SEC Form SCHEDULE 13D filed by Kailera Therapeutics Inc.

c/o Bain Capital Investors, LLC, 200 Clarendon Street, Boston, Massachusetts 02116.

Investment in securities.

During the last five years, none of the Bain Capital Entities have been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).

During the last five years, none of the Bain Capital Entities have been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

See Item 2(a) hereof.

Prior to the Issuer's initial public offering, the Reporting Person held 17,857,143 shares of the Issuer's Series B Preferred Stock. Upon the closing of the Issuer's initial public offering, each share of the Issuer's Series B Preferred Stock automatically converted into one share of Common Stock. As a result, following the conversion, the Reporting Person held 17,857,143 shares of Common Stock. On April 20, 2026, the Reporting Person purchased 8,398,438 shares of Common Stock from the underwriters in the Issuer's initial public offering at a price of $16.00 per share for a total purchase price of $134,375,008. The Reporting Person used its own working capital to acquire all of the foregoing equity securities of the Issuer.

The information set forth in Item 3 of this Schedule 13D is incorporated by reference in its entirety into this Item 4. Andrew Kaplan, a Partner of BCI, is a member of the Issuer's board of directors (the "Board"). The Reporting Person acquired the securities reported herein for investment purposes. In its capacity as a significant stockholder of the Issuer, the Reporting Person intends to take an active role in working with the Issuer's management and the Board on operational, financial and strategic initiatives. The Reporting Person reviews and intends to continue to review, on an ongoing and continuing basis, their investment in the Issuer. Depending upon the factors discussed below and subject to applicable law, the Reporting Person may from time to time acquire additional securities of the Issuer or sell or otherwise dispose of some or all of their securities of the Issuer. Any transactions that the Reporting Persons may pursue may be made at any time and from time to time without prior notice and will depend upon a variety of factors, including, without limitation, current and anticipated future trading prices of the securities of the Issuer, the financial condition, results of operations and prospects of the Issuer, general economic, financial market and industry conditions, other investment and business opportunities available to the Reporting Person, tax considerations and other factors.

The information set forth in Items 2 and 3 and on the cover pages of this Schedule 13D is incorporated by reference in its entirety into this Item 5. As of the date hereof the Reporting Person directly holds 26,255,581 shares of Common Stock, representing approximately 20.3% of the outstanding shares of Common Stock. The percentage of the outstanding shares of Common Stock held by the Reporting Person is based on 129,537,314 shares of Common Stock issued and outstanding, as reported by the Issuer in its prospectus relating to its initial public offering (after giving effect to the full exercise of the underwriters' option to purchase additional shares), filed with the Securities and Exchange Commission pursuant to Rule 424(b) under the Securities Act of 1933, as amended, on April 17, 2026.

See Item 5(a) hereof.

See Item 3 hereof.

Except as otherwise described in this Item 5, no one other than the Reporting Person has the right to receive, or the power to direct the receipt of, dividends from, or the proceeds from the sale of, any of the shares of Common Stock beneficially owned by the Reporting Person as described in this Item 5.

Not applicable.

The information set forth in Item 3 of this Schedule 13D is incorporated by reference in its entirety into this Item 6. Investor Rights Agreement. The Reporting Person is party to the Amended and Restated Investor Rights Agreement (the "Investor Rights Agreement"), dated October 5, 2025, with the Issuer and certain other stockholders of the Issuer. The Investor Rights Agreement provides the Reporting Person with the following rights with respect to the registration of its shares of Common Stock: Form S-1 Registration Rights. If at any time beginning 180 days after the closing date of the Issuer's initial public offering the holders of the majority of the registrable securities request in writing that the Issuer effect a registration with respect to all or part of such registrable securities then outstanding and having an anticipated aggregate offering price that would exceed $25,000,000, net of expenses, the Issuer may be required to register their shares. The Issuer is obligated to effect at most two registrations in response to these demand registration rights. Piggyback Registration Rights. If, at any time after the Issuer's initial public offering, the Issuer proposes to register any shares of its Common Stock under the Securities Act of 1933, as amended, subject to certain exceptions, the holders of registrable securities will be entitled to notice of the registration and to include their shares of registrable securities in the registration. Form S-3 Registration. If, at any time after the Issuer becomes entitled under the Securities Act of 1933, as amended, to register its shares on a registration statement on Form S-3, the holders of at least 25% of the registrable securities request in writing that the Issuer effect a registration with respect to registrable securities at an aggregate price to the public in the offering of at least $10,000,000, the Issuer will be required to effect such registration. Lock-Up Agreement. In connection with the Issuer's initial public offering, the Reporting Person and Mr. Kaplan each entered into a lock-up agreement (a "Lock-Up Agreement") with the representatives of the several underwriters. Pursuant to the Lock-Up Agreement, the Reporting Person and Mr. Kaplan each agreed, subject to certain exceptions, not to sell or otherwise transfer any shares of the Issuer's Common Stock or securities convertible into or exercisable or exchangeable for, shares of Common Stock for 180 days after the date of the prospectus relating to the Issuer's initial public offering without the prior written consent of the representatives. The foregoing summaries of the Investor Rights Agreement and Lock-Up Agreement do not purport to be complete and are qualified in their entirety by reference to the Investor Rights Agreement and Lock-Up Agreement, each of which is filed as an exhibit hereto and incorporated by reference herein.

Exhibit A. Investor Rights Agreement (incorporated by reference from Exhibit 10.11 to the Issuer's Registration Statement on Form S-1 (File No. 333-294690). Exhibit B. Lock-Up Agreement.