RA Capital boosts Karyopharm (KPTI) stake to 9.99% beneficial ownership cap

Rhea-AI Filing Summary

RA Capital Management, L.P. and affiliated reporting persons report beneficial ownership of 2,302,504 shares of Karyopharm Therapeutics Inc. common stock as of June 30, 2026, representing 9.99% of the class. The position is held through RA Capital Healthcare Fund, L.P., with all voting and dispositive power shared among the reporting persons.

The Fund directly holds 1,917,354 shares of common stock plus pre-funded and common warrants. Warrant exercises are limited by Beneficial Ownership Blockers that prevent ownership above 9.99% of outstanding common stock.

Key Figures

Beneficially owned shares: 2,302,504 shares Beneficial ownership percentage: 9.99% Shares outstanding baseline: 22,662,943 shares +5 more

8 metrics

Beneficially owned shares 2,302,504 shares Shares of Karyopharm common stock beneficially owned by the reporting persons as of June 30, 2026

Beneficial ownership percentage 9.99% Beneficial ownership of Karyopharm common stock limited by Beneficial Ownership Blockers

Shares outstanding baseline 22,662,943 shares Karyopharm common stock outstanding as of May 7, 2026, used to calculate ownership

Shares issuable upon warrant exercise 385,150 shares Portion of Karyopharm shares from warrants included in the 9.99% calculation

Common shares held by Fund 1,917,354 shares Karyopharm common stock directly held by RA Capital Healthcare Fund, L.P.

Pre-funded warrants 3,391,164 shares Karyopharm shares underlying pre-funded warrants held by the Fund

Common warrants 4,421,518 shares Karyopharm shares underlying common warrants held by the Fund

Shared voting and dispositive power 2,302,504 shares Shares over which each reporting person has shared voting and dispositive power

Key Terms

Beneficial Ownership Blockers, pre-funded warrants, Section 13(d) of the Act, Sole Voting Power, +1 more

5 terms

Beneficial Ownership Blockers regulatory

"Each of the Warrants contains a provision (the "Beneficial Ownership Blockers") which precludes exercise"

pre-funded warrants financial

"The Fund directly holds (i) 1,917,354 shares of common stock, (ii) pre-funded warrants exercisable"

Pre-funded warrants are financial instruments that give investors the right to purchase a company's stock at a set price, but with most or all of the purchase price paid upfront. They function like a coupon or gift card for stock, allowing investors to buy shares later at a fixed price, which can be beneficial if they want to avoid future price increases. This makes them important for investors seeking flexibility and certainty in their investment plans.

Section 13(d) of the Act regulatory

"may be deemed a beneficial owner, for purposes of Section 13(d) of the Act"

Sole Voting Power financial

"5 | Sole Voting Power 0.00 6 | Shared Voting Power 2,302,504.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

Shared Dispositive Power financial

"8 | Shared Dispositive Power 2,302,504.00"

FAQ

What percentage of KPTI does RA Capital report owning in this Schedule 13G/A?

RA Capital and related reporting persons report beneficial ownership of 9.99% of Karyopharm Therapeutics Inc. common stock, based on 22,662,943 shares outstanding plus 385,150 shares issuable upon warrant exercise as of the referenced dates.

How many KPTI shares does RA Capital beneficially own according to this filing?

The reporting persons disclose beneficial ownership of 2,302,504 shares of Karyopharm Therapeutics Inc. common stock. This includes currently held shares and warrant-based shares that can be counted under the 9.99% Beneficial Ownership Blocker limit.

What KPTI securities are held by RA Capital Healthcare Fund, L.P.?

RA Capital Healthcare Fund, L.P. holds 1,917,354 common shares, pre-funded warrants exercisable for up to 3,391,164 shares, and common warrants exercisable for up to 4,421,518 shares of Karyopharm Therapeutics Inc., subject to Beneficial Ownership Blockers.

How is the 9.99% KPTI ownership stake calculated in this Schedule 13G/A?

The 9.99% beneficial ownership is based on 22,662,943 shares of Karyopharm common stock outstanding as of May 7, 2026, plus 385,150 shares issuable upon warrant exercise. EDGAR cover-page percentages are rounded down to 9.9%.

Who are the reporting persons in the KPTI Schedule 13G/A amendment?

The reporting persons are RA Capital Management, L.P., Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P.. They disclaim group status and certain beneficial ownership except for determining obligations under Section 13(d).

What is the role of Beneficial Ownership Blockers in RA Capital’s KPTI position?

The warrants held by the Fund contain Beneficial Ownership Blockers that prevent exercise if it would cause ownership of Karyopharm common stock, together with affiliates, to exceed 9.99%, limiting exercisability at any time.

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

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Available on EDGAR 08/14/2026 - 04:45 PM Accepted by SEC EDGAR 08/14/2026 - 04:44 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)

Karyopharm Therapeutics Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

48576U205

(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): 48576U205

1

Names of Reporting Persons

RA 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 2,302,504.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,302,504.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,302,504.00

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

Peter Kolchinsky

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 2,302,504.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,302,504.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,302,504.00

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

Rajeev Shah

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 2,302,504.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,302,504.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,302,504.00

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

RA Capital Healthcare Fund, 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 2,302,504.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,302,504.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,302,504.00

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

Item 1.
(a)	Name of issuer: Karyopharm Therapeutics Inc.
(b)	Address of issuer's principal executive offices: 85 Wells Avenue, 2nd Floor, Newton, MA, 02459.
Item 2.
(a)	Name of person filing: The names of the persons filing this report (collectively, the "Reporting Persons") are: RA Capital Management, L.P. ("RA Capital") Peter Kolchinsky ("Dr. Kolchinsky") Rajeev Shah ("Mr. Shah") RA Capital Healthcare Fund, L.P. (the "Fund") The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G/A.
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each of the Reporting Persons is: c/o RA Capital Management, L.P., 200 Berkeley Street, 18th Floor, Boston MA 02116
(c)	Citizenship: RA Capital and the Fund are Delaware limited partnerships. Dr. Kolchinsky and Mr. Shah are United States citizens.
(d)	Title of class of securities: Common Stock, $0.0001 par value per share
(e)	CUSIP No.: 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: Row 9 of each Reporting Person's cover page to this Schedule 13G/A sets forth the aggregate number of shares of common stock of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. The Fund directly holds (i) 1,917,354 shares of common stock, (ii) pre-funded warrants (the "Pre-Funded Warrants") exercisable for up to 3,391,164 shares of common stock, and (iii) warrants (the "Common Warrants" and, together with the Pre-Funded Warrants, the "Warrants") exercisable for up to 4,421,518 shares of common stock. Each of the Warrants contains a provision (the "Beneficial Ownership Blockers") which precludes exercise of the Warrants to the extent that, following exercise, the Fund, together with its affiliates and other attribution parties, would own more than 9.99% of the common stock outstanding. The Fund is currently prohibited from exercising the Warrants to the extent that such exercise would result in the Reporting Persons' beneficial ownership of more than 2,302,504 shares of common stock. RA Capital Healthcare Fund GP, LLC is the general partner of the Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities of the Issuer held by the Fund. The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund's portfolio, including the shares of the Issuer's common stock reported herein. Because the Fund has divested voting and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days' notice, the Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13G/A other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13G/A shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah is the beneficial owner of such securities for any other purpose.
(b)	Percent of class: Due to the Beneficial Ownership Blocker listed in the Warrants, each Reporting Person's beneficial ownership percentage was 9.99% as of June 30, 2026. Such percentage is based upon the sum of (i) 22,662,943 shares of common stock outstanding as of May 7, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q, filed with the Securities and Exchange Commission (the "SEC") on May 14, 2026, and (ii) 385,150 shares of common stock issuable upon the exercise of the Warrants. Due to field limitations of the EDGAR filing system, the percentages listed in Row 11 of the Reporting Persons' cover pages have been rounded down to 9.9%.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Row 5 of each Reporting Person's cover page to this Schedule 13G/A sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
	(ii) Shared power to vote or to direct the vote: Row 6 of each Reporting Person's cover page to this Schedule 13G/A sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
	(iii) Sole power to dispose or to direct the disposition of: Row 7 of each Reporting Person's cover page to this Schedule 13G/A sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
	(iv) Shared power to dispose or to direct the disposition of: Row 8 of each Reporting Person's cover page to this Schedule 13G/A sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated 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.
	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.

RA Capital Management, L.P.

Signature:	/s/ Peter Kolchinsky
Name/Title:	By Peter Kolchinsky, Authorized Signatory
Date:	08/14/2026

Peter Kolchinsky

Signature:	/s/ Peter Kolchinsky
Name/Title:	Peter Kolchinsky
Date:	08/14/2026

Rajeev Shah

Signature:	/s/ Rajeev Shah
Name/Title:	Rajeev Shah
Date:	08/14/2026

RA Capital Healthcare Fund, L.P.

Signature:	/s/ Peter Kolchinsky
Name/Title:	By RA Capital Healthcare Fund GP, LLC, its General Partner, By Peter Kolchinsky, Manager
Date:	08/14/2026

Exhibit Information

Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to Schedule 13G filed on April 2, 2026)