHRH receptor gene (46 +/- 14.5 yr; 122 +/- 7.7 cm; 36.7 +/- 5.4 kg; 10 men). Subjects were studied at baseline, after 6-month bimonthly depot GH injections (Nutropin Depot; Genentech, Inc., South San Francisco, CA) [post GH (pGH)], and after 6- and 12-month washout.

RESULTS

Despite modest trough serum IGF-I increase, GH replacement therapy caused a decrease in skinfolds and in waist-hip ratio, with a rebound increase at 12 months. Total and low-density lipoprotein cholesterol were reduced pGH and returned to baseline at 6 months. High-density lipoprotein cholesterol increased pGH, but at 12 months was lower than baseline. A progressive increase in left ventricular mass index, posterior wall, and septum thickness occurred from pGH to 12 months, and of carotid intima-media thickness, from 6 to 12 months. Individuals were 6, 16, and 52 times more likely to have an atherosclerotic carotid plaque at pGH, 6 and 12 months, respectively, when compared with baseline.

CONCLUSION

In patients with lifetime isolated GHD, 6-month treatment with GH has reversible beneficial effects on body composition and metabolic profile, but it causes a progressive increase in intima-media thickness and in the number of atherosclerotic carotid plaques.

A ligand-receptor fusion of growth hormone forms a dimer and is a potent long-acting agonist

Cytokine hormones have a short plasma half-life and require frequent administration. For example, growth hormone replacement involves daily injections. In common with other cytokines, the extracellular domain of the growth hormone receptor circulates as a binding protein, which naturally prolongs the biological half-life of growth hormone. Here we have studied the biological actions of a ligand-receptor fusion of growth hormone and the extracellular domain of its receptor. The genetically engineered ligand-receptor fusion protein was purified from mammalian cell culture. In rats, the ligand-receptor fusion had a 300-times reduced clearance as compared to native growth hormone, and a single injection promoted growth for 10 d, far exceeding the growth seen after administration of native growth hormone. The ligand-receptor fusion forms a reciprocal, head-to-tail dimer that provides a reservoir of inactive hormone similar to the natural reservoir of growth hormone and its binding protein. In conclusion, a ligand-receptor fusion of cytokine to its extracellular receptor generates a potent, long-acting agonist with exceptionally slow absorption and elimination. This approach could be easily applied to other cytokines.

Prospects for the Development of Long-Acting Formulations of Human Somatropin

In healthy humans, growth hormone (GH) is secreted in distinct pulses with an underlying nyctohemeral pattern. Current forms of somatropin replacement are unable to closely mimic such a release pattern, but are still able to exert the beneficial action of GH. A limited number of short-term studies in rodents and humans suggest that longitudinal growth may be superior when somatropin is given with a pulsatile mode of administration, whereas hepatic insulin-like growth factor-I generation and beneficial changes in body composition appear to be equal or even enhanced with continuous somatropin administration.Recent developments in drug delivery technology have allowed the use of slow-release preparations of somatropin in humans. The most successful technology so far has been the encapsulation of somatropin molecules in poly(D,L-lactic-co-glycolic acid) biodegradable microspheres. Pharmacokinetic and pharmacodynamic data have been published on two such preparations; Nutropin Depot((R)) and hGH-Biosphere((R)). The latter has a superior release profile, but outcomes data from multicenter trials in both children and adults have been presented for the former: catch-up growth was observed in children, although to a lesser degree than historic comparative data obtained with the use of daily somatropin injections and the effects on metabolic derangements in GH-deficient patients appeared similar to those observed with daily injections. Improved sustained-release somatropin preparations will need further study of their long-term efficacy, but, if successful, will be highly attractive in terms of patient compliance and convenience.

A new sustained-release preparation of human growth hormone and its pharmacokinetic, pharmacodynamic and safety profile

OBJECTIVE

Adult GH replacement is currently given by daily subcutaneous (sc) injections. Recently, sustained-release (SR) preparations of GH have been developed, the preparations being characterized by a dominant early release, resulting in supraphysiological early GH peaks, and a rapid decline thereafter. We present data on a new SR GH preparation.

DESIGN

Phase I/II study of hGH-Biosphere(R) (SkyePharma AB, Malmo, Sweden), a new SR preparation of recombinant human GH in amylopectin microspheres coated with polylactide-coglycolide.

PATIENTS

Eight adults with severe, untreated GH deficiency (stimulated GH peaks between < 1 and 1.7 microg/l), aged 36.1 years (range 22-49 years) in good general health.

MEASUREMENTS

Pharmacokinetic (PK), pharmacodynamic (PD) and safety data over a period of 28 days.

RESULTS

The systemic and local tolerability of the drug was satisfactory, and no serious adverse events occurred. PK analysis showed a smaller early serum hGH peak followed by a broad sustained second peak of hGH (C(max) 1.20 microg/l at 7.2 days), and hGH levels were maintained above baseline for at least 14 days. The mean GH level never exceeded 1.1 microg/l, making the GH fluctuations comparable to continuous sc infusion. Resultant IGF-I concentrations were characterized by sustained elevation at a level near C(max) of 103 microg/l (at t(max) of 9.7 days), equal to an SD score of +0.8. IGF-I generation per administered GH was more efficient compared with reports of other SR preparations.

CONCLUSION

hGH-Biosphere(R) is a well-tolerated SR GH preparation with superior efficacy in achieving target IGF-I levels without causing supraphysiological GH concentrations. Our data suggest the suitability of this preparation for longer-term trials in adults with injection frequencies of no more than once every 2-3 weeks.

The production of protein-loaded microparticles by supercritical fluid enhanced mixing and spraying

In this study, we use supercritical carbon dioxide as a processing medium for the fabrication of poly(DL-lactic acid) P(DLLA) microparticles that encapsulate a protein material. We have previously demonstrated that this polymer and a dry powder of a protein can be mixed under supercritical carbon dioxide conditions (above 31.1 degrees C and 73.8 bar) and that the protein component retains its biological activity. In this paper, we progress the work to demonstrate that the plasticized polymer and dry powder protein mixture can be sprayed to form solid polymer particles that encapsulate the protein. Particle size range is between 10 and 300 microm after spraying. Ribonuclease A and lysozyme were encapsulated in the polymer without significant loss of enzymatic activity. Biological assays of insulin and calcitonin confirm retention of activity after fabrication of the microparticles and release of the peptides/proteins.

Growth hormone replacement for adult growth hormone deficiency

Growth hormone deficiency (GHD) in childhood causes growth retardation, short stature and significant impairment of adult height. Growth hormone (GH) has been given successfully to these children for > 40 years but only since the introduction of recombinant DNA technology, has enough GH been available for paediatric needs and also for other indications. Adults with pituitary disease and hypopituitarism commonly develop GHD. Adult GHD is associated with an array of body composition alterations and metabolic abnormalities, as well as impaired physical performance and psychological well-being. None of these abnormalities are pathogenic for GHD but they constitute a characteristic clinical syndrome. GH substitution for adult GHD has been approved since 1996 in the US and most Western countries and since then, the clinical experience with this novel therapeutic modality is exponentially increased. GH replacement in this population has resulted in considerable clinical benefits. This article reviews the therapeutic principles, available GH formulations and current treatment guidelines for adult patients with GHD.

Solvent exchange method: a novel microencapsulation technique using dual microdispensers

PURPOSE

A new microencapsulation method called the "solvent exchange method" was developed using a dual microdispenser system. The objective of this research is to demonstrate the new method and understand how the microcapsule size is controlled by different instrumental parameters.

METHOD

The solvent exchange method was carried out using a dual microdispenser system consisting of two ink-jet nozzles. Reservoir-type microcapsules were generated by collision of microdrops of an aqueous and a polymer solution and subsequent formation of polymer films at the interface between the two solutions. The prepared microcapsules were characterized by microscopic methods.

RESULTS

The ink-jet nozzles produced drops of different sizes with high accuracy according to orifice size of a nozzle, flow rate of the jetted solutions, and forcing frequency of the piezoelectric transducers. In an individual microcapsule, an aqueous core was surrounded by a thin polymer membrane; thus, the size of the collected microcapsules was equivalent to that of single drops.

CONCLUSIONS

The solvent exchange method based on a dual microdispenser system produces reservoir-type microcapsules in a homogeneous and predictable manner. Given the unique geometry of the microcapsules and mildness of the encapsulation process, this method is expected to provide a useful alternative to existing techniques in protein microencapsulation.

Diagnosis and treatment of hypopituitarism: an update

Diagnosis and treatment of patients with hypopituitarism needs careful clinical evaluation and individual optimization. Symptoms of hypopituitarism are variable, often insidious in onset and dependent on the degree of hormone deficiency. Diagnosis of hypopituitarism can be straightforward by measuring reduced basal hormone levels. Frequently, dynamic stimulation tests are indicated in equivocal basal hormone levels or to diagnose partial hormone deficiencies. Knowledge of the use and limitations of these dynamic tests is mandatory for proper interpretation. Hormone replacement therapy should be individualized, taking into account possible interactions. Persisting symptoms and reduced quality of life are frequently reported, explained by, at least in part, intrinsic imperfections of hormone replacement strategies in mimicking normal hormone secretion. In the present overview, the principles of diagnosis and treatment of hypopituitarism are discussed.