Valneva SE, a leading pure-play vaccine company, announced Monday, positive Phase II results for its prophylactic vaccine candidate against Clostridium difficile (C. difficile) infection (CDI).

The key objectives of this Phase II trial have been met, the vaccine candidate generated strong immune responses against C. difficile toxins A and B, and the safety and tolerability profile was good.

Clostridium difficile Image/CDC
Clostridium difficile

Valneva’s vaccine candidate is targeting the prevention of primary symptomatic C.difficile infection (CDI). The vaccine is designed to produce an immune response to neutralize the effects of C. difficile toxins A and B, considered to be largely responsible for CDI, which is emerging as a leading cause of life-threatening, healthcare-associated infections (HAIs) worldwide.

Thomas Lingelbach, President and CEO and Franck Grimaud, Deputy CEO of Valneva, commented, “C. difficile has become the most frequent hospital-acquired infection and is now linked to almost 30 thousand deaths every year in the US alone. Our Phase II results provide a strong basis for the further development of a much needed vaccine for the prevention of C. difficile infection (CDI) in a growing target population of older patients”

Valneva’s C. difficile Phase II trial was a randomized, placebo-controlled, observer-blind multi-center trial designed to further study and confirm the candidate vaccine’s safety, immunogenicity and proposed doses of immunizations in two different age groups (50 to 64 years of age and 65 years of age and older). The study design was agreed with regulators in Europe and the U.S. with the aim of potentially supporting a subsequent progression into Phase III.

The trial was conducted in Germany and the United States under an Investigational New Drug application (IND) and included 500 volunteers who were randomized in several study groups: low-dose vaccine without adjuvant, high-dose vaccine with or without adjuvant (Aluminiumhydroxid), or placebo.

Valneva’s vaccine candidate was immunogenic at all doses and formulations tested, in that IgG and functional (neutralizing) antibody responses were seen.

The study met its primary endpoint in terms of identifying the dose/formulation with the highest seroconversion rate against both toxins A and B on Day 56. The high-dose without adjuvant vaccine formulation generated a superior immune response.

The observed seroconversion rate in this difficult to vaccinate older adults population, was considered at an appropriate response level and broadly in-line with published data from comparable prophylactic C. difficile vaccine trials.

The vaccine was generally safe and well tolerated in all treatment groups and there were no severe local reactions noted in any group. The adverse events (AE profile) of all tested doses / formulations appear in a range comparable to other well tolerated vaccines.

Immune response and safety parameters will now be monitored until Day 210 and final study close-out is expected in the second quarter of 2016.

Valneva’s C. difficile vaccine program is part of the Strategic Alliance Agreement (SAA) which was signed between Valneva Austria GmbH (Intercell AG at that time) and Novartis in 2007 and was transferred to GlaxoSmithKline (GSK) at the beginning of 2015.

Valneva estimates that the total market potential for prophylactic C. difficile products may exceed USD 1 billion annually.