Synthetic Biologics Announces Public Offering of Common Stock

ROCKVILLE, Md., July 15, 2015 /PRNewswire/ -- Synthetic Biologics, Inc. (NYSE MKT: SYN), a clinical-stage company focused on developing therapeutics to protect the microbiome while targeting pathogen-specific diseases, today announced that it has commenced an underwritten public offering of shares of its common stock. All of the shares in the offering are to be sold by Synthetic Biologics. The Company intends to grant the underwriters a 30-day option to purchase up to an additional 15 percent of the share amount sold to cover over-allotments, if any. The offering is subject to market conditions, and there can be no assurance as to whether or when the offering may be completed, or as to the actual size or terms of the offering.

William Blair & Company, L.L.C. and RBC Capital Markets, L.L.C. are the joint book-running managers for the offering. BTIG, L.L.C. is serving as co-manager for the offering.

Synthetic Biologics anticipates using the net proceeds from the offering to fund its clinical programs including Phase 2 clinical candidates, SYN-004 for the prevention of C. difficile and SYN-010 for the treatment of irritable bowel syndrome with constipation (IBS-C), research & development, potential licensing and acquisition of intellectual property, investments in and acquisition of complementary businesses or partnerships, and for general corporate purposes.

The shares will be issued by Synthetic Biologics pursuant to a shelf registration statement that was previously filed with, and declared effective on April 20, 2015, by the Securities and Exchange Commission (SEC). A preliminary prospectus supplement related to the offering has been filed with the SEC and is available on the SEC's website located at www.sec.gov. A final prospectus supplement related to the offering will be filed with the SEC.

This press release does not constitute an offer to sell or a solicitation of an offer to buy nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. Any offer, if at all, will be made only by means of a prospectus supplement and accompanying prospectus forming a part of the effective registration statement, copies of which may be obtained, when available, from William Blair & Company, L.L.C., Attention: Prospectus Department, 222 West Adams Street, Chicago, IL 60606, by telephone at (800) 621-0687, or by e-mail at [email protected]. RBC Capital Markets, L.L.C., Attention: Equity Syndicate, 200 Vesey Street, 8^th Floor, New York, NY 10281-8098, or by telephone at (877) 822-4098.

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE MKT: SYN) is a microbiome-focused, clinical-stage company developing therapeutics to protect the microbiome while targeting pathogen-specific diseases. The Company's lead candidates in Phase 2 development include SYN-004 which is designed to protect the gut microbiome from the effects of certain commonly used intravenous (IV) antibiotics for the prevention of C. difficile infection and antibiotic-associated diarrhea (AAD), and SYN-010 which is intended to reduce the impact of methane producing organisms in the gut microbiome to treat the underlying cause of irritable bowel syndrome with constipation (IBS-C). In addition, the Company is developing a Phase 2 oral estriol drug, Trimesta, for the treatment of relapsing-remitting multiple sclerosis (MS) and cognitive dysfunction in MS, and a monoclonal antibody combination for the treatment of Pertussis. For more information, please visit Synthetic Biologics' website at www.syntheticbiologics.com.

This release includes forward-looking statements on Synthetic Biologics' current expectations and projections about future events. In some cases forward-looking statements can be identified by terminology such as "may," "should," "potential," "continue," "expects," "anticipates," "intends," "plans," "believes," "estimates," and similar expressions. These statements are based upon current beliefs, expectations and assumptions and are subject to a number of risks and uncertainties, many of which are difficult to predict and include statements with respect to this offering and the successful execution of the Company's business strategy, including its intended use of proceeds. The forward-looking statements are subject to risks and uncertainties that could cause actual results to differ materially from those set forth or implied by any forward-looking statements. Important factors that could cause actual results to differ materially from those reflected in Synthetic Biologics' forward-looking statements include, among others, the additional clinical studies and results not meeting expectations, the inability to commence and complete clinical trials when anticipated and other factors described in Synthetic Biologics' report on Form 10-K for the year ended December 31, 2014 and any other filings with the SEC. The information in this release is provided only as of the date of this release, and Synthetic Biologics undertakes no obligation to update any forward-looking statements contained in this release on account of new information, future events, or otherwise, except as required by law.

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SOURCE Synthetic Biologics, Inc.

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http://www.syntheticbiologics.com