SMaRT™ RNA Platform
VIRxSYS’ RNA platform technology, SMaRT™ (Spliceosome-Mediated RNA Trans-splicing) (“SMaRT™ RNA”), is novel, fully patented, and currently gaining recognition within major bio-pharmaceutical companies for potential uses in multiple diseases. This proprietary technology is capable of repairing or re-programming the genome. SMaRT™ accomplishes this by targeting a gene in a cell, deleting the defective or otherwise unwanted gene sequences, and inserting or “splicing-in” a portion of or a complete, healthy gene. The result of this process is a functional, effective gene of choice. SMaRT™ is analogous to a genomic word processor which can delete and add letters, correcting a misspelled word or creating an entirely new word which is desired for a situation.
SMaRT™ is a much broader technology than RNAi. SMaRT™ can be used to repair genes which are defective or to reprogram genes instructing them to express other genes. The RNA technology also has applications for 2nd generation antibody therapy (in vivo antibody manufacturing), real-time molecular imaging, iPS generation, genomics and molecular evolution. The SMaRT™ technology has a proof of principle in a multitude of diseases and is currently the foundational technology in RNA therapy for preclinical programs in hemophilia A and cardiovascular disease. There have been 41 separate publications in top tier medical journals on SMaRT™ technology.
SMaRT™ should be viewed as a substantially enhanced second generation RNA therapy. Most RNA technologies currently being advanced deploy RNA modifications as “gene silencers” to block selected gene functions (RNAi, where “i” represents “interference”). The SMaRT™ technology enables reprogramming of gene expression at the pre-mRNA level, to alter a gene to make a different protein. The SMaRT™ platform is significantly broader than other RNA platforms such as RNA interference, antisense, and ribozymes.
One of the challenges all RNA therapies face is the delivery of therapeutic molecules into cells. While other companies are trying to identify suitable delivery options and methods for their RNAi payloads, VIRxSYS has already successfully designed and tested lentiviral vectors for RNA anti-sense and pre-messenger RNA therapies, which are at varying stages of in vivo development. VIRxSYS believes that the combination of the SMaRT™ RNA platform with its lentiviral vector delivery platform will make a dominating combination in gene therapy, thus transforming the space.
SMaRT™ RNA Technology
RNA splicing is one of the most frequently occurring processes in biology and is an essential step in the flow of genetic information from DNA to protein synthesis. At any time, approximately 60,000 introns require splicing in a human cell nucleus. The average human gene encodes a primary transcript or pre-messenger RNA (pre-mRNA) containing seven introns. Splicing removes introns from the pre-mRNA to yield the mature mRNA and typically occurs within a single RNA molecule (cis-splicing).
SMaRT™ reprograms genes by trans-splicing between two different RNA molecules: a target cellular pre-mRNA and a pre-trans-splicing molecule or PTM. VIRxSYS’ PTMs are delivered by viral vectors, plasmid or other delivery methods, which then express the PTM as an RNA molecule. The PTM consists of a binding domain that directs the PTM to a specific sequence in the target pre-mRNA, a splicing domain and a coding domain, which contains the new or modified genetic information that is inserted or trans-spliced into the targeted pre-mRNA. The coding domain can be a single exon, multiple exons or an entire coding sequence. Utilizing SMaRT™, VIRxSYS has been able to achieve trans-splicing of up to 15% of endogenous target pre-mRNAs and 35% of targets introduced by transfection, although efficiencies as high as 50% and 75% have also been observed in cell models of endogenous and transfected targets respectively.
SMaRT™ RNA Applications
SMaRT™ RNA provides an effective means to reprogram mRNAs and the proteins they encode. There are large numbers of trans-splicing applications, each governed by the nature of the coding sequences included in the pre-trans-splicing molecule (PTM). PTMs that encode correct genetic sequences or toxins have been used as RNA therapies to repair mutant mRNAs from genes associated with human disease or to kill diseased cells (e.g. cancer cells). Because the coding sequence can consist of one or more exons, a single PTM can be used to correct all the mutations in the region of the target RNA that is replaced. PTMs have also been developed that contain reporter genes. These PTMs have been used for real-time imaging of gene expression. Alternatively, PTMs containing mutant sequences or stop codons can be used to reduce wild-type gene expression and may be useful for target validation. In addition to PTMs with binding domains comprised of sequences complementary to specific pre-mRNA targets, populations of PTMs with randomized binding domain sequences are capable of nonspecific trans-splicing, desirable in certain applications. Such nonspecific trans-splicing can be used to identify alternative splice sites, and to map intron – exon junctions. Additionally, such randomized trans-splicing could be used for molecular evolution by shuffling specific exon(s) in the PTM with other exons expressed by the genome. The resulting library of exon-shuffled proteins could then be selected for recombinant proteins with optimized or modified function.
