Sanofi pasteur: H5N1 flu vaccine candidate demonstrates significant immune response

By E. Janene Geiss

Philadelphia, May 11 - The sanofi aventis Group said late Wednesday that the multiple dosage formulations of H5N1 influenza vaccine candidate developed by sanofi pasteur was well-tolerated and generated an immune response in a clinical study.

Of the formulations being tested, an alum-adjuvanted 30 microgram dosage generated the most substantive immune response at 66.7% haemaggluttination inhibition seroconversion rate after two vaccinations, according to a company news release.

This is the first trial of an H5N1 pre-pandemic influenza vaccine candidate comparing vaccines with and without adjuvants, officials said.

Results of the study were published online in The Lancet on Thursday, officials said.

A study of a similar, unadjuvanted candidate H5N1 vaccine that was published in the New England Journal of Medicine in March required two 90 microgram doses to generate a significant immune response in about 50% of trial participants.

Because the French and U.S. studies were conducted independently, it is not possible to make direct comparisons of the results, officials said.

The immune response of the adjuvanted 30 microgram formulation was consistent with requirements of the European Agency for the Evaluation of Medicinal Products for licensing of seasonal influenza vaccine. The French study was sponsored by sanofi pasteur using vaccine produced by the company in France, officials said.

The data will be submitted as part of the company's core vaccine dossier to the EMEA. The core dossier is being developed in strict accordance with EMEA guidelines. This process is expected to reduce the time necessary for approval of a pandemic vaccine in Europe once a strain is identified and a pandemic is declared, officials said.

In subsequent trials, sanofi pasteur said it will explore different dosages that may be helpful in answering questions about dose-sparing strategies, which are being widely discussed among the public health community.

The lower the dosage of a pandemic vaccine, the more doses can be produced and the more people that can be vaccinated should a pandemic occur.

The vaccine for the study was produced at sanofi pasteur's Marcy L'Etoile facility in France. Follow-up studies, currently being planned, will be performed using vaccine produced at the company's Val de Reuil, France facility, where it will be produced on an industrial scale, which will mimic the manufacturing scale that will be used during a declared pandemic, officials said.

A similar study with a U.S.-produced, adjuvanted H5N1 candidate sanofi pasteur vaccine is currently being conducted by the U.S. National Institutes of Health's National Institute for Allergy and Infectious Diseases.

Sanofi pasteur said it also is exploring alternative adjuvants that may further enable expansion of capacity.

The study published in The Lancet was multi-center, randomized, open-label and non-controlled with 300 healthy, 18 to 40 year-old participants. Each study volunteer received one of six inactivated split influenza A/Vietnam/1194/2004 (H5N1) influenza vaccine formulations.

Enrolled subjects were randomly allocated to one of six groups that received 7.5, 15 or 30 microgram of haemmagglutinin, with or without adjuvant.

The trial objectives were to describe the safety profile and the immune response 21 days after each vaccination. Subjects attended three trial visits for vaccination, blood sampling and safety data collection. Subjects were kept under observation for 30 minutes after vaccination and were given safety diaries, digital thermometers and rulers to assess and record adverse events.

All formulations induced an immune response, and responses were detectable in some subjects after only one dose, officials said. The adjuvanted 30 microgram formulation induced the greatest response. An adjuvant did not improve the response to the lower doses.

The sanofi-aventis Group is a Lyon, France pharmaceutical company. Sanofi pasteur is its vaccines business.

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