Apellis Pharmaceuticals Inc. has raised $404.2 million in a previously announced public offering after underwriters fully exercised their overallotment option.

The Waltham, Mass.-based biopharmaceutical company sold 10,925,000 shares at $37 apiece, including the additional 1,425,000 shares in the underwriters' overallotment option.

Apellis develops treatments for autoimmune and inflammatory diseases.

Citigroup, J.P. Morgan and Evercore ISI were joint book-running managers for the offering, while Cantor Fitzgerald & Co. and Baird were lead managers.