Amgen Ventures, the investment arm of Thousand Oaks biopharmaceutical firm Amgen Inc., has invested an undisclosed sum in Syapse Inc., a San Francisco software company that has developed an integrative platform designed to streamline the “precision medicine” approach to cancer treatment. “Precision medicine is transforming health care and there is no better example than in the treatment of cancer,” Janis Naeve, managing director of Amgen Ventures, told the Business Journal in an e-mail. “(We) are excited to be an investor in Syapse.” Amgen declined to provide the financial details of the investment, which was part of a $30 million Series D funding cycle that closed on Nov. 14. The Merck Global Health Innovation Fund and the Roche Investment Fund also contributed to the round, according to online database company Crunchbase. Syapse’s software integrates patient information, results from clinical trials, diagnostic data and more into a single system, making it easier for oncologists to put the principles of precision medicine into practice. Precision medicine is an approach to treatment of serious illness that bases decisions on a patient’s lifestyle, genes and exposure to environmental hazards. Amgen stock fell $1.21, or less than 1 percent, on Monday to close at $168.79 on the Nasdaq.