Final results from Novavax' Phase II clinical trial of trivalent seasonal influenza VLP vaccine announced

Novavax, Inc. (Nasdaq: NVAX) a clinical-stage vaccine company, released the final results from a Phase II clinical trial evaluating Novavax's trivalent seasonal influenza Virus-like particle (VLP) vaccine candidate in healthy adults. The study enrolled healthy volunteers 18 to 49 years in age who were immunized with a single injection of Novavax's trivalent seasonal influenza VLP vaccine matched to the influenza strains recommended for the 2008-2009 influenza vaccine.  Preliminary data from this trial were reported in 2009.

The complete analysis included 232 volunteers in total; with 49 receiving placebo, 83 given Novavax's trivalent seasonal influenza VLP vaccine at 15 mcg/dose, 81 injected with Novavax's trivalent seasonal influenza VLP vaccine at 60 mcg/dose and 19 volunteers receiving an inactivated trivalent influenza vaccine Fluzone® (TIV) at 15 mcg/dose. The three strains were H1N1 A/Brisbane/59/2007, H3N2 A/Brisbane/10/2007, and B/Florida/04/2006. The data show that Novavax's trivalent seasonal influenza VLP vaccine induced a robust hemagglutination inhibition (HAI) antibody response against all three strains in the vaccine.  Seroconversion rates as defined by the FDA (including lower and upper 95% Confidence Intervals (CI)) for the 15 mcg group were as follows:  51% (39, 62), 76% (65, 85), and 58% (47, 69) against the H1N1, H3N2, and B strains, respectively.  Seroprotection (titer greater than or equal to 1:40) rates for volunteers in the 15 mcg group (with 95% CIs) were 70% (59, 80), 89% (80, 94), and 84% (75, 91) against the H1N1, H3N2, and B strains, respectively. 

Preliminary HAI results from this study were presented at the 47^th Annual Meeting of the Infectious Diseases Society of America (IDSA) on October 31, 2009 and were described in a company press release dated November 2, 2009. Those interim results were based on evaluation of a total of 190 volunteers, of which 37 received placebo, 69 received trivalent seasonal influenza VLP vaccine at 15 mcg/dose, 67 received trivalent seasonal influenza VLP vaccine at 60 mcg/dose and 17 received TIV.  For volunteers in the 15 mcg group, seroconversion rates (greater than or equal to 4-fold rise in titer from baseline) with the accompanying 95% CI were 57% (44, 68), 86% (75, 93), and 62% (50, 74) against the H1N1, H3N2, and B strains, respectively.  For volunteers in the 15 mcg group, seroprotection rates (titer greater than or equal to 1:40) with 95% CI were 67% (54, 78), 91% (82, 97), and 84% (73, 92) against the H1N1, H3N2, and B strains, respectively.  In the final results reported today, the H3N2 and B strain data in the 15 mcg VLP dose met the FDA seroconversion guidelines of 40 (lower 95% CI) while the H1N1 data fell just short (39.4 versus 40.0).  However, the mean seroprotection rate against the H1N1 strain rose slightly from an original 67% to a final 70%.

In addition to the HAI titers, functional antibody against the Neuraminidase enzyme was measured in the sera of immunized subjects using a neuraminidase inhibition assay (NAI).  Inhibition of neuraminidase activity may be important in reducing the spread and severity of influenza infection.  Novavax tested volunteers for NAI against B/Florida, H3N2/Brisbane and H1N1/Brisbane components of the vaccine before and after immunization.  Against the B strain, 59% of the patients receiving the 15 mcg dose of VLP showed a 4-fold or higher rise in NAI titers over pre-immune levels.  At the 60 mcg VLP dose, 73% had a 4-fold rise while only one subject (5%) from the TIV population had a 4-fold rise.  In the NAI assay against the H3N2 strain, 50% of the patients immunized with the 15 mcg VLP dose had a 4-fold rise in NAI titers.  At the 60 mcg VLP dose, 56% had a 4-fold rise.  In the small subset of subjects tested against H1N1 NAI activity (10 placebo and 20 at the 60 mcg VLP dose), the NAI in the VLP treated group increased about 30% over preimmunization levels while the placebo treated group had no increase over pre-immunization levels.

"The data released today show that our VLP influenza vaccine not only induces a robust HAI response but also enhances the NAI response far above that induced by TIV," said Dr. Rahul Singhvi, President and Chief Executive Officer of Novavax. "We will continue measurement of NAI activity in other clinical trials since we believe that the ability of the VLP vaccine to elicit an NAI response may differentiate our vaccine from others.  These NAI results support our position that VLP influenza vaccines have the potential to induce a broad-based immune response that could lead to improved clinical outcomes.  We now await comparative immunological and safety data from a larger head to head clinical trial in older adults (>60 years of age) between TIV and our VLP vaccine," said Dr. Singhvi.

SOURCE Novavax, Inc.