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.

It is valuable to compare similarly acting treatments to determine their relative benefits and risks. Direct comparisons of long-acting growth hormones (LAGHs) are lacking, so analyses were performed to indirectly compare the efficacy and safety of the LAGH somapacitan versus the LAGHs somatrogon and lonapegsomatropin in children with growth hormone deficiency. Studies of once-weekly LAGHs for the treatment of pediatric growth hormone deficiency were identified using a systematic literature review, then the data obtained were indirectly compared using standard statistical methods with daily growth hormone 0.034 mg/kg/day (base case) or 0.024­0.034 mg/kg/day (alternative analyses) as the common comparator. Height outcomes to 52 weeks (annualized height velocity, height velocity standard deviation score, and height standard deviation score) were compared between treatments. Sufficient information to allow indirect comparison of safety or longer-term efficacy outcomes were not found so these were qualitatively described. The systematic literature review identified two somapacitan trials, three somatrogon trials (one included in alternative analyses only) and one lonapegsomatropin trial comparing the LAGH with daily growth hormone in previously untreated pre-pubertal children for inclusion in the indirect comparison. Indirect comparisons identified no differences to 52 weeks between somapacitan versus somatrogon and lonapegsomatropin, as well as daily growth hormone, with respect to all growth outcomes considered in children with growth hormone deficiency. All three LAGHs had sustained efficacy and were generally well tolerated, with comparable efficacy and safety to daily growth hormone, with the possible exception of injection site pain with somatrogon.

Somapacitan in Children Born SGA: 52-week Efficacy, Safety, and IGF-I Response Results from the Phase 2 REAL5 Study.

CONTEXT: Somapacitan, a once-weekly reversible albumin-binding GH derivative, is evaluated in short children born small for gestational age (SGA). OBJECTIVE: Evaluate efficacy, safety, tolerability as well as total and bioactive insulin-like growth factor-I (IGF-I) response of once-weekly somapacitan compared to daily GH in children born SGA. METHODS: REAL5 is a randomized, multi-center, open-label, controlled phase 2 study comprising a 26-week main phase, 26-week extension, and an ongoing 4-year safety extension (NCT03878446). SETTING: Thirty-eight sites across 12 countries. PATIENTS: Sixty-two GH-treatment-naïve, prepubertal short children born SGA were randomized; 61 completed 52-weeks of treatment. INTERVENTIONS: Patients randomized (1:1:1:1:1) to somapacitan (0.16, 0.20 or 0.24 mg/kg/week) or daily GH (0.035 or 0.067 mg/kg/day), all administered subcutaneously. RESULTS: Estimated mean height velocity (HV; cm/year) at week 52 was 8.5, 10.4 and 10.7 cm/year for somapacitan 0.16, 0.20 and 0.24 mg/kg/week, respectively, and 9.3 and 11.2 cm/year for daily GH 0.035 and 0.067 mg/kg/day, respectively. Dose-dependent increases in total IGF-I as well as peak IGF-I bioactivity were observed for both treatments and were similar between comparator groups. For somapacitan, exposure-response modelling indicated highest efficacy with 0.24 mg/kg/week after 52 weeks of treatment. Similar safety and tolerability were demonstrated across all groups. CONCLUSIONS: A sustained dose-dependent growth response was demonstrated for somapacitan after 52 weeks of treatment. Overall, somapacitan 0.24 mg/kg/week provides similar efficacy, safety, and tolerability, as well as comparable bioactive and total IGF-I response, as daily GH (0.067 mg/kg/day) in children born SGA.

Somapacitan-induced reversible lipoatrophy in an adult woman with hypopituitarism.

BACKGROUND: Lipoatrophy is rare adverse event (AE) in daily recombinant human growth hormone (rhGH). Data on lipoatrophy in newly developed long-acting GH (LAGH) are scarce. We report the first case of lipoatrophy in adult patient treated with LAGH somapacitan. CASE PRESENTATION: A 38-year-old woman with congenital panhypopituitarism was transitioned from daily rhGH 0.4 mg QD to somapacitan dose 4 mg QW due to non-adherence to daily rhGH. Despite adequate education and regular changing of injection sites, the patient reported reduced subcutaneous tissue at all four injection sites, after the 4th application of somapacitan. Somapacitan was discontinued at patient preference and lipoatrophy completely reversed after 3 months. CONCLUSIONS: Lipoatrophy caused by somapacitan was completely reversible. We speculate that high initial dose and volume of somapacitan caused delayed diffusion and a direct local lipolytic effect in our patient. Although, titration of somapacitan was initiated as previously reported in REAL2 study protocol, recent clinical guidelines advise more gradual increase of somapacitan dose also in women on oral estogens that are switched from daily rhGH. Importantly, our case and the two previously described cases in children in the REAL 3 study showed that lipoatrophy caused by somapacitan was transient and completely reversible, and that discontinuation of the drug is not always mandatory.

Utilizing Somapacitan, a Long-acting Growth Hormone Formulation, for the Treatment of Adult Growth Hormone Deficiency: A Guide for Clinicians.

OBJECTIVE: Somapacitan is the first approved and currently the only long-acting growth hormone (GH) formulation in the United States for treatment of adults with growth hormone deficiency (GHD). The aim of this review was to provide a practical approach for clinicians on how to utilize somapacitan in the treatment of adults with GHD. METHODS: Literature search was performed on PubMed using key words, including adult GHD, long-acting growth hormone, somapacitan, treatment, and management. The discussion of treatment aspects utilizing somapacitan was based on evidence from previous clinical studies and personal experience. RESULTS: Clinical trial data demonstrated that somapacitan, a once-weekly reversible albumin-binding GH derivative, decreased truncal fat, improved visceral fat and lean body mass, increased insulin-like growth factor-I standard deviation score and exerted neutral effects on glucose metabolism. Overall, somapacitan was well-tolerated, adverse event rates were comparable with daily GH, antisomapacitan or anti-GH antibodies were not detected, and treatment satisfaction was in favor of somapacitan vs daily GH. CONCLUSION: Somapacitan is an efficacious, safe, convenient and well-tolerated once-weekly long-acting GH formulation that reduces the treatment burden of once-daily GH injections for adults with GHD. This article provides a review of the pharmacology of somapacitan and offers practical recommendations based on previous clinical trial data on how to initiate, dose titration, monitoring and dose adjustments whilst on therapy in adults with GHD. Timing of measurement of serum insulin-like growth factor-I levels, information on administration, recommendations on missed doses, and clinical recommendations on dosing in certain sub-population of patients are also discussed.

Once-Weekly Somapacitan as an Alternative Management of Growth Hormone Deficiency in Prepubertal Children: A Systematic Review and Meta-Analysis of Randomized Controlled Trial.

Growth hormone treatment has effectively restored normal growth in children with growth hormone deficiency (GHD); however, it poses challenges in compliance with a daily growth hormone injection regimen, leading to low adherence and persistence rates. Once-weekly Somapacitan is a potential alternative for treating children with GHD. This study aimed to evaluate the efficacy, safety, and adherence of once-weekly subcutaneous Somapacitan compared to daily growth hormone injection in prepubertal children with GHD. A search for the published records was carried out on 17 October 2023 utilizing the searching feature available on PubMed, Embase, and Scopus. Primary study outcomes included (1) efficacy, measured by height velocity (HV), standard deviation score (SDs), height SDs, insulin-like growth factor-SDs (IGF-I SDs), and bone age vs. chronological age ratio (BA vs. CA); (2) safety, assessed through adverse events and injection site reactions; and (3) adherence, determined by the percentage of the sample completing treatments. Secondary outcomes evaluated disease burden scores, divided into three subgroup domains: emotional well-being, physical functional, and social well-being scores. We retrieved 6 studies that were eligible for the systematic review (417 versus 186 for intervention and control, respectively). Only 2 of the total included studies were eligible for pooled analysis (175 versus 82 for intervention and control, respectively). The efficacy profile of Somapacitan was similar to daily growth hormones, indicated by HV (mean difference (MD = 0.04; p = 0.96), HV SDs (MD = -0.71; p = 0.09), height SDs (MD = 0.11; p = 0.69), IGF-I SDs (MD = 0.06; p = 0.70), and CA vs. BA (MD = 0.67; p = 0.70)), demonstrated similar and non-inferior outcomes. Treatment adherence is 3 times higher in the Somapacitan group as compared to control (OR = 3.02; p = 0.03) with adherence rates reaching 95% and 88% for Somapacitan and Norditropin®, respectively. The disease burden measurement is similar in Somapacitan and daily growth hormones (MD = -0.62; p = 0.83), as indicated by the Growth Hormone Deficiency-Child Impact Measure. In almost all outcomes, the level of confidence is strong. The confidence level in the data is generally strong, but for CA vs. BA and the subgroup of severe adverse events with heterogeneity >50%, the confidence level is moderate. Although the efficacy and safety profiles of Somapacitan were found to be similar to those of daily growth hormones, a reduced frequency of once-weekly Somapacitan injections led to increased adherence. PROSPERO registration: CRD42023473209.

Effective growth hormone replacement with once-weekly somapacitan in Japanese children with growth hormone deficiency: Results from REAL4, a phase 3 clinical trial.

OBJECTIVE: Somapacitan is a long-acting growth hormone (GH) derivative developed for the treatment of GH deficiency (GHD). This study evaluates the efficacy and tolerability of somapacitan in Japanese children with GHD after 104 weeks of treatment and after switch from daily GH. DESIGN: Subanalysis on Japanese patients from a randomised, open-labelled, controlled parallel-group phase 3 trial (REAL4, NCT03811535). PATIENTS AND MEASUREMENTS: Thirty treatment-naïve patients were randomised 2:1 to somapacitan (0.16 mg/kg/week) or daily GH (0.034 mg/kg/day) up to Week 52, after which all patients received somapacitan. Height velocity (HV; cm/year) at Weeks 52 and 104 were the primary measurements. Additional assessments included HV SD score (SDS), height SDS, bone age, insulin-like growth factor-I (IGF-I) SDS, and observer-reported outcomes. RESULTS: At Week 52, observed mean HV was similar between treatment groups (10.3 vs. 9.8 cm/year for somapacitan and daily GH, respectively). Similar HVs between groups were also observed at Week 104: 7.4 cm/year after continuous somapacitan treatment (soma/soma) and 7.9 cm/year after 1-year somapacitan treatment following switch from daily GH (switch). Other height-related endpoints supported continuous growth. IGF-I SDS increased in both groups with mean IGF-I SDS within -2 and +2 during the study. Somapacitan was well tolerated, one mild injection site reaction was reported, with no reports of injection site pain. Patient preference questionnaires showed that most patients and their caregivers (90.9%) who switched treatment at Week 52 preferred once-weekly somapacitan over daily GH treatment. CONCLUSIONS: Somapacitan showed sustained efficacy in Japanese children with GHD over 104 weeks and for 52 weeks after switching from daily GH. Somapacitan was well tolerated and preferred over daily GH.

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.

Gene Expression Signatures Predict First-Year Response to Somapacitan Treatment in Children With Growth Hormone Deficiency.

CONTEXT: The pretreatment blood transcriptome predicts growth response to daily growth hormone (GH) therapy with high accuracy. OBJECTIVE: Investigate response prediction using pretreatment transcriptome in children with GH deficiency (GHD) treated with once-weekly somapacitan, a novel long-acting GH. METHODS: REAL4 is a randomized, multinational, open-label, active-controlled parallel group phase 3 trial, comprising a 52-week main phase and an ongoing 3-year safety extension (NCT03811535). A total of 128/200 treatment-naïve prepubertal children with GHD consented to baseline blood transcriptome profiling. They were randomized 2:1 to subcutaneous somapacitan (0.16 mg/kg/week) or daily GH (0.034 mg/kg/day). Differential RNA-seq analysis and machine learning were used to predict therapy response. RESULTS: 121/128 samples passed quality control. Children treated with somapacitan (n = 76) or daily GH (n = 45) were categorized based on fastest and slowest growing quartiles at week 52. Prediction of height velocity (HV; cm/year) was excellent for both treatments (out of bag [OOB] area under curve [AUC]: 0.98-0.99; validation AUC: 0.83-0.84), as was prediction of secondary markers of growth response: HV standard deviation score (SDS) (0.99-1.0; 0.75-0.78), change from baseline height SDS (ΔHSDS) (0.98-1.0; 0.61-0.75), and change from baseline insulin-like growth factor-I SDS (ΔIGF-I SDS) (0.96-1.0; 0.85-0.88). Genes previously identified as predictive of GH therapy response were consistently better at predicting the fastest growers in both treatments in this study (OOB AUC: 0.93-0.97) than the slowest (0.67-0.85). CONCLUSION: Pretreatment transcriptome predicts first-year growth response in somapacitan-treated children with GHD. A common set of genes can predict the treatment response to both once-weekly somapacitan and conventional daily GH. This approach could potentially be developed into a clinically applicable pretreatment test to improve clinical management.

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.

Effective GH Replacement With Somapacitan in Children With GHD: REAL4 2-year Results and After Switch From Daily GH.

CONTEXT: Somapacitan is a long-acting GH derivative for treatment of GH deficiency (GHD). OBJECTIVE: Evaluate the efficacy and tolerability of somapacitan in children with GHD after 2 years of treatment and after the switch from daily GH. DESIGN: A randomized, multinational, open-labelled, controlled parallel group phase 3 trial, comprising a 52-week main phase and 3-year safety extension (NCT03811535). SETTING: Eighty-five sites across 20 countries. PATIENTS: A total of 200 treatment-naïve prepubertal patients were randomized and exposed; 194 completed the 2-year period. INTERVENTIONS: Patients were randomized 2:1 to somapacitan (0.16 mg/kg/wk) or daily GH (0.034 mg/kg/d) during the first year, after which all patients received somapacitan 0.16 mg/kg/wk. MAIN OUTCOME MEASURES: Height velocity (HV; cm/year) at week 104. Additional assessments included HV SD score (SDS), height SDS, IGF-I SDS, and observer-reported outcomes. RESULTS: HV was sustained in both groups between 52 and 104 weeks. At week 104, mean (SD) for HV between weeks 52 and 104 was 8.4 (1.5) cm/year after continuous somapacitan treatment and 8.7 (1.8) cm/year after 1 year of somapacitan treatment following switch from daily GH. Secondary height-related endpoints also supported sustained growth. Mean IGF-I SDS during year 2 was similar between groups and within normal range (-2 to +2). Somapacitan was well tolerated, with no safety or tolerability issues identified. GH patient preference questionnaire results show that most patients and their caregivers (90%) who switched treatment at year 2 preferred once-weekly somapacitan over daily GH treatment. CONCLUSIONS: Somapacitan in children with GHD showed sustained efficacy and tolerability for 2 years, and after switching from daily GH. Patients/caregivers switching from daily GH expressed a preference for somapacitan. CLINICAL TRIAL REGISTRATION: NCT03811535.

Corrigendum: Guidance for the treatment of adult growth hormone deficiency with somapacitan, a long-acting growth hormone preparation.

[This corrects the article DOI: 10.3389/fendo.2022.1040046.].

Weekly Somapacitan in GH Deficiency: 4-Year Efficacy, Safety, and Treatment/Disease Burden Results From REAL 3.

CONTEXT: Growth hormone deficiency (GHD) in children is currently treated with daily injections of GH, which can be burdensome for patients and their parents/guardians. Somapacitan is a GH derivative in development for once-weekly treatment of GHD. OBJECTIVE: This work aimed to assess the efficacy and safety of somapacitan, and associated disease/treatment burden, after 4 years of treatment and 1 year after switching to somapacitan from daily GH. METHODS: This long-term safety extension of a multicenter, controlled phase 2 trial (NCT02616562) took place at 29 sites in 11 countries. Patients were prepubertal, GH-naive children with GHD. Fifty patients completed 4 years of treatment. Patients in the pooled group received somapacitan (0.04, 0.08, 0.16 mg/kg/week) for 1 year, followed by the highest dose (0.16 mg/kg/week) for 3 years. Patients in the switched group received daily GH 0.034 mg/kg/day for 3 years, then somapacitan 0.16 mg/kg/week for 1 year. Main outcome measures were height velocity (HV), change from baseline in HV SD score (SDS), change from baseline in height SDS, disease burden, and treatment burden for patients and parents/guardians. RESULTS: Changes from baseline in HV and HV SDS were similar and as expected in both groups. Observer-reported outcomes showed that patients and parents/guardians seem to have experienced a reduced treatment burden when switching from daily GH to somapacitan. Most parents/guardians (81.8%) strongly/very strongly preferred somapacitan over daily GH. CONCLUSIONS: Somapacitan showed similar efficacy and safety in patients who continued somapacitan treatment and those who switched from daily GH to somapacitan. Once-weekly injections may lead to a reduced treatment burden relative to once-daily injections. A plain-language summary of this work is available.

Somapacitan in children born small for gestational age: a multi-centre, open-label, controlled phase 2 study.

OBJECTIVE: Investigate efficacy, safety, and tolerability of 3 once-weekly somapacitan doses compared with daily growth hormone (GH) administration in short children born small for gestational age (SGA). DESIGN: Randomised, multi-centre, open-label, controlled phase 2 study comprising a 26-week main phase and a 4-year extension (NCT03878446). The study was conducted at 38 sites across 12 countries. 26-week main phase results are presented here.Sixty-two GH treatment-naïve, prepubertal short children born SGA were randomised and exposed; 61 completed the main phase. Three somapacitan doses (0.16 [n = 12], 0.20 [n = 13], 0.24 [n = 12] mg/kg/week) and 2 daily GH doses (0.035 [n = 12], 0.067 [n = 13] mg/kg/day) were administered subcutaneously. RESULTS: After 26 weeks of treatment, the estimated mean annualised height velocity (HV) was 8.9, 11.0, and 11.3 cm/year for somapacitan 0.16, 0.20, and 0.24 mg/kg/week, respectively, compared to 10.3 and 11.9 cm/year for daily GH 0.035 and 0.067 mg/kg/day. Changes from baseline in HV standard deviation score (SDS), height SDS, and insulin-like growth factor I (IGF-I) SDS showed similar dose-dependent responses. Exposure-response modelling indicated the greatest efficacy correlated with the highest somapacitan exposure. Similar safety and tolerability were demonstrated for all weekly somapacitan and daily GH doses. CONCLUSIONS: Based on the totality of data on improvements in height-based parameters combined with exposure-response analyses, somapacitan 0.24 mg/kg/week appears most efficacious, providing similar efficacy, safety, and tolerability as daily GH 0.067 mg/kg/day in short children born SGA after 26 weeks of treatment.

Weekly somapacitan had no adverse effects on glucose metabolism in adults with growth hormone deficiency.

PURPOSE: The long-term effects of long-acting growth hormone (LAGH) analogues on glucose metabolism in adult growth hormone deficiency (AGHD) are not known. We investigated the impact of LAGH somapacitan, administered once-weekly, on glucose metabolism in patients with AGHD. METHODS: In post hoc-defined analyses, we compared the effects of somapacitan with daily growth hormone (GH) and placebo on fasting plasma glucose (FPG), glycated hemoglobin (HbA1c), fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and beta-cell function (HOMA-ß) in patients with AGHD across a unique data set from three phase 3 randomized controlled trials (REAL 1, REAL 2 and REAL Japan). RESULTS: No new cases of diabetes mellitus were reported with somapacitan. Among GH-naïve patients (n = 120 somapacitan, n = 119 daily GH), higher changes from baseline in FPG, HOMA-IR and fasting insulin levels were observed with daily GH versus somapacitan at 34 weeks, but not at 86 weeks. HbA1c and HOMA-ß did not differ between groups at either timepoint. Among treatment-naïve patients, sex, age, fasting insulin, glucose tolerance status and body mass index did not influence changes in glucose metabolism. In previously treated patients (REAL 1 extension: n = 51 somapacitan, n = 52 daily GH; REAL 2: n = 61 and n = 31, respectively; REAL Japan: n = 46 and n = 16, respectively), the difference in changes from baseline were not statistically significant between somapacitan and daily GH for any glucose metabolism parameters. CONCLUSIONS: Somapacitan, compared with daily GH, did not adversely affect glucose metabolism up to 86 weeks in a large cohort of treatment-naïve or previously treated patients with AGHD. Trial registrations (date of registration): NCT02229851 (2 September 2014), NCT02382939 (3 March 2015), NCT03075644 (7 March 2017).

Somapacitan: a long-acting growth hormone derivative for treatment of growth hormone deficiency.

Growth hormone deficiency (GHD) is characterized by inadequate HG production from the anterior pituitary gland. Adult patients with GHD have increased fat mass, an abnormal lipid profile, decreased lean body mass and bone mineral density, decreased muscle strength and exercise endurance, and a diminished quality of life. Adult GHD (AGHD) has been treated with GH replacement therapy by daily subcutaneous injections. However, the administration of daily injections can be burdensome for some patients and affect treatment adherence. Somapacitan is a new long-acting human GH (hGH) analogue that is administered once a week by subcutaneous injection. It was first approved by the U.S. Food and Drug Administration (FDA) as GH replacement therapy for adults with GHD, becoming the first hGH therapy for AGHD administered by once-weekly injection, compared with other approved hGH therapies for AGHD administered by daily injection. This article reviews the pharmacokinetic, clinical and safety data that led to the approval of somapacitan as the first long-acting GH therapy for adults 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.

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.

Structure identification of circulating metabolites from somapacitan, a long-acting growth hormone derivative, and pharmacokinetics after single and multiple subcutaneous dosing in rats.

Somapacitan is a growth hormone derivative approved for once-weekly treatment of growth hormone deficiency in adults and currently in clinical development for once-weekly dosing in children. The purpose of this study was to obtain non-clinical data from rats to support the safety evaluation of the most abundant metabolites of somapacitan in humans. The aims were to identify somapacitan metabolites and their relative proportions in rat plasma, identify the structure of abundant metabolites and measure the systemic metabolite exposure at the no-observed-adverse-effect level in the rat. After a single dose of radiolabelled somapacitan and analysis by high-performance liquid chromatography with radiochemical detection, seven somapacitan-related metabolites were detected in plasma from male rats, of which six were seen in plasma from female rats. The three most abundant metabolites (M1, M2 and M3) were structurally identified from liquid chromatography and mass spectrometry data, and a fourth metabolite (P1) was characterised from its specific retention time (lacking retention to the stationary phase) in plasma analysis with reversed-phase liquid chromatography and radiochemical detection. The metabolites were products from proteolysis of the peptide backbone in somapacitan. A deamidation product of the M1 metabolite (M1B) was also identified. Following multiple, twice-weekly dosing for 4 weeks, somapacitan was the principal plasma component up to 36 h after dosing. After 36 h, metabolites M1+M1B were the most abundant plasma components. Pharmacokinetic models were developed for somapacitan and metabolite P1 and used for steady-state assessment in the rat. Comparison of our data generated from rats with data from the parallel human study demonstrated that the most abundant metabolites were present in rats at higher levels than in humans. This study has provided non-clinical safety data that contribute to an overall safety assessment of somapacitan.

Guidance for the treatment of adult growth hormone deficiency with somapacitan, a long-acting growth hormone preparation.

Adult growth hormone deficiency (AGHD) is a rare endocrine disorder characterized by an abnormal body composition, metabolic abnormalities associated with increased cardiovascular diseases, bone loss, and impaired quality of life. Daily subcutaneous injections with recombinant growth hormone (GH) can alleviate the abnormalities associated with AGHD. Several long-acting GH (LAGH) preparations are currently in development that aim to reduce treatment burden for patients receiving daily GH injections. Somapacitan (Sogroya®; Novo Nordisk, Denmark) is the first LAGH preparation that has been approved for treatment of AGHD in the United States, Europe, and Japan. The recent approval of somapacitan and anticipated approval of other LAGH molecules presents new questions for physicians planning to treat AGHD with LAGH in the future. Differences in the technologies used to prolong the half-life of recombinant GH are expected to result in variations in pharmacokinetic and pharmacodynamic profiles between preparations. Therefore, it is essential that physicians understand and consider such variations when treating patients with these novel GH replacement therapies. Here, we present a set of treatment recommendations that have been created to guide physicians initiating therapy with somapacitan in patients with AGHD who are eligible for GH replacement. Furthermore, we will review the published data that underlie these recommendations to explain the rationale for the treatment and monitoring advice provided.

Effective GH Replacement With Once-weekly Somapacitan vs Daily GH in Children with GHD: 3-year Results From REAL 3.

CONTEXT: Current GH therapy requires daily injections, which can be burdensome. Somapacitan is a long-acting GH derivative in development for treatment of GH deficiency (GHD). OBJECTIVE: Evaluate the efficacy, safety, and tolerability of once-weekly somapacitan after 3 years of treatment. DESIGN: A multicenter, randomized, controlled, phase 2 study comparing somapacitan and once-daily GH for 156 weeks (NCT02616562). SETTING: Twenty-nine sites in 11 countries. PATIENTS: Fifty-nine children with GHD randomized (1:1:1:1) and exposed to treatment. Fifty-three children completed the 3-year period. INTERVENTIONS: Patients received somapacitan (0.04 [n = 14], 0.08 [n = 15], or 0.16 [n = 14] mg/kg/wk) or daily GH (n = 14) (0.034 mg/kg/d, equivalent to 0.238 mg/kg/wk) subcutaneously during the first year, after which all patients on somapacitan received 0.16 mg/kg/wk. MAIN OUTCOME MEASURES: Height velocity (HV) at year 3; changes from baseline in height SD score (HSDS), HVSDS, and IGF-I SDS. RESULTS: The estimated treatment difference (95% CI) in HV for somapacitan 0.16/0.16 mg/kg/wk vs daily GH at year 3 was 0.8 cm/y (-0.4 to 2.1). Change in HVSDS from baseline to year 3 was comparable between somapacitan 0.16/0.16 mg/kg/wk, the pooled somapacitan groups, and daily GH. A gradual increase in HSDS from baseline was observed for all groups. At year 3, mean HSDS was similar for the pooled somapacitan groups and daily GH. Change from baseline to year 3 in mean IGF-I SDS was similar across treatments. CONCLUSIONS: Once-weekly somapacitan in children with GHD showed sustained efficacy over 3 years in all assessed height-based outcomes with similar safety and tolerability to daily GH. A plain language summary (1) is available for this study. CLINICAL TRIAL INFORMATION: This study has been registered at ClinicalTrials.gov, number NCT02616562 (REAL 3).