Muddled Data Dents Medarex Shares

Medarex(MEDX Quote) reported top-line results from three pivotal studies of its skin cancer drug ipilimumab Monday, and the data appear to be -- on a downward sliding scale -- negative to frustratingly confusing.

In fact, Medarex didn't tell investors much in its ipilimumab announcement, which shouldn't be terribly reassuring to those who were waiting for definitive proof that the drug is the long-awaited panacea for skin cancer.

Yet hope springs eternal, so the company and partner Bristol-Myers Squibb(BMY Quote) say they plan to seek approval for ipilimumab with the Food and Drug Administration in the first half of 2008.

Based on the little information provided in Monday's announcement, that quest isn't likely to have a happy ending.

Clearly, my bearish take on ipilimumab's chances for success in melanoma (at least this go-round) haven't changed much since early September, when I predicted that the data from these three phase III studies in melanoma wouldn't be strong enough to warrant the drug's approval.

Medarex shares dipped $2.58, or 19%, to $10.77 in Monday's after-hours trading session. The stock closed the regular session down 2 cents to $13.55.

Without providing any detail, Medarex said Monday that the key ipilimumab phase III study failed to meet its primary endpoint, "which was to rule out a best objective response rate of less than 10 percent."