AMAG Pharmaceuticals, Inc. (NASDAQ:AMAG) shares are skyrocketing Thursday as the company received regulatory approval for one of its treatments.

The company announced that the U.S. Food and Drug Administration gave the green light for its Makena subcutaneous auto injector drug-device combination product, which is a treatment that is designed to reduce the risk of preterm birth in women who are pregnant with one baby, as well as those who spontaneously delivered one preterm baby in the past.

AMAG Pharmaceuticals developed the medication along with Antares Pharma Inc (NASDAQ:ATRS) as the two companies agreed back in a 2014 deal that AMAG will make and supply the drug product to Antares. The latter will then manufacture the treatment device, assemble it and package it for sale to AMAG at cost plus margin.

The partnership will net Antares a high, single-digit to low, double-digit figure in royalties on sales, plus the company will also be eligible for milestone payments as the drug’s sales start surging.

“The Makena QuickShot device was designed to enhance performance on the attributes we believe are most critical to healthcare providers and patient acceptance, including decrease time to administer and use of a shorter, thinner nonvisible needle for subcutaneous injection, while potentially providing an alternative to the existing intramuscular methods of administration,” said Robert F. Apple, President and CEO of Antares.

AMAG stock soared 28.1% after the bell Thursday.