With the SPDR S&P Biotech Index up 34% year to date, it's very 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.

As I noted over the weekend, two key Food and Drug Administration rulings should have been on investors' radars this week, so let's begin with those.

On Thursday, Theravance (NASDAQ:THRX) went before the FDA panel to present its case for Vibativ as a treatment for nosocomial pneumonia, or NP. Approved as a treatment for complex skin infections, Theravance is attempting to expand Vibativ's indications without running any additional clinical trials related to the NP trials run in 2009. Based on the FDA panels' mixed response, they voted in favor of approval of Vibativ, noting that it showed evidence of safety and efficacy if other treatments are exhausted, however, the panel also commented that the trial data didn't provide enough evidence of safety or efficacy. Talk about a coin that could wind up flipping either way come PDUFA time! 

Also on Thursday, Exelixis (NASDAQ:EXEL) received a favorable decision from the FDA in which it granted approval of Cometriq (formerly cabozantinib). The metastatic medullary thyroid cancer, or MTC, drug performed incredibly well in trials, extending progression-free survival nearly three times longer than the placebo, 11.2 months compared with four months, so assuming it met all safety criteria, approval seemed likely. With few alternatives available to MTC patients (of which 2,250 are diagnosed annually within the U.S.), this is a great step in patient care. Cometriq will now compete directly with AstraZeneca's (NYSE:AZN) Caprelsa, which gained FDA approval last year, but it's hard to imagine that Cometriq won't gain the upper hand considering its strong PFS performance in clinical trials. Pundits fully expect Cometriq to gain additional indications as its other clinical studies progress through the pipeline. 

The other major story this week was Acadia Pharmaceuticals' (NASDAQ:ACAD) incredible run after reporting very positive late-stage data on its experimental Parkinson's disease psychosis drug, pimavanserin. Shares scorched higher by 134% on the week after data showed that pimavanserin reduced psychosis in Parkinson's patients and helped them sleep better and stay awake longer. Most importantly, relative to the placebo and other limited available treatments, pimavanserin showed no negative effects on motor skills. As my Foolish colleague Brenton Flynn has pointed out, AstraZeneca's Seroquel and Johnson & Johnson's (NYSE:JNJ) Risperdal are other approved treatments for Parkinson's, but few address the psychosis aspect of the disease. Acadia's run higher looks to be well deserved.

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Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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