As the week comes to the close, we are reminded how that no matter how calm the broader market looks, there are always waves being made in the biotech sector. Today we have obesity drama, the death of a drug, and the lift of a clinical hold moving several high-profile stocks. Let's dive into these headlines and highlight key investor takeaways.

First up is Halozyme (Nasdaq: HALO), our day's biggest gainer, soaring 30% on news that partner ViroPharma (Nasdaq: VPHM) can continue trials for Cinryze. The FDA put a hold on trials using Halozyme's subcutaneous platform in early August when HyQ was rejected. Shares were cut in half that day but rebounded nicely after a pipeline update for a phase 3 drug with Roche looked good. The lift of the clinical hold on Cinryze allays investor fears that Halozyme's platform was in jeopardy. With those fears abated, expect Halozyme to continue to trade back up to where it was before all of the drama began.

Astex Pharmaceuticals (Nasdaq: ASTX) investors unfortunately are on the other side of the drug development coin. The company announced it will discontinue development of amuvantinib after not meeting its primary endpoint in a phase 2 small-cell lung cancer trial. The good news is the drug appears safe, and if anyone is interested in licensing it out, Astex is all ears. Anyone? Hello?

Astex shares are off 9%, which isn't terrible considering the news. Amuvantinib was one of five phase 2 drug candidates, but since the drug isn't partnered, success would have been huge for the company. However, because Astex has so many partners, it is insulated from any single failure. Investors now are left to focus on Dacogen sales, which recently suffered a setback when the FDA denied an expanded indication into AML, and the rest of the company's development pipeline. Because of all the irons in the fire, this stock is definitely one to watch, but investors may be better served watching from a distance until we see further development of the pipeline.

Finally, that brings us to the hottest little corner of biotech: obesity drugs. VIVUS (Nasdaq: VVUS) is down 11% over worries that Qsymia will face rejection overseas. And this isn't just an idle rumor; it came straight from the horse's mouth -- a VIVUS press release! After discussion with the CHMP (the Euro-equivalent of our FDA) VIVUS "expects an opinion recommending against approval," but the company intends to either appeal or resubmit if the decision doesn't go their way. The big winner in this, of course, is rival Arena Pharmaceuticals (Nasdaq: ARNA), up nearly 4% as any stumble by one leads to investor confidence in the other. Ultimately, both drugs should end up with EU approval, even if it takes a couple of tries, similar to what we saw here at home. Both stocks enjoyed massive gains over the past year, which should make investors leery, but if you believe in the long term future of obesity treatments, buying both stocks after 30% pullbacks from their 52-week highs will ensure you are poised to profit, no matter which company wears the sales crown.

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