Vosoritide for Treatment of Short Stature in Girls With Turner Syndrome
Turner syndrome (TS) is characterized by a missing whole or part of the second sex chromosome in a phenotypic female, resulting in short stature due to haploinsufficiency of the short-stature homeobox-containing (SHOX) gene. Growth hormone (GH) is an approved therapy for this condition, although not associated with GH deficiency, and benefits are modest. Vosoritide, a C-type natriuretic peptide (CNP) analog, targets chondrocytes within the growth plate leading to increased cell proliferation and hypertrophy. We hypothesize that patients with TS and short stature will respond to vosoritide treatment leading to increased growth velocity. This study will enroll pre-pubertal girls with TS who are either naïve to GH or have had a poor response to GH therapy. All subjects will be treated with vosoritide for 12 months and will be assessed for safety monitoring and improvement in height outcomes. Annualized growth velocity (AGV) on vosoritide will be compared to AGV in the 6-18 months prior to initiation of vosoritide based on historical data available in the medical record. Subjects with a positive response to therapy will be given the option to continue in the extension phase of the study during which they will continue to receive vosoritide until growth cessation.
• Parent(s) or guardian(s) are willing and able to provide written, signed informed consent after the nature of the study has been explained and prior to performance of any research-related procedure. Also, subjects under the age of 18 are willing and able to provide assent (if required) after the nature of the study has been explained and prior to performance of any research-related procedure.
• Stated willingness to comply with all study procedures and availability for the duration of the study
• Age \>3 years 0 days AND \<10 years 364 days
• Pre-pubertal defined as Tanner Stage 1 breasts in females.
• Patient height \<-2 SDS. All height SDS values are calculated using the CDC growth charts/data tables.
• Patients must have a confirmed diagnosis of Turner Syndrome based on a karyotype with a minimum of 30 cells or on a chromosomal microarray. Subjects with Turner Syndrome 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.
• Subjects must either be naïve to growth hormone or have a poor response to growth hormone therapy defined as either:
‣ Subjects completed at least one year of treatment with GH and first year height velocity (HV) below -1 SD according to the National Cooperative Growth Study TS 1st year response to growth hormone height velocity curve.
⁃ 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 longer showing catch up growth and may benefit from an alternative form of therapy.