BlackRock reports 6.8% stake in SELLAS

SELLAS LIFE SCIENCES GROUP INC ownership update: BlackRock, Inc. reports beneficial ownership of 12,136,331 shares, representing 6.8% of common stock.

Rhea-AI Filing Summary

SELLAS LIFE SCIENCES GROUP INC ownership update: BlackRock, Inc. reports beneficial ownership of 12,136,331 shares, representing 6.8% of common stock. The filing attributes sole voting power for 11,966,938 shares and sole dispositive power for 12,136,331 shares, reported by a Managing Director.

Insights

Institutional Ownership Analyst

BlackRock discloses a 6.8% stake in SELLAS (SLS) held through reporting business units.

BlackRock's Schedule 13G/A lists 12,136,331 shares beneficially owned with sole voting power over 11,966,938 shares. The filing notes holdings reflect aggregated Reporting Business Units per SEC Release No. 34-39538.

Cash-flow treatment and specific business-unit breakdown are not included in the excerpt; subsequent filings may provide additional allocation details.

Key Figures

Beneficial ownership: 12,136,331 shares Percent of class: 6.8% Sole voting power: 11,966,938 shares +1 more

4 metrics

Beneficial ownership 12,136,331 shares Amount beneficially owned reported on Schedule 13G/A

Percent of class 6.8% Percent of common stock beneficially owned

Sole voting power 11,966,938 shares Number with sole power to vote or direct the vote

Sole dispositive power 12,136,331 shares Number with sole power to dispose or direct disposition

Key Terms

Schedule 13G/A, beneficially owned, sole dispositive power, Reporting Business Units

4 terms

Schedule 13G/A regulatory

"In accordance with SEC Release No. 34-39538 (January 12, 1998)"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially owned financial

"Amount beneficially owned: 12136331"

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 dispositive power financial

"Sole power to dispose or to direct the disposition of: 12136331"

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.

Reporting Business Units financial

"reflects the securities beneficially owned ... by certain business units"

FAQ

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

What stake does BlackRock report in SELLAS LIFE SCIENCES GROUP (SLS)?

BlackRock reports beneficial ownership of 12,136,331 shares, equal to 6.8% of SELLAS common stock. The filing lists sole voting power for 11,966,938 shares and sole dispositive power for 12,136,331 shares.

What does Schedule 13G/A mean for BlackRock's filing on SLS?

Schedule 13G/A is a passive investor disclosure; BlackRock states the filing reflects holdings of aggregated Reporting Business Units under SEC Release No. 34-39538. It reports ownership and voting/dispositive powers rather than transaction activity.

Who signed the BlackRock Schedule 13G/A for SELLAS (SLS)?

The filing is signed by Spencer Fleming, identified as Managing Director, with the signature date shown as 04/24/2026. The cover lists BlackRock's principal office at 50 Hudson Yards, New York, NY.

Does the filing identify other holders or delegation within BlackRock?

The filing explains amounts reflect securities held by certain Reporting Business Units of BlackRock and its affiliates. It does not provide a unit-level breakdown or name individual sub-holders in the provided excerpt.

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

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Accepted by SEC EDGAR 04/24/2026 - 04:11 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. 1)

SELLAS LIFE SCIENCES GROUP INC

(Name of Issuer)

Common Stock

(Title of Class of Securities)

81642T209

(CUSIP Number)

03/31/2026

(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

BlackRock, Inc.

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 11,966,938.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 12,136,331.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

12,136,331.00

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)

6.8 %

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: 7 TIMES SQUARE, SUITE 2503 NEW YORK NY 10036
Item 2.
(a)	Name of person filing: BlackRock, Inc. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units (collectively, the "Reporting Business Units") of BlackRock, Inc. and its subsidiaries and affiliates. It does not include securities, if any, beneficially owned by other business units whose beneficial ownership of securities are disaggregated from that of the Reporting Business Units in accordance with such release.
(b)	Address or principal business office or, if none, residence: BlackRock, Inc., 50 Hudson Yards New York, NY 10001
(c)	Citizenship: See Item 4 of Cover Page
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 81642T209
Item 4.	Ownership
(a)	Amount beneficially owned: 12136331
(b)	Percent of class: 6.8 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 11966938
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 12136331
	(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.
	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. Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of SELLAS LIFE SCIENCES GROUP INC. No one person's interest in the common stock of SELLAS LIFE SCIENCES GROUP INC is more than five percent of the total outstanding common shares.
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. See Exhibit 99
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.

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.

BlackRock, Inc.

Signature:	Spencer Fleming
Name/Title:	Managing Director
Date:	04/24/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7