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State Street Corporation reported beneficial ownership of 10,373,074 shares of SELLAS Life Sciences Group, Inc. (SLS) common stock, equal to 5.1% of the class, as of September 30, 2026. It reported shared voting power over 9,945,783 shares and shared dispositive power over 10,373,074 shares; sole voting power and sole dispositive power were each 0 shares. The report names SSGA Funds Management, Inc. and State Street Global Advisors subsidiaries in connection with the reported securities.
Key Figures
Beneficial ownership:10,373,074 sharesPercent of class:5.1%Shared voting power:9,945,783 shares+3 more
6 metrics
Beneficial ownership10,373,074 sharesAs of September 30, 2026
Percent of class5.1%State Street Corporation's reported ownership
Shared voting power9,945,783 sharesReported by State Street Corporation
Shared dispositive power10,373,074 sharesReported by State Street Corporation
Sole voting power0 sharesReported by State Street Corporation
Sole dispositive power0 sharesReported by State Street Corporation
Key Terms
beneficially owned, shared voting power, shared dispositive power, sole voting power
4 terms
beneficially ownedregulatory
"Amount beneficially owned: 10,373,074"
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.
shared voting powerregulatory
"Shared Voting Power 9,945,783"
Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.
shared dispositive powerregulatory
"Shared Dispositive Power 10,373,074"
sole voting powerregulatory
"Sole Voting Power 0"
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.
FAQ
AI-generated questions and answers. How Rhea-AI works. Not financial advice.
How many SLS shares does State Street Corporation beneficially own?
State Street Corporation reported beneficial ownership of 10,373,074 SLS common shares, equal to 5.1% of the class, as of September 30, 2026.
How much SLS stock can State Street Corporation vote or dispose of?
State Street Corporation reported shared voting power over 9,945,783 shares and shared dispositive power over 10,373,074 shares. Sole voting power and sole dispositive power were each 0 shares.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
SELLAS LIFE SCIENCES GROUP INC
(Name of Issuer)
COMMON STOCK
(Title of Class of Securities)
81642T209
(CUSIP Number)
09/30/2026
(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):
81642T209
1
Names of Reporting Persons
STATE STREET CORPORATION
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
MASSACHUSETTS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
9,945,783.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
10,373,074.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
10,373,074.00
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)
5.1 %
12
Type of Reporting Person (See Instructions)
HC
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
SELLAS LIFE SCIENCES GROUP INC
(b)
Address of issuer's principal executive offices:
15 WEST 38TH STREET 10TH FLOOR, NEW YORK, NEW YORK, 10018
Item 2.
(a)
Name of person filing:
STATE STREET CORPORATION;
(b)
Address or principal business office or, if none, residence:
ONE CONGRESS STREET, SUITE 1, BOSTON MA 02114, UNITED STATES
(c)
Citizenship:
MA
(d)
Title of class of securities:
COMMON STOCK
(e)
CUSIP Number(s):
81642T209
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:
10373074.00
(b)
Percent of class:
5.1 %
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
0
(ii) Shared power to vote or to direct the vote:
9,945,783
(iii) Sole power to dispose or to direct the disposition of:
0
(iv) Shared power to dispose or to direct the disposition of:
10,373,074
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.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
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.
If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary.
SSGA FUNDS MANAGEMENT, INC. (IA);STATE STREET GLOBAL ADVISORS EUROPE LIMITED (IA);STATE STREET GLOBAL ADVISORS LIMITED (IA);STATE STREET GLOBAL ADVISORS TRUST COMPANY (IA);STATE STREET GLOBAL ADVISORS, LTD. (IA);
Item 8.
Identification and Classification of Members of the Group.
If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(K), so indicate under Item 3(k) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group.
NOT APPLICABLE
Item 9.
Notice of Dissolution of Group.
Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5.
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.
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.
