Vosoritide for Short Stature in Turner Syndrome

Inclusion Criteria:

1. Parent(s) or guardian(s) are willing and able to provide written, signed informedconsent after the nature of the study has been explained and prior to performance ofany research-related procedure. Also, subjects under the age of 18 are willing andable to provide assent (if required) after the nature of the study has beenexplained and prior to performance of any research-related procedure.

2. Stated willingness to comply with all study procedures and availability for theduration of the study

3. Age >3 years 0 days AND <10 years 364 days

4. Pre-pubertal defined as Tanner Stage 1 breasts in females.

5. Patient height <-2 SDS. All height SDS values are calculated using the CDC growthcharts/data tables.

6. Patients must have a confirmed diagnosis of Turner Syndrome based on a karyotypewith a minimum of 30 cells or on a chromosomal microarray. Subjects with TurnerSyndrome mosaicism (such as a 46,XX/45,X karyotype) must have a minimum of 10%mosaicism of 45,X cell line in order to participate in the study.

7. Subjects must either be naïve to growth hormone or have a poor response to growthhormone therapy defined as either:

8. Subjects completed at least one year of treatment with GH and first year heightvelocity (HV) below -1 SD according to the National Cooperative Growth Study TS 1st year response to growth hormone height velocity curve.

9. Subjects receiving GH for more than a year with AGV in the last 6 months < 50%ile for US girls for age/sex). Subjects meeting this criterion are no longershowing catch up growth and may benefit from an alternative form of therapy.

Exclusion Criteria:

1. Growth plate fusion - Defined as a bone age via the Greulich and Pyle method of 13years. These patients have limited remaining growth potential.

2. Concomitant treatment with growth hormone or recombinant insulin-like growthfactor-1 (IGF-1). Patients may have been previously treated with growth hormone orIGF-1 therapy. If the patient is currently on one of these therapies, they will berequired to discontinue at least 1 week prior to the screening visit. That decisionwill be deferred to their treating clinical endocrinologists in conjunction with thepatient's guardians. We anticipate that only patients who are having a poor responseto their therapy will be interested in enrolling in the current study as there is norationale for a patient who is receiving growth hormone therapy and having apositive response to enroll in the current study.

3. Prior or concomitant treatment with any form of estrogen, gonadotropin-releasinghormone (GnRH) analog, aromatase inhibitor or oxandrolone

4. History of any type of malignancy

5. Subjects known to have Y-chromosome material unless they have undergone gonadectomyand have fully external female genitalia

6. Chronic medical condition known to affect growth including but not limited to: A. Cystic fibrosis B. Diabetes C. Inflammatory Bowel Disease D. Untreated CeliacDisease - If a subject has been diagnosed with celiac disease and has been on agluten free diet for >12 months and has a tissue transglutaminase antibody withinthe normal range at screening, then they are eligible for the trial. E. Asthma requiring a daily inhaled steroid dose > 400 micrograms of inhaledbudesonide per day or equivalent F. Taking daily oral glucocorticoids for any reasonG. Note - Attention Deficit hyperactivity Disorder (ADHD) treated with a stimulantand treated hypothyroidism with a normal thyroid stimulating hormone (TSH) will NOTexclude the subject from participating in the trial. Subjects on either stimulantmedication or thyroid hormone replacement must be on a stable dose for 3 monthsprior to the screening visit. H. Congenital heart disease which places the subject at increased risk of an adversecardiac outcome in the setting of hypotension including but not limited to:hypertrophic cardiomyopathy, aortic stenosis with peak gradient >50mmHg, severeaortic regurgitation (defined as pressure half time >500ms by echocardiogram),coronary insufficiency, or any anatomy with a need for an afterload reducing agent.Any patient with baseline abnormalities on echocardiogram will be reviewed with apediatric cardiologist for appropriateness for inclusion in the study.

7. Malnutrition - Defined as a BMI <5th percentile (CDC growth charts)

8. Any clinically significant abnormality on screening tests as determined by theprincipal investigator. Abnormal screening labs may be repeated up to 3 months afterthe screening visit. If those labs are normal on repeat, the subject may proceedinto the trial.

9. Known or suspected allergy to trial medication, excipients, or related products

10. The receipt of any investigational drug within 90 days prior to this trial