Five-year follow-up of growth hormone antibodies in growth hormone deficient children treated with recombinant human growth hormone

Short stature related to Growth Hormone Insensitivity (GHI) in childhood

Linear growth during childhood is the result of the synergic contribution of different factors. The best growth determinant system during each period of life is represented by the growth hormone-insulin-like growth factor axis (GH-IGF), even if several other factors are involved in normal growth. Within the broad spectrum of growth disorders, an increased importance has been placed on growth hormone insensitivity (GHI). GHI was reported for the first time by Laron as a syndrome characterized by short stature due to GH receptor (GHR) mutation. To date, it is recognized that GHI represents a wide diagnostic category, including a broad spectrum of defects. The peculiar characteristic of GHI is the low IGF-1 levels associated with normal or elevated GH levels and the lack of IGF-1 response after GH administration. Recombinant IGF-1 preparations may be used in the treatment of these patients.

Analysis of N15-rat growth hormone after incubation with rat subcutaneous tissue and immune cells using ultra-pressure chromatography-mass spectrometry

Therapeutic proteins (TPs) are exposed to various immune cells like macrophages and neutrophils, especially after subcutaneous (SC) administration. It is well known that the immune cells can generate reactive oxygen species (ROS) and this may lead to oxidation of TPs. The oxidation can occur in the SC tissue after SC administration, during distribution to the immune organs like lymph nodes and spleen, and even in the blood circulation. The oxidation can lead to alteration of their pharmacokinetics and efficacy. Therefore, it is important to study the oxidation of TPs in the biological matrices using ultra-pressure chromatography-mass spectrometry. Rat growth hormone (rGH) was selected as a test protein due to its similarity with human growth hormone (hGH), which is widely used for treatment of growth hormone deficiency. In this manuscript, we have summarized sample processing strategy and ultra-pressure chromatography-mass spectrometry methodology to identify rGH and its degradation products after ex-vivo incubation with rat SC tissue, and in vitro incubation with rat splenocytes and canine peripheral blood mononuclear cells (cPBMCs) as a model foreign host species. We did not observe oxidation of rGH in these biological matrices. This could be due to very minor yields of oxidation products, lack of sensitivity of the mass spectrometry method, loss of protein during sample processing, rapid turnover of oxidized protein or a combination of all factors.

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

BACKGROUND

The occurrence of antidrug antibodies is common in children treated with recombinant human growth hormone (rhGH). However, their clinical significance is unclear.

OBJECTIVE

This study aimed to examine the clinical significance of anti-GH antibodies by analyzing the phenotype of patients who tested positive in relation to the quantity of anti-GH antibodies.

METHOD

In this laboratory-based retrospective study encompassing a time span of 6 years, all positive samples were identified, and senders were contacted. Anti-GH antibodies were measured using a radioprecipitation assay; positive samples underwent a confirmatory assay.

RESULTS

Out of a total of 104 samples from 66 patients, positive test results were found in 28 samples from 13 patients. Clinical data were available from all but one. The group with positive test results comprised 6 patients with a normal response to GH provocative tests (group A) and 6 with an insufficient response or with isolated GH deficiency (IGHD) type 1A (group B). Diagnoses in group A were neurosecretory dysfunction, bioinactive GH syndrome and constitutional delay of growth and puberty. Diagnoses in group B were IGHD type 1A, septo-optic dysplasia, and cerebral midline defect with multiple pituitary hormone deficiency. Insufficient growth response to rhGH was absent except in one sibling pair with IGHD type 1A and a patient with cerebral midline defect. These patients had the highest concentrations of anti-GH antibodies.

CONCLUSIONS

The biological significance of anti-GH antibodies seems to be limited to patients with high concentrations of anti-GH antibodies. For all other patients, we recommend a careful "wait and see" strategy and monitoring antibody titers.

Effect of Iron Oxide Nanoparticles on the Oxidation and Secondary Structure of Growth Hormone

Oxidation of therapeutic proteins (TPs) can lead to changes in their pharmacokinetics, biological activity and immunogenicity. Metal impurities such as iron are known to increase oxidation of TPs, but nanoparticulate metals have unique physical and chemical properties compared to the bulk material or free metal ions. Iron oxide nanoparticles (IONPs) may originate from equipment used in the manufacturing of TPs or from needles during injection. In this study, the impact of IONPs on oxidation of a model protein, rat growth hormone (rGH), was investigated under chemical stress. Hydrogen peroxide (H2O2)- and 2,2'-azobis (2-methylpropionamidine) dihydrochloride oxidized methionine residues of rGH, but unexpectedly, oxidation was suppressed in the presence of IONPs compared to a phosphate buffer control. Fourier transform infrared spectroscopy indicated splitting of the α-helical absorbance band in the presence of IONPs, whereas circular dichroism spectra showed a reduced α-helical contribution with increasing temperature for both rGH and rGH-IONP mixtures. The results collectively indicate that IONPs can increase the chemical stability of rGH by altering the kinetics and preference of amino acid residues that are oxidized, although the changes in protein secondary structure by IONPs may lead to alterations of physical stability.

Molecular genetics of growth hormone deficient children: correlation with auxology and response to first year of growth hormone therapy

BACKGROUND

With the paucity of available literature correlating genetic mutation and response to treatment, we aimed to study the genetic makeup of children with growth hormone (GH) deficiency in Western India and correlate the mutation with auxology and response to GH treatment at end of 1 year.

METHODS

Fifty-three (31 boys and 22 girls) children with severe short stature (height for age z-score <-3) and failed GH stimulation test were studied. Those having concomitant thyroid hormone or cortisol deficiencies were appropriately replaced prior to starting GH treatment. A magnetic resonance imaging (MRI) brain scan was done in all. Genetic mutations were tested for in GH1, GHRH, LHX3, LHX4 and PROP1, POU1F1 and HESX1 genes.

RESULTS

Mean age at presentation was 9.7±5.1 years. Thirty-seven children (Group A) had no genetic mutation detected. Six children (Group B) had mutations in the GH releasing hormone receptor (GHRHR) gene, while eight children (Group C) had mutation in the GH1 gene. In two children, one each had a mutation in PROP1 and LHX3. There was no statistically significant difference in baseline height, weight and BMI for age z-score and height velocity for age z-score (HVZ). HVZ was significantly lower, post 1 year GH treatment in the group with homozygous GH1 deletion than in children with no genetic defect.

CONCLUSIONS

Response to GH at the end of 1 year was poor in children with the homozygous GH1 deletion as compared to those with GHRHR mutation or without a known mutation.

Effect of growth hormone and IgG aggregates on dendritic cells activation and T-cells polarization

Patients treated with therapeutic biological products (BP) frequently develop anti-drug antibodies (ADA) with potential neutralizing capacities leading to loss of clinical response or serious side effects. BP aggregates have been suggested to promote immunogenicity, thus enhancing ADA production. Dendritic cells (DC) are key effectors in T-cell and B-cell fates, and the subsequent generation of immunogenicity. The objective of this work was to determine if BP aggregates can participate to DC maturation and T-cell activation. We compared aggregates from three different proteins: human growth hormone (hGH), Rituximab, a chimeric anti-CD20 antibody and a serum-purified human IgG1. All three proteins underwent a stir stress, generating comparable populations of aggregated particles. Maturation of human monocyte-derived DC (moDC) upon exposure to native BPs or aggregates was evaluated in vitro. Results showed that hGH aggregates induced an increased expression of moDC co-stimulation markers, and augmented levels of IL-6, IL-8, IL-12p40, CCL2, CCL3, CCL4 and CXCL10. Both antibodies aggregates were also able to modify DC phenotype, but cytokine and chemokine productions were seen only with IL-6, IL-8, IL-12p40 and CXCL10. Aggregates-treated moDC enhanced allogenic T-cell proliferation and cytokines production, suggesting Th1 polarization with hGH, and mixed T-cell responses with antibodies aggregates. These results showed that BP aggregates provoked DC maturation, thus driving adaptive T-cell responses and polarization.

Growth Hormone Antibodies Formation in Patients Treated with Recombinant Human Growth Hormone

Human growth hormone (hGH) is normally produced by acidophilic cells of the anterior lobe of the pituitary gland. Recombinant DNA technology has made it possible to produce rhGH. There have been reports of immunological reactions in patients treated with rhGH. For this reason, it is necessary to check sera of patients for presence of antibody against rhGH. Forty-seven children were treated for up to 6 months with recombinant human growth hormone (rhGH-Novo), 0.1 IU/Kg body weight, subcutaneously, three times weekly. The magnitude of growth response was similar to those expected from clinical experience with pituitary growth hormone. We examined sera for specific antibodies against rhGH by ELISA methods. Four patients developed serum antibodies against growth hormone. The analysis of these four sera by Dot blotting method also showed presence of antibodies against rhGH. In the sera of treated patients, pre-incubated with different concentration of rhGH, specific antibodies were detected by neutralizing assay. This finding was confirmed by ELISA technique. In conclusion, the main concern with anti-GH antibodies could be their ability to neutralize circulating growth hormone and inhibition its growth promoting effect.

Growth hormone insensitivity: diagnostic and therapeutic approaches

INTRODUCTION

Growth hormone resistance defines several genetic (primary) and acquired (secondary) pathologies that result in completely or partially interrupted activity of growth hormone. An archetypal disease of this group is the Laron-type dwarfism caused by mutations in growth hormone receptors. The diagnosis is based on high basal levels of growth hormone, low insulin like growth factor-I (IGF-1) level, unresponsiveness to IGF generation test and genetic testing. Recombinant IGF-1 preparations are used in the treatment

CONCLUSION

In this article, clinical characteristics, diagnosis and therapeutic approaches of the genetic and other diseases leading to growth hormone insensitivity are reviewed.

[Recombinant granulocyte-colony stimulating factor (filgrastim): optimization of conditions of isolation and purification from inclusion body]

We developed a unified process platform for two recombinant human GCSF medicines--one with the non-prolonged and the other with prolonged action. This unified technology led to a simpler and cheaper production while introduction of the additional pegylation stage to the technological line eased obtaining of the medicines with different action and allowed to standardize technological process documenting according to GMP requirements.

Recombinant murine growth hormone particles are more immunogenic with intravenous than subcutaneous administration

Evaluation and mitigation of the risk of immunogenicity to protein aggregates and particles in therapeutic protein products remains a primary concern for drug developers and regulatory agencies. To investigate how the presence of protein particles and the route of administration influence the immunogenicity of a model therapeutic protein, we measured the immune response in mice to injections of formulations of recombinant murine growth hormone (rmGH) that contained controlled levels of protein particles. Mice were injected twice over 6 weeks with rmGH formulations via the subcutaneous, intraperitoneal, or intravenous (i.v.) routes. In addition to soluble, monomeric rmGH, the samples prepared contained either nanoparticles of rmGH or both nano- and microparticles of rmGH.The appearance of anti-rmGH IgG1, IgG2a, IgG2b, IgG2c, and IgG3 titers following the second injection of both preparations implies that multiple mechanisms contributed to the immune response. No dependence of the immune response on particle size and distribution was observed. The immune response measured after the second injection was most pronounced when i.v. administration was used. Despite producing high anti-rmGH titers mice appeared to retain the ability to properly regulate and use endogenous growth hormone.

Preparing for Subsequent Entry Biologies in Dermatology and Rheumatology in Canada

Background:

Patents on several biologies will expire in Canada in the coming years. As they expire, applications to market subsequent entry biologies (SEBs) may be filed in Canada.

Objective:

To provide an understanding of the regulatory pathway and types of trials used for SEB authorization in Canada.

Methods:

Health Canada's draft guidance on SEBs was reviewed in regards to key issues and challenges in the development and authorization of SEBs.

Results:

Health Canada states that SEBs are not “generic biologies” and their authorization is not a declaration of pharmaceutical or therapeutic equivalence to the originator. The agency recommends that physicians make well-informed decisions regarding therapeutic interchange.

Conclusions:

Decisions on how to determine the place of SEBs in clinical practice for biologic-naive patients and those already receiving biologies should be made on a case-by-case basis, considering the patient's needs, the characteristics of the biologic required, and the clinical development programs of the applicable SEB.

Development of antibodies against growth hormone (GH) during rhGH therapy in a girl with idiopathic GH deficiency: a case report

A 12.5-year-old Italian girl was referred to our institute for progressive growth failure from the age of 6 years, with a height of 128.2 cm (-3.37 SDS) and a bone age of 9 years. Endocrinological evaluation revealed a partial growth hormone deficiency (GHD) and GH therapy was started at a dosage of 0.25 mg/kg/week. During the first 3 years, she showed an increase in growth rate and experienced pubertal development onset. Then a poor growth rate (2 cm/year=0.43 SDS) was observed, notwithstanding an increase in GH dosage (0.35 mg/kg/week) and good compliance. We found a positive anti-GH antibody titre (1:1850, cutoff 1/100), confirmed 6 months later (1:2035); the antibodies had low binding capacity (0.63 μg/mL) and were only partially capable of inhibiting the GH effect. However, GH treatment was discontinued, and after 3 months the antibody titre decreased (1:950). In conclusion, we suggest evaluation of anti-GH antibodies in GH-treated idiopathic GHD children in whom growth response decreases after some years of therapy.

Immunogenicity of biotherapeutics-an overview

With the recent increase in the approval and use of biotherapeutics in clinical practice, management of the development of anti-drug antibodies (ADA) has become a key issue for effective long-term use of these drugs. In most instances, the clinical benefit derived from the use of the therapeutics outweighs the risk of developing ADA. In rare instances, however, safety issues accompany development of ADA. Although it is unclear why certain individuals generate an immune response while others tolerate the drug, growing experience from the clinic has facilitated a better appreciation of many patient-, disease- and product-related factors that contribute to immunogenicity. Furthermore, improvements in protein production, purification and delivery methods along with use of humanized or fully human recombinant proteins have helped to reduce the rates of immunogenicity considerably. This document provides an overview of the scientific reasons for developing an immunogenic response, factors that contribute to the immunogenicity of biotherapeutics, clinical impact of immunogenicity and general strategies used to manage this risk.

Growth hormone: the expansion of available products and indications

Growth hormone is a widely used hormone. This article describes its historical use, current indications and studies for possible future uses.

Emerging options in growth hormone therapy: an update

Growth hormone (GH) was first used to treat a patient in 1958. For the next 25 years it was available only from cadaver sources, which was of concern because of safety considerations and short supply. In 1985, GH produced by recombinant DNA techniques became available, expanding its possible uses. Since that time there have been three indications approved by the US Food and Drug Administration (FDA) for GH-deficiency states and nine indications approved for non-GH-deficiency states. In 2003 the FDA approved GH for use in idiopathic short stature (ISS), which may indirectly cover other diagnoses that have short stature as a feature. However, coverage for GH therapy is usually more reliably obtainable for a specific indication, rather than the ISS indication. Possible future uses for GH therapy could include the treatment of syndromes such as Russell-Silver syndrome or chondrodystrophy. Other non-short-stature indications could include wound healing and burns. Other uses that have been poorly studied include aging and physical performance, in spite of the interest already shown by elite athletes in using GH. The safety profile of GH developed over the past 25 years has shown it to be a very safe hormone with few adverse events associated with it. The challenge for the future is to follow these patients into adulthood to determine whether GH therapy poses any long-term risks.

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.

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.

Managing idiopathic short stature: role of somatropin (rDNA origin) for injection

Idiopathic short stature (ISS) is a term that describes short stature in children who do not have growth hormone (GH) deficiency and in whom the etiology of the short stature is not identified. Between 1985 and 2000, more than 40 studies were published regarding GH therapy for ISS. Only 12 of these had data to adult height, of which only 4 were controlled studies. A subsequent placebo-controlled study that followed subjects to adult height indicated that there was a gain of 3.7–7.5 cm in height with GH treatment. In 2003, the US Federal Drug Administration (FDA) approved GH for treatment of short stature. Even before FDA approval, patients with ISS made up about 20% of patients in GH databases, which is largely unchanged since FDA approval. There remains some controversy as to whether GH should be used to treat ISS. This controversy centers on the fact that there has been no definitive demonstration that short stature results in a disadvantage or problems with psychological adjustment, and thus, no demonstration that GH therapy results in improvement in quality of life.

Resistance to leptin-replacement therapy in Berardinelli-Seip congenital lipodystrophy: an immunological origin

CONTEXT

Recently, in a 4-month proof-of-concept trial, beneficial metabolic effects were reported in non-diabetic children with Berardinelli-Seip congenital lipodystrophy (BSCL); this information prompted us to hypothesize that long-term leptin-replacement therapy might improve or reverse the early complications of the disease in these patients.

PATIENTS AND METHODS

A 28-month trial was implemented in eight patients. Efficacy assessment was based on a decrease in serum triglyceride concentrations, and/or a decrease in liver volume and/or an increase in insulin sensitivity of at least 30% respectively. The response was defined as follows: total (3/3 positive criteria), partial (1 or 2/3), or negative (0/3). Anti-leptin antibodies were measured with a radiobinding assay, and a neutralizing effect was assessed in primary cultures of embryonic neurons incubated with an apoptotic agent (N-methyl-D-aspartate) and the patient serum, with or without leptin.

RESULTS

A negative or partial response to treatment was observed in five of eight patients even when leptin dosages were increased. A displaceable leptin binding was detectable in all patients after 2 months of treatment. At 28 months, binding was higher in the patients with a negative response than in the total responders, and it paralleled both the increase in leptin dosage and serum leptin concentrations. Co-incubation of embryonic neurons with serum from two patients with a negative response inhibited the neuroprotective effect of leptin.

CONCLUSION

Under leptin therapy, patients with BSCL may develop a resistance to leptin, which could be partly of immunological origin, blunting the previously reported beneficial effects.

Somatotropin in the treatment of growth hormone deficiency and Turner syndrome in pediatric patients: a review

Growth hormone (GH), also known as somatotropin, is a peptide hormone that is synthesized and secreted by the somatotrophs of the anterior pituitary gland. The main action of GH is to stimulate linear growth in children; however, it also fosters a healthy body composition by increasing muscle and reducing fat mass, maintains normal blood glucose levels, and promotes a favorable lipid profile. This article provides an overview of the normal pathophysiology of GH production and action. We discuss the history of GH therapy and the development of the current formulation of recombinant human GH given as daily subcutaneous injections. This paper reviews two of the longest standing FDA-approved indications for GH treatment, GH deficiency and Turner syndrome. We will highlight the pathogenesis of these disorders, including presentations, presumed mechanism(s) for the associated short stature, and diagnostic criteria, with a review of stimulation test benefits and pitfalls. This review also includes current recommendations for GH therapy to help maximize final height in these children, as well as data demonstrating the efficacy and safety of GH treatment in these populations.

Growth hormone: the expansion of available products and indications

Growth hormone is a widely used hormone. This article describes its historical use, current indications and studies for possible future uses.

Immunogenicity of therapeutic proteins. Part 3: Impact of manufacturing changes

Immunogenicity of biopharmaceuticals relates to the intrinsic complexity of proteins as well as the complexities of the manufacturing process. The manufacture of biopharmaceuticals involves a number of complex processing steps designed to create a highly pure, stable, safe, and effective product. The process often lasts many months and can be divided into seven stages - host cell development, master cell bank establishment, protein production, purification, analysis, formulation, and storage and handling. Even minor variations at any of these stages can lead to clinically relevant changes in efficacy and/or safety of the end product. Due to the complexity of the process and the inherently unstable nature of proteins outside the body, compositional changes can occur, leading to decreased biological activity, alteration of molecular structure, and possible increased risk of host immune responses following administration. Examples are discussed whereby immunogenicity associated with some of these changes has occurred with potentially serious clinical consequences.

Massspectrometrical analysis of recombinant human growth hormone Norditropin® reveals amino acid exchange at M14_V14 rhGH

Recombinant human growth hormone (rhGH) is used for the treatment of several disorders. Structural integrity of rhGH is of critical importance for its clinical use and modifications thereof may act as markers in situations such as rhGH doping, as illegal rhGH-abuse in sports is of increasing interest. In the current study we investigated homogeneity of Norditropin, a recombinant human growth hormone frequently used in medicine, expressed in E. coli, strain MC1061. The most recent proteomics technologies including 2-DE, MALDI-MS followed by MALDI-MS/MS and LC-MS followed by LC-MS/MS were used for the characterisation of rhGH. MALDI-TOF-TOF and electrospray LC-MS analysis revealed one major protein with an average molecular mass of 22 126.0 Da and some additional minor components. Electrospray LC-MS/MS of the enzymatically digested Norditropin sample showed deamidation of N(12)N(149) and N(159), oxidation of M(14), M(125) and M(170) and one amino acid exchange V(14) for M(14) present in <1% of Norditropin. While deamidation and oxidation may be due to technical reasons, the single amino acid exchange may reflect infidelity of translation rather than codon usage and copy editing by E. coli.

A method for rapidly confirming protein N-terminal sequences by matrix-assisted laser desorption/ionization mass spectrometry

The N-terminal sequence is important for the identification of a protein and the confirmation of its N-terminal processing. Although mass spectrometry (MS) is a sensitive and high-throughput method to sequence and identify peptides and proteins, N-terminal peptides, diluted among most of the peptides that do not originate at the N-termini, are not easy to identify directly with MS. To develop a simple and rapid method to identify and sequence the N-terminal peptide of a protein, a new strategy based on specific sulfonation of terminal amino groups and selective monitoring of the sulfonated peptide was introduced. After a protein had been guanidinated, 2-sulfobenzoylated, and reduced, it was digested with trypsin and analyzed by MS. Because of the strong acidity of sulfonic groups and the specific sulfonation of alpha-amino groups, the sulfonated N-terminal peptide dominated as base peak in the negative mode peptide mass fingerprint (PMF) and was easy to identify. The N-terminal peptide was then selected as precursor ion for tandem mass spectrometric (MS/MS) analysis. Four proteins were tested with this method and their N-terminal peptides were successfully recognized and sequenced. The results suggest that the addition of a sulfonic acid group facilitates the identification and de novo sequencing of N-terminal peptides.

An IL-7 fusion protein that shows increased thymopoietic ability

The role of IL-7 during thymopoiesis has led to it being the focus of a number of therapeutic interventions. However, its small size and pleiotropic nature present problems for thymus-directed therapies. We have created a fusion molecule between the extracellular N-terminal domain of CCR9 and IL-7, which has the potential to overcome these difficulties. This novel fusion protein retains the thymopoietic activity of IL-7 and the ligand-binding ability of CCR9. As a thymopoietic agent, compared with IL-7, it shows an enhanced retention in the thymus, increased de novo T cell production, and increased thymic output. Old mice receiving the fusion protein show improved CD8 T cell responses and reduced viral load after infection with influenza virus compared with those receiving IL-7. This chimeric molecule offers a novel therapeutic strategy that may result in the production of an effective immunorestorative agent.

Mass spectrometrical analysis of recombinant human growth hormone (Genotropin(R)) reveals amino acid substitutions in 2% of the expressed protein

BACKGROUND: The structural integrity of recombinant proteins is of critical importance to their application as clinical treatments. Recombinant growth hormone preparations have been examined by several methodologies. In this study recombinant human growth hormone (rhGH; Genotropin(R)), expressed in E. coli K12, was structurally analyzed by two-dimensional gel electrophoresis and MALDI-TOF-TOF, LC-MS and LC-MS/ MS sequencing of the resolved peptides. RESULTS: Electrospray LC-MS analysis revealed one major protein with an average molecular mass of 22126.8 Da and some additional minor components. Electrospray LC-MS/MS evaluation of the enzymatically digested Genotropin(R) sample resulted in the identification of amino acid substitutions at the residues M14, M125, and M170; di-methylation of K70 (or exchange to arginine); deamidation of N149, and N152, and oxidation of M140, M125 and M170. Peak area comparison of the modified and parental peptides indicates that these changes were present in ~2% of the recombinant preparation. CONCLUSION: Modifications of the recombinant human growth hormone may lead to structural or conformational changes, modification of antigenicity and development of antibody formation in treated subjects. Amino acid exchanges may be caused by differences between human and E. coli codon usage and/or unknown copy editing mechanisms. While deamidation and oxidation can be assigned to processing events, the mechanism for possible di-methylation of K70 remains unclear.

Strategies for detection, measurement and characterization of unwanted antibodies induced by therapeutic biologicals

An important aspect of evaluating the safety of therapeutic biologicals is the assessment of the unwanted immunogenicity of such biologicals in recipients. Properly planned immunogenicity studies with appropriately devised strategies are critical if valid conclusions concerning the unwanted immunogenicity are to be derived. Such studies need to be conducted using carefully selected and validated procedures. Several techniques are available for detection and measurement of immunogenicity including immunoassays, radioimmunoprecipitation assays (RIPAs), surface plasmon resonance (SPR) and bioassays. A combination of methods for characterization of the induced antibodies is usually necessary for a detailed understanding of the type(s) of antibodies generated against a therapeutic product. This review considers the benefits and limitations of the various techniques available for antibody detection and outlines a strategy for the assessment of unwanted immunogenicity of therapeutic products.

Growth hormone receptor antagonists: discovery, development, and use in patients with acromegaly

An understanding of the events that occur during GH receptor (GHR) signaling has facilitated the development of a GHR antagonist (pegvisomant) for use in humans. This molecule has been designed to compete with native GH for the GHR and to prevent its proper or functional dimerization-a process that is critical for GH signal transduction and IGF-I synthesis and secretion. Clinical trials in patients with acromegaly show GHR blockade to be an exciting new mode of therapy for this condition, and pegvisomant may have a therapeutic role in diseases, such as diabetes and malignancy, in which abnormalities of the GH/IGF-I axis have been observed. This review charts the discovery and development of GHR antagonists and details the experience gained in patients with acromegaly.

Pegvisomant: a growth hormone receptor antagonist for the treatment of acromegaly

Growth hormone receptor (GHR) dimerization is a prerequisite to the generation of growth hormone (GH) action. Pegvisomant is a GHR antagonist that has been designed to bind to the GHR at the cell surface and hence block this process. Initial studies suggest that pegvisomant is a highly effective antagonist of GH action in patients with acromegaly. The blockade of GH action, rather than the inhibition of pituitary GH secretion, represents a novel concept in the medical management of acromegaly. In this review, the design, efficacy, challenges and future role of pegvisomant are discussed.

Growth hormone receptor antagonists therapy for acromegaly

Knowledge of the interaction between growth hormone (GH) and the growth hormone receptor (GHR) has led to the rational design of a GHR antagonist. An analogue of GH able to block the action of GH at the cellular level offers greater specificity of effect compared with current medical therapies and is not dependent on tumour characteristics. This chapter reviews the interaction between GH and the GHR, and discusses the outstanding issues regarding GHR antagonist therapy in acromegaly.