1. Introduction: Eteplirsen and Exon 51 Skipping

Eteplirsen is a phosphorodiamidate morpholino oligomer (PMO) designed to restore **dystrophin production** in patients with **Duchenne muscular dystrophy (DMD)** amenable to **exon 51 skipping**. This study evaluates the **safety, tolerability, and pharmacokinetics** of eteplirsen in young boys aged **6 to 48 months**.

2. Study Design: Open-Label, Dose-Escalation Trial

• Participants: 15 boys divided into two age cohorts:
  • 24 to 48 months group.
  • 6 to 24 months group.
• Treatment: Weekly intravenous **eteplirsen infusions** with doses increasing from **2 mg/kg to 30 mg/kg** over **96 weeks**.

3. Primary Outcome: Safety and Tolerability

**Most treatment-emergent adverse events (TEAEs) were mild**, with the most common including:

• Pyrexia (**fever**).
• Cough and nasopharyngitis (**common cold symptoms**).
• Gastrointestinal symptoms (**vomiting, diarrhea**).

Importantly, there were **no treatment-related discontinuations** and **no evidence of kidney toxicity**.

4. Pharmacokinetics: Consistency with Older Patients

• Eteplirsen was **well-absorbed**, with predictable distribution.
• Findings were **consistent with previous studies** in older children.
• Supportive evidence for **safe use in younger DMD patients**.

5. Conclusion: Expanding the Treatment Age Range

This study confirms that **eteplirsen is safe and well-tolerated** even in **very young boys with DMD**. However, as this trial was not designed to measure **efficacy**, **ongoing studies** are needed to evaluate **long-term benefits** and further refine **its safety profile**.