With the SPDR S&P Biotech Index up 28% 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.

For a third week in a row, it's a mixed bag in the biotechnology sector: We have both positive and negative late-stage clinical trials, an FDA approval that wasn't a huge surprise, and an earnings miss that practically no one saw coming.

Beginning on a positive note, Navidea Biopharmaceuticals (NAVB 1.90%) -- less than 24 hours after discussing what I felt would be the inevitable approval of its Lymphoseek injection in my Tackling Cancer series -- received an approval from the FDA for Lymphoseek. Lymphoseek is a revolutionary injection that helps physicians stage the spread of cancer throughout the body's lymph nodes. With considerable more accuracy and far fewer adverse events that the previous standard of treatment offered by Pharmalucence, Lymphoseek will enable physicians to provide more personalized cancer treatments. Although shares dipped on the news, I'm holding by my assertion that share are worth about double where they're trading now!

Keeping with the positive theme, small Chinese biotechnology company Sinovac Biotech (SVA) released positive late-stage data this week for its hand, foot, and mouth disease, or HFMD, drug, EV71. Based on clinical trial results of children tested between the age of 6 months and 35 months, Sinovac's EV71 vaccine was 95.4% effective in against HFMD. However, my Foolish biotech guru David Williamson aptly points out it may not be worthwhile getting in an uproar about these results given the very low fatality figures of HFMD. According to David, less than 0.1% of all infection have proved fatal, meaning the Chinese government may not step up with big orders even if Sinovac's drug gains approval. 

But to every good there's usually a bad -- and that honor went to a small personal holding of mine, Aeterna Zentaris (AEZS). Aeterna shares lost about a quarter of their value this week on Monday, when it announced that the independent data safety monitoring board had recommended that it discontinue its late-stage study of perifosine for the treatment of multiple myeloma. While not great news, this was hardly a shock to me, given perifosine's late-stage failure in metastatic colorectal cancer. I'm more intrigued by Aeterna's remaining pipeline including AEZS-108, which is in midstage trials for breast, prostate, and bladder cancer, as well as AEZS 130, its oral growth hormone deficiency test for adults. This week's trading to perifosine news that we already should have known seems a bit of an overreaction, and I may actually look to beef up my position -- in accordance with the Fool's disclosure policy of course!

Last, but certainly not least, was this week's disaster du jour, Spectrum Pharmaceuticals (SPPI). Analysts had expected Spectrum's Fusilev, which is a palliative treatment used in patients with metastatic colorectal cancer, to bring in around $300 million this year. Even Spectrum, which had been dealing with generic competition for Fusilev, anticipated that a generic shortage would keep revenue for its brand-name drug growing. However, that quickly went up in smoke when Sagent Pharmaceuticals (NASDAQ: SGNT) announced that it'd be picking up the slack of making generic Fusilev, known as leucovorin. Spectrum responded by lowering its sales forecast to a mere $160 million to $180 million -- a 40% to 47% shortfall below the Street's expectations.Not surprisingly, Spectrum shares were hammered to the tune of 34% on the week.