Advances in Mitochondrial Disease

Darius J. Adams, M.D.

Genetics and Metabolism

Diagnostics and Therapeutics

Mitochondrial Function

• 1200-1500 genes involved in mitochondrial function

• Combination of:– Nuclear DNA– Mitochondrial DNA

• 37 genes

Reference: http://www.kathleensworld.com/mitochon.html

Diagnostics

• Critical to potential future therapies• Nuclear Gene discovery

– Autosomal recessive mitochondrial genes– Autosomal dominant mitochondrial genes– X-linked

Next Generation Genomic Sequencing

• Can analyze the coding regions 20,000 genes with one blood test

• The targeted panels are based on clinical findings– Mito panels now with over 1,200 genes

Goals of Treatment

• Slow or arrest progression of symptoms– Increase mitochondrial ATP production– Support electron transfer– Inhibit free radicals– Stabilize OXPHOS complexes– Avoid drugs capable of affecting the

respiratory complexes

Current Cofactor Treatment of Mitochondrial Disorders

• L-Carnitine• Coenzyme Q10/Ubiqinone/CytoQ• L-Arginine• Alpha Lipoic Acid• Dietary manipulation (low carbohydrate diet)• Creatine (high energy phosphate bond)• Vit. C up to 4g/day• Vit. E 10 U/Kg/day• Vit. B1 (PDH), B2(CI&II), Nicotinamide/Niacin• Vit. B6, B12 and Biotin• Vit. K Menadione and Phylloquinone• Exercise

Experimental Cofactor Treatment of Mitochondrial

disorders• Idebenone 90 mg/day similar to CoQ10

(experimental)• Succinate 6 g/day in MELAS and Complex I

deficiency• Uridine (support general enzyme function)• Dichloroacetate (found to be harmful)• Organ transplantation• Physical therapy

Medications That Impact Mitochondria

• AZT (Inhibitor to gamma polymerase)• Fialuridine antiviral agent for Treatment of

Hepatitis B• Valproate, aspirin due to (effect on FAO or

CoA sequestration)• Nucleoside analogues: didanosine,

zalcitabine• Lamivudine and famciclovir are permitted• Gentamicin and Tetracyclines

Gene Therapy

Gene Therapy Challenges and Successes

• Targeting gene insertion– Successfully inserting plasmids

• Immune reactions– Use of Adeno-associated viral (AAV)

vectors minimizes immune response• Differential tissue targeting

– AAV vectors can target specific tissues like brain and liver

Gene Therapy

• Success demonstrated in individuals with severe combined immunodeficiency (SCID)

• Exploring direct injection vs. IV infusion of gene therapy

• Advances in DNA diagnostics for mitochondrial disease allowing of possible gene correction

Lysosome

Active Trials in Gene Therapy

• University of North Carolina, Dr. Steven Gray and Thomas Jefferson, Dr. David Wenger– Using AAV9 to transfer corrective gene for

Krabbe disease (lysosomal storage disorder)

– Discovered that may need a combination of a bone marrow transplant, intrathecal gene therapy and blood gene therapy

Going Forward

• Now that we are able to obtain more precise diagnostics, targeting specific mutations associated with mitochondrial disorders can be explored

• Start to prepare for human phase I trials

Personalized Treatment

• It is likely, given the variety of mutations, gene therapy treatment will need to be customized to the individual

• Will need specific replacement gene and to be placed in the transport vector

Model Vector Cassette

• Rep 68/78 mRNA needed to integrate into chromosome 19 region that is devoid of active genes for permanent correction

ITR RBE sequence

Transgene - ssDNA

Rep 68/78 mRNA

Promoter

PolyA

Model of Gene Correction

Plasmids

How Do We Get There?

• Likely will need proof of concept to be done at Academic Medical Centers

• BioTech will likely be needed for clinical trial work as this will require vast resources to prove safety and efficacy

• However, making advances on multiple fronts

Conclusion

• Advancing our diagnostic abilities will allow for the implementation of targeted therapies

• Nutritional and cofactor interventions continue to be refined

• Genetic therapeutics are now much closer with advances in vector technology