Synthetic Biologics Reports Year End 2013 Financial Results and Operational Update -- Conference Call Today

Synthetic Biologics Reports Year End

2013 Financial Results and Operational Update

-- Conference Call Today, March 31,

2014, at 10:00 a.m. (EDT) --

Rockville, MD, March 31, 2014 -

Synthetic Biologics, Inc. (NYSE MKT: SYN), a developer of novel anti-infective biologic and drug candidates targeting specific

pathogens that cause serious infections and other diseases, today reported financial results for the year ended December 31, 2013

and provided operational highlights.

Recent Operational Highlights

Relapsing-Remitting Multiple Sclerosis

(RRMS) - Trimesta (oral estriol)

Prevention of C. difficile (C. diff.)

Infections - SYN-004 Oral Enzyme

Pertussis (Whooping Cough) - Monoclonal

Constipation-Predominant Irritable Bowel Syndrome (C-IBS)

"Over the past two years, Synthetic

Biologics has built a strong pipeline of novel anti-infective biologic and drug candidates targeting specific pathogens, such as

C. diff, b. pertussis, methanogens and Acinetobacter. We believe that the Company is well positioned to achieve

several key milestones during 2014, and should create significant shareholder value," stated Jeffrey Riley, CEO of Synthetic

Biologics. "Relevant to a topic gaining increased awareness in the healthcare community, two of the Company's compounds

in development are designed to protect the microbiome. When the natural balance of the millions of bacteria in the gut microbiome

is disrupted, a person's health can be compromised. We believe we have solutions."

Mr. Riley concluded, "We look forward

to the AAN Annual Meeting at the end of April, when Dr. Rhonda Voskuhl will present topline results from the Phase II clinical

trial evaluating Synthetic Biologics' oral estriol compound. This represents an important milestone for the Company, and

for the potential development of a treatment for MS patients."

Year Ended December 31, 2013 Financial Results

General and administrative expenses increased

to $5.8 million for the year ended December 31, 2013, compared to $5.0 million for the same period in 2012. The increase of 16%

is primarily the result of bad debt expense of $763,000 associated with the determination that the note and interest receivable

from the sale of Adeona Clinical Laboratory is uncollectible. Charges related to stock-based compensation were $1.3 million for

the year ended December 31, 2013, compared to $1.5 million for the same period in 2012.

Research and development expenses decreased

to $6.5 million for the year ended December 31, 2013, compared to $12.3 million for the same period in 2012. The decrease of 47%

is primarily the result of recording non-cash charges including, the fair value of the common stock issued to Intrexon as consideration

for the infectious disease collaboration ($7.8 million) and the fair value of the common stock issued for the acquisition of the

C. difficile program assets ($1.2 million). The decrease in research and development expenses for the year ended December

31, 2013 was off-set by increases in employee costs and program costs associated with the Company's infectious disease programs.

Charges related to stock-based compensation were $375,000 for the year ended December 31, 2013, compared to $400,000 for the same

Other income was $21,000 for the year ended

December 31, 2013, compared to $15,000 for the same period in 2012.

Cash as of December 31, 2013 was $14.6

million, compared to $10.0 million as of December 31, 2012. As of March 27, 2014, the Company's cash balance was approximately

Synthetic Biologics will hold a conference

call today, Monday, March 31, 2014, at 10:00 am EDT. During the call, Jeffrey Riley, Synthetic

Biologics' Chief Executive Officer, will provide a brief update of the Company's multiple sclerosis program and its

anti-infective drug pipeline for infections and other diseases, including the prevention of C. difficile infections, reducing

the impact of methane producing organisms on constipation-predominant irritable bowel syndrome (C-IBS) and the treatment of Pertussis.

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

year ended December 31, 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=98657.

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=98657

for 30 days after the call.

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE MKT: SYN)

is a biotechnology company focused on the development of novel anti-infective biologic and drug candidates targeting specific

pathogens that cause serious infections and other diseases. The Company is developing an oral treatment to reduce the impact of

methane producing organisms on constipation-predominant irritable bowel syndrome (C-IBS), an oral biologic to protect the gastrointestinal

microflora from the effects of IV antibiotics for the prevention of C. difficile infection, a series of monoclonal antibodies

for the treatment of Pertussis and Acinetobacter infections, and a biologic targeted at the prevention and treatment of

a root cause of a subset of IBS. In addition, the Company is developing an oral estriol drug for the treatment of relapsing-remitting

multiple sclerosis (MS) and cognitive dysfunction in MS. For more information, please visit Synthetic Biologics' website at www.syntheticbiologics.com.

Copaxone is a registered trademark

of Teva Pharmaceutical Industries Ltd.

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 the Company's

clinical programs, the Company's opportunities and its position in the infectious disease market, the anticipated timing

and results of the Company's development efforts and the expected size of the future market for sales of therapies for C.

difficile infection, and the Company's 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 the Company's therapeutics, a failure of the Company's clinical trials, and those conducted by

investigators, to be commenced or completed on time or to achieve desired results, a failure of the Company's clinical trials

to receive anticipated funding, a failure of the Company's monoclonal antibodies for the treatment of infectious diseases

to be successfully developed or commercialized, the Company's inability to maintain its licensing agreements, or a failure

by the Company or its strategic partners to successfully commercialize products and other factors described in Synthetic Biologics'

report on Form 10-K for the year ended December 31, 2013 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 -