Efficacy and Safety of Weekly Somatrogon vs Daily Somatropin in Children With Growth Hormone Deficiency: A Phase 3 Study

Efficacy and Safety of Somapacitan Relative to Somatrogon and Lonapegsomatropin in Pediatric Growth Hormone Deficiency: Systematic Literature Review and Network Meta-analysis

INTRODUCTION

Since direct comparisons of long-acting growth hormones (LAGHs) are lacking, analyses were performed to indirectly compare the efficacy and safety of somapacitan versus somatrogon and lonapegsomatropin in children with growth hormone deficiency (GHD).

METHODS

A systematic literature review (SLR) identified studies of once-weekly LAGHs for the treatment of pediatric GHD. Indirect comparisons (ICs) using a Bayesian hierarchical network meta-analysis and a random effects model were performed using daily growth hormone (GH) 0.034 mg/kg/day (base case) or 0.024-0.034 mg/kg/day (alternative analyses) as the common comparator to compare height outcomes to 52 weeks [annualized height velocity, height velocity standard deviation score (SDS), and height SDS]. Identified evidence did not allow IC of safety or longer-term efficacy outcomes so these were qualitatively described.

RESULTS

The SLR identified two somapacitan trials, three somatrogon trials (one included in alternative analyses only), and one lonapegsomatropin trial comparing the LAGH with daily GH in treatment-naïve pre-pubertal children for IC. ICs revealed no differences at 52 weeks between somapacitan versus somatrogon and lonapegsomatropin, as well as daily GH, with respect to all growth outcomes considered in children with GHD. All three LAGHs had sustained efficacy and were generally well tolerated, with comparable efficacy and safety to daily GH, with the exception of observed injection site pain for somatrogon.

CONCLUSION

No efficacy and safety differences were identified in comparisons of once weekly somapacitan versus somatrogon and lonapegsomatropin, as well as daily GH. All treatments were generally well tolerated, with the exception of observed injection site pain for somatrogon.

Food and Drug Administration (FDA) Approvals of Biological Drugs in 2023

An increase in total drug (small molecules and biologics) approvals by the Food and Drug Administration (FDA) was seen in 2023 compared with the previous year. Cancer remained the disease most targeted by monoclonal antibodies (mAbs), followed by autoimmune conditions. Our data reveal the prevalence of approvals for biologics even during years when the total number of authorizations was low, such as in 2022. Over half the drugs that received the green light in 2023 benefited from expedited programs, as the incidence of many diseases increased. In addition, over half of the biologics approved received Orphan Drug Designation from the FDA. This narrative review delves into details of the most significant approvals in 2023, including mAbs, enzymes, and proteins, explaining their mechanisms of action, differences from previous drugs, placebo, and standards of care, and outcomes in clinical trials. Given the varying number of drugs authorized annually by the U.S. health authority, this review also examines the limits of external influences over the FDA's decisions and independence regarding drug approvals and withdrawals.

Impact of Daily Growth Hormone Adherence on Height Velocity Among Children With Growth Hormone Deficiency (GHD)

OBJECTIVE

To describe adherence to daily somatropin treatment and impact on height velocity within 1 year of treatment start among patients with pediatric growth hormone deficiency in a real-world US population.

METHODS

This retrospective cohort study included pediatric patients aged ≥3 years to <16 years with pediatric growth hormone deficiency prescribed somatropin by a pediatric endocrinologist at a US-based center of excellence between January 1, 2015 and December 31, 2020. Patient data were collected using hospital electronic health records linked to a specialty pharmacy patient prescription records. Adherence, evaluated over 12 months, was measured using the proportion of days covered metric and patients were categorized as adherent if their proportion of days covered ≥80%. Height velocity was annualized to compare across adherent and nonadherent patients.

RESULTS

One hundred eighty-one patients were identified and included in this study, of which 70.2% were male,73.5% were white, and mean age (standard deviation [SD]) at index was 12.1 (2.8). In the height velocity analysis, 174 patients were included and the mean (SD) annualized change in height was 10.2 (5.7) cm/y in the adherent group (n = 108) and 9.8 (7.6) in the nonadherent group (n = 66). The difference in height velocity between the groups was not statistically significant.

CONCLUSIONS

Minor improvements in average height velocity were observed in the patient group who were adherent to somatropin therapy, although not statistically significant. Lack of observed significance may be due to small sample sizes, short observation period, a likely heterogenous population in terms of growth hormone prescribing, data bias due to single-center origin, or potential patient misclassification.

Long-acting growth hormone in the management of GHD in France

Approximately 10,000 children in France with growth hormone deficiency (GHD) are being administered daily recombinant human growth hormone (rhGH). Although this treatment has long proved efficient for restoring children's growth and metabolism, daily injections of rhGH have a few limitations, such as difficulties in terms of adherence to treatment, which may compromise growth during childhood but also metabolism in adulthood. In addition to the disease burden and besides the adherence hurdles, the obligations related to daily injection have a negative impact on the quality of life of patients and their families. The hypothesis that injections administered at intervals of 1 week, or even 1 month, could improve compliance, reduce treatment discontinuations, and optimize quality of life and therapeutic effectiveness has led to the emergence of new long-acting growth hormone (LAGH). Recent access to LAGHs (somatrogon MA) on the European and French market will likely be followed by a high demand from the families concerned and may raise questions on their effectiveness, safety, and practical use. Numerous practical and practice-related points are needed to guide prescribing physicians while many concerns are still left unresolved (treatment effectiveness or ineffectiveness endpoints, long-term effectiveness, etc.). These issues can only be addressed in the future by compiling registries and conducting long-term real-world studies.

Update on the use of long-acting growth hormone in children

PURPOSE OF REVIEW

After extensive research and many years of waiting, long-acting growth hormone (LAGH) formulations have finally become a reality in clinical practice and emerge as a potential solution to address the challenges of daily injections of recombinant human GH (rhGH). In this review, we present a brief history of the development of LAGH and provide a critical analysis of the existing literature on the five LAGH available and approved to date for treatment in children.

RECENT FINDINGS

In clinical trials, LAGH therapy has shown noninferiority compared with daily rhGH therapy in promoting linear growth in children with GH deficiency, with similar rates of adverse events.

SUMMARY

In the real world, many questions still need to be answered, such as whether a specific group of patients will benefit most from the weekly injection, whether compliance will be better compared with daily rhGH, whether long-term efficacy, monitoring and safety profile will be the same for the different LAGH compounds, and whether the cost-effectiveness will justify their use in different settings.

Detection of the GH analog somatrogon in sports drug testing: Immunological approaches and LC-HRMS/MS

Due to the presumed lipolytic and anabolic properties, the misuse of human growth hormone (hGH) and its synthetic analogs in sports is prohibited both in- and out-of-competition. Within this research project, the detectability of somatrogon, a recombinant fusion glycoprotein of 22 kDa hGH and the C-terminal peptide (CTP) of the human chorionic gonadotropin (hCG) β-subunit, with current WADA-approved doping control assays for hGH and hCG was investigated. For that purpose, cross-reactivity tests and a somatrogon administration study were conducted, and only "Kit 2" of the GH isoform differential immunoassays proved applicable to the detection of somatrogon administration in serum. In urine, the immunoassay specific for total hCG yielded presumptively positive findings for several post-administration samples, which can probably be attributed to the presence of an immunoreactive fragment of the hCG β-subunit. As the detectability of somatrogon with these approaches was found to be limited, a highly specific detection assay (LOD: 10 ng/mL) for the drug in serum samples was developed by using affinity purification with GH receptor (GHR)-conjugated magnetic beads, proteolytic digestion, and liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). Following optimization, the approach was comprehensively characterized, and authentic post-administration serum samples were successfully analyzed as proof-of-concept, indicating a detection window of at least 96 h. Consequently, the presented method can be employed to confirm the presence of somatrogon in serum samples, where only "Kit 2" of the currently used immunoassay kits yielded an abnormally high Rec/Pit ratio.

Post hoc subgroup analysis of Asian children with paediatric GHD from the global phase 3 efficacy and safety study of once-weekly somatrogon vs. once-daily somatropin

OBJECTIVES

Somatrogon is a long-acting recombinant human growth hormone used to treat patients with paediatric growth hormone deficiency (pGHD). This global phase 3 study compared the efficacy and safety of once-weekly somatrogon with once-daily somatropin in children with GHD.

METHODS

Prepubertal patients were randomized 1:1 to once-weekly somatrogon (0.66 mg/kg/week) or once-daily somatropin (0.24 mg/kg/week) for 12 months. The primary endpoint was height velocity (HV) at month 12; secondary endpoints included HV at month 6 and change in height standard deviation score (SDS) at months 6 and 12 and insulin-like growth factor 1 (IGF-1) SDS.

RESULTS

This post hoc subgroup analysis focused specifically on Asian children (somatrogon: n=24 and mean age=7.76 years; somatropin: n=21 and mean age=8.10 years) across eight countries. Mean HV at month 12 was 10.95 cm/year (somatrogon) and 9.58 cm/year (somatropin); the treatment difference of 1.38 cm/year favoured somatrogon. The lower bound of the two-sided 95 % CI of the treatment difference (somatrogon-somatropin) was -0.20, similar to the overall study population (-0.24). Compared with the somatropin group, the somatrogon group had numerically higher HV at month 6 (8.31 vs. 11.23 cm/year); a similar trend was observed for height SDS and IGF-1 SDS at months 6 and 12. Safety and tolerability were similar between treatment groups; adverse events occurred in 83 % of somatrogon-treated children and 76 % of somatropin-treated children.

CONCLUSIONS

This subgroup analysis demonstrated that somatrogon efficacy and safety in Asian children were consistent with the overall study population, where once-weekly somatrogon was non-inferior to once-daily somatropin. Clinicaltrials.gov: NCT02968004.

A Randomized, Cross-Over Study Investigating the Comparability of Somatrogon-ghla in 2 Different Drug Product Presentations

Somatrogon-ghla is a long-acting, recombinant human growth hormone approved for the treatment of pediatric patients with growth hormone deficiency. Forty-nine healthy, adult males were enrolled in a randomized, crossover study to compare somatrogon exposure after subcutaneous doses administered using a frozen vial presentation or a prefilled, multiple dose pen. Somatrogon, insulin-like growth factor-I, and IGF-1 binding protein-3 concentrations were collected for up to 240 hours post dose to assess pharmacokinetic and pharmacodynamic responses. There was a 2-week washout between administration of the doses. Seven participants did not complete the study due to withdrawal of consent (n = 2) or loss to follow-up. Two treatment-emergent adverse events, headaches, were judged by the investigator as possibly related to study drug administration. Both were mild. Injection site reactions were observed in 6/48 participants after administration with the pen and 12/46 after administration using the vial. Drug and biomarker concentrations were assessed using validated assays and noncompartmental methods were used to determine pharmacokinetic and pharmacodynamic parameters. Bioequivalence was demonstrated for somatrogon area under the concentration-time curve, but not for the peak somatrogon concentration, where the lower limit of the 90% confidence interval for the ratio of pen/vial was 74.2%, which is less than the lower limit, 80.0%, dictated by bioequivalence criteria. The IGF-1 responses were largely within bioequivalence limits. It was concluded that the 2 formulations are comparable.

Approach to the Peripubertal Patient With Short Stature

CONTEXT

The assessment and treatment of children with growth retardation is increasingly complex, and due to availability of targeted genetic sequencing, an ever-expanding number of conditions impeding growth are being identified. Among endocrine-related etiologies of short stature amenable to hormonal treatment, defects in the growth hormone (GH)-insulin-like growth factor I axis remain pre-eminent, with a multiplicity of disorders causing decreased secretion or insensitivity to GH action. Sex steroids in puberty increase epiphyseal senescence and eventual growth plate closure. This is mediated mostly via estrogen receptor (ER)α in males and females, effects that can greatly limit time available for growth.

EVIDENCE ACQUISITION

Extensive literature review through PubMed and other search engines.

EVIDENCE SYNTHESIS

Therapeutic strategies to be considered in peripubertal and pubertal children with disordered growth are here discussed, including daily and weekly GH, low-dose sex steroids, gonadotropin hormone releasing hormone (GnRH) analogues in combination with GH, aromatase inhibitors (AIs) alone and in combination with GH in boys. When used for at least 2 to 3 years, GnRH analogues combined with GH can result in meaningful increases in height. AIs used with GH permit puberty to progress in boys without hindrance, selectively decreasing estrogen, and resulting in taller height. With more than 20 years of cumulative experience in clinical use of these medications, we discuss the safety profile of these treatments.

CONCLUSION

The approach of growth retardation in the peripubertal and pubertal years must consider the sex steroid milieu and the tempo of bone acceleration. Treatment of affected children in this period must be individualized.

Tackling access and payer barriers for growth hormone therapy in Saudi Arabia: a consensus statement for the Saudi Working Group for Pediatric Endocrinology

Prompt diagnosis and early treatment are key goals to optimize the outcomes of children with growth hormone deficiency (GHD) and attain the genetically expected adult height. Nonetheless, several barriers can hinder prompt diagnosis and treatment of GHD, including payer-related issues. In Saudi Arabia, moderate-to-severe short stature was reported in 13.1 and 11.7 % of healthy boys and girls, respectively. Several access and payer barriers can face pediatric endocrinologists during the diagnosis and treatment of GHD in Saudi Arabia. Insurance coverage policies can restrict access to diagnostic tests for GHD and recombinant human growth hormone (rhGH) due to their high costs and lack of gold-standard criteria. Some insurance policies may limit the duration of treatment with rhGH or the amount of medication covered per month. This consensus article gathered the insights of pediatric endocrinologists from Saudi Arabia to reflect the access and payer barriers to the diagnostic tests and treatment options of children with short stature. We also discussed the current payer-related challenges endocrinologists face during the investigations of children with short stature. The consensus identified potential strategies to overcome these challenges and optimize patient management.

A year in pharmacology: new drugs approved by the US Food and Drug Administration in 2023

With 54 new drugs and seven cellular and gene therapy products, the approvals by the US Food and Drug Administration (FDA) recovered 2023 from the 2022 dent back to the levels of 2020-2021. As in previous years of this annual review, we assign these new drugs to one of three levels of innovation: first drug against a condition ("first-in-indication"), first drug using a novel molecular mechanism ("first-in-class"), and "next-in-class," i.e., a drug using an already exploited molecular mechanism. We identify four (7%) "first-in-indication," 22 (36%) "first-in-class," and 35 (57%) "next-in-class" drugs. By treatment area, rare diseases (54%) and cancer drugs (23%) were once again the most prevalent (and partly overlapping) therapeutic areas. Other continuing trends were the use of accelerated regulatory approval pathways and the reliance on biopharmaceuticals (biologics). 2023 marks the approval of a first therapy based on CRISPR/Cas9 gene editing.

Evolving growth hormone deficiency: proof of concept

Introduction

We present the evolution of GHD in adolescent males with persistent growth failure, in whom the diagnosis was established after a second GH stimulation test (GST).

Methods

We performed a retrospective chart review of children who presented for short stature (height less < 2SD for mean/mid-parental height) and/or growth failure (sustained growth velocity < 0 SD) to pediatric endocrinology at Mount Sinai Kravis Children's Hospital, New York and who had 2 GSTs. Data collected from electronic medical records were analyzed using SPSS v28.0.

Results

Of 53 patients included, 42 were males. Average GH peak on initial GST was 15.48 ± 4.92 ng/ml, at 10.07 ± 2.65 years, mean height -1.68 ± 0.56SD(28% had <2SD), IGF-1 -1.00 ± 0.88SD. After 2.23 ± 1.22 years, at 12.04 ± 2.41years, height SDs decreased to -1.82 ± 0.63SD and IGF-1 was -1.08 ± 0.84SD. At repeat GST, average GH peak was 7.59 ± 2.12 ng/dL, with 36% ≤7 ng/dl and 32% in puberty. 12 males reached adult height of 0.08 ± 0.69 SD with a mean height gain of 1.83 ± 0.56SD(p<0.005), IGF-1 of -1.15 ± 0.81SD after 4.64 ± 1.4 years of GH.

Conclusion

We offer evidence for Evolving Growth Hormone Deficiency (EGHD) through repeat GST in children with persistent growth slowdown, even with pubertal progression; emphasizing the need for careful longitudinal follow-up to make accurate diagnosis.

Long-acting growth hormone in the treatment of growth hormone deficiency in children: a systematic literature review and network meta-analysis

The purpose of this study is to compare the relative efficacy and safety of long-acting growth hormone (LAGH) as a growth hormone replacement therapy in prepubertal children with growth hormone deficiency (GHD). We searched the PubMed, Embase, CNKI, and Wanfang databases from inception to July 2023 and identified eleven relevant studies. PEG-LAGH showed better effect on height velocity (mean difference [MD]: - 0.031, 95% credibility interval [CrI]: - 0.278, 0.215) than somatrogon (MD: 0.105, 95% CrI: - 0.419, 0.636), somapacitan (MD: 0.802, 95% CrI: - 0.451, 2.068) and lonapegsomatropin (MD: 1.335, 95% CrI: - 0.3, 2.989) when compared with daily growth hormone (DGH). Furthermore, in terms of height standard deviation score, PEG-LAGH demonstrated better improvement (MD: - 0.15, 95% CrI: - 1.1, 0.66) than somatrogon (MD: - 0.055, 95% CrI: - 1.3, 0.51) and somapacitan (MD: 0.22, 95% CrI: - 0.91, 1.3). PEG-LAGH (risk ratio [RR]: 1.00, 95% CrI: 0.82, 1.2) reduced the risk of adverse events compared with other LAGH (somatrogon, RR: 1.1, 95% CrI: 0.98, 1.2; somapacitan, RR: 1.1, 95% CrI: 0.96, 1.4; lonapegsomatropin, RR, 1.1, 95% CrI: 0.91, 1.3) and was comparable with DGH. This is the first study to indirectly compare the LAGH thorough a network meta-analysis and provide evidence of the optimal efficacy of various LAGH specifically PEG-LAGH and acceptable safety profile in prepubertal children with GHD.

Novel therapies for growth disorders

As we continue to understand more about the complex mechanism of growth, a plethora of novel therapies have recently been developed that aim to address barriers and optimize efficacy. This review aims to explore these novel therapies and provide a succinct review based on the latest clinical studies in order to introduce clinicians to therapies that will soon constitute the future in the field of short stature.  Conclusion: The review focuses on long-acting growth hormone formulations, a novel growth hormone oral secretagogue, novel treatments for children with achondroplasia, and targeted therapies for rare forms of skeletal dysplasias. What is Known: • Recombinant human growth hormone has been the mainstay of treatment for children with short stature for years. • Such therapy is not always effective based on the underlying diagnosis (e.g achondroplasia, Turner syndrome). Compliance with daily injections is challenging and can directly affect efficacy. What is New: • Recent development of long-acting growth hormone regimens and oral secretagogues can overcome some of these barriers, however several limitations need to be taken into consideration. • Newer therapies for achondroplasia, and other rare forms of skeletal dysplasias introduce us to a new era of targeted therapies for children with short stature. Clinicians ought to be aware of pitfalls and caveats before introducing these novel therapies to every day practice.

The Treatment of Growth Disorders in Childhood and Adolescence

BACKGROUND

3% of all children are unusually short, and 3% are unusually tall. New approaches have broadened the range of therapeutic options in treating growth disorders.

METHODS

This review is based on publications retrieved by a selective review of the literature and on the authors' clinical experience.

RESULTS

Pituitary growth hormone deficiency is treated with recombinant growth hormone. Long-acting preparations of this type became available recently, but their long-term safety and efficacy are still unknown. Vosoritide, a CNP analogue, has also been approved for the treatment of achondroplasia, and severe primary deficiency of insulin-like growth factor 1 (IGF-1) can be treated with recombinant IGF-1. In the treatment of excessively tall stature, new information on the safety of growth-attenuating treatment and an altered perception of above-average height in society have led to a change in management.

CONCLUSION

There are new options for the treatment of rare causes of short stature, while new information on the safety of treatment strategies for excessive tallness have led to a reconsideration of surgical intervention. There is insufficient evidence on the benefits and risks of supraphysiological GH therapy and of newer treatment options for which there are as yet no robust data on adult height. Therefore, before any treatment is provided, physicians should give patients and their families detailed information and discuss their expectations from treatment and the goals that treatment can be expected to achieve.

Developments in the Management of Growth Hormone Deficiency: Clinical Utility of Somapacitan

Growth hormone (GH) replacement therapy for growth hormone deficiency (GHD) in children and adults has for over 25 years, until recently, been administered as daily injections. This daily treatment regimen often incurs a burden to patients and caregivers, leading to high rates of non-adherence and, consequently, decreased treatment efficacy outcomes. To address this shortcoming, long-acting growth hormones (LAGHs) have been developed with the aim of reducing the burden of daily injections, thereby potentially improving treatment adherence and outcomes. Somapacitan (Sogroya®) (Novo Nordisk, Bagsværd, Denmark) is a LAGH currently approved for the treatment of adult and childhood GHD (AGHD and CGHD, respectively) in several countries. Other LAGHs, such as somatrogon (Ngenla®) (Pfizer, New York, United States) and lonapegsomatropin/TransCon GH (Skytrofa®) (Ascendis Pharma, Copenhagen, Denmark), are also currently approved and available for the treatment of CGHD in several countries. In this review, we will consider the method of protraction, pharmacokinetics (PK) and pharmacodynamics (PD), efficacy, and safety results of somapacitan in adult and pediatric trials and how these characteristics differ from those of the other aforementioned LAGHs. Additionally, the administration of somapacitan and timing of measurement of serum insulin-like growth factor-I (IGF-I) levels are summarized. Information on administration, advice on missed doses, and clinical guidelines are discussed, as well as identifying which patients are suitable for somapacitan therapy, and how to monitor and adjust dosing whilst on therapy.

Health-related quality of life in pre-pubertal children with pediatric growth hormone deficiency: 12-month results from a phase 3 clinical trial of once-weekly somatrogon versus once-daily somatropin

OBJECTIVE

Treatment of pediatric growth hormone deficiency (pGHD) with daily injection of recombinant human growth hormone (somatropin) aims to increase height velocity and improve health-related quality of life (HRQoL). The Quality of Life in Short Stature Youth (QoLISSY) questionnaire was administered in a phase 3 clinical trial that evaluated efficacy and safety of once-weekly somatrogon versus once-daily somatropin in children with pGHD (ClinicalTrials.gov no NCT02968004).

METHODS

Treatment-naïve prepubertal children with pGHD received once-weekly somatrogon or once-daily somatropin for 12 months. The QoLISSY core module (physical/social/emotional subscales) was administered at baseline and 12 months after treatment initiation. QoLISSY-Parent was completed by parents/caregivers of children <7 years old and some parents/caregivers of children ≥7 years old; children ≥7 years old self-completed QoLISSY-Child.

RESULTS

Baseline characteristics were similar between treatment groups (N = 117). Among children <7 years old, QoLISSY-Parent total and subscale scores showed similarly improved HRQoL at 12 months relative to baseline in both treatment groups. Self-reported QoLISSY-Child total and subscale scores in children ≥7 years old indicated HRQoL improvements at 12 months that were numerically better with somatrogon than somatropin (similar results with QoLISSY-Parent in this age group). At both time points, children reported better HRQoL than perceived by their parents/caregivers.

CONCLUSION

Treatment for 12 months with once-weekly somatrogon or once-daily somatropin resulted in comparable improvements in HRQoL among children with pGHD. Lower HRQoL perceived by parents/caregivers possibly reflect children's tendency to emphasize adaptation. These results suggest that evaluation of HRQoL could help support treatment decisions in children with pGHD treated with growth hormone.

Recent insights into the role of hormones during development and their functional regulation

Introduction

Hormones play a vital role in development from conception to birth and throughout the human lifespan. These periods are logically divided into fetal development, pre-pubertal growth, puberty, and adulthood. Deviations from standard physiological levels and release patterns of constituent hormones can lead to pathology affecting the normal developmental trajectory. Research is ongoing to better understand the mechanisms of these hormones and how their modulation affects development.

Methods

This article focuses on recent developments in understanding the role hormones play in development. We also cover recent discoveries in signaling pathways and hormonal regulation.

Results

New and continuing research into functional hormone regulation focuses on sex hormones, gonadotropic hormones, growth hormones, insulin-like growth factor, thyroid hormone, and the interconnectedness of each of these functional axes. Currently, the abundance of work focuses on fertility and correction of sex hormone levels based on an individual's condition and stage in life.

Discussion

Continuing research is needed to fully understand the long-term effects of hormone modulation in growth and sexual development. The role of each hormone in parallel endocrine axes should also be more thoroughly investigated to help improve the safety and efficacy in endocrine pharmacotherapeutics.

Somatrogon injection for the treatment of pediatric growth hormone deficiency with comparison to other LAGH products

INTRODUCTION

Somatrogon (NGENLA™) is a long-acting GH (LAGH) formulation that was approved in Canada in October 2021 for the treatment of pediatric growth hormone deficiency (GHD). Somatrogon has also received approval in Australia, Japan, the European Union, the USA, and the UK. Somatrogon is a glycoprotein that utilizes three copies of the C-terminal peptide of human chorionic gonadotropin to delay its clearance allowing for once-weekly administration.

AREAS COVERED

The purpose of this article is to describe the development of somatrogon for treatment of individuals with GHD. Trials of somatrogon demonstrated positive efficacy results in adults (Phase 2) and children (Phase 2 and 3) with GHD including non-inferiority of height velocity compared to daily GH, with no concerning side effects. Growth responses, pharmacodynamics and safety data are compared to other LAGH products, lonapegsomatropin and somapacitan, in Phase 3 trials in pediatric GHD.

EXPERT OPINION

New LAGH products, including somatrogon, have the potential to increase patient adherence as well as improve quality of life and clinical outcomes. Clinicians will need to identify the best candidates for LAGH therapy and understand how to safely monitor and adjust therapy. Long-term surveillance studies are necessary to demonstrate adherence, efficacy, cost-effectiveness, and safety of LAGH preparations.

Therapeutic Fusion Proteins

Therapeutic fusion proteins are a class of hybrid constructs that combine distinct biomolecules into a single platform with the additive effects of the components. The ability to fuse two unrelated proteins provides a means to localize mechanisms to better treat a range of diseases. Fusion proteins can be designed to impart diverse functions, including increasing half-life, providing targeting, and enabling sustained signaling. Of these, half-life extenders, which are fused to a therapeutic protein to increase exposure, are the most established group of fusion proteins, with many clinical successes. Rapid advances in antibody and antibody-derivative technology have enabled the fusion of targeting domains with therapeutic proteins. An emerging group of therapeutic fusion proteins has two separate active functions. Although most research for therapeutic fusion proteins focuses on cancer, prior successes provide a foundation for studies into other diseases as well. The exponential emergence of biopharmaceuticals gives precedence for increased research into therapeutic fusion proteins for a multitude of diseases.

Physician experience with once-weekly somatrogon versus once-daily rhGH regimen in pediatric patients with growth hormone deficiency: a cross-sectional survey of physicians from the global phase 3 study

Introduction

The standard of care for pediatric growth hormone deficiency (pGHD) is once-daily recombinant human growth hormone (rhGH). Somatrogon, a long-acting rhGH, requires less frequent, once-weekly, dosing. We describe physicians' preference for, experiences, and satisfaction with once-weekly somatrogon vs once-daily rhGH.

Methods

English-speaking investigators from somatrogon's global phase III study (NCT02968004) with prior experience using once-daily rhGH were included. Participants answered an online survey containing 14 closed- and open-ended items.

Results

Twenty-four pediatric endocrinologists (41.7% men; 79.2% practiced at public/private hospitals) from 12 countries with 25.8 ± 12.0 years' experience treating pGHD completed the survey. In terms of the time and effort required to explain device instructions, injection regimen, procedure for missed injection, and address patients'/caregivers' concerns, a similar proportion of physicians chose once-weekly somatrogon and once-daily rhGH; 62.5% physicians indicated that once-daily rhGH required greater effort to monitor adherence. Overall, 75% preferred once-weekly somatrogon over once-daily rhGH, 79.2% considered once-weekly somatrogon to be more convenient and less burdensome, and 83.3% were likely to prescribe somatrogon in the future. Overall, 50% felt that once-weekly somatrogon was more beneficial to patients, while 50% chose "No difference". Most physicians (62.5%) felt both regimens were equally likely to support positive long-term growth outcomes and reduce healthcare utilization. More physicians were "very satisfied" with once-weekly somatrogon (62.5%) than with once-daily rhGH (16.7%). Reduced injection frequency, patient and caregiver burden, increased convenience, and improved adherence were reasons for these choices.

Conclusion

Physicians had a positive experience with, and perception of, treating pGHD with once-weekly somatrogon.

Model-Based Analysis of IGF-I Response, Dosing, and Monitoring for Once-Weekly Somapacitan in Children With GH Deficiency

Context

Growth hormone (GH) replacement therapy improves longitudinal growth and adult height in children with GH deficiency (GHD). GH stimulates insulin-like growth factor (IGF)-I release, the biomarker used for monitoring GH activity during treatment.

Objective

This study aims to provide model-based insights into the dose-IGF-I responses of once-weekly somapacitan, a novel long-acting GH, compared with daily GH in children with GHD.

Methods

Analyses included dosing information and 1473 pharmacokinetic samples from 210 somapacitan-treated pediatric patients with GHD across 3 trials, including phase 1 (NCT01973244), phase 2 (NCT02616562; REAL 3), and phase 3 (NCT03811535; REAL 4), as well as 1381 IGF-I samples from 186 patients with GHD treated with somapacitan in REAL 3 and REAL 4. Pharmacokinetic/pharmacodynamic modeling to characterize somapacitan dose-IGF-I response and predict the response to dosing day changes.

Results

Relationships were established between somapacitan dose, exposure, change from baseline IGF-I SD score (SDS), and height velocity (HV). A linear model permitted the development of a tool to calculate estimated average weekly IGF-I exposure from a single IGF-I sample obtained at any time within the somapacitan dosing interval at steady state. In practice, the use of this tool requires knowledge of somapacitan injection timing relative to IGF-I sample collection timing. IGF-I SDS simulations support flexible dosing day changes while maintaining at least 4 days between doses.

Conclusion

We characterized the dose-IGF-I response of somapacitan in children with GHD. To support physicians in IGF-I monitoring, we present a practical guide about expected weekly average IGF-I concentrations in these patients and provide insights on dosing day flexibility.

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.

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.

Cost-effectiveness of somatrogon in the Spanish pediatric population with growth hormone deficiency

OBJECTIVE

To analyze the cost-effectiveness of weekly somatrogon compared to daily growth hormones (GH-d) in the pediatric population of Spain with growth hormone deficiency (GHD).

METHODS

Markov model with two states (patients with or without GH-d or somatrogon treatment) in prepubertal children (3 to 11 years and 3 to 12 years in girls and boys, respectively) with GHD in isolation or as part of multiple pituitary hormone deficiency and without previous treatment, from the perspective of the National Health System. The simulation of the economic model ends at the age of 18. The costs of hormones and monitoring were obtained from Spanish sources. The utilities were obtained from the literature. Spanish clinical experts validated the assumptions of the model.

RESULTS

In the deterministic analysis, somatrogon would be cost-effective, compared to GH-d, with a cost per QALY (quality-adjusted life year) gained of €19,259 and a clinically relevant QALY gain (0.336). This result was confirmed in deterministic sensitivity analyses. According to the probabilistic analysis, somatrogon would be the dominant treatment, with a 61% probability of a willingness to pay of €25,000 per QALY gained.

CONCLUSION

Compared to GH-d, somatrogon is cost-effective in the Spanish pediatric population with GHD.

Efficacy, safety, quality of life, adherence and cost-effectiveness of long-acting growth hormone replacement therapy compared to daily growth hormone in children with growth hormone deficiency: a systematic review and meta-analysis

We evaluated the efficacy, safety, adherence, quality of life (QoL) and cost-effectiveness of long-acting growth hormone (LAGH) vs daily growth hormone (GH) preparations in the treatment of growth hormone deficiency (GHD) in children. Systematic searches were performed in PubMed, Embase and Web of Science up to July 2022 on randomized and non-randomized studies involving children with GHD receiving LAGH as compared to daily GH. Meta-analyses for efficacy and safety were performed comparing different LAGH/daily GH formulations. From the initial 1,393 records, we included 16 studies for efficacy and safety, 8 studies for adherence and 2 studies for QoL. No studies reporting cost-effectiveness were found. Pooled mean differences of mean annualized height velocity (cm/year) showed no difference between LAGH and daily GH: Eutropin Plus® vs Eutropin® [-0.14 (-0.43, 0.15)], Eutropin Plus® vs Genotropin® [-0.74 (-1.83, 0.34)], Jintrolong® vs Jintropin AQ® [0.05 (-0.54, 0.65)], Somatrogon vs Genotropin® [-1.40 (-2.91, 0.10)], TransCon vs Genotropin® [0.93 (0.26, 1.61)]. Also, other efficacy and safety outcomes, QoL and adherence were comparable for LAGH and daily GH. Our results showed that, although most of the included studies had some concerns for risk of bias, regarding efficacy and safety all the LAGH formulations were similar to daily GH. Future high quality studies are needed to confirm these data. Adherence and QoL should be addressed from real-world data studies for both the mid and long term and in a larger population. Cost-effectiveness studies are needed to measure the economic impact of LAGH from the healthcare payer's perspective.

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.

Cost-effectiveness and cost-utility analysis of somatrogon once-weekly injections vs. daily growth hormone injection for treating paediatric growth hormone deficiency in Ireland

OBJECTIVES

Paediatric growth hormone deficiency (pGHD) manifests as growth failure associated with inadequate growth hormone (GH) production. Daily injections of recombinant human GH (dGH) [somatropin] is the current standard of care, which has been shown to be well tolerated and effective, but associated with suboptimal adherence, leading to reduced effectiveness. Somatrogon, a once-weekly injectable long-acting human GH, has demonstrated clinical non-inferiority and significantly lower life interference (i.e. treatment burden) vs. somatropin in two Phase 3 studies. This work evaluated cost-effectiveness and cost-utility of somatrogon vs dGHs from an Irish payer perspective.

METHODS

A Markov model was developed for patients starting somatrogon or dGHs treatment at 3-12 years and continuing up to achievement of near adult height (NAH), with growth driven by trial-based height velocity (HV) and treatment-specific adherence. Patients could discontinue treatment at the end of Year 1 (4%). DGH adherence (95.3%-65% over treatment duration) and adherence-growth relationship were based on published evidence. Higher Year 1 adherence of 4%, tapering over time, for somatrogon vs. dGHs was based on clinical consultation. Treatment costs, monitoring costs and costs due to different wastage types (device setting and adherence) were sourced from local data. Health utilities based on height and injection frequency were derived from published literature. Scenario analysis, deterministic and probabilistic sensitivity analysis were performed.

RESULTS

Somatrogon treatment led to 1.87-3.66 cm greater NAH gain and 0.21-0.50 higher quality adjusted life years (QALYs) vs. dGHs, across the base case and scenarios evaluated. Somatrogon treatment was associated with cost savings of €5,699-€21,974 and lower cost per cm gained vs. dGHs (€197-€527), per patient. Somatrogon was cost-effective vs. dGHs, with the result consistent across the sensitivity analyses conducted.

CONCLUSION

Somatrogon weekly injections were estimated to result in higher NAH, higher QALYs, lower overall costs and lower costs per cm gained than dGHs, in pGHD.

Weekly Somapacitan is Effective and Well Tolerated in Children With GH Deficiency: The Randomized Phase 3 REAL4 Trial

CONTEXT

Somapacitan, a once-weekly reversible albumin-binding GH derivative, is evaluated in children with GH deficiency (GHD).

OBJECTIVE

To demonstrate efficacy and safety of somapacitan vs daily GH.

METHODS

REAL4 is a randomised, multinational, open-labeled, active-controlled parallel group phase 3 trial, comprising a 52-week main trial and 3-year extension (NCT03811535).

SETTING

Eighty-six sites across 20 countries.

PATIENTS

200 treatment-naïve patients were randomized and exposed.

INTERVENTIONS

Patients were randomized 2:1 to somapacitan (0.16 mg/kg/wk) or daily GH (Norditropin; 0.034 mg/kg/d), administered subcutaneously.

MAIN OUTCOME MEASURES

The primary endpoint was annualized height velocity (HV; cm/y) at week 52. Additional assessments included HV SD score (SDS), height SDS, bone age, IGF-I SDS, patient-reported outcomes, and safety measures.

RESULTS

Estimated mean HV at week 52 was 11.2 and 11.7 cm/y for somapacitan and daily GH, respectively. Noninferiority was confirmed. Changes in HV SDS, height SDS, bone age, and IGF-I SDS from baseline to week 52 were similar between treatment groups. At week 52, mean IGF-I SDS values were similar between treatment groups and within normal range (-2 to +2). Safety of somapacitan was consistent with the well-known daily GH profile. Low proportions of injection-site reactions were reported for somapacitan (5.3%) and daily GH (5.9%). Both treatments similarly reduced disease burden from baseline to week 52, whereas a greater treatment burden reduction was observed for somapacitan.

CONCLUSIONS

Similar efficacy for somapacitan compared to daily GH was demonstrated over 52 weeks of treatment with comparable safety and mean IGF-I SDS levels in treatment-naïve children with GHD.

What do we do now that the long-acting growth hormone is here?

In standard 52-week phase III clinical trials, once weekly lonapegsomatropin, somatrogon and somapacitan have been found to yield non-inferior height velocities and similar safety profiles to daily GH (DGH) in children with pediatric growth hormone deficiency (PGHD). Lonapegsomatropin, a long-acting GH therapy (LAGH), was approved by the United States Food and Drug Administration (FDA) in August 2021 for the treatment of PGHD and has also been approved in other regions of the world. Somatrogon was approved for the treatment of PGHD beginning in some regions beginning in late 2021. Somapacitan was approved by the FDA for the treatment of Adult GHD in August 2020. The phase III clinical trial of somapacitan for the treatment of PGHD has been completed and demonstrated non-inferiority of somapacitan to DGH. New LAGH products may improve patient adherence, quality of life and clinical outcomes, particularly in patients with poor adherence to daily GH injections in the future. With the availability of new LAGH products, clinicians will need to identify the best candidates for LAGH therapy and understand how to monitor and adjust therapy. Long-term surveillance studies are needed to demonstrate adherence, efficacy, cost-effectiveness and safety of LAGH preparations and to understand how the non-physiological pharmacokinetic and pharmacodynamic profiles following administration of each LAGH product relate to short- and long-term safety and efficacy of LAGH therapy.