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    SEC Form SCHEDULE 13G filed by C3is Inc.

    2/27/26 4:00:16 PM ET
    $CISS
    Marine Transportation
    Consumer Discretionary
    Get the next $CISS alert in real time by email



    SECURITIES AND EXCHANGE COMMISSION
    Washington, D.C. 20549


    SCHEDULE 13G


    UNDER THE SECURITIES EXCHANGE ACT OF 1934
    C3is Inc.

    (Name of Issuer)


    Common Stock, par value $0.01 per share

    (Title of Class of Securities)


    Y18284177

    (CUSIP Number)


    02/27/2026

    (Date of Event Which Requires Filing of this Statement)


    Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
    Checkbox not checked   Rule 13d-1(b)
    Checkbox checked   Rule 13d-1(c)
    Checkbox not checked   Rule 13d-1(d)






    SCHEDULE 13G

    CUSIP No.
    Y18284177


    1Names of Reporting Persons

    Alta Partners LLC
    2Check the appropriate box if a member of a Group (see instructions)

    Checkbox not checked  (a)
    Checkbox not checked  (b)
    3Sec Use Only
    4Citizenship or Place of Organization

    NEW YORK
    Number of Shares Beneficially Owned by Each Reporting Person With:
    5Sole Voting Power

    56,176.00
    6Shared Voting Power

    0.00
    7Sole Dispositive Power

    56,176.00
    8Shared Dispositive Power

    0.00
    9Aggregate Amount Beneficially Owned by Each Reporting Person

    56,176.00
    10Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

    Checkbox not checked
    11Percent of class represented by amount in row (9)

    5.2 %
    12Type of Reporting Person (See Instructions)

    OO


    SCHEDULE 13G

    Item 1. 
    (a)Name of issuer:

    C3is Inc.
    (b)Address of issuer's principal executive offices:

    331 KIFISSIAS AVENUE, ERITHREA, ATHENS, GREECE, 14561
    Item 2. 
    (a)Name of person filing:

    Alta Partners LLC
    (b)Address or principal business office or, if none, residence:

    1205 Franklin Avenue Garden City, New York 11530
    (c)Citizenship:

    New York Limited Liability Company
    (d)Title of class of securities:

    Common Stock, par value $0.01 per share
    (e)CUSIP No.:

    Y18284177
    Item 3.If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
    (a)Checkbox not checked   Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
    (b)Checkbox not checked   Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
    (c)Checkbox not checked   Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
    (d)Checkbox not checked   Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
    (e)Checkbox not checked   An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
    (f)Checkbox not checked   An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
    (g)Checkbox not checked   A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
    (h)Checkbox not checked   A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
    (i)Checkbox not checked   A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
    (j)Checkbox not checked   A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
           please specify the type of institution:
    (k)Checkbox not checked   Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
     
    Item 4.Ownership
    (a)Amount beneficially owned:

    56,176 shares, representing shares issuable upon exercise of warrants.
    (b)Percent of class:

    5.2%
    (c)Number of shares as to which the person has:
     (i) Sole power to vote or to direct the vote:

    56,176 shares

     (ii) Shared power to vote or to direct the vote:

    0 shares

     (iii) Sole power to dispose or to direct the disposition of:

    56,176 shares

     (iv) Shared power to dispose or to direct the disposition of:

    0 shares

    Item 5.Ownership of 5 Percent or Less of a Class.
     
    Not Applicable
    Item 6.Ownership of more than 5 Percent on Behalf of Another Person.
     
    Not Applicable
    Item 7.Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
     
    Not Applicable
    Item 8.Identification and Classification of Members of the Group.
     
    Not Applicable
    Item 9.Notice of Dissolution of Group.
     
    Not Applicable

    Item 10.Certifications:
     
    By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

        SIGNATURE 
     
    After reasonable 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.

     
    Alta Partners LLC
     
    Signature:/s/ Steven Cohen
    Name/Title:Steven Cohen, Managing Member
    Date:02/27/2026
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