UPDATED: FDA agrees to review Pfizer's abuse-deterring opioid candidate

Pharma bigwig Pfizer ($PFE) announced that the FDA has agreed to review the New Drug Application of its abuse-deterring extended-release opioid capsules, dubbed ALO-02.

The capsules' pellets contain ‚Äčthe opioid receptor antagonist naltrexone hydrochloride surrounded by the opioid receptor agonist oxycodone hydrochloride. Agonists bind to and activate opioid receptors in the brain, while receptor antagonists bind to and thereby block receptors from activation.

When ALO-02 is used as directed, the naltrexone is inactive, but it is released when the capsules are crushed for the purposes of abuse. Release of the opioid antagonist is designed to counter the addictive effects of oxycodone, Pfizer says in the release.

The company ran three tests of the abuse potential of ALO-02 among recreational users when taken via the oral, intranasal or intravenous routes.

If the FDA accepts the NDA submission, ALO-02 would become Pfizer's second abuse-deterring opioid formulation. It received an abuse deterrent label for its previously approved extended-release painkiller Embeda in October of last year.

Embeda's abuse-deterring mechanism is similar to that of ALO-02. Both release naltrexone when crushed. In the case of Embeda, the active ingredient is morphine sulfate, Pfizer says. The release notes that Embeda is expected to reduce abuse when the medication is taken orally or intranasally, but more postmarketing data is needed to prove abuse deterrence if the drug is improperly taken intravenously.

Having succeeded once, Pfizer now hopes the FDA will approve the use of naltrexone with oxycodone this time. Following the FDA's Embeda decision, the company was confident enough in the approach to kill a partnership with Pain Therapeutics to develop a different abuse-deterring formulation of oxycodone.

The FDA's decision to review ALO-02 comes on the heels of its acceptance of an NDA for Collegium Pharmaceutical's abuse-deterrent, extended-release oxycodone formulation, dubbed Xtampza ER. The candidate uses the DETERx microsphere-in-capsule delivery platform. Collegium says the platform also allows patients with difficulty swallowing to open the capsule and sprinkle the drug onto their food or into a feeding tube. 

Meanwhile, this month the FDA approved a new formulation of Zogenix's ($ZGNX) painkilling Zohydro ER designed to be abuse resistant, but made the company do more postmarketing work for the abuse-deterrent label.

That decision marked another step in the battle against opioid abuse, in which some have gone as far as to call for FDA Commissioner Margaret Hamburg's resignation over the 2013 approval of the conventional Zohydro formulation.

Citing a federal survey, Pfizer says almost 10 million Americans reported abusing prescription drugs in 2012.

- read the Pfizer release | read Collegium's release

Editor's Note: This story was updated with information from Collegium Pharmaceuticals