---
schema_version: "secwatch.filing_event.v1"
accession: "0000879407-25-000010"
form_type: "8-K"
ticker: "ARWR"
cik: "0000879407"
company_name: "ARROWHEAD PHARMACEUTICALS, INC."
filed_at: "2025-09-12T23:59:59+00:00"
generated_at: "2026-05-17T06:48:27.350709+00:00"
event_type: "litigation"
sentiment: "negative"
materiality_score: 0.82
calibrated_materiality_score: 0.82
confidence: "high"
source: SEC EDGAR
---

# Ionis sues Arrowhead for patent infringement over plozasiran, threatening FCS launch

## Summary
- Ionis filed complaint in Central District of California alleging Arrowhead's plozasiran infringes U.S. Patent No. 9,593,333.
- Arrowhead had preemptively sought declaratory judgment in Delaware to invalidate the same patent on Sept. 10, 2025.
- Arrowhead expects FDA decision on plozasiran NDA by Nov. 18, 2025 (PDUFA) and plans Q4 2025 launch.
- The '333 patent covers method of reducing triglycerides in adults with familial chylomicronemia syndrome (FCS).
- Ionis says it sent a pre-suit notice on Sept. 3, 2025; Arrowhead did not engage before filing DJ action.

## SEC filing metadata
- accession: 0000879407-25-000010
- form_type: 8-K
- ticker: ARWR
- cik: 0000879407
- company_name: ARROWHEAD PHARMACEUTICALS, INC.
- filed_at: 2025-09-12T23:59:59+00:00
- event_type: litigation
- sentiment: negative
- materiality_score: 0.82
- calibrated_materiality_score: 0.82
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/879407/000087940725000010/0000879407-25-000010-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/879407/000087940725000010/arwr-20250911.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000879407-25-000010
- JSON: https://secwatch.observer/filing/0000879407-25-000010.json
- Plain text: https://secwatch.observer/filing/0000879407-25-000010.txt

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