Despite a low incidence, the economical burden of genetic diseases to families and the health system is extremely high, due to the cost of therapies ($100,000/patient-year) mostly suboptimal in alleviating these chronic conditions. This is the case for enzyme replacement therapies (ERTs) for treatment of lysosomal storage disorders (LSDs), prevalent genetic defects due to deficiency of lysosomal enzymes. ERT success is restricted to a few diseases affecting liver, spleen, and kidneys, where injected enzymes gain access via mechanisms of blood clearance. However, ERT delivery to the lungs, or brain for most common neurological LSDs, is hindered by the lack of affinity and transport of the enzymes to and into tissues. An example is ERT for Niemann-Pick disease (NPD) due to acid sphingomyelinase (ASM) deficiency, where lysosomal excess of sphingomyelin causes strong neurological disorder (type A phenotype) and affects lungs, liver and spleen (type B phenotype). Our goal is to develop strategies to improve ERT delivery to disease sites (lungs and brain). We propose to target ASM to intercellular adhesion molecule-1 (ICAM-1) expressed on the endothelium of all organs and cell targets in the parenchyma of tissues, and up-regulated in NPD. Our results indicate that classical endocytosis associated to vesicular transport from the blood to the tissue and the cell surface to lysosomes are defective in NPD, yet the non-classical pathway induced by ICAM-1 engagement by multivalent anti-ICAM/polystyrene prototype carriers is fully active in NPD. These prototypes enhance ASM targeting to lysosomes and sphingomyelin reduction in cultured endothelial cells and mice. A fraction of anti-ICAM prototype carriers are transported across endothelial cultures. We hypothesize that biocompatible ICAM-1- targeted carriers can provide vesicular transport of ASM across endothelial barriers (without affecting permeability) and endocytosis and lysosomal delivery in cells of the tissue parenchyma, attenuating NPD lung and brain phenotype. We will test this in cells and mouse models, using our new biocompatible PLGA carriers targeted to ICAM-1 by a peptide derived from its natural ligand, in Aims to evaluate and optimize: 1-Efficacy and safety of transendothelial transport, 2-Non-endothelial delivery, and 3-Effects in the NPD phenotype. The benefits of this strategy to transport therapeutics across endothelial barriers and into cells may transcend other LSDs and CNS treatments.
Our advanced knowledge, enhanced medical awareness, and improved capacity for early detection of genetic defects, have not resulted yet in safe and effective treatments for this group of conditions, which continues to grow increasingly relevant. Although the incidence of each particular one of these diseases is still relatively low, their economical burden to the affected families and the health system is disproportionally overwhelming, due to the high cost of current therapies (averaging $100,000/patient-year), which are mostly suboptimal in alleviating these chronic and, in many instances, fatal conditions. A clear example is that of the lysosomal storage disorders, one of the most prevalent monogenic defects in humans, which comprises more than 40 life-threatening diseases. Although still underdiagnosed, it is estimated that lysosomal disorders affect 1:2,000 live births in the general population and, in particular cases, carrier frequencies may be as high as 1:80. However, despite the medical and social need, the development of effective therapeutic means for treatment of these diseases has been long hampered due the fact than the pharmaceutical industry has cataloged them as non profitable diseases, and today insurance companies are troubled in considering high cost reimbursement for quite ineffective treatments. The scholarly and economical support of non-profit federal, academic, and private organizations is crucial to advance research and translation on new therapeutic means. Paradoxically, some promising approaches have become available, which could and should serve as platforms for further improvement toward developing definitive, safe and efficient treatments for these conditions. This is the case for enzyme replacement therapies by infusion of recombinant enzymes in the circulation, to replace the genetically-deficient enzymatic activities. Yet, after one decade of its clinical implementation for lysosomal disorders, it is apparent that the success of this strategy is restricted to a few diseases that affect visceral organs (liver, spleen, and kidneys), since the injected enzymes access these organs via natural mechanisms of blood clearance. However, enzyme delivery to the heart, lungs, and mainly brain, most commonly affected in lysosomal disorders, is hindered by the lack of affinity and transport of the enzymes to and into these tissues. Taking a representative lysosomal storage disorder as an example, Niemann-Pick disease, our proposal aims at developing and optimizing a new strategy to deliver available enzyme therapies to disease-target sites within the body (focusing on lung and brain), by designing biotechnological means capable of exploiting natural pathways of transport which control traffic of substances from the bloodstream to the tissues within organs, and from the surface of cells into their compartments, where the therapeutic action is required. By developing more controlled, precise and efficient treatments we hope and expect to contribute to prolong and improve the quality of life of these patients and that of their families, also alleviating the associated economical burden to the health system. Beyond the scope of the project, the benefits of this strategy to transport therapeutics across barriers and into cells may transcend to treatments for common (non-genetic) diseases affecting the central nervous system, which are among the most important clinical conditions in rich countries.
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