With the SPDR S&P Biotech Index up 31% 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.

This week was so busy in terms of clinical data, a Food and Drug Administration panel meeting, and FDA PDUFA decisions that we can skip right over biotech earnings reports and jump right into the meat and potatoes of this week's data.

This week saw two new drugs approved by the FDA: Raptor Pharmaceuticals' (NASDAQ: RPTP) Procysbi and Merck's (NYSE:MRK) Liptruzet.

The approval of Procysbi certainly didn't come as a surprise to many, with Raptor's neuropathic cystinosis drug proving non-inferior to Mylan's Cystagon in trials. As a twice-daily tablet, Procysbi doesn't inconvenience patients like Cystagon, which is required to be taken four times daily and can potentially disrupt sleep patterns. Peak sales of the drug are estimated at $60 million in the U.S., so it'll certainly need an approval in the EU if it has any chance of becoming profitable, but it'll gladly take the $25 million payment triggered by the FDA approval under its loan agreement with HealthCare Royalty Partners.

Merck (NYSE:MRK), on Friday, announced that the FDA had approved its cholesterol combination drug known as Liptruzet, which combines a generic version of Pfizer's Lipitor and its own cholesterol drug, Zetia. The drug, which is used as an adjuvant therapy when diet alone isn't enough, lowers high levels of LDL cholesterol. With lifetime Lipitor sales of $131 billion, the market for preventative high-cholesterol medications is only growing, so investors should keep a close eye on sales of this drug combination over the coming quarters.

But not all news can be good news as we learned this week.

AVEO Pharmaceuticals (NASDAQ:AVEO) shareholders would just assume bury their heads in the sand following an FDA panel meeting that delivered a 13-to-1 vote against recommending metastatic renal cell carcinoma drug Tivozanib for approval. If you recall, Tivozanib delivered statistically better progression-free survival results in a late-stage head-to-head against Onyx Pharmaceuticals' and Bayer's Nexavar, but its median overall survival slightly lagged Nexavar. For AVEO to justify the benefits of Tivozanib, another trial seems all but inevitable. AVEO shares fell a whopping 67% on the week.

Arena Pharmaceuticals (NASDAQ:ARNA) didn't have nearly as rough a go of things, but it certainly didn't have a good week, either. Following a first-quarter report that saw the company drastically miss the Street's revenue and profit estimates as it continues to wait for the final labeling of its chronic weight management drug, Belviq, from the Drug Enforcement Agency, Arena also announced it was pulling its EU marketing application for Belviq. The move isn't a complete shock given that VIVUS' Qsymia failed to gain approval in Europe as well because of safety concerns, but it certainly takes any chance of garnering any EU revenue off the table for both companies, at least in the interim.

Finally, Allergan (NYSE: AGN) shareholders drew the short end of the straw after the company announced an update to its mid-stage vision loss trial of DARPin. According to the results, the drug demonstrated some differentiation when compared to Lucentis, but it failed to deliver statistically significant reasons to advance it to late-stage trials. As a prospective competitor to Regeneron Pharmaceuticals' Eylea, the delay in development gives Eylea a continued free and clear path to grow unabated. Allergan shareholders were given some relief later in the week with the FDA panel unanimously recommending Juvederm Voluma for cheek augmentation to correct age-related volume deficit in the mid-face, but that hardly made up for the sales potential that DARPin possessed in wet age-related macular degeneration.

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