The cardiovascular drug candidate developed by Cardiokine was the centerpiece of Cornerstone Therapeutics‘ (Nasdaq:CRTX) acquisition of the drug developer announced last week. But while it’s clear Cornerstone hopes lixivaptan helps fill out its drug portfolio, regulatory approval won’t make Cornerstone the initial beneficiary. That honor belongs to a company that had nothing to do with lixivaptan’s discovery or development — Pfizer (NYSE:PFE).

Cardiokine licensed lixivaptan from Wyeth in 2004. The Philadelphia-based biopharmaceutical company developed the compound as a treatment for hyponatremia, a condition in which the sodium levels of the blood are abnormally low that is commonly diagnosed in patients with heart failure. Lixivaptan achieved positive phase 3 clinical trial results in November leading to a New Drug Application (NDA) submission filed just prior to the close of 2011. Had Cardiokine remained a standalone company, it would have owed product payments to Wyeth up to $20 million after the drug was commercialized.

But Wyeth is no more. Pfizer acquired Wyeth in 2009. With Cornerstone’s acquisition of Cardiokine, the Cary-based company takes over responsibility for making that $20 million lixivaptan payment.

Cornerstone is ponying up relatively little up front to get Cardiokine. The company paid $1 million at closing and is assuming $2 million in Cardiokine’s debt, according to securities filings. Cornerstone will pay up to another $8.5 million if the lixivaptan NDA is approved by the U.S. Food and Drug Administration.

The real money comes when the lixivaptan is commercialized; payments to Cardiokine start at $7.5 million for the first sales milestone and reach $25 million if the drug reaches $250 million in sales. Cornerstone could be paying Cardiokine up to $147.5 million in total milestones alone.

Cornerstone, which reported $125 million in 2010 revenue, clearly has high hopes for the drug candidate. If lixivaptan reaches the sales projections outlined in the milestones, the drug would become Cornerstone’s top-selling product.

The money for Cardiokine doesn’t end with the milestone payments. Cardiokine shareholders stand to earn additional royalties between 8 percent and 12 percent, depending on the FDA’s labeling of the approved product. And if lixivaptan is licensed outside of the United States, Cornerstone will also pay Cardiokine shareholders half of any proceeds from that licensing deal.

The acquisition of Cardiokine and lixivaptan demonstrates Cornerstone’s strategy to grow revenue by selling more products that are used in hospitals. Lixivaptan will be sold by the same hospital-focused sales force that sells Curosurf, the respiratory distress drug that is currently Cornerstone’s top product.

The thinking here is that Cornerstone’s Curosurf sales force is already talking with doctors in hospitals about Curosurf. Lixivaptan gives the company another drug for that sales force to sell to the hospital contacts it has already established.

Cornerstone’s foundations were as as a respiratory therapeutics firm. But with the acquisition of Cardiokine and the cardiovascular candidate lixivaptan, the company is broadening its reach by positioning itself as a seller of hospital-based drugs. If lixivaptan does reach the projected sales targets, the $20 million payment to Pfizer will look like small change.

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