PROJECT ABSTRACT Pseudomyxoma peritonei (PMP), an insidious but lethal malignancy, refers to peritoneal metastases from appendix mucinous neoplasms (AMN). PMP is characterized by abundant extracellular mucus that accumulates in the abdominal cavity and forms a protective barrier around cancer cells, hindering chemotherapeutic drug delivery. We hypothesize that destruction (mucolysis) and/or modulation (disruption) of extracellular mucus structure is a promising therapeutic strategy to overcome the protective mucus barrier posed by extracellular mucus in PMP, enabling chemotherapeutic drug delivery. In our prior research we utilized patient derived xenograft (PDX) models of PMP in order to demonstrate that intraperitoneal (IP) administration of a novel combination of mucolytic drugs, bromelain (BRO; a cysteine protease) and N-acetylcysteine (NAC, a reducing agent that breaks disulfide bonds), successfully dissolves extracellular mucus (mucolysis) and enhances chemotherapeutic drug delivery to cancer cells. The aim of this proposal is to leverage nanotechnology to enhance IP retention time and intratumoral (IT) penetration by BRO+NAC in order to optimize mucolysis and chemotherapeutic drug delivery in PMP. To this end, we have generated preliminary data demonstrating that it is possible to successfully engineer mucus modulating multipurpose BRO nanoparticles (MBN) comprised of four components; (a) a BRO nanoparticle core, for enzymatic mucolysis; (b) conjugated L-cysteine, for mucoadhesion through disulfide bond formation; (c) conjugated NAC, for mucus disruption through reduction of disulfide bonds; and (d) conjugated doxorubicin (DOX), for cancer therapy. In addition, we have also successfully synthesized iron oxide nanoparticle clusters coated with hydrogen ions and glutathione (INC-H+G), for co- delivery with our MBN, to increase the reduction potential of mucus and enhance the function of the MBN. The specific aims of this research proposal are to (a) assess the ability of MBN to modulate mucus structure and enhance chemotherapeutic drug delivery using patient-derived in vitro models of PMP; and (b) observe the effect of MBN on mucinous tumor growth in PDX models of PMP. We expect to demonstrate that the proposed MBN will provide a pharmacokinetic and pharmacodynamic advantage over free mucolytic/cytotoxic drugs. Notably, the proposed MBN are also synthesized from biocompatible and biodegradable materials, increasing the translatability of the approach. We are uniquely positioned to conduct the preclinical studies in this proposal given that we have already developed the proposed in vitro and in vivo models of AMN/PMP in our own laboratory and our institution is one of the major international referral centers for the management of patients with PMP.