ProMIS Neurosciences (PMN) gets 7.77% stake disclosure by Wellington fund

Rhea-AI Filing Summary

Wellington Biomedical Innovation Master Investors (Cayman) II, L.P. filed an amended ownership report for ProMIS Neurosciences, Inc. common stock. The fund reports beneficial ownership of 696,378 shares, representing 7.77% of the class. All of these shares are held with shared voting and shared dispositive power, with no sole voting or dispositive authority reported. The reporting person is organized in the Cayman Islands, with its principal business office in Boston, Massachusetts, and files this as Amendment No. 1 to its Schedule 13G.

Key Figures

Shares beneficially owned: 696,378 shares Percent of class: 7.77% Shared voting power: 696,378 shares +2 more

5 metrics

Shares beneficially owned 696,378 shares Common stock of ProMIS Neurosciences, Inc. reported by Wellington Biomedical Innovation Master Investors (Cayman) II, L.P.

Percent of class 7.77% Percentage of ProMIS Neurosciences, Inc. common stock class beneficially owned

Shared voting power 696,378 shares Shares over which the reporting person has shared power to vote or direct the vote

Sole voting power 0 shares Shares over which the reporting person has sole power to vote or direct the vote

Shared dispositive power 696,378 shares Shares over which the reporting person has shared power to dispose or direct disposition

Key Terms

beneficially owned, Schedule 13G/A, shared voting power, dispositive power

4 terms

beneficially owned financial

"Amount beneficially owned: 696,378"

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.

Schedule 13G/A regulatory

"filed as Amendment No. 1 to its Schedule 13G"

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.

shared voting power financial

"Shared power to vote or to direct the vote: 696,378"

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.

dispositive power financial

"Shared power to dispose or to direct the disposition of: 696,378"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

FAQ

What ownership stake in PMN does Wellington Biomedical Innovation Master Investors (Cayman) II, L.P. report?

Wellington Biomedical Innovation Master Investors (Cayman) II, L.P. reports beneficial ownership of 696,378 shares of ProMIS Neurosciences, Inc. common stock, representing 7.77% of the outstanding class, according to its Schedule 13G/A Amendment No. 1 filing.

Does the Wellington fund have sole or shared voting power over its PMN shares?

The fund reports 0 shares with sole voting power and 696,378 shares with shared voting power. It similarly shows no sole dispositive power and shared dispositive power over the same 696,378 shares of ProMIS Neurosciences, Inc.

What type of security in PMN is reported by Wellington Biomedical Innovation Master Investors (Cayman) II, L.P.?

The position reported is in common stock of ProMIS Neurosciences, Inc. The Schedule 13G/A identifies the title of the class of securities as common stock with CUSIP number 74346M505.

Where is the reporting person for this PMN Schedule 13G/A organized and located?

Wellington Biomedical Innovation Master Investors (Cayman) II, L.P. is organized in the Cayman Islands, with its principal business office at 280 Congress Street, Boston, MA 02210, c/o Wellington Management Company LLP.

Who signed the Schedule 13G/A for PMN on behalf of the Wellington fund?

The filing is signed by Ihsan Speede as an Authorized Person. The comments indicate the signatory acts for Wellington Alternative Investments LLC, the general partner of Wellington Biomedical Innovation Master Investors (Cayman) II, L.P.

What percentage of PMN’s common stock class is reported as beneficially owned in this filing?

The filing reports that 7.77% of ProMIS Neurosciences, Inc. common stock is beneficially owned by Wellington Biomedical Innovation Master Investors (Cayman) II, L.P., based on the total outstanding shares of that class.

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Available on EDGAR 08/13/2026 - 04:30 PM Accepted by SEC EDGAR 08/13/2026 - 04:29 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)

ProMIS Neurosciences, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

74346M505

(CUSIP Number)

06/30/2026

(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): 74346M505

1

Names of Reporting Persons

Wellington Biomedical Innovation Master Investors (Cayman) II, L.P.

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

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 696,378.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 696,378.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

696,378.00

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)

7.8 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: ProMIS Neurosciences, Inc.
(b)	Address of issuer's principal executive offices: Suite 200, 1920 Yonge Street, Toronto ON M4S 3E2
Item 2.
(a)	Name of person filing: Wellington Biomedical Innovation Master Investors (Cayman) II, L.P.
(b)	Address or principal business office or, if none, residence: c/o Wellington Management Company LLP, 280 Congress Street, Boston MA 02210
(c)	Citizenship: Cayman Islands
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 74346M505
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: 696,378
(b)	Percent of class: 7.77 %
(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: 696,378
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 696,378
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.

Wellington Biomedical Innovation Master Investors (Cayman) II, L.P.

Signature:	Ihsan Speede
Name/Title:	Authorized Person
Date:	08/14/2026

Comments accompanying signature: Wellington Alternative Investments LLC; Its General Partner Signature: Ihsan Speede Name/Title: Authorized Person Date: 08/14/2026