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Highlights

  • PRTA informs that partner Roche will initiate Phase III trials of prasinezumab in early-stage Parkinson’s disease following Phase IIb results.
  • The company reports prasinezumab showed trends toward delayed motor progression and biological impact in the PADOVA study.
  • PRTA confirms over 750 patients are enrolled in ongoing open-label extension studies evaluating long-term efficacy and safety.

Prothena Corporation plc (NASDAQ:PRTA) is a clinical-stage biotechnology company focused on developing therapies targeting protein dysregulation in neurodegenerative and rare peripheral amyloid diseases. Its pipeline includes investigational therapies for conditions such as ATTR amyloidosis, Alzheimer’s disease, Parkinson’s disease, and other disorders involving misfolded proteins. The company’s portfolio comprises both wholly owned and partnered programs, including collaborations with Roche and other pharmaceutical firms.

The company has announced that its development partner Roche will advance prasinezumab, an investigational anti-alpha-synuclein antibody, into Phase III clinical trials for early-stage Parkinson’s disease. The decision is based on findings from the Phase IIb PADOVA study and continued data from open-label extension (OLE) studies, including both PADOVA and the earlier Phase II PASADENA trial.

Prasinezumab is designed to target alpha-synuclein, a protein believed to play a key role in the progression of Parkinson’s disease. The antibody therapy is being developed to address disease-modifying outcomes rather than solely treating symptoms. According to Prothena, the PADOVA study evaluated prasinezumab in combination with standard symptomatic therapies in early Parkinson’s disease.

While the PADOVA trial did not achieve statistical significance in its primary endpoint—time to confirmed motor progression—the data showed a directional signal suggesting a possible delay in disease progression. At the 104-week mark, trends indicated reduced motor deterioration compared to placebo. Roche’s decision to move prasinezumab into Phase III development reflects the potential observed in these clinical trends and the additional insights from ongoing long-term OLE data.

The OLE studies are evaluating the long-term efficacy and safety of prasinezumab in more than 750 patients with early-stage Parkinson’s disease. The studies aim to provide a broader understanding of how extended treatment with the antibody may impact disease trajectory over time. Importantly, the PADOVA study included the first biomarker-based evidence that prasinezumab may influence the underlying biological processes associated with Parkinson’s disease.

The investigational therapy’s development through the next phase will focus on further confirming clinical benefit and exploring whether biomarker effects translate into measurable long-term outcomes for patients. The planned Phase III program is expected to begin enrollment based on insights from the Phase II studies and input from regulatory agencies.

The PASADENA and PADOVA trials, along with their respective open-label extensions, are part of a larger clinical collaboration between Prothena and Roche, initiated under a licensing agreement. Under this partnership, Roche is responsible for the clinical development and potential commercialization of prasinezumab, while Prothena retains certain rights and milestone-based financial considerations.