For the past five years, Thousand Oaks biotech Amgen Inc. has seen its stock sit mostly dormant. For the most part, the stock traded between $50 and $60.

But lately, Amgen stock has treated shareholders better, with a steady and significant increase.

In fact, the stock hit a 52-week high of $85.28 on Aug. 27 before settling back down to close at $83.72 for the week ended Aug. 29. Still, that’s up more than 50 percent from a year earlier and more than 30 percent since Jan. 1.

So what makes a former “zombie stock” sustain such steady growth?

Michael Yee, an analyst who covers the company at RBC Capital Markets Corp. in San Francisco, said a variety of things are going right at the large biotech. But he points to changes in leadership and the company’s dedication to cutting costs as driving forces.

“They instituted a new leadership plan, which has brought hope for some investors that there will be new refreshing change at the company,” he said.

Amgen promoted former chief operating officer Robert Bradway to chief executive earlier this year, replacing Kevin Sharer, who retired after leading the company for more than a decade. Sharer remains chairman, but will step down at the end of the year. The company also switched leadership in research and development this year, naming Sean Harper vice president of the department.

The new management has the company on its way to meet goals of increasing operating margins, primarily by lowering general and administrative expenses but also by improving drug production, distribution and purchasing practices.

Also, Amgen’s profits have exceeded analysts’ expectations. In fact, the company updated its earnings guidance for the year by roughly 30 cents a share.

Stock moves, including an aggressive buy-back campaign, also have contributed to the stock’s viability. And last year, Amgen became the first large biotech to begin paying dividends.

The dividend payouts attract investors, but Yee said they aren’t solely responsible for the rising stock value. “If that was all it took, everyone would do that,” he said.

The company has benefited in particular from investors who consider the pharmaceutical industry a safe haven during economic turmoil. “Their exposure to the struggling economy is a lot less because people continue to need their drugs,” Yee said.

Meanwhile, the company’s prospects are good. Amgen has two major drugs in development – one to treat heart disease and another osteoporosis – expected to go on the market in the next few years. “They could be significant blockbusters,” Yee said.