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.

M&A mania
Perhaps no story stood out as more this week than the incredible amount of merger and acquisition rumors and deals within the health-care sector. While I'll leave the rumor mill on the sidelines for now -- although we discussed one of the bigger rumors earlier in the week -- all eyes were on the transformative deal announced by Novartis (NYSE:NVS). Under the terms of its multiple deals, Novartis agreed to acquire GlaxoSmithKline's (NYSE:GSK) oncology unit for $14.5 billion, with an additional $1.5 billion in milestone and royalties payable if certain clinical trial goals are reached. In return, GlaxoSmithKline is purchasing Novartis' vaccine unit for $7.1 billion. And to round out the house cleaning, Eli Lilly is purchasing Novartis' animal health division for $5.4 billion. 

This is clearly big news for all companies involved. This will solidify Novartis' position as an oncology powerhouse that could potentially rival Roche, while it'll allow GlaxoSmithKline to focus on its growing respiratory segment and add scalability to its current vaccine program. For Eli Lilly, the deal is crucial to giving it sustainable cash flow in the wake of key patent losses over the past couple of years.

Sarepta in the fast lane
About face. Forward, march!

That was the mantra for Sarepta Therapeutics (NASDAQ:SRPT) shareholders this week after the company announced that the FDA would allow Sarepta to file for a new drug application for Duchenne muscular dystrophy drug eteplirsen before the end of the year. This earlier-than-expected NDA filing has investors excited that Sarepta may burn through less of its cash. I would, however, caution that the FDA clearly requested, and Sarepta blatantly put in its press release, that it would need "additional data to support the efficacy and safety of eteplirsen for the treatment of DMD." In other words, there's still work to be done and Sarepta is in no way off the hook, but the path to approval may have gotten just a bit easier. Whether that ease is worth a 50% one-week rise is an entirely different debate.

Sitting pretty
Shareholders of clinical-stage biotech company Revance Therapeutics (NASDAQ:RVNC) are also sitting pretty this week after it reported positive results from a phase 1/2 study involving RT002 as a treatment for moderate-to-severe frown lines. According to the results, 94% of patients in this study were rated as having "none" or "mild" frown lines at maximum frown just four weeks after treatment. Perhaps more impressive was RT002's median duration of response of 29.4 weeks, or better than seven months. Needless to say, RT002 met both its primary and secondary endpoints and looks poised for success, at least early on. Investors, though, may want to contain their optimism as we're talking about a wholly clinical-stage company with a whopping $640 million valuation. Much of that optimism appears to already be baked into Revance's share price.  

Cytokinetics swings and misses
Not everyone could be a winner this week, just ask shareholders of clinical-stage biopharmaceutical company Cytokinetics (NASDAQ:CYTK), this week's disaster du jour. Shares absolutely imploded, losing 65% on Friday, after the company announced that its midstage BENEFIT-ALS study involving tirasemtiv didn't meet its primary efficacy endpoint of a mean change from baseline in ALS Functional Rating Scale. Furthermore, its secondary endpoints, which included respiratory and skeletal function measures, were mixed. Long story short, it doesn't look as if there's much future for Lou Gehrig's disease therapy tirasemtiv, and shareholders should instead turn their focus toward experimental acute heart failure drug omecamtiv mecarbil which is currently in phase 2b trials.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.