After Prana (ASX:PBT) announced a result we would rather forget from their Alzheimer's drug, the biotech sector closed down 7.9% last week. This was the second clinical trial result in 6 weeks for the company's PBT2 drug and pretty much confirmed that the drug is unlikely to provide a significant therapeutic benefit for patients. Reva Medical (ASX:RVA) also continued to weigh heavily on the sector after it announced it was no longer investing in its ReZolve2 resorbable stent because it had a newer, better version. Unfortunately, this puts the company back to where it was when it listed in 2010 and is not the first time it has switched to a new product. Sirtex (ASX:SRX), fortunately, came to the rescue announcing 18.2% growth in unit sales of their SIR-Spheres. While the company continues to deliver solid growth, positive data from their clinical trials could provide a massive boost to sales.