With the SPDR S&P Biotech Index up 22% 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.

It was most definitely a wild week for sure, with both positive and somewhat negative clinical stage data, an approval by the Food and Drug Administration, and buyout rumors circling one small-cap biotech.

The week began on a high note after Johnson & Johnson (NYSE:JNJ) announced that its revolutionary Type 2 diabetes drug, Invokana, had been approved by the FDA. Invokana is an SGLT2 inhibitor -- the first of which to be approved in the U.S. -- and works in the kidneys to suppress glucose reabsorption as opposed to DPP-4 inhibitors like Merck's Januvia, which go to work in the pancreas and liver. Having beaten Januvia in a head-to-head test in trials, and with the added benefit of weight loss, J&J's Invokana appears to be the next blockbuster diabetes treatment.

Just a day later, on Tuesday, Optimer Pharmaceuticals (NASDAQ: OPTR) shares soared after GlaxoSmithKline and Cubist Pharmaceuticals were named as potential buyers of Optimer by sources familiar with the matter in a Bloomberg report. The news shouldn't be a huge surprise, as it announced a strategic review in February, which is fancy terminology that it could be looking to put itself up for sale. While the Street appears excited, I'm a little more tempered in my enthusiasm, as its only FDA-approved drug, Dificid, isn't exactly a huge profit-maker.

The end of the week also brought good news for Biogen Idec (NASDAQ:BIIB) investors -- as if you haven't been riding high already from the approval of Tecfidera -- when the company announced positive midstage results for Daclizumab for the treatment of multiple sclerosis. Data from the trial demonstrated that Daclizumab reduced the annual relapse rate by a whopping 54%. In addition, both dosing regimens met the secondary endpoints as well which involved reducing relapses after one year, and shrinking MS-related brain lesion activity at specified time intervals. Between its recent purchase of the full right to Tysabri from Elan and Tecfidera's approval, Biogen is asserting itself as the name to be reckoned with in multiple sclerosis.

However, the week ended on a sour for investors in AstraZeneca (NASDAQ:AZN) and Rigel Pharmaceuticals (NASDAQ:RIGL), whose rheumatoid arthritis drug, Fostamatinib, delivered mixed results in the first of three phase 3 trials. Fostamatinib, which Rigel licensed out to AstraZeneca in 2010, demonstrated a statistically significant improvement in the ACR20 response rate in terms of RA symptoms, but it failed to reach the second primary endpoint of stalling the progression of joint damage. X-rays taken of patients' joints delivered the sobering news. Given that Fostamatinib was shown to be inferior to the leading RA medication Humira, made by AbbVie, in a head-to-head trial in December -- and noting that Pfizer's Xeljanz had a higher ACR20 response rate score in its phase 3 trials than Fostamatinib -- the approvability of AstraZeneca and Rigel's drug is quickly fading.

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