Multimodal, PSMA-Targeted, PAMAM Dendrimer-Drug Conjugates for Treatment of Prostate Cancer: Preclinical Evaluation

Abstract

Wojciech G Lesniak,1 Srikanth Boinapally,1 Gabriela Lofland,1 Zirui Jiang,1 Catherine A Foss,1 Babak Behman Azad,1 Anna Jablonska,1,2 Mauro A Garcia,1 Maria Brzezinski,1 Martin G Pomper1,3 1Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, 21287, USA; 2Institute for Cell Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA; 3Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USACorrespondence: Wojciech G Lesniak, Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, 600 N. Wolfe Street, Baltimore, MD, 21287, USA, Email [email protected]: Prostate cancer (PC) is the second most common cancer and the fifth most frequent cause of cancer death among men. Prostate-specific membrane antigen (PSMA) expression is associated with aggressive PC, with expression in over 90% of patients with metastatic disease. Those characteristics have led to its use for PC diagnosis and therapies with radiopharmaceuticals, antibody-drug conjugates, and nanoparticles. Despite these advancements, none of the current therapeutics are curative and show some degree of toxicity. Here we present the synthesis and preclinical evaluation of a multimodal, PSMA-targeted dendrimer-drug conjugate (PT-DDC), synthesized using poly(amidoamine) (PAMAM) dendrimers. PT-DDC was designed to enable imaging of drug delivery, providing valuable insights to understand and enhance therapeutic response.Methods: The PT-DDC was synthesized through consecutive conjugation of generation-4 PAMAM dendrimers with maytansinoid-1 (DM1) a highly potent antimitotic agent, Cy5 infrared dye for optical imaging, 2,2′,2”-(1,4,7-triazacyclononane-1,4,7-triyl)triacetic acid (NOTA) chelator for radiolabeling with copper-64 and positron emission tomography tomography/computed tomography (PET/CT), lysine-urea-glutamate (KEU) PSMA-targeting moiety and the remaining terminal primary amines were capped with butane-1,2-diol. Non-targeted control dendrimer-drug conjugate (Ctrl-DDC) was formulated without conjugation of KEU. PT-DDC and Ctrl-DDC were characterized using high-performance liquid chromatography, matrix assisted laser desorption ionization mass spectrometry and dynamic light scattering. In vitro and in vivo evaluation of PT-DDC and Ctrl-DDC were carried out in isogenic human prostate cancer PSMA+ PC3 PIP and PSMA− PC3 flu cell lines, and in mice bearing the corresponding xenografts.Results: PT-DDC was stable in 1×PBS and human blood plasma and required glutathione for DM1 release. Optical, PET/CT and biodistribution studies confirmed the in vivo PSMA-specificity of PT-DDC. PT-DDC demonstrated dose-dependent accumulation and cytotoxicity in PSMA+ PC3 PIP cells, and also showed growth inhibition of the corresponding tumors. PT-DDC did not accumulate in PSMA− PC3 flu tumors and did not inhibit their growth. Ctrl-DDC did not show PSMA specificity.Conclusion: In this study, we synthesized a multimodal theranostic agent capable of delivering DM1 and a radionuclide to PSMA+ tumors. This approach holds promise for enhancing image-guided treatment of aggressive, metastatic subtypes of prostate cancer. Keywords: prostate cancer, PSMA, PAMAM dendrimer, targeted cancer treatment, theranostics

Keywords

• prostate cancer
• psma
• pamam dendrimer
• targeted cancer treatment
• theranostics.