(RxWiki News) A vaginal gel containing progesterone that developers hoped would prevent early birth was rejected by the FDA for lack of adequate evidence that it's effective.
The gel's risks and benefits were reviewed at Friday's meeting of the Reproductive Health Drugs Advisory Committee at the FDA, but background materials were released by the FDA before the meeting took place.
"Consult your OB/GYN about your risk factors for pre-term delivery."
"The information and data in this application do not support the efficacy of progesterone gel compared with placebo in reducing the risk of pre-term births before 33 completed weeks of gestation among women with a short cervical length," the FDA background documents conclude.
Women who have a short cervix, generally defined as less than 2.5 cm when she is 24 weeks pregnant, are at a higher risk for giving birth early.
This gel was supposed to decrease the cervical shortening and thereby prevent delivery before full term, according to the companies that created it, Watson Pharmaceuticals and Columbia Laboratories.
The FDA reviewed a study conducted by Columbia Laboratories in ten countries where 465 women used either the progesterone gel or a placebo gel that they needed to apply themselves once each morning.
While the gel did appear to help prevent preterm births before 33 weeks, it did not prevent delivery before 27, 34 or 36 weeks.
Just under 9 percent of the women who used the progesterone gel gave birth before 33 weeks, but 15 percent of the women with the placebo gel gave birth before 33 weeks.
Yet, the FDA said it was concerned that the study's results were not consistent across different countries and that the data from some countries may have skewed the overall conclusions.
U.S. women in particular, who comprised 45 percent of the women in the study, did not appear to show significantly better prevention of preterm birth with the gel compared to the placebo.
Only about 2 percent fewer American women who used the gel gave birth early compared to those who used the placebo.
Watson Pharmaceuticals and Columbia Laboratories attributed this lower U.S. effectiveness to a lower level of compliance among American women, but the FDA said that U.S. women using the gel correctly more than 80 percent of the time still did not result in significant reduction of early births.
"From a clinical perspective, it does not appear that the applicant has identified a population of U.S. women who are likely to benefit from the use of progesterone gel to reduce their risk of preterm birth," the FDA documents state.
The FDA documents also state that not enough of the women in some of the subsets of the study had short enough cervixes to show the gel was necessarily what prevented a preterm delivery.
There were no differences in apparent side effects between the women using the progesterone gel and the women using a placebo gel.
Currently, the only drug marketed to reduce early delivery is the gel Makena, which was approved in February, 2010.