---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-189765"
form_type: "8-K"
ticker: "PRTA"
cik: "0001559053"
company_name: "PROTHENA CORP PUBLIC LTD CO"
filed_at: "2025-08-27T23:59:59+00:00"
generated_at: "2026-05-17T09:42:06.683081+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.65
calibrated_materiality_score: 0.65
confidence: "high"
source: SEC EDGAR
---

# Prothena PRX012 shows amyloid reduction but higher ARIA-E rates; seeks partnership

## Summary
- Phase 1 ASCENT: PRX012 400 mg achieved mean amyloid PET reduction to 27.47 CL at month 12.
- ARIA-E rates at 400 mg (41.7%) and 200 mg (38.1%) exceeded those of FDA-approved anti-Aβ antibodies.
- One death in 45 mg cohort deemed unrelated to study drug; injection site reactions low (4.1%).
- Company plans to explore partnership to advance PRX012 and preclinical PRX012-TfR antibody.

## SEC filing metadata
- accession: 0001193125-25-189765
- form_type: 8-K
- ticker: PRTA
- cik: 0001559053
- company_name: PROTHENA CORP PUBLIC LTD CO
- filed_at: 2025-08-27T23:59:59+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 0.65
- calibrated_materiality_score: 0.65
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1559053/000119312525189765/0001193125-25-189765-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1559053/000119312525189765/d38911d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-189765
- JSON: https://secwatch.observer/filing/0001193125-25-189765.json
- Plain text: https://secwatch.observer/filing/0001193125-25-189765.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.