BAIN CAPITAL INVESTORS LLC 4

What Happened

• Bain Capital Investors LLC, reported as a 10% owner of Kailera Therapeutics, acquired 8,398,438 shares of Kailera common stock in an open market/private purchase on April 20, 2026 at $16.00 per share for a total of $134,375,008. On the same date Bain also converted 17,857,143 shares of the issuer’s Series B Preferred Stock into common stock on a 1:1 basis (automatic conversion upon the issuer’s IPO per footnote F1).

Key Details

• Transaction date: 2026-04-20.
• Open-market/private purchase: 8,398,438 shares at $16.00 each — total consideration $134,375,008.
• Conversion: 17,857,143 Series B Preferred shares converted into common stock (1:1 conversion; preferred had no expiration) — recorded as acquisition of common and disposition of the derivative preferred.
• Shares owned after transaction: not specified in this Form 4.
• Filing timeliness: filed as of the transaction date (no late filing indicated).
• Footnotes: holdings reported as held by BCPE Perseus Investor, LP (F2). Bain Capital Investors LLC disclaims beneficial ownership except to the extent of its pecuniary interest and is identified as manager of related entities (F3).

Context

• This filing reflects institutional activity by a reported 10% owner, not an executive’s personal trade. The purchase of over $134M of common stock is a substantial cash acquisition and may be of interest to investors tracking insider/institutional buying. The conversion simply reflects preferred stock converting to common on a 1:1 basis upon the issuer’s IPO and is not an independent cash transaction.