Shares in UK speciality pharma Diurnal plummeted more than 50 percent on news that a late-stage study of an experimental treatment for congenital adrenal hyperplasia (CAH) failed to meet its primary objective.

CAH is a potentially life-threatening orphan condition caused by a block in cortisol production, an essential adrenal steroid hormone required for healthy life.

A lack of cortisol causes the over-production of male steroid hormones (androgens), which together can lead to increased mortality, infertility and severe development defects, including ambiguous genitalia, precocious puberty and short stature.

The condition is estimated to affect a total of approximately 47,000 patients in Europe, with over 400,000 in the rest of the world.

Chronocort is a modified release preparation of hydrocortisone that has been designed to mimic the circadian rhythm of cortisol when given in a twice-a-day to control androgen excess and chronic fatigue in patients with diseases of cortisol deficiency.

While both regimens of the treatment used in the Phase III trial controlled androgens over a 24-hour period, they did not show superiority over conventional therapy, and thus failed to meet the study’s primary objective.

On the plus side, Chronocort achieved control on a lower overall dose of glucocorticoid with fewer patients requiring rescue therapy, and the modified release formulation eliminated the early morning peak in androgen levels seen using conventional therapy.

“We are surprised by these results, following our previously successful Phase II clinical trial in CAH,” said Diurnal’s chief executive Martin Whitaker. “However, these initial results confirm the concept of Chronocort, that early morning control of androgens can be achieved with a modified release preparation of hydrocortisone”.

He added that the firm will now analyse the full data set from the trial, along with interim data from the ongoing Chronocort long-term dosing study, to determine the next steps in the drug’s development.

“We remain confident that Chronocort will be a valuable treatment option for CAH patients.”