A Phase 3 interventional study of Lonapegsomatropin [SKYTROFA®] and Somatropin Pen Injector in Turner Syndrome, Short Stature Homeobox Gene Mutation and Idiopathic Short Stature, sponsored by Ascendis Pharma A/S. Recruiting at 56 sites in 7 countries. Open to participants aged 2 Years to 17 Years. Per ClinicalTrials.gov, last updated 2026-11-05.
Sponsored by Ascendis Pharma A/S · Phase 3, Interventional, and Treatment
This basket trial will enroll prepubertal children and adolescents with clinically diagnosed and genetically confirmed (if applicable) TS, SHOX-D, SGA, or ISS between ages of ≥2 and \<18 years with open growth plates. The purpose of the study is to see how well treatment with once-weekly lonapegsomatropin works compared to treatment with daily somatropin. Approximately 186 participants will be distributed equally (1:1), to receive either lonapegsomatropin for 2 years or somatropin for 1 year followed by lonapegsomatropin for 1 year. This trial will be conducted in the United States, France, Germany, Italy, Romania, Spain and South Korea.
125 studies on the registry are indexed under Turner Syndrome; 33 are open to participants now.
This study's planned enrollment of 186 is above the median of 67 across 52 interventional studies indexed under Turner Syndrome.
Browse Turner Syndrome studies →Ascendis Pharma A/S is the lead sponsor of 17 studies on the registry; 7 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Inclusion Criteria:
Diagnosis of TS, SHOX-D, SGA, or ISS with impaired growth or short stature, according to the following disease-specific criteria:
TS or SHOX-D (Léri-Weill dyschondrosteosis):
(i.) AHV \<25th percentile over a time span of 6-16 months prior to screening utilizing a historical height properly documented in a health care setting (self-measurement record is not accepted) OR (ii.) Height \<5th percentile for sex and age according to the Centers for Disease Control Growth Charts for the United States
SGA without catch-up growth:
c. Birth weight and/or birth length \< -2.0 SDS for gestational age according to the 2006 World Health Organization Child Growth Standards. For infants born premature, the Fenton Preterm Infant Growth Chart (Fenton 2013) should be used.
d. Impaired growth or short stature defined as: (i.) AHV \<25th percentile over a time span of 6-16 months prior to screening properly documented in a health care setting (self-measurement record is not accepted) OR (ii.) Height \< -2.0 SDS for age and sex according to the 2000 Centers for Disease Control Growth Charts for the United States for children ≥ 3 years or height \< -2.5 SDS for age and sex according to the for children ≥ 2 years and \< 3 years
ISS:
e. Height \< -2.25 SDS for sex and age according to the Centers for Disease Control Growth Charts for the United States with no identifiable cause for short stature.
f. Documented normal GH-IGF-1 axis, defined as either: (i.)IGF-1 SDS >0 at screening based on central laboratory OR (ii.)Historical documentation of normal peak GH upon stimulation test (as defined by local institution) g. 46,XX chromosome as determined by karyotype or microarray if female. For karyotypes, a minimum of 30 cells must be counted.
Exclusion Criteria:
Any diagnosis or presence at screening of the following:
Exclusion Criteria only applicable to TS:
Exclusion Criteria only applicable to SGA:
a. Any known clinically significant abnormality likely to affect growth or the ability to evaluate growth with standing height measurements: (i.)Chromosomal aneuploidy, significant gene mutations, or medical syndromes with short stature, including but not limited to Turner syndrome, Laron syndrome, Noonan syndrome, Prader-Willi syndrome, abnormal SHOX-1 gene analysis or absence of GH receptors.
(ii.)Congenital abnormalities (causing skeletal abnormalities), including but not limited to skeletal dysplasias.
Exclusion Criteria only applicable to ISS:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HbA1c
A blood test of average blood sugar over the past two to three months, given as a percentage or in mmol/mol. 6.5% (48 mmol/mol) or more is the usual threshold for diabetes, normally confirmed by a second test.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive Lonapegsomatropin by subcutaneous injection for 2 years (104 weeks)
Combination Product: Lonapegsomatropin [SKYTROFA®]
Participants will receive somatropin by subcutaneous injection for 1 year (52 weeks) followed by lonapegsomatropin for 1 year (52 weeks)
Combination Product: Somatropin Pen Injector
Subcutaneous injection once weekly
Subcutaneous injection once daily
Annualized Height Velocity (AHV) (cm/year)
To evaluate the efficacy of lonapegsomatropin as compared to somatropin in children and adolescents with TS, SHOX-D, SGA, or ISS
Time frame: 52 Weeks
Annualized Height Velocity (AHV) (cm/year)
To evaluate lonapegsomatropin as compared to somatropin on additional measures of efficacy in children and adolescents with TS, SHOX-D, SGA, or ISS
Time frame: 104 Weeks
Change from baseline in height standard deviation score (SDS)
To evaluate lonapegsomatropin as compared to somatropin on additional measures of efficacy in children and adolescents with TS, SHOX-D, SGA, or ISS
Time frame: 52 Weeks and 104 Weeks
Change from baseline in Bone Age (years)
To evaluate the safety and tolerability of lonapegsomatropin in children and adolescents with TS, SHOX-D, SGA, or ISS via Central Reader
Time frame: 52 Weeks and 104 Weeks
Change from baseline in ratio of Bone Age/chronological age
To evaluate the safety and tolerability of lonapegsomatropin in children and adolescents with TS, SHOX-D, SGA, or ISS via Central Reader
Time frame: 52 Weeks and 104 Weeks
Number of participants with treatment-related adverse events (AEs)
To evaluate the safety and tolerability of lonapegsomatropin in children and adolescents with TS, SHOX-D, SGA, or ISS
Time frame: 52 Weeks and 104 Weeks
Started Dec 2025 (actual). Primary completion is estimated for Feb 2028, 26 months after the start.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Lonapegsomatropin
Ascendis Pharma A/S