Optical and MRI-GuidedTheranostic Application ofUltrasmall Superparamagnetic Iron Oxide Nanodrug Conjugate for PSMA-PositiveProstate Cancer Therapy

Active targeting is more effective than conventional passive targeted drug delivery systems in increasing therapeutic efficacy and minimizing systemic toxicities. Importantly, the nanoparticle-based targeted drug delivery systems combine active and passive targeting properties and significantly enhance therapeutic efficacy. In this study, we utilized ultrasmall superparamagnetic iron oxide (uSPIO) nanoparticles conjugated with anti-prostate-specific membrane antigen (PSMA) 5D3 monoclonal antibody, mertansine (DM1) antitubulin agent, and fluorophore to develop a targeted uSPIO-5D3-DM1-AF488/CF750 nanotheranostic for PSMA(+) prostate cancer (PC) therapy. This agent enables multimodality <i>in vivo</i> imaging using near-infrared (NIR) fluorescence and magnetic resonance imaging (MRI). uSPIO-5D3-DM1-AF488 is selectively internalized into PSMA-positive cells by receptor-mediated endocytosis, and uSPIO-5D3-DM1-CF750 exhibited 1.62 and 166.2 ng/mL IC₅₀ values in PSMA(+) and PSMA(−) cells, respectively. The image-guided therapeutic study was conducted <i>in vivo</i> in human PC xenograft mouse models bearing bilateral PSMA(±) tumors (<i>n</i> = 10, two 10 mg/kg doses on days 1 and 14). The therapeutic results exhibited a significant control of the growth of PSMA(+) tumors starting at day 5 (<i>p</i> = 0.05) and significantly improved efficacy after day 9 (<i>p</i> = 0.0005) during the treatment period (<i>t</i> = 21 days). We observed the PSMA-specific uptake of uSPIO-5D3-DM1-CF750 in tumors in NIR IVIS Xenogen images and <i>T</i>₁- and <i>T</i>₂-weighted MRI with 20.6% and 42% reduction of overall <i>T</i>₁ and <i>T</i>₂, respectively. Approximately 70% of mice with PSMA(+) tumors treated with uSPIO-5D3-DM1-CF750 survived or did not exceed the threshold level of the tumor size during the treatment. <i>Ex vivo</i> biodistribution study proved 50% and 45% higher uptake of uSPIO-5D3-DM1-CF750 by PSMA(+) tumors compared to untargeted uSPIO-DM1-CF750 by PSMA(+) tumors and uSPIO-5D3-DM1-CF750 by PSMA(−) tumors, respectively. ICP-MS analysis demonstrated a 73% increase in uSPIO-5D3-DM1-CF750 uptake by PSMA(+) tumors compared to PSMA(+) tumors treated with pure uSPIO. The toxicological results reveal the safe profile in systemic toxicities without life-threatening changes in the complete blood count and clinical chemistry profile of toxicology.