Histone Deacetylase Inhibitors as Therapeutics for Friedreich's ataxia

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DESCRIPTION (provided by applicant): Friedreich's ataxia (FRDA) is an inherited neurodegenerative disease caused by a deficiency in the nuclear- encoded mitochondrial protein frataxin. At present there is no effective cure or treatment for FRDA. The DNA abnormality found in 98% of FRDA patients is the unstable hyper-expansion of a GAA triplet in the first intron of the frataxin gene that interferes with gene transcription, either at the level of DNA or chromatin structure. Based on the hypothesis that the acetylation state of the core histones might be responsible for silencing the frataxin gene harboring expanded GAA repeats, we screened a representative collection of commercial histone deacetylase (HDAC) inhibitors, and identified one compound (BML-210 from BioMol) that partially relieves repression of the frataxin gene in lymphoid cells derived from FRDA patients. Based on this result, we have devised a synthetic scheme to obtain a library of derivatives of this lead compound. ICSOs for the HDAC inhibitors will be determined in cell lines derived from FRDA patient lymphocytes. Real-time PCR will be used to determine whether BML-210 and/or its derivatives increase frataxin mRNA expression in human FRDA cell lines, lymphoid cells isolated from FRDA donor blood, and in neuronal cell lines established from GAA-expanded frataxin knock-in mice. The effects of the inhibitors on cellular frataxin protein will be determined by western blotting, and the genome-wide effects of the most active inhibitors will be assessed by DNA microarray analysis. Animal studies will be performed in normal mice to determine the bioavailability, tissue distribution, pharmacokinetics, half-lives of the compounds in serum, toxicity, and maximum tolerated dosage. We will determine whether the HDAC inhibitors cross the blood brain barrier and function in vivo. Knock-in mice harboring frataxin genes with expanded GAA alleles will be utilized to determine whether HDAC inhibitors activate frataxin gene expression in vivo, and relieve neurological deficits in these animals. This proposal is aimed at the development of new drugs to treat the inherited neurological disease Friedreich's ataxia (FRDA), which is caused by expansion of repeats of the simple sequence GAA in an essential human gene. These repeats silence the gene, possibly by packaging the DNA in an inactive chromosomal environment. We are developing small molecules to reverse this effect, with the hope that these molecules may be therapeutic for FRDA.