Phase I trial of NY-ESO-1/LAGE1 peptide vaccine for metastatic castration resistant prostate cancer (mCRPC).

Abstract

4643 Background: The NY-ESO-1 and LAGE-1 antigens are amplified in malignancies including prostate cancer. Preclinical induction of immune responses and anti-tumor activity has been demonstrated upon administration of these peptides. A phase I/II clinical trial evaluated the feasibility of a combined HLA class-I and class-II peptide vaccine in mCRPC. Methods: Men with progressive mCRPC, Performance Status ≤2, PSA ≥10 ng/ml and had appropriate HLA class I (A2) and class II haplotypes (DR4, DP4, DR13) were eligible. Three groups with 3 patients each received the vaccine subcutaneously every 2 weeks for 6 doses. Group 1 was treated with a peptide directed at a HLA class I haplotype (HLA A2), Group 2 was treated with a peptide reacting to a HLA class II haplotype (DR4, DP4, or DR13), and Group 3 received peptides directed at both Class I and II haplotypes. Group I and Group II received 1 dose of 1000 mcg and Group III received doses of 1000 mcg for each of 2 peptides. Androgen-deprivation was continued. Results: Of 14 patients enrolled, all were evaluable for toxicities and 9 patients completed all 6 treatments per amended protocol and were evaluable for efficacy. The median baseline PSA was 85.19 ng/ml. Four patients were chemo naive and 5 were post-docetaxel. One patient had a grade 5 event (myocardial infarction) unlikely therapy-related. Potential therapy related toxicities were local grade 1 injection site erythema (n=5), fatigue (n=2), flu-like symptoms (n=1), myalgias (n=1), anorexia (n=1), nausea (n=1) and leukocytosis (n=1). The median PSA doubling time pre-therapy and during therapy were 3.1 and 4.92 months, respectively. The PSA-DT was prolonged compared to baseline in 6 patients, including a negative PSA slope in 2 patients. Antigen-specific immune response determined by ELISPOT was observed, and its association with slowing of PSA-doubling time will be further examined. Conclusions: In men with mCRPC, HLA class-I and/or class-II restricted NY-ESO-1 and LAGE-1 peptides administered subcutaneously demonstrated excellent tolerability, slowing of PSA doubling time and antigen-specific immune responses. Further development of peptide vaccines alone or in combination with other regimens may be warranted.