Adage Capital Management, L.P. and affiliated filers reported ownership of 2,100,000 Class A Ordinary Shares of Mountain Lake Acquisition Corp. II. The filing states this represents 5.68% of the class based on 36,980,000 shares outstanding as of March 20, 2026. The holdings are reported as shared voting and dispositive power through affiliated entities.
Positive
None.
Negative
None.
Insights
Adage reports a 5.68% passive position in MLAA held via affiliated partnerships.
The Schedule 13G shows 2,100,000 shares held with shared voting and dispositive power through Adage entities. The filing cites an outstanding base of 36,980,000 shares as of March 20, 2026, which is the denominator for the percentage.
Holdings are presented under joint filing arrangements; timing and any future trading intentions are not stated in the excerpt.
Disclosure clarifies control lines: shared voting/dispositive authority via investment manager and affiliated GP entities.
The statement identifies Adage Capital Management, L.P., Robert Atchinson and Phillip Gross as Reporting Persons and describes the governance structure (ACM, ACP, ACA, ACPLLC, ACPGP). Signatures include both entity and individual attestations.
Useful for tracking large-holder registers and potential coordination among affiliated holders; no transaction activity or intent is disclosed here.
Key Figures
Shares owned:2,100,000 sharesPercent of class:5.68%Shares outstanding:36,980,000 shares
3 metrics
Shares owned2,100,000 sharesAmount beneficially owned by Adage and affiliated filers
Percent of class5.68%Calculated using 36,980,000 shares outstanding as of March 20, 2026
Shares outstanding36,980,000 sharesShares outstanding used as denominator, as reported in Form 10-K
Key Terms
Schedule 13G, beneficially owned, shared dispositive power
3 terms
Schedule 13Gregulatory
"This statement is filed by: Adage Capital Management, L.P."
A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.
beneficially ownedregulatory
"Amount beneficially owned: The information required by Item 4(a)"
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.
Adage Capital and affiliated filers report ownership of 2,100,000 Class A shares, representing 5.68% of the class. This percentage uses a base of 36,980,000 shares outstanding as of March 20, 2026.
Who are the reporting persons on the Schedule 13G for MLAA?
The filing is by Adage Capital Management, L.P., and affiliated reporting persons Robert Atchinson and Phillip Gross, identifying their roles with the related Adage entities and partnerships.
Does the filing state whether Adage has sole voting power over the shares?
No. The filing shows 0 sole voting power and reports shared voting power and shared dispositive power over the 2,100,000 shares held through affiliated entities.
What date is used to calculate the percentage ownership in the MLAA filing?
The percentage is calculated using 36,980,000 Class A Ordinary Shares outstanding as of March 20, 2026, as reported in the company’s Form 10-K for the year ended December 31, 2025.
Does the Schedule 13G disclose intent to buy or sell MLAA shares?
The excerpt does not state any intent to buy or sell. It presents a passive ownership report under a joint filing agreement and does not disclose trading plans or intentions.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Mountain Lake Acquisition Corp. II
(Name of Issuer)
Class A Ordinary Shares, par value $0.0001 per share
(Title of Class of Securities)
G6301L109
(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):
G6301L109
1
Names of Reporting Persons
Adage Capital Management, 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,100,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,100,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,100,000.00
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)
5.68 %
12
Type of Reporting Person (See Instructions)
IA, PN
SCHEDULE 13G
CUSIP Number(s):
G6301L109
1
Names of Reporting Persons
Robert Atchinson
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
2,100,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,100,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,100,000.00
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)
5.68 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
CUSIP Number(s):
G6301L109
1
Names of Reporting Persons
Phillip Gross
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
2,100,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,100,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,100,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
This statement is filed by:
(i) Adage Capital Management, L.P., a Delaware limited partnership ("ACM"), as the investment manager of Adage Capital Partners, L.P., a Delaware limited partnership ("ACP"), with respect to the Class A Ordinary Shares, par value $0.0001 per share ("Class A Ordinary Shares") of Mountain Lake Acquisition Corp. II, a Cayman Islands exempted company (the "Company") directly held by ACP;
(ii) Robert Atchinson ("Mr. Atchinson"), as (1) managing member of Adage Capital Advisors, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACA"), managing member of Adage Capital Partners GP, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACPGP"), general partner of ACP, and (2) managing member of Adage Capital Partners, L.L.C., a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Class A Ordinary Shares directly held by ACP; and
(iii) Phillip Gross ("Mr. Gross"), as (1) managing member of ACA, managing member of ACPGP, and (2) managing member of ACPLLC, general partner of ACM, with respect to the Class A Ordinary Shares directly held by ACP.
The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party.
The filing of this statement should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein.
(b)
Address or principal business office or, if none, residence:
The address of the business office of each of the Reporting Persons is 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116.
(c)
Citizenship:
ACM is a limited partnership organized under the laws of the State of Delaware. Messrs. Gross and Atchinson are citizens of the United States.
(d)
Title of class of securities:
Class A Ordinary Shares, par value $0.0001 per share
(e)
CUSIP Number(s):
G6301L109
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:
The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(b)
Percent of class:
The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 36,980,000 Class A Ordinary Shares outstanding as of March 20, 2026, as reported in the Company's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the Securities and Exchange Commission on March 20, 2026.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
5.68%
(ii) Shared power to vote or to direct the vote:
The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(iii) Sole power to dispose or to direct the disposition of:
The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(iv) Shared power to dispose or to direct the disposition of:
The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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.
See Item 2(a).
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 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.
Adage Capital Management, L.P.
Signature:
/s/ Robert Atchinson
Name/Title:
By: Adage Capital Partners, L.L.C., its General Partner, By: Robert Atchinson, its Managing Member
