With the SPDR S&P Biotech Index up 33% 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 unmistakably good week for biotechnology stocks with everything from new drug filings, to clinical data and buyout rumors fueling much of the sector higher.

Biotechnology juggernaut Pharmacyclics (NASDAQ: PCYC) -- a company that has returned close to 19,000% since its recession lows -- ignited investor optimism when it and licensing partner Johnson & Johnson (NYSE:JNJ) filed a new drug application for ibrutinib. This is truly exciting news, because it marks the first breakthrough therapy drug that's filed for an NDA, and will act the test subject to the rest of the breakthrough therapy designated drugs. Ibrutinib delivered exceptional results in chronic lymphocytic leukemia and mantle cell lymphoma in terms of overall response rate, which should probably net it an approval from the Food and Drug Administration.

On the clinical data front, Alnylam Pharmaceuticals (NASDAQ:ALNY) and Inovio Pharmaceuticals (NASDAQ:INO) both put investors in their happy place.

For Alnylam Pharmaceuticals this was the second consecutive week that it reported positive clinical results. In this week's data, Alnylam reported positive top-line results for ALN-TTRsc, an early stage subcuteanous RNA interference therapeutic designed to treat familial amyloidotic cardiomyopathy. In the trial, ALN-TTRsc reduced serum TTR levels by greater than 80% in treated patients. If you recall, the company is also developing ALN-TTR02, an intravenous treatment for familial amyloidotic polyneuropathy that reduced serum TTR levels by 93% in a mid-stage trial. Together, these two TTR-mediated amyloidosis diseases affect 50,000 people worldwide and could kick-start Alnylam's pipeline.

In the case of the much smaller Inovio Pharmaceuticals, shareholders were treated to a double dose of good news. On Monday, Inovio reported that its universal H7N9 DNA vaccine protected 100% of vaccinated animals in trials from the H7N9 virus. Then, on Wednesday, Inovio reported that its next-generation HIV vaccine when combined with its cellectra electroporation delivery technology increased the response of CD8 T-cells from 7% to 52%! While there's plenty to be excited about for Inovio shareholders, I'd certainly urge some caution as it's delivered nothing but consistent losses over the past 30 years and will face a lot of competition in H7N9 vaccines.

Finally, on Friday, shares of Alexion Pharmaceuticals (NASDAQ:ALXN) shot higher on a report from Bloomberg that Roche was gathering funding for an attempted bid for Alexion. This isn't the first time Alexion has been a rumored buyout candidate, and it may not be the last. The company's only FDA approved drug is Soliris, the most expensive drug in the world, which is a therapy designed to treat rare diseases with little to no competition. Although orphan diseases do offer the allure of high drug prices and little competition, I'd rather keep my distance from Alexion here considering that it's valued at $22.3 billion and is valued at more than six times the peak sales estimate of $3.5 billion from Morningstar.