It's always nice when everything goes according to plan for a development-stage drugmaker. Yesterday, Pain Therapeutics (NASDAQ:PTIE) and partner King Pharmaceuticals (NYSE:KG) announced successful phase 3 results for lead drug Remoxy.

Remoxy is Pain's attempt at bringing to market an opioid drug that's harder to abuse than Purdue Pharma's blockbuster OxyContin but has the same effectiveness as a painkiller. Remoxy was out-licensed to Pain by Durect (NASDAQ:DRRX), and then Pain gave marketing rights to King in a milestone $300 million cash deal for Remoxy and other unnamed abuse-resistant pain drugs.

In the phase 3 trial results announced yesterday, Remoxy succeeded on the primary endpoint of reducing pain in osteoarthritis sufferers and on the secondary endpoints compared to placebo. These results weren't unexpected, considering that Remoxy contains oxycodone, which is a proven painkiller, and the placebo patients were getting no pain relief other than the happy thoughts a sugar pill can sometimes provide.

Pain and King had negotiated a Special Protocol Assessment with the FDA before the study. Essentially, this means that the FDA gave its stamp of approval to the phase 3 trial design and endpoints, which raises the likelihood of marketing approval for the drug when King and Pain file a marketing application for it in the second quarter of next year.

Once Pain files the marketing application for Remoxy, it will receive a $15 million milestone payment from King, and then another $15 million if the FDA approves it. Regulatory risk is always present with any drug, but the likelihood of the FDA denying approval to Remoxy seems low.

Pain and Alpharma (NYSE:ALO) are racing to be the first to develop an abuse-deterrent oral opioid. Just last week, Alpharma reported positive phase 3 trials for its abuse-deterrent drug, and the company expects to file a marketing application for it in the first half of 2008. Other, smaller competitors, like Acura Pharmaceuticals and Elite Pharmaceuticals (AMEX:ELI), are also working on similar drugs.

Now that Pain has gotten the clinical trial risk behind it, if Purdue doesn't try to delay Remoxy's approval via a patent infringement suit, it looks like we'll get to see in 2009 whether King can overcome the last obstacles to Remoxy's success -- getting insurers and other payors to cover the drug's cost.

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Fool contributor Brian Lawler owns shares of Pain Therapeutics, but no other company mentioned in this article. The Fool has a painless disclosure policy.