N-cadherin is a protein expressed in prostate cancers that have become resistant to standard therapies including enzalutamide and abiraterone. N-cadherin is a marker of cellular plasticity and the acquisition of stem cell characteristics by these cancers. In addition, N-cadherin is both required and sufficient for this resistance phenotype. We have generated humanized antibodies that target N-cadherin and shown activity in both stem cell tests and in animal models of prostate cancer. We have produced sufficient quantities of our two lead antibodies to demonstrate their safety in initial testing in non-human primates, indicating that these can be moved forward towards testing in patients with advanced, resistant forms of prostate cancer, a leading cause of death among American men.