Phase 3 flop puts Versartis on life support

Somavaratan is the only drug in Versartis' clinical-phase pipeline. (Courtesy of Versartis)

Versartis’ somavaratan has failed to match Pfizer’s Genotropin in a phase 3 pediatric growth hormone deficiency (pGHD) trial. The potentially company-killing data wiped more than 80% off the biotech’s stock price, leaving it looking to the readout from an ongoing trial in Japan for a shot at redemption.  

Menlo Park, California-based Versartis has essentially bet the farm on somavaratan, the only drug in its clinical-phase pipeline. Development of the long-acting recombinant human growth hormone in pGHD was the only task listed in the “use of proceeds” section when Versartis pulled off an upsized $126 million IPO in 2014. The failure of the phase 3 means its prospects now look grim.

Investigators enrolled 136 prepubertal children with GHD and randomized them to receive either twice-monthly administrations of somavaratan or daily doses of Genotropin, Pfizer’s short-acting growth hormone.

Somavaratan failed to match the height velocity (HV) achieved by Genotropin in the intent to treat population. Participants in the control arm had a 12-month HV of 10.70 cm, compared with 9.44 cm in the somavaratan cohort. That means the trial missed its primary endpoint of noninferiority, leaving Versartis reeling.

“We are very surprised and disappointed to learn the outcome of the Velocity trial. Somavaratan showed height velocity in the range we had hoped, but it was not sufficient to demonstrate non-inferiority in this trial,” Versartis CEO Jay Shepard said in a statement. “We have done an initial analysis of the top-line data and are continuing to thoroughly review the results to gain greater insight into the trial outcome. We plan to provide a corporate update later this year.”

Versartis has readouts scheduled for after that planned corporate update. Somavaratan moved into the 48-patient phase 3 stage of a phase 2/3 trial in Japan one year ago. Top-line results are due in 2018. Versartis is also studying somavaratan in adults with GHD in a phase 2 trial.

The inability of somavaratan to beat Genotropin in the main phase 3 casts doubt about its chances of moving the needle in these studies, though. And with the only other asset in Versartis’ pipeline yet to reach the clinic, the biotech has no fallback option if somavaratan is a busted flush.