With the SPDR S&P Biotech Index up 23% year to date, it's very 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.

Similar to last week, we've just been inundated with clinical data and trial updates -- so much so that I've extended this week's wrap-up into two parts yet again. In the second part of this week's biotech review, we'll look at more individualized stories making news. But for now, let's start with hepatitis C companies that couldn't throw clinical data at us quickly enough this past week.

Four companies made waves this week regarding hepatitis C clinical trial updates, and we'll look at each of them, one by one.

Gilead Sciences (NASDAQ:GILD) reported earlier this week that sofosbuvir (previously GS-7977), acquired when its purchased Pharmasset last year, when combined with GS-5885 and an antiviral ribavirin, completely eliminated detectable levels of the hepatitis C virus in all 25 patients tested four weeks after the 12-week dosing regimen. The last time I checked, 100% was a pretty darn good success rate. Gilead is planning to run a third late-stage trial without ribavirin, but this seems like a mere formality on the way to an eventual new drug submission. 

Abbott Laboratories (NYSE:ABT) also released data on two phase 2 hepatitis C trials. The first, which combined three drugs as well as a booster called ritonavir, eliminated the virus in 87% of patients after 12 weeks of dosing. The second trial, which paired these drugs with ribavirin, was successful in eliminating detectable levels of the virus in 97% of patients (77 of 79). Gilead clearly has the convenience advantage award with regard to patients needing to take fewer pills, but the long-term studies, as my Foolish colleague Brian Orelli notes, should separate which drug eventually comes out on top.

Not to be left out on the fun was Idenix Pharmaceuticals (NASDAQ: IDIX) which, if you recall, has struggled ever since Bristol-Myers Squibb's (NYSE:BMY) experimental treatment, BMS-986094, was linked to the death of a patient and subsequently discontinued. With Bristol's drug being a nucleotide inhibitor, the Food and Drug Administration took a cautious stance on Idenix's line of nucleotide-based hepatitis-C therapies and placed clinical holds on both IDX-184, its lead compound, and IDX-19368 back in August. While those holds still stand, Idenix reported earlier this week that an internal evaluation of IDX-184 demonstrated "no evidence of severe cardiac findings." I'm sure the FDA will be the judge of that, but this is encouraging news nonetheless for a beaten-down stock.

On the losing front, we have non-nucleotide-based developer Achillion Pharmaceuticals (NASDAQ:ACHN), which primarily dropped because of the remarkably positive data from its peers. On Monday, Achillion announced positive proof-of-concept results for ACH-2684 targeted at treating hepatitis C in patients with cirrhosis of the liver and noted its plans to move on with additional testing. Achillion also announced that it has completed its studies of the drug-drug interaction between sovaprevir and its lead compound ACH-3102 and determined there was no interaction between the two. The company is now outlining phase 2 safety protocol to submit to the FDA for its all-oral treatment, although it's still well behind its peers

Be sure to check out Part 2 of my weekly recap, because this is really just the tip of the iceberg in terms of biotech news this week.

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