Preclinical evidences of safety of a new synthetic adjuvant to formulate with the influenza human vaccine: absence of subchronic toxicity and mutagenicity.

Context: Influenza is a severe, life-threatening viral disease that can be prevented by vaccination. However, the anti-influenza human vaccine failed to show the required efficacy both in infants under 5 years old and in the elder population, who are among those with the highest risk of developing severe complications after influenza infection. Therefore, it is of high importance to improve the vaccine efficacy and ensure its safety in these susceptible populations. GK-1, a novel 18-aa peptide adjuvant, has been proved to increase the immunogenicity of the human influenza vaccine in both young and aged mice. Objective: A preclinical study of the toxicity profile of GK-1 following the World Health Organization guidelines to support its use was herein conducted. Material and methods: GK-1 was synthetically produced following Good Manufacturing Practices. The toxicological evaluation of GK-1 peptide was performed in rats after repeated dose-ranging trials by the subcutaneous route. The mutagenic potential of GK-1 was assessed by the micronucleus, chromosomal aberration, and Ames tests, in accordance with OECD Guidelines. Results: GK-1 did not show toxic effects at doses up to 12.5mg/kg, corresponding to 25 times the dose intended for human use. No indications of mutagenic potential were observed. GK-1 after dermal administration was well tolerated locally. Conclusion: The efficacy of GK-1 to improve influenza vaccine protection, along with the absence of toxicity and mutagenicity, as reported herein, support the evaluation of this peptide in a clinical trial as a novel adjuvant for human use.