With the SPDR S&P Biotech Index up 32% 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 certainly a wild week in the biotech arena with two FDA approvals and one promising clinical trial leading the way for optimists.

The FDA thumbs up
Antares Pharmaceuticals
(NASDAQ:ATRS) started the week off on a positive note when it announced on Monday that the Food and Drug Administration had approved its Otrexup injection for the treatment of adults with rheumatoid arthritis, in children with polyarticular idiopathic arthritis, and adults with psoriasis. The once-weekly subcutaneous injection has an opportunity to become the go-to second-line treatment in cases where patients show intolerance to oral methotrexate or oral methotrexate proves ineffective. In trials, Otrexup also demonstrated increased bioavailability relative to its oral counterpart. It should be interesting to see how well this drug does following its launch and I would certainly recommend adding Antares to your Watchlist.

Novo Nordisk (NYSE:NVO), not wanting to be left out, also announced an FDA approval of its own on Wednesday. According to the company press release, the FDA approved the company's biologic license application for recombinant coagulation factor VIII drug, Novoeight, for use in adults and children with hemophilia A. The 210 patient study that was the basis of the approval demonstrated good efficacy in terms of preventing and treating bleeds in patients. Novo Nordisk is set to launch Novoeight sometime after April 2015 once existing patents expire. With an estimated 350,000 people worldwide suffering from hemophilia A, this will definitely be a launch to keep an eye on as well.

Clinically impressive
Antares Pharmaceuticals and Novo Nordisk may be the one's racking up FDA approvals this week, but it was Sanofi and Regeneron Pharmaceuticals (NASDAQ:REGN) which stole the show for bulls. On Wednesday the two reported impressive top-line results from its first late-stage study for alirocumab for LDL-cholesterol reduction. The study showed that those taking alirocumab saw their bad LDL-cholesterol levels reduced by 47.2% compared to just 15.6% for those taking Merck's cholesterol-absorption inhibitor Zetia. Furthermore, those in the alirocumab arm saw fewer reported treatment-related adverse events. Consider alirocumab among the most exciting cholesterol control candidates currently being studied.

A nightmare of a week
On the other hand, it was an absolute nightmare of a week yet again for shareholders in Ariad Pharmaceuticals (NASDAQ:ARIA) and Amarin (NASDAQ:AMRN).

After last week's monstrous tumble in Ariad's share price where it disclosed increased adverse blood-clotting events in patients taking its FDA-approved blood cancer drug Iclusig in a 24-month follow-up, Ariad followed it up this week by discontinuing its Epic trial for patients recently diagnosed with chronic myeloid leukemia. The premise for the trial stoppage was the same: an increased number of aterial thrombotic events (i.e., blood clots discovered in a patient's arteries). This recently diagnosed CML indication had been the study investors were banking on. Now, Ariad is left with eight ongoing clinical trials, of which seven involve the (at the moment) highly questionable Iclusig. Shares shed an additional 37% this week and are now down a whopping 86% in just the past two weeks!

Embracing the "misery loves company" theme, shares of Amarin were absolutely annihilated on Thursday after the FDA's panel voted 9-2 against recommending an expanded approval of Amarin's FDA-approved fish oil drug, Vascepa. The panel didn't seem to question the efficacy of Vascepa in lowering patients' high triglyceride levels, but does question whether lower triglyceride levels will lead to a lower risk of heart attack. Although the FDA isn't required to follow the advice of its panel, these votes usually offer a good indication of which way the FDA will lean when it does eventually make its decision (and in this case the outcome is not positive). Amarin was really counting on this new indication to vastly expand its marketing potential of Vascepa -- without it, I'm not certain the company will reach profitability with Vascepa alone. Shares are now off 72% over just the past nine sessions.