Not reported in the public reviews. Reviewers summarise selectively, so this usually means it wasn't discussed publicly, not that it wasn't studied.
Biodistribution & persistence
Wide distribution in rat; highest in eye uvea, kidney, liver, gastric mucosa and small intestine
“[14C]SDX-related radioactivity widely distributed in rat tissues with the highest radioactivity concentrations observed in eye uvea, kidney cortex and medulla, liver, gastric mucosa of stomach, and small intestine.”
✓ VerifiedFDA multi-discipline review, p. 44Source ↗
Modality-specific risk
New prodrug with longer human half-life and species PK differences: need to exclude SDX-unique toxicity vs d-MPH, chronic/juvenile toxicity
“However, even though SDX is a prodrug of an approved product (d-MPH), we determined that a chronic study adequately assessing SDX toxicity in an appropriate species was needed because SDX is an NME that has a longer half-life in humans (~5.7 hours) compared to other species (~0.5-2 hours).”
✓ VerifiedFDA multi-discipline review, p. 60Source ↗