SAT-304 Targeted Inhibition of Prostate Cancer Cells upon Acrolein-enabled Bioorthogonal Activation of Prodrugs

Abstract Disclosure: B. Park: None. D.K. Jha: None. M.V. Muppidi: None. M. Torres: None. Y. Liu: None. J.C. Zhao: None. B. Chatterjee: None. Background: Chemotherapy is a standard of care for advanced prostate cancer that fails hormone therapy. However, off-tumor toxicity limits the tolerable dose of systemically administered drugs. To increase a drug’s therapeutic index, selective targeting of malignant tissue is paramount. Bioorthogonal activation of prodrugs conjugated to aryl azides has been reported as a strategy for tumor site specific targeting1. The activation is due to bioorthogonal addition of an aryl azide to endogenous acrolein molecule (a 3-carbon aldehyde) and subsequent multi-step reactions that lead to the cleavage and release of the active drug molecule. Drug release is tumor-selective since acrolein is abundant in most cancer cells and tumor microenvironment due to elevated oxidative stress, while normal cells and tissues present with low acrolein1. We explored the efficacy of docetaxel, a chemotherapy drug, and BO-264, an anticancer biologic2, for targeting prostate cancer cells without impacting normal epithelial cells, upon their delivery as aryl azide conjugates.Methods and Results: Conjugates, synthesized in-house and validated for correct structures based on NMR and high-resolution mass spectroscopy, were purified by column chromatography. Sensitivity to drug conjugates for castration-resistant prostate cancer (CRPC) cells (PC3, DU-145, CWR22RV1) and non-cancer prostate epithelial cells (RWPE-1), was investigated in cell culture with regard to proliferation, migration and invasion using the Incucyte® Live Cell Analysis System. Acrolein was assayed by incubating cells with an aryl azide conjugate of the fluorescent probe TAMRA, and quantifying fluorescence from released TAMRA using FACS. Results show that acrolein is >10-fold higher in PC3 and DU-145, and ∼ 4-fold higher in CWR22RV1 compared to RWPE-1. CRPC cells were inhibited by azide conjugates of docetaxel and BO-264 - the sensitivity being higher for docetaxel conjugate (IC-50 ∼ 10nM) than BO-264 conjugate (IC50 ∼125nM). RWPE-1 cells were completely resistant to these conjugates at 1μM. In contrast, similar sensitivity of RWPE-1 and CRPC cells to unconjugated drugs was observed. Notably, PC3 cells engineered to overexpress oxysterol sulfotransferase (SULT2B) - an enzyme which interferes with CRPC progression, as we reported3 - showed higher sensitivity to drug conjugates than control PC3 cells, despite having similar acrolein levels. In ongoing studies, we are exploring responses of prostate tumor in vivo to drug conjugates using mouse xenograft and allograft models.Significance: Acrolein-aided drug activation is potentially a new avenue for targeted anticancer treatment beyond antibody-drug conjugates. The strategy can be especially productive for immunologically cold tumors like prostate tumor. Reference, PMIDs: 1) 38939146; 2) 32217742; 3) 31894239 Funds: DoD-W81XWH-21-1-0307; NIH-R21CA289167 Presentation: Saturday, July 12, 2025