---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-077105"
form_type: "8-K"
ticker: "RNA"
cik: "0002093101"
company_name: "Atrium Therapeutics, Inc."
filed_at: "2026-02-26T23:59:59+00:00"
generated_at: "2026-05-15T23:53:46.756076+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Atrium Therapeutics completes spin-off from Avidity; 15.5M shares distributed, trading begins Feb 27 under RNA

## Summary
- Avidity distributed 15,514,966 Atrium shares at a ratio of 1 share per 10 Avidity shares; holds no equity interest after.
- Atrium shares expected to begin trading on Nasdaq under symbol RNA on February 27, 2026.
- Registration statement declared effective and spin-off consummated on February 26, 2026.
- Novartis acquisition of Avidity expected to close on February 27, 2026, subject to conditions.
- Atrium focused on early-stage precision cardiology programs ATR-1086 (phospholamban) and ATR-1072 (PRKAG2 syndrome).

## SEC filing metadata
- accession: 0001193125-26-077105
- form_type: 8-K
- ticker: RNA
- cik: 0002093101
- company_name: Atrium Therapeutics, Inc.
- filed_at: 2026-02-26T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2093101/000119312526077105/0001193125-26-077105-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2093101/000119312526077105/d14901d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-077105
- JSON: https://secwatch.observer/filing/0001193125-26-077105.json
- Plain text: https://secwatch.observer/filing/0001193125-26-077105.txt

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