Colloidal Gold Nanoparticles: A Versatile Platform for Developing Tumor Targeted Cancer Therapies Giulio F. Paciotti 1 , Lonnie Myer 1 , David G.I. Kingston 2 , Thota Ganesh 2 , and Lawrence Tamarkin 1 . 1 CytImmune Sciences, Inc. 9640 Medical Center Drive, Rockville, MD, 20850: email: gpaciotti@cytimmune.com 2 Virginia Polytechnic Institute and State University, Department of Chemistry Blacksburg, VA 24061 Colloidal gold nanoparticles represent a versatile biomedical platform. Our efforts have focused on the development of these nanoparticles into a platform technology for developing tumor targeted drug delivery vectors. In the current communication, we describe the development of two colloidal gold nanoparticle drugs. The first drug, Aurimune-T, is a multivalent drug assembled on 25 nm colloidal gold nanoparticles and designed to sequester TNF in solid tumors. While developing Aurimune-T we recognized that TNF not only serves as the therapeutic responsible for anti-tumor efficacy but also a tumor targeting ligand. Support for this hypothesis is presented in the description of the second nanoparticle drug, AuriTax, a colloidal gold-based TNF targeted paclitaxel drug. Keywords: TNF targeted colloidal gold nanoparticle drugs. Introduction: Tumor Targeted Drug Delivery and The Biology of Aurimune-T Targeting cancer therapeutics to solid tumors is facilitated by particle delivery systems capable of escaping phagocytic clearance by the reticuloendothelial system (RES. Under ideal conditions such delivery systems preferentially extravasate the tumor vasculature and accumulate within the tumor microenvironment. By design, a particle delivery system capable of sequestering a cancer drug solely within a tumor may also reduce the accumulation of the drug in healthy organs. Consequently, these delivery systems may increase the relative efficacy or safety of a cancer therapy, and thus serve to increase the drug’s therapeutic index. Aurimune-T (Figure 1) is a multivalent drug that is assembled on nanoparticles of colloidal gold and designed to actively sequester recombinant human tumor necrosis factor alpha (TNF) within solid tumors. The drug is manufactured by covalently linking molecules of TNF and Thiol- derivatized polyethylene glycol (PEG-THIOL) onto the surface of colloidal gold nanoparticles. Each component of the drug serves a specific function in achieving tumor specific drug delivery. First, the PEG-THIOL moiety serves to hydrate the colloidal gold nanoparticles and in so doing, shields the nanoparticle drug from detection and clearance by the RES (Figure 2A-C). Second, TNF not only serves as the therapeutic responsible for anti-tumor effects, but also serves as a targeting ligand that “targets” the nanoparticle drug specifically to solid tumors (Figure 2A). Aurimune-T achieves tumor targeted drug by passive extravasation of the tumor vasculature and by TNF binding to cell surface receptors expressed on cells in and around the tumor mass. The end result is a 7- to10-fold increase in the amount of TNF that is delivered to the tumor. The pattern of TNF accumulation is specific to the tumors, since TNF concentrations decrease over time in healthy organs, such as liver, lungs, and brain, while over this same time period TNF levels increase within tumors. Figure 2. A. Effect of PEG-THIOL on the uptake of the Aurimune-T by the RES (i.e., the liver and spleen) in MC-38 tumor-burdened C57/BL6 mice. [NOTE: Black staining in Figure 2B is due to precipitation of the cAu particles in the RES. B. Physical sequestration of Aurimune-T in MC-38 tumors. The accumulation is documented as the tumors acquire the characteristic red-purple color of the particles (red arrows). The ability of Aurimune-T to concentrate TNF in MC-38 tumors improved the efficacy of a given dose of TNF. In dose escalation and toxicity studies we demonstrated that Aurimune-T was safer and more effective than native TNF in MC-38 tumor-burdened mice since maximal anti-tumor responses were achieved at doses that did not induce toxicity. B. Aurimnue-T without PEG-THIOL C. Aurimnue-T with PEG-THIOL A. Untreated Control A. 0 1 2 3 5 Time Hours B. NSTI-Nanotech 2005, www.nsti.org, ISBN 0-9767985-0-6 Vol. 1, 2005 7