With the SPDR S&P Biotech Index up 57% 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.

Let's just say I hope you like good news, because we have no negative events to discuss this week.

Furiex's furious rally
No discussion of the biotech happenings for the week can begin this week without starting off with Furiex Pharmaceuticals (NASDAQ: FURX), which ended the week 137% higher than where it started.

Furiex's furious rally on Tuesday was precipitated by positive results in two late-stage studies involving eluxadoline as a treatment for diarrhea-predominant irritable bowel syndrome. Although the 75 mg dose failed to meet statistical significance in one of the two studies, the 100 mg met its primary endpoint of improving stool consistency by 30% to 37% and lowering abdominal pain in both studies. Based on this data, it seems relatively likely that eluxadoline will be approved by the Food and Drug Administration, but considering that the stock vaulted to a $1.1 billion valuation on this news, the launch of eluxadoline and FDA review of this medication had better be flawless if it hopes to maintain its triple-digit share price.

Walk this way
The positive data just kept on coming this week from Sarepta Therapeutics (SRPT 0.60%), which reported positive pulmonary function test data for eteplirsen through 120 weeks in its phase 2b study. The experiment therapy, which is designed to treat Duchenne muscular dystrophy, demonstrated stable pulmonary function with a 14.6% mean increase in maximum inspiratory pressure and a 15% mean increase in maximum expiratory pressure. There was also an 8.7% increase in forced vital capacity, a measure of lung volume, from baseline through week 120.

Though the patient pool is but a tiny 12 patients, this DMD therapy continues to shine. The real test is whether or not this exon-skipping drug will perform well in a larger patient pool or if it'll crash like Prosensa's drisapersen in September.

All's well that ends well
Shareholders in Repros Therapeutics (NASDAQ: RPRX), a biopharmaceutical company focused on hormonal and reproductive system disorders, were taken for a wild ride this week, but the stock ultimately ended the week modestly higher. The impetus for the ferocious late-week rally was a meeting with the Food and Drug Administration that hashed out the regulatory approval pathway for experimental testosterone drug Androxal.

In October, if you recall, the FDA had told the company that it would need to run a year-long safety study on the highest dose of Androxal, forcing Repros to delay its new drug application filing at the time. This week's meeting notes no need for additional safety studies, places Repros on track for an NDA filing before the end of 2014, and points out that the FDA's only request was to be provided endpoint data which Repros can do concurrently while enrolling in its two studies. With Androxal back on track, Repros could indeed have significant upside from here.

In the fast lane
It was a modestly positive week as well for clinical-stage biopharma Omeros (OMER 6.22%) which on Wednesday announced that the FDA had granted the company's experimental compound, OMS824, the fast-track designation for Huntington's disease. OMS824 has thus far been tested for safety and tolerability in phase 1 studies, which turned up no red flags.

Keep in mind that the fast-track designation offers a drug developer more one-on-one interaction with the FDA, so there's little question what sort of endpoints, efficacy, or safety data the FDA will be looking for to approve the drug, and it can also result in a priority review of the drug once an NDA is filed. Omeros plans to initiate a phase 2 study involving OMS824 on Huntington's disease patients within the next few weeks. While certainly good news, I'd keep my excitement here limited until late-stage studies are available as brain disorder drugs have delivered very low clinical success rates in recent years.

Three's a crowd, but four's a party!
Finally, global pharmaceutical powerhouse Merck (MRK -0.15%) announced three separate collaborations this week involving its anti-PD-1 immunotherapy drug, MK-3475, also known as lambrolizumab. On top of initiating a phase 1 signal finding study involving 20 new cancer types, Merck partnered with Pfizer, Incyte, and Amgen to potentially improve the effectiveness of its drug and broaden its scope of uses.

Lambrolizumab with be given in combination with Pfizer's Inlyta in phase 1/2 studies examining its effect on renal cell carcinoma patients. Separately, Incyte and Merck will combine lambrolizumab with INCB24360 to examine this combo's effect on previously treated metastatic and recurring non-small-cell lung cancer. Finally, Merck's collaboration with Amgen will involve combining lambrolizumab with Amgen's experimental immunotherapy talimogene laherparepvec in a phase 1/2 study of previously untreated advanced melanoma.

The short story here is that Merck understands it has a potential blockbuster on its hands, but it's wisely increasing its chances of success by extended its hands to previous rivals. Patent exclusivity losses are set to strike Merck hard, so these collaborations could prove very fruitful in the coming years.