Biotech stocks are a volatile bunch, and there is no shortage of big winners over the previous three months. Certainly not for the faint of heart, the direction of a biotech stock is typically dictated by the outcome of drug clinical trials. A positive result can result in massive triple-digit gains, while adverse side effects or a lack of effectiveness can send a stock into abyss.

Take Ariad Pharmaceuticals (ARIA) , for example. After dropping below $1 per share during the recession, Ariad stock hit $23.00 last year amid encouraging trial results and hopeful sales projections. Investors could have made a maximum of 23 times their money on Ariad stock. Not too shabby for a four-year investment.

However, Ariad stock crashed to around $2.15 this year after the FDA expressed concerns that the drug Iclusig, may cause blood clots. Ariad was forced to suspend distribution and shares lost around 90 percent. The stock has since tripled to $6.60, and who knows whether the wild ride is over.

Such volatility is simply the nature of biotech. Here are the five best performers in the industry over the previous three months:

1) Intercept Pharmaceuticals (ICPT)

Up 508%. Shares soared after clinical trials of its liver disease drug were enormously successful. The trials were halted after patients taking the drug showed a “highly statistical improvement” in overall liver health, as compared to the placebo. The drug specifically targets NASH, which is a very common liver disease that results in scarring, inflammation, or fibrosis.

Shares jumped fro $72 to $497 in only two days, but have since pulled back to $326 after some patients reportedly showed higher cholesterol levels after taking the drug. Intercept, which is up over 800% over the previous twelve months, will likely trade with volatility this year as more trial results roll in.

2) Puma Biotechnology (PBYI)

Up 216%.  On December 4, 2013, Puma announced that the results of its I-Spy 2 trial, which enrolled women with Stage 2 or higher breast cancer to take the drug neratinib, were extremely positive. Neratinib is a pan-HER inhibitor that blocks the signal transduction through a number of growth factor receptors.

There is certainly great demand for the drug because approximately 70 percent of patients with HER-2 amplified breast cancer have at least some resistance to popular breast cancer drugs like Herceptin, a demographic of people that the drug intends to treat. In response to this opportunity, shares rose from $46 to $77 in on December 5 and continued to rise all the way to $140 as of January 21.

3) Galena Pharmaceuticals (GALE)

Up 88%. Galena is a producer of oncology drugs and has had recent success in its drug NeuVax, which is a vaccine designed to prevent the recurrence of breast cancer. Galena has a strategic partnership with Dr. Reddy’s Laboratories, and the two have decided that the drug could also be developed to prevent gastric cancer.

Galena’s strategic partnership and the potential multiple uses for NeuVax opens up a potentially enormous market for the drug. Consequently, shares have almost tripled since the beginning of November amid numerous analyst upgrades. However, the stock has since pulled back almost 20 percent from annual highs due to some doubts surrounding the science of the drug.

4) OncoMed Pharmaceuticals (OMED)

Up 155%. Oncomed shares doubled on December 3 after the company announced that Celgene Corp ($CELG) would help develop and market six of its anti-cancer stem cell drugs. In addition to Celgene’s support and resources, OncoMed received $177.25 million upfront, $22.5 million of which goes to new stock that Celgene will receive.

The deal is certainly mutually beneficial, as OncoMed will have the benefit of exposure to Celgene's incredible resources. Meanwhile, Celgene gains exposure to stem cells, of which it previously had none. Following a barrage of price increases, OncoMed now sits just south of $38, almost triple from its price at the beginning of December.

5) Ariad Pharmaceuticals (ARIA)

Up 106%. As discussed above, Ariad stock was crushed last year when it was reported that one of its drugs may cause harmful side effects. The stock has doubled over the last three months, but has still lost three quarters of its value since it hit multi-year highs.

The drug is currently under heavy scrutiny and analysis. The stock will remain in limbo until regulators and researchers come to a conclusion.