Atrium Therapeutics, Inc. 8-K

What Happened

• Atrium Therapeutics, Inc. filed an 8-K (Regulation FD disclosure) stating the registration statement for its pro rata distribution was declared effective by the SEC on February 26, 2026. Avidity Biosciences completed the Distribution that day, issuing 15,514,966 shares of Atrium common stock to Avidity shareholders (one Atrium share for every ten Avidity shares; record date Feb 12, 2026). Avidity no longer holds any equity in Atrium. Atrium’s final information statement dated February 26, 2026 is attached as Exhibit 99.1. The newly distributed shares are expected to begin trading on The Nasdaq Global Select Market on February 27, 2026 under the ticker symbol RNA. In connection with these transactions, Avidity’s previously announced acquisition by Novartis AG is also expected to close on February 27, 2026, subject to customary closing conditions.

Key Details

• Registration statement declared effective: February 26, 2026.
• Distribution ratio and record date: 1 Atrium share per 10 Avidity shares; record date February 12, 2026.
• Total shares distributed: 15,514,966 shares; Avidity now holds no equity in Atrium.
• Expected Nasdaq trading start: February 27, 2026 under ticker "RNA"; Avidity acquisition by Novartis expected to close on or about February 27, 2026.

Why It Matters

• Investors: Atrium is now an independent, publicly listed company, which provides direct market liquidity and a ticker (RNA) for trading and valuation.
• Avidity shareholders: Received Atrium shares pro rata, changing their direct holdings and enabling separate investment exposure to Atrium’s business and management.
• Corporate context: Avidity’s planned acquisition by Novartis may affect Avidity’s business going forward but does not leave Novartis with equity in Atrium following the completed Distribution.
• Next steps for investors: Review Atrium’s information statement (Exhibit 99.1) for details on the company’s business, management, and risks before making investment decisions.