Neurocrine Biosciences (NBIX) said late Wednesday it has started a phase 2 clinical trial of crinecerfont in children aged 3 months to under 4 years with classic congenital adrenal hyperplasia, a rare genetic condition that results in an enzyme deficiency altering adrenal steroid hormone production.

Crinecerfont is approved in the US as an adjunctive treatment to glucocorticoid replacement to control androgens in adults and pediatric patients 4 years of age and older with classic CAH, according to a statement.

The study will evaluate the safety and tolerability of crinecerfont in about 20 children, with results expected to support a supplemental US new drug application to expand the drug's approved indication to patients younger than 4 years.

Separately, Neurocrine said it has completed enrollment in a phase 2 study in the European Union evaluating the drug in children from birth to under 2 years of age with classic congenital adrenal hyperplasia.