Pharmaceutical company Pharmacyclics (UNKNOWN:PCYC.DL) shot skyward today, up nearly 20%, because of some unusual news from a critical phase 3 trial. The company's drug Ibrutinib, now called Imbruvica, has already been approved for mantle cell lymphoma, and just had its phase 3 trial for chronic lymphocytic leukemia stopped early. While in most cases, stopping a clinical trial early is a sign of an ineffective drug, in some rare cases the drug is so effective that it is considered cruel to keep the drug from those acting as the control group for the study, which was the case here with Pharmacyclics' Imbruvica. While the drug showed a clear improvement over its head-to-head competitor, GlaxoSmithKline's (NYSE:GSK) Arzerra, which proved to be more of a bust than a blockbuster, there are much bigger competitive fish in this sea. In this video, Motley Fool health-care analyst David Williamson discusses why Roche's (OTC:RHHBY) Rituxan and AbbVie's (NYSE:ABBV) may have major competitive advantages against Pharmacyclics' Imbruvica, and why, despite the likelihood that this drug will be a mega-blockbuster both for PCYC and its partner Johnson & Johnson (NYSE:JNJ), those wins are already priced into the stocks, and investors today may be facing more downside than upside.