Vaxart Inc. raised $3.3 million to conduct preclinical studies with a vaccine platform designed to deliver its payload straight to the gut, an "elegant solution" to hurdles that have stumped other vaccine makers, said Mark Backer, CEO of the San Francisco-based firm. The result is an adenoviral vector that delivers easily substitutable target antigens along with an adjuvant.

While Vaxart's adenoviral vector is "fairly standard," Backer said, its oral delivery is not. The oral approach may avoid the safety concerns that have been associated with injected adenoviral vectors, and enhance efficacy at the same time. Antivector antibodies that can limit how well adenoviral vectors work are not found in the intestine, thus allowing for a strong immune response.

This lack of antivector antibodies in the gut is also the key to the vaccine's applicability as a platform. Many people produce antibodies to adenovirus after coming into contact with the bug in daily life, and vaccination with an adenoviral vector can trigger further antibody production, making the vector less effective. Using Vaxart's approach, however, Backer said the "antivector response is generally not even measurable."

Encoded in Vaxart's vector is an immune adjuvant, specifically a double-stranded RNA Toll-like receptor 3 (TLR-3) agonist. TLR-3 is the only TLR known to be fully active in the gastrointestinal tract, and preliminary data have shown significant increases in T-cell production when the adjuvant is added to an adenoviral vector.

Although most TLR research has been focused on TLR-7 and TLR-9, Philadelphia-based Hemispherx Biopharma Inc. has a double-stranded RNA TLR-3 agonist under FDA review for chronic fatigue syndrome. The product, called Ampligen, also is being studied as a vaccine adjuvant, but Backer noted that oral use of a TLR-3 agonist is unique. (See BioWorld Today, Oct. 12, 2007.)

Along with the TLR-3 agonist, Vaxart can encode into its vector any one of a number of target antigens. The company's lead program utilizes antigens for avian flu and is slated to enter the clinic next year. Also in the pipeline are vaccines for annual flu and biodefense applications.

Sean Tucker, the company's founder, vice president of research and director of immunology, developed Vaxart's technology. Since its inception in 2004, Vaxart (previously known as West Coast Biologicals) has raised a small amount of seed financing, followed by a $600,000 SBIR grant from the National Institutes of Health and a $2.7 million Series A financing, led by Quantum Technology Partners and Life Science Angels, with additional participation by Bay Partners and Sand Hill Angels.

Chris Cummings, entrepreneur in residence with Bay Partners, said his firm has been impressed with Vaxart's plan to get to animal proof-of-concept data on a very small investment. He also noted that the modular nature of the vaccine will allow rapid production and lower cost of goods.

Backer said the new financing will carry the company until about the second quarter of next year. Although Vaxart currently is focused on flu and biodefense applications, he said the technology might be applied to infectious diseases such as HIV and hepatitis C virus, where the ability to give repeated doses might allow for increased efficacy. Use in therapeutic vaccines is also a possibility.

For many indications, Vaxart eventually plans to seek partners. Becker said the company has "generated considerable interest already" but plans to further develop the platform before making any commitments. The exception is in biodefense, where Becker said Vaxart soon will announce a partnership with a UK biodefense agency.

Vaccines and TLRs have generated significant partnering interest. This week, Cambridge, UK-based Acambis plc partnered its Phase II West Nile virus vaccine with Sanofi Pasteur, the vaccines business of Sanofi-Aventis, of Paris, in a potential $80 million deal. Earlier this year, Intercell signed a vaccine deal worth up to $366 million with Basel, Switzerland-based Novartis AG. (See BioWorld Today, July 5, 2007, and Nov. 14, 2007.)

On the TLR side, Coley Pharmaceutical Group Inc., Anadys Pharmaceuticals Inc. and Idera Pharmaceuticals Inc. each have pulled in deals worth close to half a billion. (See BioWorld Today, March 25, 2005, June 3, 2005, and Dec. 12, 2006.)

In other financing news:

• BioVex Inc., of Woburn, Mass., raised $13 million in the second close of its Series E financing, bringing the total for the round to $35 million. Triathlon Medical Ventures led the round, which included several new and existing investors as well as a venture debt component. Proceeds will be used to complete ongoing Phase I/II trials and initiate a Phase III melanoma trial with the oncolytic virus OncoVEX GM-CSF, as well as to conduct a Phase I trial with ImmunoVEX HSV2, an engineered form of HSV designed to prevent and treat herpes. The first close of the Series E, in July, brought in $22 million. (See BioWorld Today, July 10, 2007.)

• Cardium Therapeutics Inc., of San Diego, and its subsidiary InnerCool Therapies Inc. completed a $5 million commercial credit facility with Life Sciences Capital. The loan will be used to launch InnerCool's patient temperature modulation products for therapeutic hypothermia and to support product development.

• Verenium Corp., of Cambridge, Mass., filed a shelf registration statement to raise up to $150 million through the future sale of common stock, preferred stock, debt securities or warrants. Proceeds will be used for general corporate purposes. The company also registered 3 million shares of common stock for future sale by shareholder Syngenta Biotechnology Inc., of Raleigh, N.C., and its affiliates. Verenium, an industrial enzyme company, was formed through the merger of Diversa Corp. and Celunol Corp.