This Tender Offer Statement on Schedule TO (this “Schedule TO”) relates to the offer (the “Offer”) by Concentra Merger Sub IV, Inc., a Delaware corporation (“Purchaser”) and a wholly owned subsidiary of Concentra Biosciences, LLC, a Delaware limited liability company (“Parent”), to purchase all of the issued and outstanding shares of common stock, par value $0.001 per share (“Shares”), of Kronos Bio, Inc., a Delaware corporation (“Kronos”), for: (i) $0.57 per Share in cash (the “Cash Amount”); plus (ii) one non-transferable contractual contingent value right for each Share (each, a “CVR,” and each CVR together with the Cash Amount, the “Offer Price”), all upon the terms and subject to the conditions described in the Offer to Purchase (together with any amendments or supplements or supplements hereto, the “Offer to Purchase”) and in the related Letter of Transmittal (together with any amendments or supplements thereto, the “Letter of Transmittal”), copies of which are attached hereto as Exhibits (a)(1)(A) and (a)(1)(B), respectively. The Offer is being made pursuant to the Agreement and Plan of Merger, dated as of May 1, 2025 (together with any amendments or supplements thereto, the “Merger Agreement”), among Kronos, Parent and Purchaser, a copy of which is filed as Exhibit (d)(1) hereto and incorporated herein by reference with respect to Items 4 through 11 of this Schedule TO. Capitalized terms used but not otherwise defined herein have the meanings ascribed thereto in the Merger Agreement.

All of the information set forth in the Offer to Purchase is incorporated by reference herein in response to Items 1 through 9 and Item 11 of this Schedule TO and is supplemented by the information specifically provided in this Schedule TO.

The information set forth in the section of the Offer to Purchase titled “Summary Term Sheet” is incorporated herein by reference.

(a) The subject company and the issuer of the securities subject to the Offer is Kronos. Its principal executive office is located at 301 Binney Street, 2nd Floor East Cambridge, MA, and its telephone number is (650) 781-5200.

(b) This Schedule TO relates to the Shares. According to Kronos as of the close of business on April 25, 2025, there were: (i) 60,969,214 Shares issued and outstanding; (ii) 5,940,978 Shares subject to outstanding Company Stock Options, none of which were In-the-Money Options; and (iii) 463,131 Shares subject to outstanding Company Restricted Stock Units.

(c) The information concerning the principal market on which the Shares are traded, and certain high and low sales prices for the Shares in the principal market in which the Shares are traded set forth in “Special Factors—Section 4. Price Range of Shares; Dividends” of the Offer to Purchase, are incorporated herein by reference.

(a)–(c) The filing companies of this Schedule TO, Parent, Purchaser, TCP (as defined below) and TCM (as defined below). Each of Purchaser’s, Parent’s, TCP’s and TCM’s principal executive office is located at 4747 Executive Drive, Suite 210, San Diego, California 92121. Each of Purchaser’s and Parent’s telephone number is (858) 281-5372. Each of TCP’s and TCM’s telephone number is (858) 200-3830.

Purchaser was incorporated under the laws of the State of Delaware on April 15, 2025 for the purpose of consummating the Offer and effecting the Merger pursuant to the Merger Agreement. Kevin Tang is the sole director of Purchaser and the executive officers of Purchaser are: (i) Mr. Tang, Chief Executive Officer; (ii) Michael Hearne, Chief Financial Officer; (iii) Ryan Cole, Chief Operating Officer; (iv) Stew Kroll, Chief Development Officer; and (v) Thomas Wei, Chief Business Officer. Each executive officer of Purchaser is a United States citizen and has a business address located at 4747 Executive Drive, Suite 210, San Diego, California 92121.

Parent was formed under the laws of the State of Delaware on March 8, 2023 and its principal business is currently to consummate the Offer and effect the Merger pursuant to the Merger Agreement, and to perform its obligations under the contingent value rights agreement, which is in substantially the form attached as Exhibit D to the Merger Agreement (the “CVR Agreement”), following the Merger when Kronos is a wholly owned subsidiary of Parent and the surviving entity from the Merger. The executive officers of Parent are: (i) Mr. Tang,

Chief Executive Officer; (ii) Michael Hearne, Chief Financial Officer; (iii) Ryan Cole, Chief Operating Officer; (iv) Stew Kroll, Chief Development Officer; and (v) Thomas Wei, Chief Business Officer. Each executive officer of Parent is a United States citizen and has a business address located at 4747 Executive Drive, Suite 210, San Diego, California 92121.

Tang Capital Partners, LP (“TCP”) was formed under the laws of the State of Delaware on August 16, 2002 and is the sole member of Parent. Its principal business is a life sciences-focused investment company.

Tang Capital Management, LLC (“TCM”) was formed under the laws of the State of Delaware on December 19, 2012. TCM is the sole manager of Parent and general partner of TCP. Its principal business is a life sciences-focused investment management company. Mr. Tang is the sole manager of TCM. The executive officers of TCM are: (i) Mr. Tang, President; (ii) Michael Hearne, Chief Financial Officer; and (iii) Ryan Cole, Chief Operating Officer. Each executive officer of TCM is a United States citizen and has a business address located at 4747 Executive Drive, Suite 210, San Diego, California 92121.

The information set forth in “The Tender Offer—Section 6. Certain Information Concerning Parent and Purchaser” and Schedule A of the Offer to Purchase is incorporated herein by reference.

(a)(1)(i)-(viii), (x), (xii), (a)(2)(i)-(v), (vii) The information set forth in the Offer to Purchase is incorporated herein by reference.

(a)(1)(ix), (xi), (a)(2)(vi) Not applicable.

(a), (b) The information set forth in “Special Factors—Section 1. Background of the Offer; Contacts with Kronos,” “Special Factors—Section 2. Purpose of the Offer and Plans for Kronos” “The Tender Offer—Section 5. Certain Information Concerning Kronos” “The Tender Offer—Section 6. Certain Information Concerning Parent and Purchaser” and Schedule A of the Offer to Purchase is incorporated herein by reference.

(a), (c)(1)–(7) The information set forth in the sections of the Offer to Purchase titled “Summary Term Sheet” and “Introduction” and in “Special Factors—Section 2. Purpose of the Offer and Plans for Kronos” “Special Factors—Section 5. Price Range of Shares; Dividends,” “Special Factors—Section 5. Possible Effects of the Offer on the Market for the Shares; Nasdaq Listing; Exchange Act Registration and Margin Regulations,” “The Tender Offer—Section 1. Terms of the Offer” and “The Tender Offer—Section 7. Summary of the Merger Agreement and Certain Other Agreements” of the Offer to Purchase is incorporated herein by reference.

(a), (d) The information set forth in the section of the Offer to Purchase titled “Summary Term Sheet” and in “The Tender Offer—Section 8. Source and Amount of Funds” of the Offer to Purchase is incorporated herein by reference.

(b) The Offer is not subject to a financing condition.

The information set forth in “Special Factors—Section 2. Purpose of the Offer and Plans for Kronos” “The Tender Offer—Section 6. Certain Information Concerning Parent and Purchaser” and Schedule A—“Information Concerning Members of the Boards of Directors and the Executive Officers of Purchaser, Parent and the Guarantor” of the Offer to Purchase and Item 3—“Identity and Background of the Filing Person” hereof is incorporated herein by reference.

(a) The information set forth in the section of the Offer to Purchase titled “Introduction” and in “Special Factors—Section 1. Background of the Offer; Contacts with Kronos” “The Tender Offer—Section 3. Procedures for Tendering Shares” and “The Tender Offer—Section 12. Fees and Expenses” of the Offer to Purchase is incorporated herein by reference.

Not applicable. The consideration offered to security holders: (i) consists solely of cash (which may be supported entirely by Kronos’ Closing Net Cash as finally determined in accordance with the Merger Agreement and the Limited Guaranty); (ii) any payments of CVR Proceeds will be self-funded (as more fully described in the Offer to Purchase); (iii) the Offer is not subject to any financing condition; and (iv) the offer is for all outstanding securities of the subject class.

(a) The information set forth in “Special Factors—Section 1. Background of the Offer; Contacts with Kronos” “Special Factors—Section 2. Purpose of the Offer and Plans for Kronos” “Special Factors—Section 5. Possible Effects of the Offer on the Market for the Shares; Nasdaq Listing; Exchange Act Registration and Margin Regulations,” “The Tender Offer—Section 6. Certain Information Concerning Parent and Purchaser,” “The Tender Offer—Section 7. Summary of the Merger Agreement and Certain Other Agreements” and “The Tender Offer—Section 11. Certain Legal Matters; Regulatory Approvals” of the Offer to Purchase is incorporated herein by reference.

(c) The information set forth in the Offer to Purchase is incorporated herein by reference.

Not applicable.

After due inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.