), a leading RNAi therapeutics company, today announced that the underwriters of its previously announced public offering of common stock have exercised their option to purchase an additional 1,200,000 shares at the public offering price of $20.13 per share. As a result, the company will issue a total of 9,200,000 shares in the offering and will receive aggregate net proceeds, after underwriting discounts and commissions and other estimated offering expenses, of approximately $173.8 million. The offering is expected to close on or about January 22, 2013, subject to the satisfaction of customary closing conditions.