The results of cancer studies with targeted therapies often produce results that are a mixed bag, as ImClone Systems (NASDAQ:IMCL) is proving. Last week the drugmaker announced that its only marketed compound, Erbitux, failed in phase 3 testing to prolong progression-free survival for patients with non-small cell lung cancer (NSCLC). Erbitux is already approved for colorectal cancer and head and neck cancer and is in testing for other oncology indications.

The announcement of the failed lung cancer trial does not signal the end of ImClone's hopes to get Erbitux approved to treat this difficult cancer. ImClone currently has other studies in NSCLC underway. It's always tough to achieve solid results in metastatic (spreading) cancers, and failure in one study does not always preclude success in another study in the same indication with different drug combinations or patient groups.

The failed study does come as some surprise, though, because another epidermal growth factor receptor (EGFR)-targeting compound like OSI Pharmaceuticals' (NASDAQ:OSIP) Tarceva has shown effectiveness in treating NSCLC.

Other approved cancer compounds with different molecular targets such as Genentech's (NYSE:DNA) Avastin and Onyx's (NASDAQ:ONXX) and Bayer's (NYSE:BAY) Nexavar are also in testing as treatments for NSCLC, so Erbitux is not without competitors in this space.

Investors who waited to see the positive ASCO Erbitux colorectal cancer data before buying shares of ImClone -- but were put off by the stock jumping above $47 a share in May -- have finally received the discount on shares that they have been waiting for, with shares now more than 25% lower from that 52-week high. This failed clinical trial is definitely not good news, but neither does it signal Erbitux's failure in this growing and lucrative cancer treatment space.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article.