Pieris Pharmaceuticals Inc. closed its underwritten public offering of 6,325,000 common shares at $8 apiece with gross proceeds of about $50.6 million.

The shares sold include the full exercise of the underwriters' option to buy up to an additional 825,000 common shares.

The Boston-based drugmaker plans to use the proceeds for working capital and general corporate purposes, including advancing the development of its drug candidates.

Jefferies, Cowen and Evercore ISI acted as joint book-running managers for the offering.