Aim: To assess clinical utility of MIL-38 monoclonal antibody (previously called BLCA-38a), which binds to a surface protein, glypican-1 (GPC-1), on prostate cancer (PCa) but not normal prostate cellsa. Minomic International Ltd has shown that MIL-38 could detect PCa cells in urine from patients, distinguishing PCa from benign prostate hypertrophy (BPH) with high sensitivity and specificity. We are currently testing the functional role of GPC-1 in PCa growth, invasion and metastases, and its potential for imaging PCa. Methods: Minomic has developed a MIL- 38-based ELISA assay to detect PCa in bodily fluids. Plasma/serum were collected from 3 groups of 100 male patients/arm from 10 US clinical sites: Arm 1 (Normal): textgreater50 years, PSA textless2 ng/ml if 50-60 years or textless3 ng/ml if textgreater60; Arm 2 (BPH): Normal DRE, biopsy confirmed BPH histopathology or clinical BPH if PSA in the normal range as per Arm 1. Arm 3 (PCa): ≥1 week post biopsy, Gleason score ≥7. Subjects were excluded if other cancers except non-melanoma skin cancer or in Arm 1: any recent lower urinary tract manipulation or unavailable PSA or DRE; Arm 2: HGPIN or atypia; Arm 3: recent 5 Alpha-Reductase Inhibitors (ARI), prostatectomy or Tx procedure. Results: 79% specificity with 32% sensitivity was achieved for differentiating normal and BPH from PCa. Previously MIL-38 showed promise for PET imaging and could suppress human PCa xenograft growth when labelled with alpha emittersb. Conclusions: These data demonstrate that GPC-1 is a potential biomarker for PCa in patients with this disease.