Development of New Anthrax Vaccine is Underway

A new anthrax vaccine that could be easier and faster to produce than the existing licensed product will undergo initial clinical studies through an agreement between the U.S. Department of Health and Human Services’ Office of the Assistant Secretary for Preparedness and Response (ASPR) and Pfenex, Inc. of San Diego.

The anthrax vaccine currently licensed by the Food and Drug Administration (FDA) is for use before exposure to anthrax-causing bacteria. Its wide-scale use after an exposure would require emergency use authorization from the FDA.

“It is paramount to national health security that we have a vaccine licensed to safeguard health against anthrax after exposure and that we provide protection as quickly as possible to save lives,” explains Robin Robinson, PhD, director of ASPR’s Biomedical Advanced Research and Development Authority (BARDA). BARDA will oversee the development project.

BARDA is pursuing next-generation recombinant vaccines that target the anthrax cell-binding protein, called the protective antigen, which stimulates an immune response. Vaccines using a purified recombinant form of protective antigen have the potential to reduce both the number of doses needed for the vaccine and the costs associated with manufacturing each dose, which could result in significant cost savings over time.

Pfenex’s experimental vaccines, Px563L and RPA563, performed well in nonclinical studies. Under the approximately $15.9 million, 30-month contract, BARDA will support the clinical development of the vaccine, beginning with an evaluation of the vaccine’s safety in a small number of healthy human volunteers.

The contract can be extended with additional funding over five years. Under the extension, the company would conduct additional clinical studies to determine how well the vaccine stimulates the human immune system and the minimum number of doses required to achieve the desired immune response. In nonclinical studies, the vaccine was demonstrated to be effective after two doses administered 28 days apart.

If this finding is replicated in humans, protection would occur with fewer doses than with the currently licensed vaccine which requires three doses administered over four weeks under emergency use authorization for post-exposure prophylaxis.

Under this new project the company also will compare the safety and efficacy of Px563L, which incorporates an adjuvant, and RPA563, which does not include an adjuvant. Adjuvants stimulate the immune system with less antigen, the active ingredient in vaccine. As a result, fewer doses are needed, making more vaccine regimens available from a given amount of antigen.

Studies of the company’s manufacturing indicate that millions of doses could be produced using Pfenex’s novel recombinant technology. In addition, the technology can be transferred easily to BARDA’s Centers for Innovation in Advanced Development and Manufacturing (CIADMs) to produce even greater vaccine quantities to protect against anthrax disease.

“We have multiple products in the pipeline to increase the likelihood of meeting the diverse needs of the American people in emergencies with products approved or licensed by the FDA,” Robinson says.

This project with Pfenex is one of three next-generation anthrax vaccine development projects currently in BARDA’s portfolio of medical countermeasures – drugs, vaccines, and medical products – that address the public health and medical impacts of chemical, biological, radiological, and nuclear (CBRN) accidents, incidents and attacks. Each anthrax vaccine candidate in BARDA’s advanced development program uses different vaccine technology or is administered differently, such as a nasal spray instead of shots.

Source: HHS