What's Behind Gilead Sciences Inc.'s $7.8 Billion Slide in October?

Shares of Gilead Sciences, Inc. (NASDAQ: GILD) slipped 7.5% last month, according to S&P Global Market Intelligence, reducing the biotech's market cap by $7.8 billion. Although the company reported some positive data for two key programs in development, hepatitis C virus (HCV) sales slid much further than expected.

Gilead Sciences shocked the market in February with a disturbingly bleak sales forecast for its HCV franchise, which peaked at $19.1 billion in 2015. In July, management lifted investors' spirits by nudging the lower end of its 2017 forecast from $7.5 billion to $8.5 billion after total hepatitis C sales ticked a bit higher sequentially in the second quarter.

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Source: Fool.com