Kite Pharma Inc., a cancer drug developer, on Wednesday said that it had raised $20 million in a private placement of preferred stock that included its existing backers and a new investor.

The Westwood company, which is developing a therapy that will use the body’s immune system to fight tumors and blood cancer, said that it also converted $15 million in promissory notes to shares of the same Series A preferred stock.

Kite’s new investor is Alta Partners, a San Francisco private equity firm targeting startups in biomedicine and information technology. All current major investors participated in the financing, including Kite co-founder and Executive Chairman Arie Belldegrun, a UCLA urology professor and partner at New York venture capital firm Two River Group. Other investors included Israeli venture capital firm Pontifax Ltd. and billionaire investors Michael Milken and David Bonderman.

Farah Champsi, Alta Partners managing director, and Ran Nussbaum, Pontifax managing partner, have joined Kite’s board.

Kite raised $15 million in its initial financing round in March 2012. In October, it announced a partnership with the National Cancer Institute. The institute provided funding to develop Kite’s therapy, which is designed to restore a patient’s immune system ability to recognize and kill cancer.

“The new resources will allow us to advance clinical and manufacturing activities,” Chief Executive Aya Jakobovits said in a statement.