The Palo Alto, Calif., drug developer said that it priced an offering of 4 million shares at $6 per share. The stock closed at $6.46 the day before the announcement.
Shares fell 43 cents, or 6.7 percent, to $6.03 in heavy midday trading Thursday. Its shares have traded in a range of $4.50 to $7.55 over the past year.
Anacor Pharmaceuticals expects gross proceeds of $24 million, which it will put toward research and development and working capital.
The offering is expected to close Oct. 23. Underwriters have an option to purchase an additional 15 percent of the shares, or about 600,000, to cover any excess demand.
Cowen and Co. is the offering's sole manager.