Real-Time Tracking of Gene Therapy by Bioactivated MR contrast Probes With mean survival rate of 5 years (and most cases are fatal) lysomal storage diseases (LSD) are among the most dismal of prognosis in all of medicine. LSD's represent a large number of monogenetic diseases and while rare the prevalence is to hemophilia. As monogenetic diseases with clearly defined genotype-phenotype relations, lysosomal storage diseases are excellent candidates for gene therapy. The transformative results documented in an adeno-associated virus (AAV) gene therapy clinical trial in infants affected by spinal muscular atrophy demonstrated unequivocally the potential of in vivo gene transfer to treat monogenic neurological disorder. However, to date, there is a lack of non-invasive ways to determine biodistribution or activity levels of these AAV therapies in patients. This is a significant hinderance, leaving investigators guessing which organs or structures are effectively treated and, due to the lag time associated with clinical disease progression, this limitation ultimately impacts the evolution of treatment modalities. In order to overcome these limitations, we propose the development of a new magnetic resonance imaging (MRI)-based technology to track enzymatic activity in any organ, peripheral nervous system (PNS), or central nervous system (CNS) over time and thus have the potential to be applicable to any LSD caused by an enzymatic deficiency. Magnetic resonance imaging is an ideal technique for the study of neurological disorders. This technique is has become a gold standard in diagnostic radiology as a result of the absence of ionizing radiation and is capable of true 3D imaging and has been in use for several decades . Detailed structural information can be obtained in minutes, and single slices in seconds. However, the need to differentiate regions of tissues or organs that are magnetically similar but histologically distinct has been a major impetus for the development of contrast enhancement agents. Greater than 40% of all MR procedures employ contrast agents with more than 450,000 million doses to date have been administered to patients and Gd(III) based contrast agents are among the safest clinical probes in use. We pioneered the development of bio-responsive (i.e., conditionally activated) MR contrast agents and since that time a library of this class of probes has expanded from enzyme activated agents to pH sensitive, the detection of ions such as Zn(II) and Ca(II), and redox activated. Here, we describe the development of a platform where the substrate (that prevents access of water to a Gd(III) ion) is removed by an enzyme which can be substituted to accommodate a number of gene therapy targets.
Lysosomal storage diseases (>40 different diseases) are often fatal in pediatric subjects. They are caused by a specific protein deficiency that breaks down waste products within the cell. For several of these diseases, gene therapy clinical trials are ongoing or about to start, but there is no way to track their therapeutic efficacy. We have developed a series of MRI based contrast agents that are able to non-invasively track the therapeutic protein. In this proposal, we will perform the necessary experiments to translate to patients.
