C3is: Alta Partners reports 3.072% ownership stake

The reported position includes 34,773 shares issuable upon exercise of warrants, alongside 12,000 common shares.

Rhea-AI Filing Summary

C3is Inc.’s amended beneficial-ownership disclosure reports that Alta Partners LLC beneficially owned 46,773 shares, or 3.072% of the class. The amount consists of 12,000 common shares and 34,773 shares issuable upon exercise of warrants. Alta Partners reported sole voting and dispositive power over 46,773 shares in each category, with shared voting and dispositive power of zero. Steven Cohen signed as Alta Partners’ Managing Member.

Key Figures

Beneficial ownership: 46,773 shares Percent of class: 3.072% Common Stock: 12,000 shares +2 more

5 metrics

Beneficial ownership 46,773 shares Alta Partners LLC

Percent of class 3.072% Alta Partners LLC's reported beneficial ownership

Common Stock 12,000 shares Included in Alta Partners LLC's reported beneficial ownership

Shares issuable upon exercise of warrants 34,773 shares Included in Alta Partners LLC's reported beneficial ownership

Shared voting and dispositive power 0 shares Reported for each power category

Key Terms

beneficially owned, warrants, Sole power to dispose or to direct the disposition

3 terms

beneficially owned financial

"Amount beneficially owned: 46,773 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.

warrants financial

"34,773 shares issuable upon exercise of warrants"

Warrants are special documents that give you the right to buy a company's stock at a set price before a certain date. They are often used as a way for companies to attract investors or raise money, and their value can increase if the company's stock price goes up.

Sole power to dispose or to direct the disposition technical

"Sole power to dispose or to direct the disposition of: 46,773"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many CISS shares did Alta Partners report owning?

Alta Partners LLC reported beneficial ownership of 46,773 shares, or 3.072% of the class. The amount consists of 12,000 common shares and 34,773 shares issuable upon exercise of warrants.

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

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Available on EDGAR 10/05/2026 - 04:06 PM Accepted by SEC EDGAR 10/05/2026 - 04:06 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)

C3is Inc.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

Y18284409

(CUSIP Number)

08/26/2026

(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): Y18284409

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 46,773.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 46,773.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

46,773.00

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)

3.1 %

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, 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.: Y18284409
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: 46,773 shares, consisting of 12,000 shares of Common Stock and 34,773 shares issuable upon exercise of warrants held by the Reporting Person.
(b)	Percent of class: 3.072%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 46,773
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 46,773
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
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:	10/05/2026