If you like excitement, biotech stocks provided plenty of it over the last several days. And most of the buzz stemmed from the $11.9 billion buyout of Kite Pharma (NASDAQ:KITE) announced by Gilead Sciences (NASDAQ:GILD) on Monday.

But while Kite Pharma stock shot up nearly 30% on the acquisition news and Gilead stock jumped more than 10%, neither company ranked among the best-performing biotech stocks this week. Instead, three smaller biotechs made even greater leaps -- Abeona Therapeutics (NASDAQ:ABEO), Sangamo Therapeutics (NASDAQ:SGMO), and Juno Therapeutics (NASDAQ:JUNO). Here's why these biotech stocks skyrocketed.

Man pointing to line charts going up

Image source: Getty Images.

Abeona Therapeutics

Shares of Abeona Therapeutics soared around 50% higher this week. That huge gain resulted primarily from the U.S. Food and Drug Administration (FDA) granting breakthrough therapy designation for the biotech's EB-101 gene therapy program for treating patients with recessive dystrophic epidermolysis bullosa. This rare genetic disease causes the skin to blister easily and can lead to serious medical problems. 

Breakthrough therapy designation is certainly good news, since it can speed up the drug development and approval process. The designation is especially helpful to Abeona right now, as the company is working with the FDA to finalize the design of a phase 3 study of EB-101. Abeona hopes to begin that study in early 2018. 

While EB-101 is Abeona's lead candidate, its experimental treatment for another rare genetic disease isn't too far behind. ABO-102 is in a phase 1/2 study for treating Sanfilippo syndrome type A. Abeona's pipeline also includes one other clinical gene therapy program and seven pre-clinical programs. 

Sangamo Therapeutics

Sangamo Therapeutics didn't report huge news this week, although the biotech did announce the first patient received treatment in the phase 1/2 clinical trial of SB-525, its gene therapy for patients with Hemophilia A. But Sangamo stock's performance was huge, with shares surging more than 35% over the past five days.

What was the catalyst for Sangamo? I suspect the biotech is surfing the wave of investors' excitement about cell therapy spurred by Gilead's acquisition of Kite. The company could have also benefited from Abeona's good news from the FDA.

Sangamo is a pioneer in zinc finger nuclease (ZFN) gene editing. The biotech has four clinical programs in its pipeline and three pre-clinical programs, several of which are partnered with larger drugmakers. This interest from big pharma helped make Sangamo one of the best-performing biotech stocks of the first half of 2017.

Juno Therapeutics

Juno Therapeutics had no news at all this week -- other than announcing that it would present at a couple of investor conferences in September. Yet the biotech stock shot up nearly 40% during the week.

You can definitely chalk up Juno's big increase to Gilead's buyout of Kite. Both Juno and Kite are developing chimeric antigen receptor T cell (CAR-T) and T cell receptor (TCR) therapies for treating cancer. With Kite no longer available, Juno is one of the most attractive acquisition targets for bigger companies looking to add cell therapy to their oncology portfolio.

Probably the most likely suitor for Juno is its partner, Celgene (NASDAQ: CELG). The two companies are teamed up on development of experimental CAR-T drug JCAR017 in treating non-Hodgkin lymphoma.  

Best pick? 

All three of these biotechs could see tremendous success in the future. It's a hard choice as to which is the best pick right now. My nod, though, goes to Abeona Therapeutics.

Despite its massive gains this week, Abeona has the lowest market cap of any of the three biotechs discussed. The company isn't tightly linked to a larger biopharmaceutical company yet, either. That could make it more appealing to big drugmakers that don't have a strong gene therapy focus yet.   

Keith Speights owns shares of Celgene and Gilead Sciences. The Motley Fool owns shares of and recommends Celgene and Gilead Sciences. The Motley Fool recommends Juno Therapeutics. The Motley Fool has a disclosure policy.