Erbitux's Deceptively Disappointing Results

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Since when are positive study results in a blockbuster indication not enough to get investors excited? Following last weekend's presentation of data from ImClone Systems' (Nasdaq: IMCL) lead drug Erbitux at the American Society of Clinical Oncology's annual meeting, shares of ImClone have fallen as much as 8% this week.

The Erbitux data measured the drug's effectiveness against non-small cell lung cancer (NSCLC). We already knew that the trial succeeded, but we didn't know how great a difference the drug made. The new results reveal that when combined with a common chemotherapy regimen, Erbitux increased patients' median overall survival by 1.2 months. These results are much more nuanced than their top-line overall survival data suggests, but that figure tends to draw the most attention from interested parties.

Erbitux is already approved as a treatment for cancers of the colon, head, and neck, but adding NSCLC to its label would greatly benefit ImClone and its marketing partners. Non-small-cell lung cancer is the most common type of lung cancer, which in turn is the second-most-common type of cancer in the U.S. It's also one of the most lethal and hardest to treat.

There are already targeted therapies approved to treat NSCLC, but the market potential for new compounds to treat this disease is still huge, since no magic treatment bullet has yet been found. Among treatments on the market, OSI Pharmaceuticals' (Nasdaq: OSIP) Tarceva and AstraZeneca's (NYSE: AZN) Iressa most closely resemble Erbitux. Genentech's (NYSE: DNA) Avastin is also approved to treat NSCLC as well.

In the Erbitux trials, patients with late-stage NSCLC who failed to respond to chemotherapy experienced a 1.97-month survival advantage, compared to placebo, after treatment with Tarceva in its pivotal phase 3 study. Avastin produced a two-month survival advantage when used in combination with two common chemotherapy drugs.

Did the Erbitux lung-cancer efficacy data beat out similar EGFR inhibitors? Maybe yes, maybe no. More importantly for ImClone, the data should be good enough for regulatory approval in this indication when partner Bristol-Myers Squibb (NYSE: BMY) files a marketing application for it later this year.