Synthetic Biologics Announces Planned Transformative Acquisition of VCN Biosciences; Developer of a Novel Oncolytic Virus Platform Targeting Pancreatic and other Solid Tumors Lead drug candidate VCN-01 demonstrated clini

Synthetic Biologics Announces Planned Transformative

Acquisition of VCN Biosciences;

Developer of a Novel Oncolytic Virus Platform Targeting Pancreatic and other Solid Tumors

Lead drug candidate VCN-01 demonstrated clinical

activity in multiple Phase 1 clinical trials

Designed for systemic delivery, high selectivity,

and enhanced tumor access

VCN-01 granted Orphan Drug Designation in Pancreatic

Synthetic Biologics and VCN Biosciences to host

a conference call today,

December 14th, at 10:00 a.m. Eastern Time

MD, December 14, 2021 - Synthetic Biologics, Inc. (NYSE American: SYN), a diversified

clinical-stage company developing therapeutics designed to treat diseases in areas of high unmet need, today

announced it has signed a definitive agreement to acquire VCN Biosciences, S.L. (VCN), which is developing a new oncolytic adenovirus

(OV) platform designed for intravenous (IV) delivery to trigger tumor cell death and promote immune cell infiltration into tumors. Total

upfront consideration for the acquisition is $4.7 million in cash plus the assumption of $2.4 million of VCN liabilities. Additionally,

VCN will receive shares of Synthetic Biologics' common stock representing 19.99% of the total shares outstanding of the Company's

common stock. The Company has also agreed to an additional $70.3 million of payments contingent upon the achievement of future milestones,

a majority of which are tied to late-stage clinical development and regulatory achievements. The transaction is expected to close during

the first quarter of 2022, and is subject to, among other things, the approval by the Spanish government

of the Company's acquisition of VCN under Spain's Foreign Investment Act and other customary closing conditions. Additional

details regarding the transaction are available in the Company's Current Report on Form 8-K, which has been filed with the Securities

and Exchange Commission and is available on the Company's website.

VCN's technology platform is designed to

overcome critical challenges that restrict the development of the majority of OV therapies today. Unlike many OVs that can only be administered

by direct intratumoral injection, VCN's OVs are designed for systemic intravenous administration to target primary as well as metastatic

tumors. Once inside the tumor, VCN's OVs are designed to replicate selectively and aggressively, and to produce hyaluronidase (PH20),

an enzyme that digests hyaluronan, a key component of the dense tumor stroma that often plays a crucial role in tumor progression. Degradation

of tumor stroma has been shown to diminish a significant physical and immunosuppressive barrier to cancer treatment and thereby improve

access to the tumor by additional therapies such as chemo and immuno-therapies. Results from previously completed clinical trials demonstrate

that this process can occur for weeks or months following a single intravenous injection with a VCN OV. VCN is seeking to leverage these

unique capabilities to address cancers with a high unmet need.

VCN OVs are also designed to be administered intratumorally

or intravitreally (in the eye), either as a monotherapy or in combination with standard of care, to treat a wide variety of cancer indications.

Combination treatment of VCN OVs with a variety of chemotherapies and immunotherapies such as checkpoint inhibitors and CAR-T cells are

in early clinical testing or planned. VCN has the rights to four exclusive patents for proprietary technologies, as well as technologies

developed in collaboration with the Virotherapy Group of the Catalan Institute of Oncology (ICO-IDIBELL), with a number of additional

VCN's lead drug candidate, VCN-01, has been

evaluated in four Phase 1 clinical trials to date, including in patients with pancreatic cancer, head and neck squamous cell carcinoma,

and retinoblastoma (Rb). In a Phase 1 clinical trial, patients with metastatic pancreatic ductal adenocarcinoma

(PDAC) received the combination therapy of intravenous VCN-01 with the standard of care chemotherapy Gemcitabine plus Abraxane (G/A).

Best results were observed when VCN-01 was administered one week before the first G/A dose. VCN-01 was well tolerated and when combined

with G/A demonstrated an improved median overall and progression free survival, as well as a high response rate compared to G/A alone.

These data compare favorably with current standard of care and are the basis of a planned Phase 2 clinical trial of the higher dosing

VCN-01 is also being studied as a monotherapy

in patients with retinoblastoma (RB) who previously failed chemotherapy. Intravitreal administration of VCN-01 produced a complete remission

and a reduction of tumors in several patients. These promising outcomes form the basis for an Orphan Drug application with the FDA and

are planned to be explored in a larger future clinical trial.

VCN is also developing a next generation Albumin

Shield technology platform, VCN-11, which builds upon the pre-clinical and clinical results of VCN-01. VCN-11 incorporates an albumin

binding domain in the virus outer shell designed to enable the virus to coat itself with host serum albumin, potentially preventing its

inactivation by neutralizing antibodies in the bloodstream en route to the tumor. The addition of the Albumin Shield technology is not

expected to interfere with VCN-11's ability to target tumor cells and may allow for repeated administration to optimize tumor exposure.

Steven A. Shallcross, Chief Executive Officer

of Synthetic Biologics, commented, "We are excited to announce this transformative acquisition, as VCN's platform represents

a potentially breakthrough approach to cancer treatment with oncolytic viruses by allowing for systemic delivery, high selectivity and

enhanced tumor access. In addition to triggering tumor cell death, these therapies have been shown to elicit a strong anti-tumor immune

response. The results of the Phase 1 clinical trial in PDAC, a highly aggressive and lethal malignancy, are very encouraging with respect

to tumor response and survival. Significantly, biopsies in these patients confirmed up regulation of tumor immune markers and induction

of a robust antitumor immune response, including increased tumor infiltration by cytotoxic T-cells. These results suggest VCN-01 holds

significant potential to increase the addressable market for checkpoint inhibitors and CAR-T therapies, as these therapies have historically

been less effective immunologically against "cold" tumors like PDAC."

encouraging results of prior preclinical and clinical trials of VCN-01, we plan to initiate a controlled Phase 2 clinical trial of VCN-01

at multiple centers across the US and EU. There is a significant unmet need for a safe and effective therapy for patients with pancreatic

cancer, a condition in which most people diagnosed do not survive more than a year following their initial diagnosis. Based on highly

encouraging early clinical results, we also plan to conduct a registrational trial in pediatric patients with advanced Rb. Importantly,

this is an underserved patient population and we believe VCN-01 holds tremendous promise to preserve the eyes of these patients, who are

typically less than two years old at diagnosis. We believe these trials can be conducted relatively quickly and efficiently. At the same

time, we are also evaluating investigator-sponsored studies combining VCN-01 with CAR-T therapies, as well as VCN-01 in other orphan indications

such as glioblastoma. We look forward to providing additional details on the timing and design of these trials in the near future."

"VCN was founded by internationally

recognized experts in oncolytic adenoviruses for cancer treatment and I will be delighted to welcome them to our team. VCN's

novel therapies allow for a robust and efficient manufacturing process, with an attractive cost structure. The platform is supported

by a growing intellectual property (IP) portfolio that provides it patent protection through at least 2030 with additional patents

underway that we believe would further strengthen our IP portfolio. Importantly, VCN-01 has been granted Orphan Drug Designation by

the European Medicines Agency (EMA), which may provide a number of benefits including up to ten years of market exclusivity.

Importantly, we have a strong balance sheet with over $72.1 million of cash as of September 30, 2021, which we believe will provide

us significant runway to both support our existing programs, as well as to able to advance VCN-01 and VCN-011 through important

milestones that we believe will drive significant shareholder value."

Manel Cascall , PhD, Chief Executive Officer

of VCN, noted, "Joining together with Synthetic Biologics is a significant opportunity as it allows us to partner with an experienced

team, well-versed in drug development, manufacturing, and commercialization. We anticipate the combined company will have the financial

resources to fund our clinical programs to key value inflection points and we look forward to a successful future together."

Synthetic Biologics will hold a conference call

today, December 14, 2021, at 10:00 a.m. Eastern Time.

The dial-in information for the call is as follows, U.S. toll free: 1-888-347-5280 or International: +1 412-902-4280. Participants are

asked to dial in 15 minutes before the start of the call to register. The call will also be webcast over the Internet at https://www.webcaster4.com/Webcast/Page/1096/43946.

An archive of the call will be available for replay at the same URL, https://www.webcaster4.com/Webcast/Page/1096/43946, for 90 days after

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE American: SYN)

is diversified clinical-stage company developing therapeutics designed to treat diseases in areas of high unmet need. The Company's

lead candidates are: (1) SYN-004 (ribaxamase) which is designed to degrade certain commonly used intravenous (IV) beta-lactam antibiotics

within the gastrointestinal (GI) tract to prevent (a) microbiome damage, (b) Clostridioides difficile infection (CDI), (c) overgrowth

of pathogenic organisms, (d) the emergence of antimicrobial resistance (AMR), and (e) acute graft-versus-host-disease (aGVHD) in allogeneic

hematopoietic cell transplant (HCT) recipients, and (2) SYN-020, a recombinant oral formulation of the enzyme intestinal alkaline phosphatase

(IAP) produced under cGMP conditions and intended to treat both local GI and systemic diseases. For more information, please visit Synthetic

Biologics' website at www.syntheticbiologics.com.

About A.G.P./Alliance Global Partners

A.G.P./Alliance Global Partners served as excusive

financial advisor to Synthetic Biologics in connection with the transaction.