FDA Approval Sparks Bullish Momentum In PTC Therapeutics — Here’s What Happened

The regulator approved Sephience for a broad range of PKU patients, including children as young as one month, based on Phase 3 data showing sustained reductions in phenylalanine levels.

Retail chatter around PTC Therapeutics surged Monday after the FDA approved Sephience (sepiapterin) for the treatment of phenylketonuria (PKU), a rare genetic disorder that disrupts the body’s ability to break down phenylalanine. 

The decision grants broad labeling for use in adults and children as young as one month who are responsive to sepiapterin.

The approval was supported by results from the Phase 3 Aphenity trial and its long-term extension, which showed significant reductions in blood phenylalanine levels and sustained treatment effects. 

Sephience is designed to address hyperphenylalaninemia (HPA) across all PKU subtypes.

The U.S. decision follows European Commission (EC) marketing authorization last month, which also granted a broad label across all ages and disease severities. 

PTC described the EC approval as a “great step” toward making Sephience available globally for patients with PKU.

Analysts had been closely monitoring the regulatory timeline. 

Citi raised its price target on PTC Therapeutics to $50 from $40 earlier this month, adding a 30-day "upside catalyst watch" in anticipation of the FDA decision. The firm maintained a Neutral rating and noted it remains cautious about Sephience’s longer-term sales potential.

On Stocktwits, retail sentiment for PTC Therapeutics was ‘extremely bullish’ amid ‘extremely high’ message volume.

PTC Therapeutics’ stock has declined 3.4% so far in 2025.

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