Public Citizen has petitioned the FDA to immediately withdraw the approval of AMAG Pharmaceutical’s preterm birth injection Makena (hydroxyprogesterone caproate) because of the failure of a post-market clinical trial.

AMAG announced in March that its FDA-mandated clinical trial did not demonstrate a statistically significant difference between the treatment and placebo for prevention of preterm delivery at less than 35 weeks.

Makena was granted accelerated approved in 2011 based on data from a single clinical trial of 463 women at 15 weeks to 20 weeks pregnant. The study found that weekly treatment with hydroxyprogesterone significantly reduced the rate of preterm birth before 37, 35, and 32 weeks of gestation.

However, the petition points out that agency’s reviewers raised serious concerns and identified major deficiencies in the data. In particular, the statistical reviewer expressed strong opposition to the approval.