---
schema_version: "secwatch.filing_event.v1"
accession: "0001140361-23-058152"
form_type: "8-K"
ticker: "IONS"
cik: "0000874015"
company_name: "IONIS PHARMACEUTICALS INC"
filed_at: "2023-12-18T23:59:59+00:00"
generated_at: "2026-06-07T11:34:39.520299+00:00"
event_type: "m_and_a"
sentiment: "positive"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Ionis licenses donidalorsen European rights to Otsuka; $65M upfront, tiered royalties

## Summary
- Otsuka receives exclusive European commercialization rights to donidalorsen (HAE prophylactic).
- Ionis gets $65M upfront plus undisclosed regulatory/sales milestones.
- Ionis eligible for tiered royalties of 20-30% on European net sales.
- Ionis retains U.S. commercialization rights; plans to launch independently if approved.
- Phase 3 donidalorsen data expected H1 2024; Phase 2 OLE showed 96% attack rate reduction.

## SEC filing metadata
- accession: 0001140361-23-058152
- form_type: 8-K
- ticker: IONS
- cik: 0000874015
- company_name: IONIS PHARMACEUTICALS INC
- filed_at: 2023-12-18T23:59:59+00:00
- event_type: m_and_a
- sentiment: positive
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 1.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/874015/000114036123058152/0001140361-23-058152-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/874015/000114036123058152/ef20016866_8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001140361-23-058152
- JSON: https://secwatch.observer/filing/0001140361-23-058152.json
- Plain text: https://secwatch.observer/filing/0001140361-23-058152.txt

## Key facts
- Material Agreements
  IONIS PHARMACEUTICALS INC entered into a license with Otsuka Pharmaceutical Co., Ltd. (effective 2023-12-18).
  - Action: entry
  - Agreement: license
  - Counterparty: Otsuka Pharmaceutical Co., Ltd.
  - Effective: 2023-12-18
  source text: On December 18, 2023, Ionis Pharmaceuticals, Inc. issued a press release announcing it has entered into a license agreement with Otsuka Pharmaceutical Co., Ltd. (“ Otsuka ”) under which Otsuka obtains exclusive rights in Europe to commercialize donidalorsen, an investigational prophylactic treatment for hereditary angioedema (HAE).
  evidence_url: https://www.sec.gov/Archives/edgar/data/874015/000114036123058152/0001140361-23-058152-index.htm

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