Expert Commentary

Progesterone supplementation does not PROLONG pregnancy in women at risk for preterm birth: What do we do now?

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What is the future for 17P now that a required trial for the drug's efficacy showed that its use did not reduce preterm birth, neonatal morbidity, or fetal/early infant deaths—and an FDA advisory committee recommended withdrawal of the drug's approval?



Preterm birth (PTB) remains a significant public health concern and a major cause of newborn morbidity and mortality. In the United States, 1 in 10 babies are born preterm (< 37 weeks), and this rate has changed little in 30 years.1

In 2011, the US Food and Drug Administration (FDA) approved progesterone supplementation—specifically, α-hydroxyprogesterone caproate (17P) injection (Makena)—to prevent recurrent PTB in women with a singleton pregnancy at high risk by virtue of a prior spontaneous PTB.2 This was the first-ever FDA-approved drug for PTB prevention, and it was the first drug approved by the FDA for use in pregnancy in more than 15 years. The approval of 17P utilized the FDA's Subpart H Accelerated Approval Pathway, which applies to therapies that: 1) treat serious conditions with unmet need, and 2) demonstrate safety and efficacy on surrogate end points reasonably likely to predict clinical benefit.3

By voting their approval of 17P in 2011, the FDA affirmed that PTB was a serious condition with unmet need, that birth < 37 weeks was an accepted surrogate end point, and that there was compelling evidence of safety and benefit. The compelling evidence presented was a single, randomized, vehicle-controlled clinical trial conducted by the Maternal-Fetal Medicine Units (MFMU) Network, which showed significant reduction in recurrent PTB < 37 weeks (from 54.9% in the placebo group to 36.3% in the 17P group; P<.001; relative risk [RR], 0.66; 95% confidence interval [CI], 0.54-0.81).4

In 2017, the Society for Maternal-Fetal Medicine (SMFM) reaffirmed the use of 17P to prevent recurrent PTB and, that same year, it was estimated that 75% of eligible patients received 17P.5,6 Importantly, Subpart H approval requires one or more follow-up clinical trials confirming safety and efficacy. And the FDA has the right—the responsibility—to revisit approval if such trials are either not performed or are unfavorable.

The recently published PROLONG study by Blackwell and colleagues is this required postapproval confirmatory trial conducted to verify the clinical benefit of 17P supplementation.7

Continue to: Study design, and stunning results...


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