for $225 million, obtaining developmental-stage research for treating fibrotic diseases and cancer. In February 2011, the company acquired Calistoga Pharmaceuticals for ($225 million plus milestone payments). The acquisition boosted Gilead's oncology and inflammation areas. Later that year, Gilead made its most important acquisition – and by then most expensive – with the purchase of Pharmasset, Inc. This transaction helped cement Gilead as the leader in treatment of the hepatitis C virus by giving it control of sofosbuvir (see below). In October 2011, Gilead broke ground on a massive multi-year expansion of its 17-building headquarters campus in Foster City. By replacing eight one or two-story buildings with seven new structures ranging as tall as 10 stories, Gilead nearly doubled its headquarters real estate footprint from about 620,000 square feet to about 1.2 million square feet. On July 16, 2012, the FDA approved Gilead's Truvada for prevention of HIV infection (it was already approved for treating HIV). The pill was a preventive measure (PrEP) for people at high risk of getting HIV through sexual activity. In 2013, the company acquired YM Biosciences, Inc. for $510 million. The acquisition brings drug candidate CYT387, an orally-administered, once-daily, selective inhibitor of the Janus kinase (JAK) family, specifically JAK1 and JAK2, into Gilead's oncology pipeline. The JAK enzymes have been implicated in myeloproliferative diseases, inflammatory disorders, and certain cancers. In 2015, the company made a trio of acquisitions: It bought Phenex Pharmaceuticals for $470 million. Its Farnesoid X Receptor (FXR) program used small-molecule FXR agonists in the treatment of liver diseases such as non-alcoholic steatohepatitis. It bought EpiTherapeutics for $65 million. This acquisition gave Gilead first-in-class small molecule inhibitors of histone demethylases involved in regulating gene transcription in cancer. It paid $425 million for a 15% equity stake in Galapagos NV, with additional payments for Gilead to license the experimental anti-inflammatory drug filgotinib, which may treat rheumatoid arthritis, ulcerative colitis, and Crohn's disease. In 2016, the company acquired Nimbus Apollo, Inc. for $400 million, giving Gilead control of the compound NDI-010976 (an ACC inhibitor) and other preclinical ACC inhibitors for the treatment of non-alcoholic steatohepatitis and for the potential treatment of hepatocellular carcinoma. Also in 2016, the company was named the most generous company on the 2016 Fortune list of The Most Generous Companies of the Fortune 500. Charitable donations to HIV/AIDS and liver disease organizations totaled over 440 million in 2015. In August 2017, the