Adage Capital Management and affiliated reporting persons disclose beneficial ownership of 1,821,736 shares of Karyopharm Therapeutics common stock, representing 8.08% of the class. This percentage is calculated on an aggregate of 22,543,316 shares outstanding as of March 26, 2026 and assumes exercise of warrants exercisable for 15,414 shares held by Adage Capital Partners, L.P.
The filing attributes shared voting and shared dispositive power for the reported shares to the reporting persons and lists the reporting entities and individuals (Adage Capital Management, L.P.; Robert Atchinson; Phillip Gross) with their Boston business address. Signatures are dated May 13, 2026.
Positive
None.
Negative
None.
Insights
Adage discloses an 8.08% stake in Karyopharm with shared control and minor warrant exposure.
Adage Capital Management and affiliated reporting persons report beneficial ownership of 1,821,736 shares, representing 8.08% of the company's common stock on a March 26, 2026 outstanding base of 22,543,316 shares. The position includes 15,414 shares issuable upon exercise of warrants held by Adage Capital Partners, L.P.
Ownership is reported as shared voting and shared dispositive power. Future disclosure of trades or amendments would clarify active buying or selling; current filings show the aggregated ownership position and legal attribution only.
Key Figures
Beneficial ownership:1,821,736 sharesPercent of class:8.08%Shares outstanding:22,543,316 shares+3 more
6 metrics
Beneficial ownership1,821,736 sharesreported holdings by Adage and reporting persons
Percent of class8.08%calculated on outstanding shares as of March 26, 2026
Shares outstanding22,543,316 sharesaggregate outstanding used to compute percentage as of March 26, 2026
Warrants issuable15,414 sharesshares issuable upon exercise of warrants held by Adage Capital Partners, L.P.
Signature date05/13/2026date signatures were executed on the filing
CUSIP48576U205Karyopharm common stock CUSIP included on cover page
"This statement is filed by: (i) 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.
Shared Dispositive Powerregulatory
"Shared Dispositive Power 1,821,736.00"
Warrants issuablefinancial
"Includes 15,414 shares of Common Stock issuable upon exercise of warrants."
Adage reports beneficial ownership of 1,821,736 shares, equal to 8.08% of common stock, calculated on March 26, 2026 based on 22,543,316 shares outstanding.
Does the reported stake include warrants for KPTI?
Yes. The reported 1,821,736 shares figure includes15,414 shares issuable upon exercise of warrants directly held by Adage Capital Partners, L.P.
Who are the reporting persons listed on the Schedule 13G for KPTI?
The Schedule 13G is filed by Adage Capital Management, L.P. with named individuals Robert Atchinson and Phillip Gross acting in their managing member capacities.
What voting and dispositive powers are reported by Adage for KPTI shares?
The filing reports 0 sole voting power and 1,821,736 shared voting power, along with 0 sole dispositive power and 1,821,736 shared dispositive power for the reported holdings.
What outstanding share base was used to calculate the 8.08% stake in KPTI?
The percentage is calculated using an aggregate of 22,543,316 shares of common stock outstanding as of March 26, 2026, per the filing's disclosed anchor.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Karyopharm Therapeutics Inc.
(Name of Issuer)
Common Stock, par value $0.0001 per share
(Title of Class of Securities)
48576U205
(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):
48576U205
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
1,821,736.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,821,736.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,821,736.00
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)
8.08 %
12
Type of Reporting Person (See Instructions)
IA, PN
Comment for Type of Reporting Person: Includes 15,414 shares of Common Stock (as defined in Item 2(a)) issuable upon exercise of warrants.
SCHEDULE 13G
CUSIP Number(s):
48576U205
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
1,821,736.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,821,736.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,821,736.00
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)
8.08 %
12
Type of Reporting Person (See Instructions)
HC, IN
Comment for Type of Reporting Person: Includes 15,414 shares of Common Stock (as defined in Item 2(a)) issuable upon exercise of warrants.
SCHEDULE 13G
CUSIP Number(s):
48576U205
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
1,821,736.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,821,736.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,821,736.00
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)
8.08 %
12
Type of Reporting Person (See Instructions)
HC, IN
Comment for Type of Reporting Person: Includes 15,414 shares of Common Stock (as defined in Item 2(a)) issuable upon exercise of warrants.
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 common stock, par value $0.0001 per share ("Common Stock") of Karyopharm Therapeutics Inc., a Delaware corporation (the "Company") and shares of Common Stock issuable upon exercise of warrants 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 Common Stock and shares of Common Stock issuable upon exercise of warrants 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 Common Stock and shares of Common Stock issuable upon exercise of warrants 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:
Common Stock, par value $0.0001 per share
(e)
CUSIP Number(s):
48576U205
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.
The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 22,543,316 shares of Common Stock outstanding as of March 26, 2026, as reported in the Company's Current Report on Form 8-K filed with the Securities and Exchange Commission on March 27, 2026, and assumes the exercise of the warrants to purchase shares of Common Stock held by ACP.
(b)
Percent of class:
8.08%
(c)
Number of shares as to which the person has:
(i) Sole 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.
(ii) Shared power to vote or to direct the vote:
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
(iii) Sole 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.
(iv) Shared power to dispose or to direct the disposition of:
The information required by Item 4(c)(iv) is set forth in Row 8 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
