Synthetic Biologics Reports First Quarter 2014 Financial Results and Operational Highlights -- Conference Call Today

Biologics Reports First Quarter 2014 Financial Results and Operational Highlights

-- Conference Call Today, May 15,

2014, at 8:30 a.m. (EDT) --

Rockville, MD, May 15, 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 diseases, today reported financial results for the three months ended March 31, 2014,

and provided an operational progress update.

Recent Operational Highlights

Prevention of C. difficile (C. diff.)

Infections - SYN-004 Oral Enzyme

SYN-004, Synthetic Biologics' lead

anti-infective product candidate, is believed to be the first and only therapy designed to neutralize intravenous (IV) antibiotics

in the gut. It is intended to protect and maintain the balance of bacterial flora in the gastrointestinal tract, to potentially

prevent the devastating effects of C. diff. The U.S. Centers for Disease Control and Prevention (CDC) has classified C.

diff as an "urgent public health threat"[i], surpassing Methicillin-resistant Staphylococcus aureus

(MRSA) as the number one hospital-acquired infection in the United States. C. diff is a multidrug-resistant bacterium that

infects 1.1 million U.S. patients annually[ii].

Pertussis (Whooping Cough) - SYN-005

Monoclonal Antibody (mAb) Combination

SYN-005, a unique combination of two humanized

antibodies designed to neutralize pertussis toxin, a major cause of Pertussis-mediated infant morbidity and mortality, is being

developed under an exclusive channel collaboration with Intrexon Corporation (NYSE: XON), and Synthetic Biologics' academic

collaborator, The University of Texas at Austin. Despite widespread vaccination, Pertussis rates in the United States continue

to rise steadily, and according to the World Health Organization, B. pertussis infection causes an estimated 300,000 deaths

worldwide each year, primarily among young, unvaccinated infants.

Constipation-Predominant Irritable Bowel Syndrome (C-IBS)

- SYN-010 Oral Compound

Dr. Mark Pimentel, M.D., of Cedars-Sinai

Medical Center (CSMC), led the investigational team whose critical discoveries into the underlying cause of gas, pain and constipation

associated with C-IBS established the foundation of Synthetic Biologics' C-IBS program, and are the basis for developing

an oral treatment to reduce the impact of methane-producing organisms on conditions such as C-IBS. Of the 40 million IBS patients

in the United States[iii], approximately 13.2 million have C-IBS[iv].

Relapsing-Remitting Multiple Sclerosis

(RRMS) - Trimesta (oral estriol)

Trimesta's differentiated mechanism of

action, combined with the convenience of once-daily oral dosing, potentially make it an ideal added therapy to address this underserved

$14.1 billion worldwide market[v]. Based on previous research findings,[vi] Trimesta may offer both inflammatory

and neuroprotective benefits for patients with MS when taken in combination with Copaxone . Available MS therapies demonstrate

anti-inflammatory and/or immunomodulatory responses but they are not considered neuroprotective.

"Synthetic Biologics' fundamental

business mission is to develop novel anti-infectives to address significant unmet medical needs. We have built a strong pipeline

of innovative anti-infective biologic and drug candidates, and we are committed to advancing these programs through preclinical

studies, toward human clinical development," stated Jeffrey Riley, CEO of Synthetic Biologics. "We are on track to

meet our goal of moving three anti-infective programs into the clinic during the coming 12 months. We look forward to reporting

the progress of our anti-infective programs, and updating shareholders on our discussions with potential MS partners."

Three Months Ended March 31, 2014 Financial Results

General and administrative expenses were

$1.1 million for both the three months ended March 31, 2014 and March 31, 2013. Charges related to stock-based compensation were

$255,000 for the three months ended March 31, 2014, compared to $353,000 for the same period in 2013.

Research and development expenses increased

to $2.7 million for the three months ended March 31, 2014, compared to $1.1 million for the same period in 2013. The increase of

143% is primarily the result of increased program costs associated with expanded research, development and manufacturing activities

within our anti-infective pipeline, including the Company's C. diff, C-IBS and Pertussis programs. Charges related

to stock-based compensation were $107,000 for the three months ended March 31, 2014, compared to $104,000 for the same period in

Other income was $1,000 for the three months

ended March 31, 2014, compared to $12,000 for the same period in 2013.

Synthetic Biologics will hold a conference

call today, Thursday, May 15, 2014, at 8:30 am EDT. During the call, Jeffrey Riley, Synthetic

Biologics' Chief Executive Officer, will provide an update of the Company's anti-infective drug pipeline for serious infections

and 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, as well as its multiple sclerosis program.

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

ended March 31, 2014.

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=99332.

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=99332,

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 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 Clostridium difficile (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 Synthetic Biologics'

clinical programs, Synthetic Biologics' opportunities and its position in the infectious disease market, the anticipated

timing and results of the Synthetic Biologics' clinical trials and development efforts and the expected size of the future

market for sales of Synthetic Biologics' therapies. 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 Synthetic Biologics'

therapeutics, a failure of Synthetic Biologics' clinical trials, and those conducted by investigators, to be commenced or

completed on time or to achieve desired results, a failure of Synthetic Biologics' clinical trials to receive anticipated

funding, a failure of Synthetic Biologics' monoclonal antibodies for the treatment of infectious diseases to be successfully

developed or commercialized, Synthetic Biologics' inability to maintain its licensing agreements, or a failure by Synthetic

Biologics 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.