With the SPDR S&P Biotech Index up 50% over the trailing-12-month period, it's evident that investment dollars are willingly flowing into the biotech sector. Keeping that in mind, let's have a look at some of the rulings, studies, and companies that made waves in the sector last week.

It was an extremely busy week on the biotech front -- so busy, in fact, that instead of looking at the week's five most important stories, I'm expanding it to six!

What's popping?
No biotech company exploded higher in greater fashion than Vanda Pharmaceuticals (NASDAQ:VNDA), which tacked on 134% (yes, 134%!) after briefing documents released Tuesday and the Food and Drug Administration's Advisory panel meeting on Thursday confirmed a recommendation for approval for Hetlioz, the proposed trade name for tasimelteon, Vanda's non-24-hour drug. For the majority of people the sun/daylight serves as a regulating marker for our sleep patterns. For those people who are blind, their sleep patterns can be irregular since they don't have the sun or daylight as a point of reference. Hetlioz has the potential to help control sleep patterns for the blind according to the FDA panel -- and since there is no drug currently approved to specifically treat non-24-hour-disorder, the market would be entirely Vanda's for the taking.

Another impressive move higher, though perhaps not as strong as Vanda, came from Cadence Pharmaceuticals (NASDAQ: CADX) on Friday after it announced a favorable ruling in a patent infringement lawsuit case against Exela Pharma Sciences. According to Cadence's press release, a Delaware U.S. District Court judge ruled that Exela's abbreviated new drug application that would be a biosimilar to Cadence's Ofirmev, an injectable acetaminophen used in cases of mild to moderate pain, would violate two of Cadence's patents. This ruling removes the potential for any generic competition for Ofirmev in the near-term and gives Cadence a clear path to grow its lead FDA-approved drug. Shares gained 37% on the week.

ImmunoGen (NASDAQ:IMGN) was able to put some of its recent weakness in the rearview mirror with the announcement on Monday that it had signed another collaborative agreement with Novartis allowing the big pharma company the rights to license its targeted antibody payload technology to research an unspecific cancer target. The licensing deal, which mirrors a deal struck a month earlier, involves an upfront payment from Novartis as well as the potential to earn up to $200 million in royalties. ImmunoGen recently shelved its lead in-house cancer drug, IMGN901, but it still has an enormous pipeline of collaborative drugs in the works. It's a name I certainly recommending adding to your watchlist.

Finally, on Wednesday Pharmacyclics (NASDAQ: PCYC) and Johnson & Johnson announced the first approval for Imbruvica (formerly ibrutinib) for the treatment of mantle cell lymphoma in patients that have had at least one prior therapy. This is big but relatively unexpected news, given how incredibly well ibrutinib performed in clinical trials. In a 111-patient trial for which the drug was approved, 66% of patients demonstrated some form of tumor shrinkage or remission. Imbruvica has the potential to be a multibillion-dollar drug -- now it's up to Pharmacyclics and J&J to masterfully price and launch this probable blockbuster.

What's dropping?
On the flipside, shareholders of Epizyme (NASDAQ: EPZM) are hoping for a better week ahead after its share price plunged 44% following the release of early stage data for EPZ-5676 for the treatment of acute leukemia. According to Epizyme's press release, EPZ-5676 delivered a partial anticancer response in four of eight patients with MLL-realignment while having no effect on patients without MLL-r. Investors seem displeased that EPZ-5676 offers only a positive impact on the smaller subset of MLL-r patients, as well as only delivered a measurable response in half of the MLL-r patients. The good news is that a maximum tolerated dose wasn't reached, and dosing escalation is still ongoing, which means improved efficacy could still be achieved.

Last, but not least, the disaster du jour this week was Sarepta Therapeutics (NASDAQ:SRPT), which plunged 60% after announcing on Tuesday that the FDA considered a new drug application filing for eteplirsen to be premature given the recent failure of GlaxoSmithKline and Prosensa's drisapersen. With the FDA unwilling to accept dystrophin as a measurable biomarker for approval now, it's looking as if Sarepta will be required to run a significantly more expansive, and costly, phase 3 trial for eteplirsen. This situation still could work out nicely for Sarepta as there are no competitors targeting exon-51 with regard to treating Duchenne muscular dystrophy, but investors are going to be staring down a much longer wait and higher expenses before this drug can be brought to market.