AstraZeneca and Nektar win FDA OK for blockbuster-hopeful constipation drug

The FDA approved a new opioid-induced constipation treatment from partners AstraZeneca ($AZN) and Nektar Therapeutics ($NKTR), shaking off some safety concerns and green-lighting a drug the two hope can bring in billions.

The treatment, naloxegol, is an oral blocker of mu-opioid receptors, designed to ease the gastrological side effects associated with common painkillers. In AstraZeneca and Nektar's 1,352-patient pivotal program, the drug proved itself effective in increasing the number of bowel movements among opioid-taking subjects reporting constipation, significantly beating out placebo.

But, like other drugs in its class, naloxegol has been linked to an increased risk of heart attacks, and while the agency didn't let that stand in the way of approval, regulators are asking AstraZeneca and Nektar to conduct a large post-market study to keep an eye on any flare-ups in cardiovascular events.

Now the two companies are gearing up to market their treatment as Movantik, eyeing a space AstraZeneca believes could make the drug a blockbuster. The treatment, discovered by Nektar, is the first mu-opioid treatment approved for OIC. AstraZeneca stepped in on the program in 2009, signing a deal worth up to $1.5 billion and touting the drug as a meaningful advance in an area of unmet medical need.

With the approval, the partners leapfrog rival Salix Pharmaceuticals ($SLXP), whose mu-opioid-blocking Relistor endured an FDA rejection for OIC in 2012 over cardiovascular concerns. That drug is up for a second chance this month, and, in light of naloxegol's approval and a change in tone at the agency, analysts have come to like its odds.

But AstraZeneca and Nektar will hardly have sole claim on the market. Even without Relistor providing competition, Sucampo Pharmaceuticals ($SCMP) markets Amitiza, a chloride channel activator approved last year, and Cubist Pharmaceuticals ($CBST) sells a mu-opioid receptor antagonist of its own in Entereg, though that drug is yet to receive an OIC nod.

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