(Reuters) - Versartis Inc said its experimental drug for the treatment of growth hormone deficiency in children did not meet the main goal of a late-stage study, sending its shares tanking 85 percent.

The drug, somavaratan, is a long-acting recombinant human growth hormone.

The company said patients receiving somavaratan failed to show non-inferiority, compared with patients on Pfizer Inc’s drug, Genotropin.

Versartis’ stock, which closed at $21.60 on Thursday, were down at $3.70 in after-hours trading.