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.

Gone shopping
Once again the big news for the week remained buyout rumors and speculation, although no large deals came to fruition.

Perhaps no potential buyout has loomed larger in recent weeks than Pfizer's (NYSE:PFE) repeated attempts to purchase U.K.-based AstraZeneca (NASDAQ:AZN). In its third and final offer Pfizer attempted to court AstraZeneca with a bid of $119 billion. The idea would be to combine the two companies with the hope of realizing research and development synergies over the coming years, and likely to move Pfizer's corporate headquarters to the U.K. where it would pay less in taxes. The deal itself would have made sense on paper since each company had what the other was looking for, but AstraZeneca ultimately walked away from the deal deeming that it undervalued the company. I see this as a positive for Pfizer, as I feel the first bid, let alone its third, overvalued AstraZeneca's stagnant pipeline. It's really AstraZeneca shareholders that should be peeved about this whole mess as it turned down one heck of a premium from Pfizer. All I can say is AstraZeneca's management team had better deliver over the next year or shareholders could be calling for their jobs come this time next year.

Weight control management drug developer VIVUS (NASDAQ:VVUS) was also the subject of takeover rumors this week following a 13-D filing with the SEC from Aspen Investments. According to its filing, Aspen Investments now holds a 9.65% stake in VIVUS and appears prepared to make an offer of up to $640 million, or $6.19 per share, to buy the company. While Aspen isn't obligated to make an offer, it has said that it anticipates submitting its offer by June 13. Although VIVUS had no comment on Aspen's actions, I'm left scratching my head as to why anyone would want to buy VIVUS. Its weight control management drug Qsymia has been an utter disappointment, a peer may soon bring another anti-obesity drug to market, and it's unlikely to be profitable anytime soon. In my opinion, if VIVUS is eventually taken private by Aspen, shareholders should send Aspen a gigantic thank-you card.

Source: Northern Ireland Executive, Flickr.

Although Durata Therapeutics (NASDAQ: DRTX) shares finished the week lower, investors have to be happy with the fact that the Food and Drug Administration approved the company's acute bacterial skin and skin structure infection drug Dalvance this past weekend. Where Dalvance could really shine is in the convenience department. Typically ABSSSI treatments involve twice-daily infusions. Dalvance, by comparison, is given as a two-dose regimen: a 30-minute infusion of 1000 mg one week followed by a 500 mg 30-minute infusion the next week. That certainly beats two infusions per day and could easily allow it to become a therapy of choice to treat acute bacterial skin and skin structure infections. I would suggest biotech-savvy investors give Durata a closer look.

Clinically significant
Lastly, in case you missed it, three important clinical updates made waves this week.

Source: Gosheshe, Flickr.

Perhaps no company stole the stage more this week than BioCryst Pharmaceuticals (NASDAQ:BCRX) which on Tuesday reported positive data from its OPuS-1 phase 2 study involving BCX4161 as a treatment for hereditary angioedema, a rare disease that can cause facial and airway swelling as well as abdominal cramping. BCX4161, according to its press release, "delivered a statistically significant mean attack rate reduction of 0.45 attacks per week versus placebo." In its four-week study it also noted that three BCX4161 HAE patients completed the study without an attack compared to zero for the placebo group, while the number of attack-free days climbed to 22 in the BCX4161 group from 19 in the control arm. Consider yourself on notice to keep a close eye on BCX4161's development.

If cancer immunotherapies are more your thing, then yesterday's mid-stage results from NewLink Genetics (NASDAQ:NLNK) should be right up your alley. NewLink reported that dorgenmeltucel-L, when combined with pegylated interferon-alpha 2b in patients with advanced metastatic melanoma, produced two complete RECIST responses, one stable disease, and four patients with no evidence of disease out of 16 stage 4 disease patients. NewLink also notes that 60% of the 25 patient trial had survived beyond one year, and that the median overall survival was 29 months. Further, it announced that it would be undertaking an additional study involving dorgenmeltucel-L and ipilimumab whereby it will be boosting its dose of dorgenmeltucel-L to determine if higher doses will result in longer survival. Using your body's immune system as a weapon against cancer is becoming a hot button topic in biotech, and I'd suggest you continue watch NewLink's pipeline as it matures.

Last, but certainly not least, on Tuesday Northwest Biotherapeutics (OTC:NWBO) announced that its phase 1/2 study involving DCVax-Direct on solid tumor cancers has produced positive responses in more than 50% of patients to date. According to its press release, better than half of patients (11 of 19) had some degree of tumor shrinkage or stabilization while completing at least half of the six-course treatment. Specifically, NW Bio lists eight of 11 patients showing signs of tumor necrosis. Northwest Biotherapeutics, as it's planned all along, will release additional study data during the American Society of Clinical Oncology's annual meeting. Like NewLink, NW Bio's approach is about enhancing the body's immune response to recognize and attack cancer cells. Though a small sample size, NW Bio's DCVax-Direct has demonstrated intriguing data to chew on thus far. I wouldn't say I'm sold yet, but I'm definitely looking forward to its later-stage study results.

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.