William P. Scully filed Amendment No. 7 to Schedule 13G with the SEC on November 13, 2026, disclosing beneficial ownership of 6,404,846 Ordinary Shares of Prothena Corp Public Ltd Co as of September 30, 2026.

Key Highlights

  • Total beneficial ownership: William P. Scully may be deemed to beneficially own 6,404,846 Ordinary Shares of Prothena Corp Public Ltd Co.
  • Percent of class: The filing reports the aggregate position as approximately 12.47% of outstanding Ordinary Shares, based on 51,349,796 shares outstanding as of October 29, 2026.
  • Sole voting and dispositive power: Scully holds sole voting and dispositive power over 1,091,000 shares.
  • Shared voting and dispositive power: Scully holds shared voting and dispositive power over 5,313,846 shares.
  • Triggering event date: The event requiring this filing occurred on September 30, 2026.
  • Beneficial ownership disclaimer: According to the filing, Scully "disclaims beneficial ownership of all Ordinary Shares in which the Reporting Person does not have a pecuniary interest."

Scully's Prothena Holdings: Structure and Composition of the 6,404,846-Share Position

According to the filing, the 6,404,846 Ordinary Shares attributed to William P. Scully are held across several vehicles. These include 100,000 shares owned directly, 187,000 shares held by Manatee Equity Fund LLC (of which Scully is the sole manager), and 804,000 shares held in Scully's own IRA, all over which he has sole voting and dispositive power. An additional 42,000 shares are held in his spouse's IRA and 172,000 shares are owned directly by his spouse, over both of which he may be deemed to have shared voting and dispositive power.

The filing also identifies 23,000 shares held in an IRA subject to an investment management agreement, over which Scully may be deemed to have shared voting and dispositive power "by reason of his right to terminate such agreement." The largest component consists of 5,036,846 shares held in aggregate by various grantor retained annuity trusts with an independent trustee, plus 40,000 shares in another trust with an independent trustee. For both categories, the filing attributes shared voting and dispositive power to Scully "by reason of his retained right to substitute assets in such trusts."

The percentage calculation is based on 51,349,796 Ordinary Shares outstanding as of October 29, 2026, as reported in Prothena's Quarterly Report on Form 10-Q for the quarter ended September 30, 2026, filed with the SEC on November 5, 2026, according to the Schedule 13G. The filing was signed on November 13, 2026, by Diana L. Hayes as attorney-in-fact, pursuant to a Limited Power of Attorney dated September 3, 2025.

What Was Disclosed

William P. Scully filed Amendment No. 7 to Schedule 13G reporting beneficial ownership of 6,404,846 Ordinary Shares, or approximately 12.47%, of Prothena Corp Public Ltd Co (NASDAQ:PRTA), with the triggering event dated September 30, 2026.