---
schema_version: "secwatch.filing_event.v1"
accession: "0001559053-25-000042"
form_type: "8-K"
ticker: "PRTA"
cik: "0001559053"
company_name: "PROTHENA CORP PUBLIC LTD CO"
filed_at: "2025-11-06T23:59:59+00:00"
generated_at: "2026-05-16T23:40:54.001016+00:00"
event_type: "earnings"
sentiment: "negative"
materiality_score: 0.7
calibrated_materiality_score: 0.7
confidence: "high"
source: SEC EDGAR
---

# Prothena Q3 net loss $36.5M, nine-month loss $222.5M on charges; pipeline advances

## Summary
- Net loss for Q3 2025 was $36.5M ($0.68/sh) vs $59.0M ($1.10/sh) in Q3 2024; nine-month loss $222.5M ($4.13/sh) vs $64.4M ($1.20/sh).
- Revenue fell to $2.4M in Q3 2025 from $1.0M in Q3 2024; nine-month revenue $9.7M vs $133.0M primarily from BMS collaboration.
- Cash and equivalents $331.7M; no debt. FY2025 guidance: net cash used $170-178M, year-end cash ~$298M midpoint.
- Roche to initiate Phase 3 PARAISO prasinezumab trial for Parkinson's by end 2025; Novo Nordisk started Phase 3 CLEOPATTRA for coramitug in ATTR-CM.
- EGM on Nov 19 to vote on share capital reduction to support potential 2026 share redemption program; up to $105M in clinical milestones by end 2026.

## SEC filing metadata
- accession: 0001559053-25-000042
- form_type: 8-K
- ticker: PRTA
- cik: 0001559053
- company_name: PROTHENA CORP PUBLIC LTD CO
- filed_at: 2025-11-06T23:59:59+00:00
- event_type: earnings
- sentiment: negative
- materiality_score: 0.7
- calibrated_materiality_score: 0.7
- confidence: high
- sec_items: 2.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1559053/000155905325000042/0001559053-25-000042-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1559053/000155905325000042/prta-20251106.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001559053-25-000042
- JSON: https://secwatch.observer/filing/0001559053-25-000042.json
- Plain text: https://secwatch.observer/filing/0001559053-25-000042.txt

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