Seattle Genetics plans to sell 7.3 million shares in a follow-on stock offering, it said today after the markets closed.

Additionally, the Bothell company plans to sell 1.1 million shares in a private placement to investment funds affiliated with Baker Brothers Investments at a share price equal to that paid by investors in the public share offering. The company did not specify an offering price.

At the stock's Tuesday close of $5.74 a share, the offering would generate $48.2 million before expenses.

Seattle Genetics had $79.2 million in cash and investments on Dec. 31. The company expected to spend $35 million to $40 million on operations this year.

The offering will be managed jointly by Banc of America Securities and CIBC World Markets.

The Baker Brothers offering requires shareholder approval. Felix Baker, a Seattle Genetics board member, is managing partner at the New York investment company.

Seattle Genetics is developing monoclonal antibodies to treat cancer and other diseases.

Benjamin J. Romano: bromano@seattletimes.com