1. Gene Therapy for Spinal Muscular Atrophy
Tuesday, November 14, 2017
Cheng Shan, Brandon Mikhael,
Olivia Gallagher, and Kathy Nguyen
PHM Fall 2016
Coordinator: Dr. Jeffrey Henderson
Instructor: Dr. David Hampson

2. What is Spinal Muscular Atrophy (SMA)?3
Spinal muscular atrophy is a rare neuromuscular disease in the autosomal 5q gene1
Main effect is loss of motor neurons, causing muscular atrophy and eventually respiratory failure1
Children and infants are the most affected1
Affects 1 in ,000 live births2
MacKenzie, Alex. "Genetic therapy for spinal muscular atrophy." Nature biotechnology 28.3 (2010):
D'Amico, A., Mercuri, E., Tiziano, F. D., & Bertini, E. (2011). Spinal muscular atrophy. Orphanet journal of rare diseases, 6(1), 71.
Picture from not really sure how to cite a picture from a website tho...

3. SMN-1 (Survival Motor Neuron -1) gene is usually homozygously deleted1
Root Causes
SMN-1 (Survival Motor Neuron -1) gene is usually homozygously deleted1
SMN protein is involved with much of RNA metabolism1
The absence of the SMN gene is lethal in all other animal species embryonically1
Humans have the presence of a SMN-2 gene, which produces a small amount of SMN protein permitting initial survival1
MacKenzie, Alex. "Genetic therapy for spinal muscular atrophy." Nature biotechnology 28.3 (2010):

4. Exact role of SMN is unclear1
SMN Function 4
Exact role of SMN is unclear1
SMN protein deficiency may cause a deficient pre-synaptic transcriptome, causing denervation1
Greater SMN-2 copy number is associated with a better outlook1
1.MacKenzie, Alex. "Genetic therapy for spinal muscular atrophy." Nature biotechnology 28.3 (2010):

5. Targets defective or missing genes
What is Gene Therapy?
Targets defective or missing genes
Introduction of nucleic acids (genetic material) into the cell
Viruses often used to deliver genetic material5
Main goal is to restore function with no adverse effects
Gene Therapy - A Revolution in Progress: Human Genetics and Medical Research. (n.d.). Retrieved November 14, 2017, from

6. Gene Augmentations for SMA6
Different approaches to gene therapy
Use of adeno-associated virus to deliver full length SMN6
Use of histone deacetylase inhibitors or small molecules to promote production of full length SMN from SMN26
Wood, M. J., Talbot, K., & Bowerman, M. (2017). Spinal muscular atrophy: antisense oligonucleotide therapy opens the door to an integrated therapeutic landscape. Human Molecular Genetics.

7. Gene Therapy for SMA - Mouse Model1
Intravenous administration of adeno- associated virus serotype 9 (scAAV9) with SMN complementary DNA that encodes for survival motor neuron (SMN)7
Coding region of recombinant virus forms intramolecular double-stranded DNA template7
Inducing expression of SMN counters effects of SMA and extends survival7

8. Gene Therapy for SMA - Human Trials
Study performed in April 20147
15 infants with SMA17
Given single dose of vector containing scAAV9 along with human survival motor neuron gene (hSMN) and a chicken beta-active promoter (scAAV9.CB.hSMN) (AVXS-101)7
Vector delivered in normal saline through intravenous infusion7
Self-complementary feature of vector with hybrid promoter enables rapid and sustained expression of SMN7

9. Gene Therapy for SMA - Human Trials
RESULTS:
All 15 patients alive and event-free at 20 months of age7
In high-dose cohort, scores on the CHOP INTEND (Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders) scale of motor function all increased7
12 patients that received high doses: 11 sat unassisted, 9 rolled over, 11 fed orally and could speak, and 2 walked independently7

10. Gene Therapy = Therapeutic Strategy to treat SMN
Increased survival7
Achievement of motor milestones7
Improved motor function7

11. Adverse Effects of Gene Therapy7
There are many adverse events related to scAAv9 gene therapy7
56 serious adverse events were observed in 13 patients7

12. Limitations of Gene Therapy
The presence of anti-AAV9 antibodies hinders universal application of scAAV9 gene therapy8
Antibodies may be present prior to therapy or in some cases, be developed as a result of therapy8
Antibodies can be detected at birth8
Anti-AAV9 causes vector clearance by the immune system and therefore could make scAAV9 gene therapy ineffective8

13. Overcoming the Limitations of Gene Therapy
Potential methods to overcome the limitations of anti-AAV9 antibodies: 1. Inducing transient immunosuppression8 2. Designing AAV9 variants that that are resistant to antibodies8
Further research and development of gene therapy are required to make treatment more universal

14. Summary Slide Spinal muscular atrophy is a rare neuromuscular disease1
Characterized by loss of motor neurons, causing muscular atrophy and eventually respiratory failure1
Usually caused by the homozygous deletion of the SMN-1 (Survival Motor Neuron-1) gene11
Humans have SMN-2 gene which produces a small amount of SMN protein permitting initial survival1
Gene therapy targets defective or missing genes by introducing nucleic acids (genetic material) into the cell using viruses
Gene therapy for spinal muscular atrophy involves the intravenous administration of adeno-associated virus serotype 9 (scAAV9) with SMN complementary DNA that encodes for survival motor neuron (SMN)7
This allows for improved motor function and increased survival7
The presence of anti-AAV9 antibodies hinders universal application of scAAV9 gene therapy by causing vector clearance8
Potential methods to overcome this include inducing transient immunosuppression and designing variants that are resistant to antibodies8
Further research and development of gene therapy are required to make treatment more universal

15. References
MacKenzie, A. (2010). Genetic therapy for spinal muscular atrophy. Nature Biotechnology, 28,
D’Amico, A., Mercuri, E., Tiziano, F. D., & Bertini, E. (2011). Spinal muscular atrophy. Orphanet journal of rare diseases, 6(1), 71.
Spinal Muscular Atrophy [Online image] Retrieved November 12, 2017 from
Baiono, M. T., & Ambiel, C. R. (2010). Spinal muscular atrophy: diagnosis, treatment and future prospects. Journal de pediatria, 86(4),
Gene Therapy - A Revolution in Progress: Human Genetics and Medical Research. (n.d.). Retrieved November 14, 2017, from
Wood, M. J., Talbot, K. & Bowerman, M. (2017). Spinal muscular atrophy: antisense oligonucleotide therapy opens the door to an integrated therapeutic landscape. Human Molecular Genetics, 26(R2), R
Mendell, J. R., Al-Zaidy, S., Shell, R., Arnold, W. D., Rodino-Klapac, L. R., Prior, T. W., … Kaspar, B. K. (2017). Single-Dose Gene-Replacement Therapy for Spinal Muscular Atrophy. The New England Journal of Medicine, 377(18),
Jeune, V. L., Joergensen, J.A., Hajjar, R.J. & Weber, T. (2013). Pre-existing Anti-Adeno-Associated Virus Antibodies as a Challenge in AAV Gene Therapy. Hum Gene Ther Methods, 24(2),