With the SPDR S&P Biotech Index up 22% 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.

Earnings season tends to steal the show around this time of year, but we had quite a few key studies announced this week that resulted in some huge share price moves, as well as the debut of one highly anticipated IPO.

The upside surprises was a lonely place to be this week, but Keryx Biopharmaceuticals (KERX) shareholders are perfectly fine with that. Shares of Keryx closed higher by 107% on the week after the company reported very positive late-stage data for its kidney disease drug, Zerenex. The drug, which is designed to treat hyperphosphatemia, reduced serum phosphate levels by 0.3mg/DL compared to the placebo where serum levels rose 1.9mg/DL. With the exception of Japan, Keryx is without a commercialization partner, so garnering an approval from the FDA and finding a licensing partner are next on its "to do" list.

On the flipside, misery had plenty of company this week, with Vanda Pharmaceuticals (VNDA -1.30%), Repros Therapeutics (NASDAQ: RPRX), and Celsion (CLSN -3.76%) all spending time in the penalty box.

Just last week, Vanda shares actually rallied on positive late-stage results for tasimelteon for the treatment on non-24-hour disorder. This week, Vanda's shares swooned slightly following disappointing phase 2b/3 data on tasimelteon as a treatment for major depressive disorder. The 507-patient trial known as Magellan noted that both tasimelteon and the placebo demonstrated a similar 40% reduction in symptoms. Vanda plans to stop development of tasimeletion with regard to major depressive disorder and instead focus on a prospective new drug application for non-24-hour disorder later this year.

If Vanda got two minutes in the penalty box for roughing up shareholders, then Repros Therapeutics certainly got five minutes and a warning after announcing that it'd be pushing its top-line data on Androxal, its secondary hypogonadism treatment, to the third-quarter. Investors had been expected Repros to report data in the second-quarter, but Repros noted an anomalous site among its 17 sites of patients indicated similar or significantly better results than the remaining sites. This patient pool, which contains 40 of the 151 patients being tested, has to be designated as either part of the general population or as a separate special population, which could throw off whom Androxal is eventually marketed toward. Assuming all goes well with the top-line data in the third quarter, Repros' plan to file a new drug application by mid-2014 remains on track. Now is the time to cross your fingers!

And then there was Celsion, which was ejected and suspended for the rest of the season after reporting terrible late-stage results for its liver cancer treatment, ThermoDox. In trials, Celsion noted that the control arm actually performed 20% better than expected, with ThermoDox actually performing worse than the control arm. Worse yet, much of Celsion's remaining pipeline is based on ThermoDox, including an ongoing mid-stage breast cancer study. With ThermoDox now off the table for liver cancer, shares imploded, falling 83% on the week.

Finally, Zoetis (ZTS 1.30%), the animal health division of Pfizer, made its debut on the NYSE on Friday to thunderous applause, rising 19% to $31.01 on huge volume. Zoetis has two key factors working in its favor over the long term that make it an intriguing buy in my eyes. For one, there's little competition among animal health medication makers, which means patent expirations can be somewhat meaningless on pet drugs. Also, the pet products market is expanding at a steady rate meaning the pie is growing for all companies involved. As a pet owner, I can tell you I'd spend whatever is needed to ensure the health of my pets, and there are millions of others out there who share my views. Zoetis could be a very strong performer moving forward.