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All Quizzes > Motor Neuron Rescue: Precision Genetic Therapeutics in SMA

Test your knowledge on SMA pathogenesis, SMN protein biology, and the clinical impact of antisense oligonucleotide therapy. Explore presymptomatic treatment outcomes, real-world data, and the evolving SMA treatment algorithm.

Motor Neuron Rescue: Precision Genetic Therapeutics in SMA

Q1.
How does the antisense oligonucleotide (ASO) used in SMA restore functional SMN protein?

A. Inhibits UsnRNP components that degrade SMN protein to extend its half-life

B. Replaces the deleted SMN1 gene through in vivo gene editing

C. Binds SMN2 pre-mRNA at the intronic splicing silencer (ISS-N1), blocking exon 7 exclusion and increasing full-length SMN protein from SMN2

D. Activates the SMN1 gene via epigenetic modification in patients with partial deletions

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Correct Answer: C

SMA results from SMN1 gene deletion, but all patients retain SMN2 — an imperfect copy that predominantly skips exon 7 due to an intronic splicing silencer (ISS-N1). The ASO binds to ISS-N1 in SMN2 pre-mRNA, blocking the silencer and promoting exon 7 inclusion, generating more full-length SMN protein.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10605203/
Motor Neuron Rescue: Precision Genetic Therapeutics in SMA

Q2.
NURTURE study final results (June 2025): What was the landmark outcome in presymptomatic SMA infants?

A. Presymptomatic treatment offered no advantage vs symptomatic-onset treatment

B. 75% achieved walking but 3 required ventilatory support due to respiratory complications

C. 60% achieved ability to sit without support at 24 months

D. 92% of 25 children achieved independent walking; all survived; none required permanent ventilation

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Correct Answer: D

NURTURE final results (June 27, 2025) showed 92% of presymptomatically treated infants achieved independent walking — a milestone most untreated SMA type 1 patients would never reach. All 25 children were alive and none required permanent ventilation.

https://investors.biogen.com/news-releases/news-release-details/new-data-nusinersen-underscore-biogens-commitment-advancing
Motor Neuron Rescue: Precision Genetic Therapeutics in SMA

Q3.
Real-world pediatric study (Orphanet J Rare Dis 2025; N=42): Which SMA type showed the greatest motor improvements?

A. SMA type I — greatest CHOP-INTEND and HINE-2 gains; type II showed greatest RULM improvement

B. All SMA types showed identical response rates with no type-specific differences

C. SMA type II — greatest improvements across all outcome scales

D. SMA type III — greatest improvements due to preserved baseline motor function

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Correct Answer: A

The real-world pediatric analysis found SMA type I showed the greatest improvements in CHOP-INTEND and HINE-2 scores, while type II showed the greatest RULM (upper limb) score improvement. Type III improvements were relatively lower, reflecting a ceiling effect in higher-functioning patients.

https://pmc.ncbi.nlm.nih.gov/articles/PMC11866593/
Motor Neuron Rescue: Precision Genetic Therapeutics in SMA

Q4.
Why is nusinersen administered intrathecally rather than systemically?

A. CSF delivery is standard for all antisense oligonucleotides regardless of target organ

B. The large ASO cannot cross the blood-brain barrier and must reach spinal motor neurons via CSF directly

C. Systemic delivery would be superior but intrathecal is used to avoid liver toxicity

D. Intrathecal delivery allows lower drug doses in pediatric patients only

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Correct Answer: B

Nusinersen is a large antisense oligonucleotide that does not readily cross the blood-brain barrier. Intrathecal delivery distributes the drug via cerebrospinal fluid directly to the target tissues — motor neurons of the spinal cord — at therapeutically relevant concentrations unachievable with systemic dosing at tolerable doses.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10605203/
Motor Neuron Rescue: Precision Genetic Therapeutics in SMA

Q5.
Meta-analysis of 21 real-world nusinersen studies in adolescent and adult SMA: What was the overall functional outcome pattern?

A. Improvements limited to upper limb function; no benefit in ambulatory capacity

B. No meaningful improvement in patients treated after the first decade of life

C. More than 44% achieved clinically meaningful 6MWT improvement at each time point; significant HFMSE and RULM gains across pooled studies

D. Real-world data showed functional decline despite treatment

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Correct Answer: C

The meta-analysis of 21 real-world studies showed more than 44% of patients achieving clinically meaningful 6MWT improvement at each time point, with significant HFMSE and RULM improvements — confirming adolescent and adult SMA patients outside pivotal trial populations also benefit meaningfully from nusinersen.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10605203/

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