With the SPDR S&P Biotech Index up 20% 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.

Buyout mania continues
Although the past week was filled with literally dozens up dozens of biotech earnings reports, the talk of the town continues to be ongoing merger and acquisition activity within the sector. Most eyes may be on big pharma, but it was small-cap Chelsea Therapeutics (UNKNOWN:CHTP.DL) that earned all the praise this week with Danish pharmaceutical company H. Lundbeck agreeing to buy Chelsea for $6.44 in cash and up to $1.50 per share in contingent value rights.

The deal represents a nearly 29% premium based solely on cash for Chelsea shareholders from its close prior to the announcement, and it'll give H. Lundbeck access to Northera, Cheslea's recently approved blood-pressure drug used to treat dizziness in patients with Parkinson's disease. As I stated earlier this week it looks like a pretty square deal with Chelsea not seeming to keen on marketing Northera on its own and H. Lundbeck protecting itself with those aforementioned contingent value rights in case Northera sales don't approach their peak potential of $400 million in annual sales.

Theravance and shareholders tack on victories
It was an equally positive week for shareholders of Theravance (UNKNOWN:THRX.DL) which received positive news from Europe, as well as had many of their questions regarding Theravance's upcoming split answered.

As is probably no surprise, on Thursday Theravance and its collaborative partner GlaxoSmithKline announced the marketing approval of inhaled COPD therapy Anoro Ellipta in Europe. With a peak sales potential north of $1 billion, Anoro Ellipta is one of the many respiratory drugs expected to sustain both companies' pipelines over the next decade.

Theravance also outlined the details of its split into two separate companies: Royalty Management Co. and Theravance BioPharma. According to its press release, shareholders on record as of May 15 will receive shares of Theravance BioPharma via a dividend on June 2. Royalty Management Co. will be comprised of the company's partnered COPD assets, while Theravance BioPharma will represent its clinical and development-stage compounds in all other areas. Furthermore, Royalty Management Co. declared what will become a regular $0.25/quarter dividend, pumping Theravance's yield up near 4%!

Let the good times roll
Clinically speaking, the good times continued well after the closing bell on Friday when the collaborative team of AstraZeneca (NYSE:AZN) and Amgen (NASDAQ:AMGN) announced that brodalumab had met all primary and secondary endpoints for both doses in a phase 3 study of patients with moderate-to-severe plaque psoriasis known as AMAGINE-1.

According to the results of the study 83.3% of the 210 mg group and 60.3% of the 140 mg group achieved PASI 75 responses (at least a 75% improvement from baseline at week 12 in the Psoriasis Area Severity Index). Furthermore, 41.9% of 210 mg patients and 23.3% of 140 mg patients achieved PASI 100, or a complete clearance of the skin disease, compared to just 0.5% for the placebo. This study represents the first phase 3 data for the duo on the effectiveness of their experimental drug in treating plague psoriasis, and they anticipate obtaining additional data from their AMAGINE-2 and AMAGINE-3 studies which will pit brodalumab against Stelara in a head-to-head study. Based on this initial data, and given the chronic and widespread nature of the disease, this is an experimental therapy that should be squarely on your radar.

Corcept implodes
Yet as we witness nearly every week not every company can be a winner. Shares of biopharmaceutical company Corcept Therapeutics (NASDAQ:CORT) were clobbered on Wednesday, losing about half their value, after it announced that the independent data safety monitoring committee had determined, based on a planned interim phase 3 analysis that mifepristone, the company's experimental psychotic depression drug, was unlikely to meet its primary endpoint. In response, Corcept announced the discontinuation of the study. 

Making matters worse for shareholders is the fact that mifepristone makes up a large chunk of Corcept's existing pipeline. Understandably there's still plenty of hope given the fact that different diseases can have markedly unique responses to the same therapy. However, investors also have viable concerns that if mifepristone had little clinical benefit in phase 3 it may run into similar struggles with its other possible indications. With Corcept burning through its precious cash and shelving a late-stage study, I'd suggest your best option would be to stay far away from this stock.