Stock Markets February 2, 2026

ACADIA Shares Slip After EMA Panel Issues Unfavorable Opinion on Rett Syndrome Treatment

CHMP delivers a negative preliminary opinion on trofinetide; company plans to seek re-examination and maintain EU engagement

By Nina Shah ACAD
ACADIA Shares Slip After EMA Panel Issues Unfavorable Opinion on Rett Syndrome Treatment
ACAD

Shares of ACADIA Pharmaceuticals fell after the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) issued an unfavorable preliminary opinion on the company's marketing application for trofinetide, a treatment for Rett syndrome. ACADIA said it will request a re-examination after the CHMP's formal vote in February and emphasized its ongoing commitment to making the therapy available in the European Union.

Key Points

  • ACADIA's shares fell 4.4% in after-hours trading after the EMA's CHMP issued an unfavorable preliminary opinion on trofinetide.
  • The company plans to seek a re-examination following the CHMP's formal vote in February, using its right to request review within the specified 15- and 60-day windows.
  • The development impacts the biopharmaceutical sector and equity investors focused on specialty pharma, given the regulatory uncertainty and potential implications for market access in the EU.

ACADIA Pharmaceuticals Inc experienced a decline in its stock price in after-hours trading following an unfavorable preliminary opinion from European regulators on its application for trofinetide, a treatment for Rett syndrome. The company reported a 4.4% drop in after-hours trading as investors reacted to the Committee for Medicinal Products for Human Use (CHMP) assessment from the European Medicines Agency (EMA).

The CHMP delivered a negative trend vote on ACADIA's Marketing Authorization Application for trofinetide, which is being developed to treat Rett syndrome, a rare genetic neurological disorder. The CHMP's preliminary view is not final; a formal vote is scheduled for February.

Following the CHMP opinion, ACADIA said it intends to exercise its right to request a re-examination. The company must request this re-examination within 15 calendar days of receipt of the opinion, and it must submit the grounds for that request within 60 days. ACADIA indicated that it will pursue that regulatory pathway.

In a company statement, Chief Executive Officer Catherine Owen Adams acknowledged the setback while pointing to previously accepted clinical results. "While the negative trend vote is disappointing and not what we hoped for, we believe the strong data that supported the approval of trofinetide for the treatment of Rett syndrome in the United States, Canada, and Israel speak to the meaningful benefits that trofinetide can deliver," Adams said.

ACADIA noted that more than 1,000 patients worldwide are currently being treated with trofinetide, spanning newly diagnosed children as young as two years old and adults who have lived with Rett syndrome for decades. The company emphasized that trofinetide already holds regulatory approvals in multiple countries, including the United States, Canada, and Israel.

The company also reiterated its commitment to advancing access to the therapy within the European Union. ACADIA said it will work with the EMA and other stakeholders in an effort to progress trofinetide as a potential treatment option for patients with Rett syndrome in Europe.

The CHMP's negative preliminary opinion and the subsequent market reaction highlight the regulatory risk that can affect biopharmaceutical companies seeking new approvals in major jurisdictions. ACADIA's path forward now includes the formal CHMP vote in February and the potential re-examination process the company plans to pursue.


Procedural timeline - as noted by the company:

  • CHMP issued an unfavorable preliminary opinion on the Marketing Authorization Application for trofinetide.
  • Formal CHMP vote scheduled for February.
  • ACADIA may request a re-examination within 15 calendar days of receiving the opinion and must submit grounds within 60 days.

Risks

  • Regulatory risk in the European Union - the CHMP's negative preliminary opinion creates uncertainty around trofinetide's approval in that jurisdiction.
  • Market reaction and stock volatility - the unfavorable opinion prompted an immediate share price decline, illustrating susceptibility to regulatory news for specialty biotech equities.
  • Uncertain outcome and timing - while a re-examination can be requested, the ultimate decision and timing remain unknown pending the CHMP formal vote and any subsequent review.

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