In the long-awaited American Society of Clinical Oncology abstracts that debuted this week, Rule Breakers pick Exelixis (NASDAQ:EXEL) was relatively well-represented, issuing multiple reports that showed promising progress in several of its anticancer compounds.

Nothing earth-shattering arose regarding Exelixis' data sets on its later-stage multitarget drugs like XL647, nor early-stage compounds such as XL184 and XL765. Still, all of Exelixis' compounds with abstracts at ASCO continued to show at least some activity in fighting cancer, and the phase 2 XL880 stomach cancer drug data particularly stood out.

Considering that Exelixis' lead drugs are only now entering late-stage testing, it's still too early to determine how its compounds will fare against the competition. (That's why I'm not yet directly comparing the company's data to that of rival compounds.) Nonetheless,  Exelixis' ASCO abstracts suggest that the safety and efficacy data for its drugs is definitely good enough to warrant future testing. Then again, GlaxoSmithKline's (NYSE:GSK) decision to pick up XL880 was a good clue that it merited further investigation.

Last week, IMS Health (NYSE:RX) estimated that cancer-drug sales could grow 67% between 2008 and 2012, to $80 billion worldwide. Exelixis' compounds, known as multiple tyrosine kinase inhibitors, attack cancer in a novel way that helps them stand out from the competition. However promising the ASCO data, however, the drugs' real test will come in subsequent trials, as survival data versus other compounds and other more comparable results arrive.

Further early-stage Foolishness: