Synthetic Biologics Inc. priced an underwritten public offering for a combination of securities to raise $18 million in gross proceeds.

The company is offering class A units consisting of 2,520,000 common shares and warrants to purchase 2,520,000 shares at a combined price of $1.15, and class B units consisting of 15,102 series B convertible preferred shares convertible into an aggregate of 13,132,173 common shares, and warrants to purchase 13,132,173 common shares.

The warrants will be exercisable upon issuance at an exercise price of $1.38 and will expire five years after issuance.

Synthetic Biologics has given underwriters the option to purchase up to an additional 15% of the common shares, warrants and common shares issued after conversion of preferred shares.

The company plans to use net proceeds from the offering to fund preclinical and clinical programs. In addition, it expects to use the proceeds for working capital and general corporate purposes.

The offering is expected to close Oct. 15, subject to customary closing conditions.

Alliance Global Partners is acting as the sole book-running manager for the offering.