5 of Last Week's Biggest Winners

What's better than momentum? Mo' momentum. Let's take a closer look at five of this past week's biggest scorchers.

Source: Barron's.

Let's start with Ariad. The biotech moved sharply higher on encouraging news in Europe. Its leukemia drug Iclusig will continue to be offered in Europe, even though the regulatory agency is suggesting some safety protocols. 

Sarepta was the Nasdaq's biggest loser three weeks ago, surrendering 60% of its value when the FDA delayed the biotech's application for its Duchenne muscular dystrophy drug. Some investors are starting to sense a buying opportunity in the rubble, and on Tuesday it was upgraded by WBB Securities. 

J.C. Penney broke into double digits for the first time in more than two months after some timely insider buying. The struggling department-store chain's CEO bought roughly $1 million of J.C. Penney's stock. It's his first purchase in years, giving the open market purchase more weight in shaping bullish opinion than usual. 

Voxeljet moved higher even as Jim Cramer had some unkind words to say about the recent 3-D printing IPO.

"When Voxeljet becomes an earnings story, I am willing to listen," he said on CNBC's Squawk on the Street show. "Right now, they are the poster boy for overvalued."

SolarCity lost 16% of its value a week earlier, but it made most of that amount back during this holiday-shortened trading week. An important catalyst was announcing the opening of 10 regional operation centers across California. The move nearly doubles the solar-energy installer's presence in California.