With the SPDR S&P Biotech Index up 43% 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.

Being that it's the holiday season and just four days from Christmas, I don't have the heart to report any negative news in the biotech sector this week; nor do I have to since we had nothing but positive results this week, including two favorable FDA actions, two positive clinical trials, and a notable buyout.

FD-Hooray!
As I mentioned in previous weeks, you might have expected the time leading up to the holidays to be relatively slow for the Food and Drug Administration, but that just wasn't the case this past week.

On Wednesday, GlaxoSmithKline (NYSE: GSK) and partner Theravance (NASDAQ:THRX) announced that the FDA had unsurprisingly approved its once-daily bronchodilator, Anoro Ellipta, for the long-term treatment of COPD. I say "unsurprising," as the FDA's advisory panel had recommended approving the once-daily treatment in mid-September by an 11-2 vote. This marks the second inhaled COPD drug approved by the FDA for these collaborators in just the past couple of months and positions both companies for strong future growth with Anoro Ellipta expected to generate approximately $1.4 billion in peak U.S. sales.

The favorable FDA news didn't stop there, however. Ariad Pharmaceuticals (NASDAQ:ARIA) shareholders can also get their pompons out because the FDA lifted its sales suspension of leukemia drug Iclusig and allowed the drug back onto the market with a new boxed warning indicating a higher risk for vascular occlusive events and a new warning for heart failure. Given that Iclusig is Ariad's only FDA-approved drug, and it currently comprises seven out of its eight ongoing clinical studies, the simple fact that the FDA would let it back onto the market is big news. Still, without an approval for chronic myeloid leukemia and a new slate of risks, Iclusig sales may struggle to get Ariad anywhere near profitability.

Putting on a clinic
In addition to positive the above positive FDA actions, two clinical trials had Wall Street abuzz this past week.

Perhaps no study caused investors' jaws to hit the floor harder this week than Gilead Sciences (NASDAQ:GILD) three late-stage trials involving its recently FDA-approved hepatitis-C drug Sovaldi in combination with ledipasvir. The three trials demonstrated a sustained virologic response (an elimination of all detectable levels of disease) of between 93.1% and 99.1% in the most common type of hepatitis-C, but also the toughest to treat, genotype 1. Even more astounding, the treatment-naïve arm without the use of a ribavirin delivered a 94% SVR in just eight weeks!  What all this means is that Sovaldi could wind up giving AbbVie's direct-acting antiviral combo a run for its money in treating genotype 1 patients, especially from a factor of convenience (one pill versus up to six for AbbVie's combo). I still believe there's plenty of room in the hepatitis-C marketplace for two blockbuster drugs and am thrilled to see such rapid progress being made.

Cubist Pharmaceuticals (NASDAQ:CBST) also got in on the excitement this past Monday by releasing late-stage data for its second of two trials involving ceftolozane/tazobactam, also known as CXA-201, for the treatment of complicated intra-abdominal infections. According to Cubist's results, CXA-201, when given in combination with metronidazole, was shown to be non-inferior to meropenem with regard to inducing a cure 26 to 30 days after initiation of treatment. With CXA-201 also meeting its primary endpoint in a complicated urinary-tract infection trial just three weeks prior, it's looking quite positive that this antibiotic could be approved by the FDA in 2014.

Merger Friday
Forget "merger Monday" -- this week it was all about merger Friday, with Jazz Pharmaceuticals (NASDAQ:JAZZ) announcing the $1 billion, or $57 all-cash per share, acquisition of rare disease drugmaker Gentium (NASDAQ: GENT). Gentium's lead drug that Jazz will now take a hold of is Defitelio, a drug approved in the EU to treat severe hepatic veno-occlusive disease in adults and children that are undergoing hematopoietic stem cell transplantation. The buyout will help Jazz diversify an already rapidly growing pipeline and should add to its bottom line from the get-go!

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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