Development of AFFITOPE vaccines for Alzheimer's disease (AD)--from concept to clinical testing.

Based on the notion that cerebral accumulation of certain Abeta species is central to AD pathogenesis and endowed with the knowledge that emerged during clinical testing of the first human Alzheimer vaccine, AN1792, we designed a new generation of Alzheimer vaccines. Rather than relying on full-length Abeta itself or fragments thereof, AFFITOPE vaccines use short peptides, mimicking parts of the native Abeta sequence, as their antigenic component. The technology created to identify these peptides, termed AFFITOPE-technology, at the same time provides the basis for the multi-component safety concept realized in AFFITOPE vaccines. First, as they are nonself, AFFITOPES don't need to break tolerance typically established against self proteins. This allows us to use aluminium hydroxide, the agent first approved as immunological adjuvant for human use and, thus, exhibiting an excellent safety profile. Second, AFFITOPES employed in Alzheimer vaccines are only 6 amino acids in length, which precludes the activation of Abeta-specific autoreactive T cells. Third, and above all, the AFFITOPE technology allows for controlling the specificity of the vaccine-induced antibody response focusing it exclusively on Abeta and preventing crossreactivity with APP. In a program based on two AFFITOPES allowing neoepitope targeting of Abeta (free N-terminus), this approach was taken all the way from concept to clinical application. Early clinical data support the safety concept inherent to AFFITOPE Alzheimer vaccines. Further clinical testing will focus on the identification of the optimal vaccine dose and immunization schedule. Together, result of these trials will provide a solid basis for clinical POC studies.