Why Amag Pharmaceuticals Is Sinking Despite Positive Top-Line Results

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AMAG Pharmaceuticals Inc. (NASDAQ: AMAG) saw its shares take a sharp turn down after the company reported top-line results from its most recent pharmacokinetic (PK) study. The results were ultimately positive and management is looking to turn this into a new drug application (NDA) later this year. However there was a hiccup in the trial, with some results falling outside of the bioequivalence range.

Essentially, the PK study was designed to demonstrate comparable bioavailability of the subcutaneous auto-injector product and the current intramuscular (IM) injection form of Makena in approximately 120 healthy post-menopausal women.

Makena was administered subcutaneously and demonstrated bioequivalence to the IM injection, with the 90% confidence interval for the ratio of AUC falling within the 80% to 125% range, which the FDA uses to define bioequivalence.

The mean maximum or peak plasma concentration (Cmax) for Makena subcutaneous was slightly higher than for the IM, with the 90% confidence interval for the ratio of Cmax (96.6% to 138.7%) falling outside of the previously mentioned bioequivalence range.

Based on the positive results from this study, AMAG is planning to submit a supplemental NDA to the U.S. Food and Drug Administration (FDA) for the Makena subcutaneous auto-injector in the second quarter of 2017, with an anticipated decision in the fourth quarter of 2017.

Julie Krop, M.D., chief medical officer and senior vice president of clinical development and regulatory affairs at AMAG, commented:

We believe the results from this definitive PK study have demonstrated comparable bioavailability between the subcutaneous and intramuscular injections of Makena, and we are pleased to have met our primary study objective of demonstrating bioequivalence on the measure of AUC. Because hydroxyprogesterone caproate, the active ingredient in Makena, is a long-acting therapy with a proven safety record, we believe AUC is the most clinically relevant PK parameter.

Shares were last seen down over 11% at $20.70 on Thursday, with a consensus analyst price target of $31.60 and a 52-week trading range of $17.92 to $36.83.