---
schema_version: "secwatch.filing_event.v1"
accession: "0001559053-26-000009"
form_type: "8-K"
ticker: "PRTA"
cik: "0001559053"
company_name: "PROTHENA CORP PUBLIC LTD CO"
filed_at: "2026-02-27T23:59:59+00:00"
generated_at: "2026-05-15T23:02:23.980715+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.65
calibrated_materiality_score: 0.65
confidence: "high"
source: SEC EDGAR
---

# Prothena authorizes up to $100M share repurchase plan through Dec 31, 2026

## Summary
- Board authorized repurchase of up to $100M of ordinary shares; plan expires Dec 31, 2026.
- Company had $308.4M cash and no debt as of Dec 31, 2025.
- Guidance (excluding buyback) expects ~$255M cash at year-end 2026.
- Potential to earn up to $105M in clinical milestone payments from partners in 2026.
- Repurchases are discretionary; no obligation to buy any shares.

## SEC filing metadata
- accession: 0001559053-26-000009
- form_type: 8-K
- ticker: PRTA
- cik: 0001559053
- company_name: PROTHENA CORP PUBLIC LTD CO
- filed_at: 2026-02-27T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.65
- calibrated_materiality_score: 0.65
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1559053/000155905326000009/0001559053-26-000009-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1559053/000155905326000009/prta-20260227.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001559053-26-000009
- JSON: https://secwatch.observer/filing/0001559053-26-000009.json
- Plain text: https://secwatch.observer/filing/0001559053-26-000009.txt

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