SUMMARY Metastatic castration-resistant prostate cancer (mCRPC) is the most recurrent and, fatal phenotype. mCRPC patients have poor recurrence-free and limited preventive options. The natural product pseurotin A (PS) dually suppressed PCSK9 secretion and interaction with LDLR. PS suppressed 94% of PC-3 PC recurrence in nude mice model. PS antimigratory activity significantly reduced when PCSK9 knocked-down. The small molecular size of PS is advantageous over the FDA-approved humanized PCSK9 mAbs acting intra- and extra-cellular unlike the later which can act extracellular only, reflecting better potency. Recently, PCSK9 proved critical driver for prostate and several other cancers. Project central hypothesis is targeting extra- and intracellular PCSK9 axis with the small molecule PCSK9 inhibitor pseurotin A can effectively prevent mCRPC recurrences and therefore PS can be developed as effective recurrence preventer in mCRPC survivors. Aim 1: Efficacy of PS to prevent mCRPC recurrence in nude mice and PCSK9 validation as a pathogenesis marker in human PC tissues microarray. Assessments will compare PS potency in wild and PCSK9- knockdown CWR-R1ca cells in adjuvant (post-primary tumor excision) mode and after neoadjuvant enzultamide- docetaxel regimen followed by primary tumor surgical excision in nude mice models. Biomax human tissue microarray will be used to validate PCSK9 relevance in human PC. Aim 2: Assess the PS safety and pharmacokinetics in Swiss albino mouse models. Expected outcomes: Proposed studies entail PS validation as a novel targeted intervention for mCRPC recurrences prevention. PCSK9 targeting is a novel therapeutic alternative for long-term prevention of metastatic castration-resistant prostate cancer recurrence in prostate cancer survivors.