Thousand Oaks-based Atara Biotherapeutics has brought on more investors to its second financing round, bringing the total raised to $52 million.

The additional $13.5 million comes weeks after Atara, which has licenses to develop Amgen drug assets, announced a $38.5 million round of financing. The company is Amgen’s first major “out licensing” deal, in which Amgen provided drug candidates and outsiders – in this case, the Silicon Valley venture capital megafirm  Kleiner Perkins Caufield & Byers – provided the capital.

The new capital will go toward its two lead programs, called PINTA 745 and STM 434. PINTA 475, which is further along in the trial process, would treat a common dialysis complication called protein energy wasting, building on one of Amgen’s core markets for kidney disease drugs. The other drug, STM 434, would treat ovarian cancer and other solid tumors. The company also has a drug for cancer-related weight loss that has not yet entered clinical testing.

With the newest closing, the company’s second round of investment includes funds from Alexandria Venture Investments, Amgen Ventures, The Baupost Group, Celgene Corporation, DAG Ventures, Domain Associates, EcoR1 Capital and Kleiner Perkins.