Open-label Extension Study to Evaluate the Safety of Long-term Twice-monthly Administration of Somavaratan in Adult Growth Hormone Deficiency (AGHD)

Open-label extension study to evaluate the safety of long-term twice-monthly administration of somavaratan in adults with Growth Hormone Deficiency (GHD).

An open-label extension study to evaluate the safety of long-term twice-monthly administration of somavaratan in adults with GHD. This multicenter study is open to participants completing a Versartis adult GHD study as well as approximately 40 new somavaratan naïve participants (either recombinant human growth hormone \[rhGH\] treatment naïve or currently receiving daily rhGH therapy). All participants will receive twice-monthly (every 15 days ± 2 days) subcutaneous (SC) somavaratan. Doses will be titrated to each participant's individual insulin-like growth factor-I (IGF-I) responses based on the IGF-I level 7 days post-dose until a maintenance dose is achieved. Participants receiving somavaratan in a previous somavaratan study will have their dose decreased by half (minimum dose of 20 milligrams \[mg\], 40 mg for women on estrogen, rounded down to the nearest even number) and will be titrated per the Dose Titration Plan. New participants enrolling in this study will be assigned to one of two cohorts based on sensitivity to rhGH and titrated per the Dose Titration Plan.

Eligibility Criteria:
Inclusion Criteria:

* Female participants of childbearing potential must have negative pregnancy test and use appropriate contraceptive methods
* Documented GHD during adulthood
* Participants naive to somavaratan must have an IGF-1 SDS value ≤ 0 at Screening
* Participants taking other hormone replacement therapy must have been on a stable course of treatment for at least 3 months
* Underlying disorders responsible for the participant's GHD must have been clinically stable for at least 6 months
* Participants receiving daily rhGH injections must washout for ≥ 14 days
* Body mass index (BMI) (kilograms \[kg\]/meter square \[m\^2\]) between 18.0 and 40.0

Exclusion Criteria:

* Untreated adrenal insufficiency
* Recently diagnosed thyroid dysfunction which is not being treated or has not been stable on therapy for at least 3 months
* Currently taking anti-inflammatory dose of glucocorticoids that could potentially compromise safety or efficacy assessments
* Currently taking a GHRH or IGF-I product
* Current significant cardiovascular disease, heart insufficiency of New York Heart Association (NYHA) class \> 2
* Current significant disease thought to increase risk of receiving growth hormone or confound assessment of study outcomes
* History of diabetes mellitus or inadequate glucose control
* Current drug or alcohol abuse
* Current human immunodeficiency virus (HIV) wasting syndrome (HIV testing not required)
* History of malignancy in adulthood (participants with a history of childhood malignancy that were subsequently treated with rhGH in childhood and remain GHD in adulthood may be enrolled)
* Women who are pregnant or breastfeeding
* Treatment with an investigational drug other than somavaratan within 30 days prior to Screening
* A significant abnormality in Screening laboratory results