Macrogenics Inc., of Rockville, Md., said it priced an underwritten public offering of 5.5 million shares at $20 per share. In addition, the company has granted the underwriters a 30-day option to purchase up to an additional 825,000 shares at the public offering price. It anticipates the gross proceeds will be approximately $110 million, and the net proceeds will be used for general corporate purposes and working capital needs.