Synthetic Biologics Reports Third Quarter

Synthetic Biologics Reports Third Quarter

2013 Financial Results and Operational Update

-- Conference Call Today, November

14, at 10 a.m. Eastern Time --

Rockville, MD, November 14, 2013 -

Synthetic Biologics, Inc. (NYSE MKT: SYN), a developer of biologics focused on the prevention and treatment of serious infectious

diseases, today reported financial results for the three and nine months ended September 30, 2013 and provided an operational update.

Recent Operational Highlights

During and since the third quarter of

2013, the Company has:

SYN-004 Product Candidate for the Prevention

of C. diff Infections

Phase II Study of Multiple Sclerosis

(MS) Candidate, Trimesta

Preclinical Monoclonal Antibody (mAb)

Program for Pertussis (Whooping Cough)

"This quarter has been a time of

well-paced progress for our preclinical and clinical programs, which position us to create significant value for shareholders going

forward. We remain on track to meet our milestones and believe we are well positioned to take advantage of meaningful catalysts

over the next several quarters," stated Jeffrey Riley, CEO of Synthetic Biologics.

Three and Nine Months Ended September

30, 2013 Financial Results

General and administrative expenses were

$1.9 million and $4.3 million for the three and nine months ended September 30, 2013, respectively, compared to $1.1 million and

$3.7 million for the same periods in 2012. These increases of 76% and 15%, respectively, are primarily the result of bad debt expense

of $763,000 associated with the determination that the note and interest receivables from the sale of Adeona Clinical Laboratory

are uncollectible. Non-cash charges related to stock-based compensation were $264,000 and $916,000 for the three and nine months

ended September 30, 2013, respectively, compared to $279,000 and $1.1 million for the same periods in 2012.

Research and development expenses were

$1.5 million and $3.8 million for the three and nine months ended September 30, 2013, respectively, compared to $763,000 and $1.7

million for the same periods in 2012. These increases of 93% and 124%, respectively, are primarily the result of additional employee

costs and increased program costs associated with our infectious disease programs. Non-cash charges related to stock-based compensation

were $74,000 and $286,000 for the three and nine months ended September 30, 2013, respectively, compared to $116,000 and $238,000

for the same periods in 2012.

Other expense was $3,000 for the three

months ended September 30, 2013, compared to other income of $10,000 for the same period in 2012. Other expense was $27,000 for

the nine months ended September 30, 2013, compared to other income of $22,000 for the same period in 2012.

Cash at September 30, 2013 was $5.1 million

compared to $10.0 million at December 31, 2012.

Synthetic Biologics will hold a conference

call today, Thursday, November 14, 2013, at 10:00 am EST. During the call, Jeffrey Riley, Synthetic Biologics' Chief

Executive Officer, will provide a brief quarterly update of the Company's multiple sclerosis program and its anti-infective

drug pipeline for infectious diseases, including SYN-004, its oral enzyme candidate for the prevention of C. difficile infections.

C. Evan Ballantyne, Synthetic Biologics' Chief Financial Officer, will review the Company's financial results for the

third quarter ended September 30, 2013.

Interested parties should call 1-877-870-4263

(U.S. toll free), 1-855-669-9657 (Canada toll free), or +1 412-317-0790 (International), fifteen minutes before the start of the

call to register. Registered callers on the toll free line may ask to be placed in the queue for the Question & Answer Session.

The call will also be webcast over the Internet at http://www.videonewswire.com/event.asp?id=96920. If you are unable to participate

during the live conference call, the webcast will be available for replay at the same URL, http://www.videonewswire.com/event.asp?id=96920

for 30 days after the call.

About Synthetic Biologics, Inc.

Synthetic Biologics (NYSE MKT: SYN) is

a biotechnology company focused on the development of biologics for the prevention and treatment of serious infectious diseases.

The Company is developing an oral enzyme for the prevention of C. difficile infections, and a series of monoclonal antibody

therapies for the treatment of Pertussis and Acinetobacter infections. In addition, the Company is developing a drug

candidate for the treatment of relapsing-remitting multiple sclerosis and cognitive dysfunction in multiple sclerosis. For more

information, please visit Synthetic Biologics' website at www.syntheticbiologics.com.

To download Synthetic Biologics'

investor relations mobile device app, which allows users access to the Company's SEC documents, press releases and events, please

click on the following links to download the IRapp on your iPhone and iPad or your Android mobile device.

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 regarding advancing our clinical programs,

the opportunities and our position in the infectious disease market, the anticipated timing and results of our development efforts

and the expected size of the future market for sales of therapies for C. difficile infection, and our ability to create significant

shareholder value. 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, a failure

to receive the necessary regulatory approvals for commercialization of our therapeutics, a failure of our clinical trials to be

commenced or completed on time or to achieve desired results, a failure of our clinical trials to receive anticipated funding,

a failure of our monoclonal antibodies for the treatment of infectious diseases to be successfully developed or commercialized,

our inability to maintain our licensing agreements, or a failure by us or our strategic partners to successfully commercialize

products and other factors described in Synthetic Biologics' report on Form 10-K for the year ended December 31, 2012 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.

For further information, please contact:

Vice President, Corporate Communication

(734) 332-7800, Ext. 22

- Financial Tables Follow -