M&G plc has disclosed a reduction in its major holding in 4basebio PLC (4BB), the UK-listed genomic medicines company, following a TR-1 notification filed with the FCA on 11 November 2026. The asset management group's aggregate voting rights in 4basebio fell from 29.9% to 27.8%, representing 5,350,075 shares, after the threshold was crossed on 10 November 2026. The disclosure involves two parties acting in concert — The Prudential Assurance Company Limited and Fort Aggregator, LP — and was filed under DTR 5.2.1. Investors in 4basebio may be watching this development closely given the scale of the combined holding and the involvement of multiple institutional entities.

Key Points

  • 4basebio PLC (4BB) — UK-listed genomic medicines company
  • M&G plc disclosed its aggregate voting rights fell from 29.9% to 27.8% in 4basebio PLC
  • Threshold crossed on 10 November 2026; issuer notified 11 November 2026; total voting rights now 5,350,075
  • Investors should watch for the separate notification expected from Elevage Medical Technologies Holdings, LLC regarding Fort Aggregator, LP's shareholding

M&G plc's Aggregate Stake in 4basebio Falls to 27.8% Across Two Concert Parties

The TR-1 notification confirms that M&G plc, acting as indirect parent shareholder under DTR 5.1.2 and 5.2.1(e), holds a combined 27.8% voting interest in 4basebio PLC following the crossing of a reporting threshold on 10 November 2026. This aggregate figure encompasses positions held by two parties acting in concert: The Prudential Assurance Company Limited, based in London, and Fort Aggregator, LP, registered in Wilmington, Delaware, United States. The concert party arrangement is disclosed pursuant to DTR 5.2.1(a), and the notification reflects their combined position across all voting rights attached to shares.

Prudential Assurance Holds 12.6% and Fort Aggregator LP Holds 15.2% of 4basebio Ordinary Shares

The announcement breaks down the aggregate 27.8% position into two distinct components. The Prudential Assurance Company Limited holds 2,426,904 ordinary shares indirectly, equating to 12.6% of voting rights, reported under DTR 5.2.1(e) through a chain including M&G plc, M&G Group Regulated Entity Holding Company Limited, M&G Group Limited, M&G FA Limited, and M&G Investment Management Limited. Fort Aggregator, LP holds 2,923,171 ordinary shares indirectly, equating to 15.2% of voting rights, reported under DTR 5.2.1(a) through Elevage Medical Technologies Holdings, LLC and Elevage Medical Technologies GP, LLC. All shares carry an ISIN of GB00BMCLYF79 and are ordinary shares of €1.00 each.

Separate Elevage Medical Technologies Notification Expected for Fort Aggregator LP's Position

The announcement states that a separate notification will be made on behalf of Elevage Medical Technologies Holdings, LLC in respect of Fort Aggregator, LP's shareholding. This indicates that additional regulatory disclosures relating to the same underlying position in 4basebio are forthcoming, which may provide further clarity on the ownership structure. The filing was completed in London on 11 November 2026. No financial instruments are reported in sections B1 or B2 of the notification, confirming the entire 27.8% position consists solely of voting rights attached to ordinary shares, with no derivative or convertible instruments disclosed.