One reason cancers continue to grow despite normal immune surveillance is that cytotoxic T cells do not recognize tumor cells as foreign or cannot keep up with tumor cell growth. To address that issue, researchers have developed vaccines to boost the normal immune response to tumors. Heat shock proteins (Hsps) have been targeted by a number of groups, including Mojave Therapeutics Inc., as an immune stimulant that can act as a carrier for antigenic peptides.

Hsps are recognized and internalized by antigen presenting cells (APCs). Therefore a peptide antigen bound to an Hsp can be targeted for internalization by the APC. However, the affinity of a selected peptide antigen for an Hsp sometimes is not sufficient for tight binding between the two. If that is the case, the antigen will not be internalized and processed correctly by the APC.