Multivalent Conjugate Vaccine Trial for Patients With Biochem. Relapsed Prostate Cancer

This is a pilot trial designed to assess safety and immunogenicity of a multivalent conjugate vaccine for use in patients with biochemically relapsed prostate cancer. This trial is based on the results of eight dose-seeking phase I monovalent glycoprotein and carbohydrate conjugate vaccine trials in a patient population with minimal tumor burden despite a rising biomarker, PSA, who have failed primary therapy such as surgery or radiation. We know that a rising PSA is indicative of micrometastatic disease - a state to which the immune system may maximally respond. Based on these trials, we have identified three glycolipid antigens, Globo H, Lewisy and GM2 and three mucin antigens, glycosylated MUC-1, Tn(c), and TF(c) for inclusion into a multivalent trial. As a result of these vaccinations, most patients generated specific high titer IgM and IgG antibodies against the respective antigen-KLH conjugates. Our previous work has shown the monovalent vaccines to be safe with local erythema and edema but minimal systemic toxicities. Our data from approximately 160 men who participated in our earlier monovalent vaccine trials against the aforementioned antigens have shown that a treatment effect in the form of a decline in PSA log slopes compared with pretreatment values could be seen in patients with minimal tumor burden. The multivalent vaccine will consist of the lowest dose of synthetic glycoprotein and carbohydrate antigens shown to elicit high titer IgM and IgG antibodies in patients with biochemically relapsed prostate cancer. A phase III double blind randomized trial with two hundred forty patients is planned based on the safety and immunogenicity data accrued from this pilot trial. The primary endpoints of this study will be the safety of the vaccine and the humoral response to each of the antigens. The secondary endpoint will be to evaluate post-therapy changes in PSA.