With the SPDR S&P Biotech Index up 58% 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.

The good news is that we weren't completely overwhelmed with biotech news, aside from earnings reports, this week – meaning no two-part series! But, rather than focusing on earnings news, which we at The Motley Fool have been hitting this week with some regularity, I'd rather focus on the important clinical news which made waves this week. All told, five events -- four being clinical updates -- helped induce big moves this week.

Hepatitis-C-ya later!
The race for a cure in hepatitis-C took another giant step forward on Friday, with AbbVie (ABBV) reporting positive phase 3 data from its final four of six trials studies involving its direct-acting antiviral combo in treating genotype 1 patients. Although I would strongly encourage you to read the press release to get the specifics on each trial, which you can do by clicking here, the basic gist of its final four trials was that of overwhelming success in treating the most common, but most difficult to treat form of the disease, genotype 1.

The overall results demonstrated a sustained virologic response (i.e., undetected levels of disease) within 12 weeks (one study tested SVR at 24 weeks) in 90% to even 100% of patients. Common SVR response was 96% to 99% in treatment-naïve patients and 92% to 96% in cirrhotic patients. This is also great news for Enanta Pharmaceuticals which contributes one of the three DAA components, ABT-450. AbbVie now anticipates a possible Food and Drug Administration approval before 2014 is over -- and barring an unforeseen curveball, I'd have to agree.

Excellent Xtandi
Just in case you were unconvinced that Medivation's (MDVN) late-stage prostate cancer drug Xtandi is effective, the release of the company's final phase 3 data on Xtandi in chemotherapy-naïve metastatic prostate cancer patients should put those skepticisms to rest.

On Wednesday, Medivation and its partner Astellas Pharma announced the results from their PREVAIL trial noting that Xtandi reduced the risk of death by 29% relative to the placebo group and significantly reduced the risk of radiographic progression by 81%. Perhaps the most striking tidbit of data was the delay in the initiation of chemotherapy from 10.8 months in the placebo group to 28 months in the Xtandi intent-to-treat arm. The ability to treat patients with Xtandi was also more than three times longer at 16.6 months compared with 4.6 months for the placebo group. Given this data, it's looking incredibly good for Medivation and Astellas that Xtandi will soon be approved in a pre-chemo setting for treating advanced-stage prostate cancer.

Hold the Mayo
For clinical-stage oncology-focused biopharma Geron (GERN) it was a uniquely odd week. It began on a sour note with Geron filing an 8-K with the Securities and Exchange Commission on Monday notifying shareholders that its investigator-sponsored trial with imetelstat for myelofibrosis being conducted by the Mayo Clinic had stopped taking patients. Furthermore, Geron notes that 20 of 79 patients dropped out of the trial, which is an inordinately high number of dropouts.

Nonetheless, Geron is planning to begin phase 2 trials involving imetelstat soon and announced a $90 million common stock offering late in the week which sent its shares soaring. As I said, it was an odd week. I'm certainly not buying into the dilution factor here and would need to see concrete data on adverse events versus efficacy with regard to imetelstat before I'd buy into the Geron hype.

Abstract data
Speaking of sending mixed signals, Progenics Pharmaceuticals (PGNX) mastered that this week with data from two mid-stage studies: an imaging agent (Progenics 1404), and its antibody-drug conjugate PSMA-ADC. The initial data from its imaging trial showed 94% sensitivity and 100% specificity in an interim analysis of detecting cancer in the prostate gland. For PSMA-ADC, Progenics also notes a positive anti-tumor response and good tolerability in treating advanced prostate cancer patients who had been treated with at least one line of taxane chemotherapy.

The concern that sent shares markedly lower was an abstract that came out just a day before its study that showed that two patients died of sepsis in the PSMA-ADC trial, signaling that the drugs' effect on the immune system may be too great for the body to handle, even in lower doses. Progenics is looking to investigate PSMA-ADC further, but the sell-off this week shows investors have mostly written it off.

Money tree
The only non-clinical newsmaker this week was Idenix Pharmaceuticals (NASDAQ: IDIX), which announced that The Baupost Group would be purchasing a direct offering of 16.42 million shares from the company, raising $106.7 million in the process. The move will push Baupost's ownership stake up to 35%, and certainly has investors wondering if a buyout could eventually be in the works. Idenix plans to use the cash from its offering to fund the development of its hepatitis-C pipeline and general corporate purposes. As for me, I remain brutally skeptical of Idenix, a company that has had three leading drug candidates scrapped, and another one put on clinical hold by the FDA (where it still remains), just since 2010. Until Idenix can advance an experimental therapy past mid-stage trials, I feel it best to keep your distance.