A T-helper 1 (Th1) multiantigen vaccine with anti-tumor activity has been tested in mice to treat 3 different antigens, including PSMA. While many vaccines in development only target a single antigen, the multiantigen vaccine can target HPN as well as AMACR.
Prostate cancer is one of the few malignancies that is able to be treated via immunotherapy; Sipuleucel-T was first approved in 2010 for the treatment of some metastatic prostate cancer, yet manufacturing a cell-based vaccine to target a single protein is complex. Other single vaccines have been developed, but most have not shown therapeutic efficacy.
Early in prostate cancer development, antigens can be identified and targeted with vaccines. Prostate cancer has a low mutational rate and a mutational burden that is below the level needed to create antigens, therefore creating a need for vaccines that stimulate a type 1 immunity against nonmutated antigens to further progress prostate cancer vaccine development.
The prophylactic vaccine study used mice that were injected with PSMA-p466/p570/p582 that were then given 4 Th1 immunizations with the multiantigen vaccine 2 weeks apart. Several mice were given Myc-CaP cells and then injected with the first Th1 vaccine dose 24 hours later. The vaccination was found to limit tumor growth in the mice, and the mean tumor volume was smaller than what was observed in the adjuvant vaccinated control group. In comparison, a Th2 vaccine did not create an anti-tumor response and did not demonstrate a significant reduction in tumor volume, showing that a Th1 selective vaccine is necessary to inhibit prostate cancer growth.
The Th1 multiantigen vaccine showed significant anti-tumor activity and inhibited the growth of Myc-CaP cells that were implanted after the immunization. Multiantigen vaccines were found to be more effective at inhibiting prostate cancer growth than single antigen vaccines.