With the SPDR S&P Biotech Index up 27% 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.

Unlike last week, we had a pretty exciting week on the biotech front, filled with plenty of clinical data -- both good and bad. Since it's the weekend, and I don't want to singlehandedly be the cause of its getting off to a poor start, let's have a look at some of this week's positive news.

On Thursday, neurological and central nervous system-focused biotechnology company Acadia Pharmaceuticals (NASDAQ:ACAD) soared after disclosing that Pimavanserin, its antipsychotic drug for those with Parkinson's disease, met both its primary and secondary endpoints in late-stage trials. According to Acadia, Pimavanserin demonstrated "highly significant antipsychotic efficacy" and also helped to improve motoric tolerability. Given that it met both primary and secondary endpoints, and was well tolerated by patients, I can only imagine a new drug application is in the offing in the second quarter.

Halozyme Therapeutics (NASDAQ:HALO) had an equally impressive vault higher on Friday after disclosing that it and partner Baxter International had received a favorable opinion from the Committee for Medicinal Products for Human Use (Europe's version of the FDA panel) for immunodeficiency drug HyQvia. HyQvia is a subcutaneous drug given just once every three to four weeks and has the chance of dramatically reducing adverse events associated with more frequently administered intravenous immunodeficiency medications. Although the European Medicines Agency isn't required to follow the opinion of the CHMP, the trial data and today’s announcement would suggest an approval is in the offing.

Also in the plus column was NPS Pharmaceuticals (UNKNOWN:NPSP.DL) which rallied by double digits after revising its collaboration agreement with Takeda Pharmaceuticals. The new terms allowed NPS to repurchase its short-bowel-syndrome drug, Revestive (known as Gattex in the U.S.) overseas from Takeda for $50 million in NPS's common shares and will necessitate a milestone payment to Takeda when it and recombinant human parathyroid hormone 1-84 (the other compound repurchased by NPS) reach sales of $750 million annually. Gattex has a good shot at making NPS a profitable company, so this is a big sustainable move by NPS.

InterMune (UNKNOWN:ITMN.DL) shares rallied on Thursday following the decision from the U.K.'s National Institute of Health and Clinical Excellence to allow the sale of Esbriet in the U.K. to treat idiopathic pulmonary fibrosis, or IPF. Investors saw this as a positive, but I'm going to lump it in the neutral column given InterMune's very shaky history of boosting sales. As I noted last week, Wall Street had originally expected $77.9 million in sales from Esbriet in 2012, and the end result was but one-third of that amount. Esbriet's extreme costs act as a major deterrent from getting it prescribed more often, which makes me leery that sales will see any meaningful impact from the U.K. approval.

Rounding out the week on a sour note was Incyte (NASDAQ:INCY), which, on Monday, reported in a regulatory filing that one patient taking its myelofibrosis medication Jafaki (known as Jakavi overseas) had developed a case of progressive multifocal leukoencephalopathy, or PML. Although this represents just one case in the nearly 10,000 prescriptions of Jakafi that have been written, it was enough to concern investors. I, on the other hand, am not as concerned given that PML is more common in patients with myelofibrosis and may not have been caused by Jakafi in the first place. It's a story that bears watching, but I wouldn’t read too deeply between the lines just yet.