With the SPDR S&P Biotech Index up 18% 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.

Source: Hobvias Sudoneighm, Flickr.

An FDA about-face
If Progenics Pharmaceuticals (NASDAQ:PGNX) and Salix Pharmaceuticals (UNKNOWN:SLXP.DL) shareholders were looking for something to cheer about this week they didn't need to wait long. On Monday, the Food and Drug Administration's Office of Drug Evaluation III granted the duo's appeal from a prior supplemental new drug application complete response letter and announced its intent to approve Relistor's new indication as an injectable subcutaneous treatment of opioid-induced constipation in patients with non-cancer pain.

Of course, this won't be a free ride for Salix or Progenics, with the FDA also requesting that a few things be completed before it gives Relistor's new indication the A-OK. The FDA has requested that Salix work with the Division of Gastroenterology and Inborn Errors Products and submit information such as proposed labeling and post-marketing observational studies over the next several weeks.

For Salix this is positive news, but with the company's entire product and pipeline portfolio expanding, it's not make-or-break news. For Progenics, though, its partnership with Salix is extremely important since Relistor is its primary revenue driver. This additional indication could help bring Progenics closer to profitability.

Excellent Exelixis
Monday was also a great day for Exelixis (NASDAQ:EXEL) shareholders like me, although the huge gains didn't last throughout the remainder of the week.

Source: Roche.

On Monday, Exelixis and its partner Roche announced that their phase 3 combination study of cobimetinib and Zelboraf in patients with BRAF V600 mutation-positive advanced melanoma had met its primary endpoint, which was a statistically significant increase in progression-free survival compared to the Zelboraf-treated control arm. Although no specific numbers were touted the duo is expected to release full data on this study later this year.

As a shareholder in Exelixis, I often get blindsided by the potential of Cometriq and its three ongoing late-stage studies that I forget Exelixis also has a number of other clinical candidates. As I've noted previously, if Exelixis can gain at least some piece of the metastatic castration-resistant prostate cancer market, coupled with a possible approval in BRAF V600 mutation advanced melanoma, then I would venture a guess that it's valued at less than two times peak sales, which would be quite cheap. Long story short, I'm hanging on to my shares.

Positive results for Amgen
Not wanting to feel left out, Amgen (NASDAQ:AMGN) also joined the positive data party on Thursday, when it announced positive phase 3 results for AMG 416 as a treatment for secondary hyperparathyroidism in patients with chronic kidney disease who are also receiving hemodialysis.

According to its after-the-close press release, AMG 416 met its primary endpoint, with 75.3% of patients achieving a 30% or greater reduction from baseline in their parathyroid hormone levels, compared with just 9.6% in the control arm. Furthermore, Amgen notes that AMG 416 produced statistically significant improvements in secondary endpoints, including corrected calcium concentration and the percent change from base during the Efficacy Assessment Phase in serum phosphorous levels relative to the placebo.

This marks just the first of three phase 3 studies involving AMG 416, but it's clearly off to a remarkable start. With even Amgen not immune to patent expirations it's encouraging to see that it could have another successful chronic treatment drug in the offing. 

Fifth time's the charm!
Maybe the luck of the Irish is actually based in five-leafed clovers? Following four previous unsuccessful bids, AbbVie (NYSE:ABBV) and Shire (NASDAQ:SHPG) have worked out an agreement that'll have AbbVie paying $54.7 billion in cash and stock to acquire Shire. That's 19% higher than AbbVie's first offer in late May and could lead to the way to a number of key cost savings for the combined entity.

Source: Geralt, Pixabay. 

The deal will obviously bring broader product and pipeline portfolio depth, as well as cost synergies from combining research and development divisions. More importantly, the combination allows AbbVie to execute the largest corporate tax inversion deal of all time and relocate its headquarters from the U.S., where corporate tax rates can top out at 40%, to Ireland, where corporate tax rates peak at just 12.5%. This could literally save AbbVie hundreds of millions, which it can use to funnel into new research, additional acquisitions, or perhaps shareholder incentives.