South San Francisco-based KaloBios Pharmaceuticals has filed a registration statement with the Securities and Exchange Commission for a proposed initial public offering of its common stock. The number of shares to be offered and the price range for the offering have not yet been determined.

The offering will be made only by means of a prospectus. While a registration statement has been filed, it is not yet effective. These securities may not be sold nor may offers to buy these securities be accepted prior to the time the registration statement becomes effective.

KaloBios Pharmaceuticals is a biopharmaceutical company developing a portfolio of proprietary, patient-targeted, first-in-class monoclonal antibodies (mAbs) designed to significantly improve the lives of seriously ill patients with difficult-to-treat diseases.