With the SPDR S&P Biotech Index up 38% 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.

All eyes are certainly on the annual American Society of Clinical Oncology meeting going on right now, but that didn't stop a gambit of positive and negative news from emerging in the biotech sector this week.

Omthera Pharmaceuticals (NASDAQ: OMTH) certainly made waves for investors by announcing its agreement to be purchased by AstraZeneca for $323 million, with $120 million in additional contingency value dependent on the success of its pipeline. Omthera's lead compound is a late-stage fish-oil capsule known as Epanova, which is being targeted at lowering triglyceride levels in patients with a high risk of developing cardiovascular disease. With obesity remaining such a big concern in the U.S., fish oil products could become a booming market in terms of heart health maintenance in the future, and AstraZeneca may have snagged itself a steal of a deal. Omthera shareholders probably aren't complaining, either, as their stock doubled this week.

GlaxoSmithKline (NYSE:GSK) turned in great news as well, with the Food and Drug Administration approving a pair of advanced melanoma drugs on Wednesday. The drugs, Tafinlar (previously dabrafenib) and Mekinist (previously trametinib), target melanoma that expresses the BRAF mutation. Tafinlar attacks tumors with the BRAF V600E mutation, while Mekinist is an MEK inhibitor that targets tumors which express V600E or V600K mutations. Furthermore, the FDA also approved the companion diagnostic test known as THxID BRAF to determine whether or not a melanoma patient has the V600E or V600K mutuation. 

In terms of clinical data, small-cap biotechnology company Immunomedics (NASDAQ:IMMU) jumped by double digits after reporting early stage, but nonetheless positive, data from its antibody-drug conjugate program. Two of Immunomedics' ADC's, IMMU-130 which is targeted at metastatic colorectal cancer, and IMMU-132, which is being tested on 13 different cancer types, demonstrated tumor shrinkage and some partial responses. We're still a long way from an approval, but ADC's certainly look like one pathway to effectively treating cancer. Make sure this is a company you've added to your Watchlist.

But, as you're probably well aware of with the biotech sector, not all news is good news.

Biogen Idec (NASDAQ:BIIB) delivered mixed news on Thursday, when it announced that it will probably delay the launch of relapse-preventing multiple sclerosis drug Tecfidera in Europe to secure exclusivity on its treatment for a longer period of time. The move does make sense, as a generalized patent could be challenged in Europe since it doesn't cover "compounds." If the EU grants Tecfidera the designation of "new active substance," as Reuters describes, it'll be protected from generic competition for 10 years. Still, with Tecfidera sales volume soaring in the U.S., waiting on Europe will be a disappointment.

Finally, Endo Health Solutions (NASDAQ:ENDP) subsidiary Endo Pharmaceuticals received its third strike on low testosterone injection Aveed yesterday in the form of a complete response letter. The FDA has rejected the hypogonadism-treating drug three times now, pointing out that the rare, but often serious, adverse events produced by the once-every-10-week injection haven't been properly addressed by Endo. Even though Endo won't need to rerun any additional trials, I think this is the end for Aveed which doesn't have much ground to stand on in a very crowded low-testosterone space that has plenty of treatments with fewer side effects. That doesn't mean you should ignore Endo Health Solutions, though, which offers a very profitable and well-diversified lineup of branded and generic drugs, as well as medical devices.

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