Commodore Group discloses 1.95M KPTI stake; 19,618,032 shares O/S

Rhea-AI Filing Summary

Karyopharm Therapeutics Inc. Schedule 13G shows Commodore Capital and related filers report beneficial ownership of 1,950,000 shares of Common Stock, representing 9.9% of the class. The filing states the ownership is based on 19,618,032 shares outstanding as of March 23, 2026.

Key Figures

Beneficial ownership: 1,950,000 shares Percent of class: 9.9% Shares outstanding: 19,618,032 shares

3 metrics

Beneficial ownership 1,950,000 shares Aggregate position reported by Commodore filers as of <date> March 26, 2026

Percent of class 9.9% Percent of common stock calculated using outstanding shares as of <date> March 23, 2026

Shares outstanding 19,618,032 shares Issuer's shares reported as issued and outstanding as of <date> March 23, 2026

Key Terms

Schedule 13G, Beneficially own, Shared Dispositive Power

3 terms

Schedule 13G regulatory

"This report on is being filed by Commodore Capital LP"

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 own financial

"the Firm may be deemed to beneficially own an aggregate of 1,950,000 shares"

Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.

Shared Dispositive Power regulatory

"Shared Dispositive Power 1,950,000.00"

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Accepted by SEC EDGAR 04/02/2026 - 04:26 PM Learn about SEC filing dates

FAQ

What stake does Commodore Capital report in KPTI?

Commodore Capital reports beneficial ownership of 1,950,000 shares of Karyopharm common stock. The filing states this equals 9.9% of the class, calculated using 19,618,032 shares outstanding as of March 23, 2026.

Who are the filers on the Schedule 13G for KPTI?

The filing is by Commodore Capital LP, Commodore Capital Master LP, and managing partners Michael Kramarz and Robert Egen Atkinson. Addresses for the filers are included in the filing cover information.

How is the 9.9% ownership calculated in the filing?

The percentage is based on 19,618,032 shares reported as issued and outstanding as of March 23, 2026. The filers state their aggregate beneficial ownership of 1,950,000 shares against that outstanding base.

Does the Schedule 13G indicate voting or dispositive powers?

The filing reports shared voting power and shared dispositive power of 1,950,000 shares for the listed filers. Sole voting and dispositive powers are reported as 0 in the cover data.

What date does the report use for the beneficial ownership amount?

The beneficial ownership is stated "as of March 26, 2026" for the filers' position, while outstanding shares used for the percentage are from March 23, 2026 as cited in the filing.

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, $0.0001 par value

(Title of Class of Securities)

48576U205

(CUSIP Number)

03/26/2026

(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

Commodore Capital LP

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 1,950,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,950,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,950,000.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): 48576U205

1

Names of Reporting Persons

Commodore Capital Master LP

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

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,950,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,950,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,950,000.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP Number(s): 48576U205

1

Names of Reporting Persons

Robert Egen Atkinson

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 1,950,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,950,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,950,000.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): 48576U205

1

Names of Reporting Persons

Michael Kramarz

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 1,950,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,950,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,950,000.00

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)

9.9 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Karyopharm Therapeutics Inc.
(b)	Address of issuer's principal executive offices: 85 Wells Avenue, 2nd Floor, Newton, MASSACHUSETTS, 02459.
Item 2.
(a)	Name of person filing: Commodore Capital LP Commodore Capital Master LP Robert Egen Atkinson Michael Kramarz Each a "Filer."
(b)	Address or principal business office or, if none, residence: The address for Commodore Capital LP, Robert Egen Atkinson, and Michael Kramarz is 444 Madison Avenue, Floor 35, New York, NY 10022. The address for Commodore Capital Master LP is c/o Maples Corporate Services Limited, Ugland House, South Church Street, PO Box 309, Grand Cayman KY1-1104, Cayman Islands.
(c)	Citizenship: See Item 4 of the cover page for each Filer.
(d)	Title of class of securities: Common Stock, $0.0001 par value
(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: See Item 9 of the cover page for each Filer. This report on Schedule 13G is being filed by Commodore Capital LP (the "Firm"), Commodore Capital Master LP ("Commodore Master"), Michael Kramarz, and Robert Egen Atkinson. The Firm is the investment manager to Commodore Master. As of March 26, 2026, the Firm may be deemed to beneficially own an aggregate of 1,950,000 shares Common Stock, $0.0001 par value (the "Common Stock"), of Karyopharm Therapeutics Inc. (the "Issuer"). The Firm, as the investment manager to Commodore Master, may be deemed to beneficially own these securities. Michael Kramarz and Robert Egen Atkinson are the managing partners of the Firm and exercise investment discretion with respect to these securities. Ownership percentages are based on 19,618,032 Common Stock reported as issued and outstanding as of March 23, 2026 in the Issuer's Current Report on Form 8-K filed with the Securities and Exchange Commission on March 24, 2026.
(b)	Percent of class: See Item 11 of the cover page for each Filer.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See Item 5 of the cover page for each Filer.
	(ii) Shared power to vote or to direct the vote: See Item 6 of the cover page for each Filer.
	(iii) Sole power to dispose or to direct the disposition of: See Item 7 of the cover page for each Filer.
	(iv) Shared power to dispose or to direct the disposition of: See Item 8 of the cover page for each Filer.
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.

Commodore Capital LP

Signature:	Michael Kramarz
Name/Title:	Managing Partner
Date:	04/02/2026

Commodore Capital Master LP

Signature:	Michael Kramarz
Name/Title:	Authorized Signatory
Date:	04/02/2026

Robert Egen Atkinson

Signature:	Robert Egen Atkinson
Name/Title:	Authorized Signatory
Date:	04/02/2026

Michael Kramarz

Signature:	Michael Kramarz
Name/Title:	Authorized Signatory
Date:	04/02/2026

Exhibit Information

Exhibit 1: Joint Filing Agreement