Alta Partners discloses 1.17M C3is Inc. (CISS) shares under beneficial ownership

Rhea-AI Filing Summary

Alta Partners LLC filed an amended Schedule 13G reporting beneficial ownership of C3is Inc. common stock. Alta Partners reports owning 1,168,303 shares, including 1,140,000 shares of common stock and 28,303 shares issuable upon exercise of warrants.

This position represents 8.198% of the outstanding common stock class. Alta Partners has sole voting and sole dispositive power over all 1,168,303 shares and no shared voting or dispositive power.

Key Figures

Beneficially owned shares: 1,168,303 shares Common shares held: 1,140,000 shares Shares issuable upon exercise of warrants: 28,303 shares +3 more

6 metrics

Beneficially owned shares 1,168,303 shares Total C3is Inc. shares reported as beneficially owned by Alta Partners LLC

Common shares held 1,140,000 shares Portion of beneficial ownership consisting of C3is Inc. common stock

Shares issuable upon exercise of warrants 28,303 shares Part of beneficial ownership that would be received upon warrant exercise

Percent of class owned 8.198% Percentage of C3is Inc. common stock class beneficially owned by Alta Partners LLC

Sole voting power 1,168,303 shares Shares over which Alta Partners LLC has sole power to vote or direct the vote

Sole dispositive power 1,168,303 shares Shares over which Alta Partners LLC has sole power to dispose or direct disposition

Key Terms

beneficially owned, Sole Voting Power, Sole Dispositive Power, Percent of class

4 terms

beneficially owned financial

"Amount beneficially owned: 1,168,303 shares, consisting of 1,140,000 shares"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole Voting Power financial

"Sole Voting Power 1,168,303.00 6 | Shared Voting Power 0.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

Sole Dispositive Power financial

"Sole Dispositive Power 1,168,303.00 8 | Shared Dispositive Power 0.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Percent of class financial

"Percent of class: 8.198%"

Percent of class is the portion of a specific category of securities—such as a company’s common shares, preferred shares, or a bond series—that takes part in or approves a corporate action (vote, consent, tender, etc.). Investors watch this number because it reveals how much support or opposition exists within that particular shareholder group; like counting how many members of a club back a proposal, it can determine whether a plan passes or how influence is distributed.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/03/2026 - 04:20 PM Accepted by SEC EDGAR 08/03/2026 - 04:19 PM Learn about SEC filing dates

FAQ

What stake in C3is Inc. (CISS) does Alta Partners LLC report?

Alta Partners LLC reports beneficial ownership of 1,168,303 C3is Inc. shares. This consists of 1,140,000 common shares and 28,303 shares issuable upon exercise of warrants, representing 8.198% of the company’s common stock class.

What percentage of C3is Inc. (CISS) does Alta Partners LLC own?

Alta Partners LLC reports owning 8.198% of C3is Inc.’s common stock. This percentage is based on its beneficial ownership of 1,168,303 shares, including both common shares and shares issuable upon exercise of outstanding warrants.

How many C3is Inc. (CISS) shares owned by Alta Partners LLC come from warrants?

Alta Partners LLC’s reported stake includes 28,303 shares issuable upon exercise of warrants. The remainder of its 1,168,303 total beneficially owned shares consists of 1,140,000 shares of C3is Inc. common stock already outstanding.

Does Alta Partners LLC share voting power over its C3is Inc. (CISS) shares?

Alta Partners LLC reports sole voting power over 1,168,303 shares of C3is Inc. and no shared voting power. It likewise has sole dispositive power over 1,168,303 shares and no shared dispositive power according to the filing.

Who signed the C3is Inc. (CISS) ownership report for Alta Partners LLC?

The report was signed by Steven Cohen, Managing Member of Alta Partners LLC. His signature appears on the document dated 08/03/2026, certifying the accuracy of the disclosed beneficial ownership information for C3is Inc.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

C3is Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

Y18284300

(CUSIP Number)

07/28/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): Y18284300

1

Names of Reporting Persons

Alta Partners LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

NEW YORK

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,168,303.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,168,303.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,168,303.00

10

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

11

Percent of class represented by amount in row (9)

8.2 %

12

Type 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, 331 KIFISSIAS AVENUE, 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.: Y18284300
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)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	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)	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)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 1,168,303 shares, consisting of 1,140,000 shares of Common Stock and 28,303 shares issuable upon exercise of warrants held by the Reporting Person.
(b)	Percent of class: 8.198%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 1,168,303
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 1,168,303
	(iv) Shared power to dispose or to direct the disposition of: 0
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 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:	08/03/2026