RA Capital Management and affiliated reporting persons reported beneficial ownership of 2,078,913 shares of Karyopharm Therapeutics common stock, representing 9.99% of the class.
The filing states the Fund directly holds 1,917,354 shares, pre-funded warrants exercisable for 3,391,164 shares, and warrants exercisable for 4,421,518 shares. The filing cites 19,618,032 shares outstanding as of March 23, 2026 and references a private placement of 1,030,354 shares that closed March 26, 2026. The Warrants include "Beneficial Ownership Blockers" that limit exercise to prevent ownership above 9.99%.
Positive
None.
Negative
None.
Insights
Reporting persons disclose a near-10% stake constrained by warrant blockers.
The filing documents an aggregate beneficial ownership figure of 2,078,913 shares (9.99%), tied to direct holdings and exercisable warrants with embedded "Beneficial Ownership Blockers". These blockers limit exercise activity to maintain the reported ownership cap.
Watch subsequent filings for any notice changing voting/dispositive delegations or amendments to the blocker provisions; timing of any exercises or revocations would appear in future Section 13 filings.
Filing clarifies attribution and Section 13(d) disclaimers across RA Capital entities.
The text explains delegation of voting and disposition powers from the Fund to RA Capital and contains explicit disclaimers about not forming a "group" and limited beneficial ownership attributions under Section 13(d). The Fund disclaims beneficial ownership for 13(d) purposes due to a delegation revocable on 61 days' notice.
Relevant items to track include any change in voting/disposition delegation, conversions/exercises of Pre-Funded Warrants or Common Warrants, and updated outstanding share counts reflected in future filings.
Key Figures
Beneficially owned shares (aggregate):2,078,913 sharesFund direct holdings:1,917,354 sharesPre-Funded Warrants exercisable:3,391,164 shares+4 more
Fund direct holdings1,917,354 sharesFund directly holds these common shares
Pre-Funded Warrants exercisable3,391,164 sharesPre-Funded Warrants exercisable into common stock
Common Warrants exercisable4,421,518 sharesCommon Warrants exercisable into common stock
Shares outstanding used19,618,032 sharesShares outstanding as of March 23, 2026
Private placement shares1,030,354 sharesShares issued in private placement closed March 26, 2026
Beneficial ownership percentage9.99%Percent of class due to Beneficial Ownership Blockers
Key Terms
Beneficial Ownership Blockers, Pre-Funded Warrants, Section 13(d), Delegation of voting and disposition
4 terms
Beneficial Ownership Blockersregulatory
"Each of the Warrants contains a provision (the "Beneficial Ownership Blockers")"
Pre-Funded Warrantsfinancial
"pre-funded warrants (the "Pre-Funded Warrants") exercisable for up to 3,391,164 shares"
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)regulatory
"RA Capital may be deemed a beneficial owner, for purposes of Section 13(d) of the Act"
Delegation of voting and dispositioncorporate
"The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose"
What percentage stake does RA Capital report in KPTI?
The filing reports a 9.99% beneficial ownership stake. This percentage is tied to 2,078,913 shares and reflects exercise limits in the reported warrants.
How many Karyopharm shares does the Fund directly hold?
The Fund directly holds 1,917,354 shares of common stock. The filing lists this as the Fund's direct equity holding within its broader position.
What warrants are included in RA Capital's position for KPTI?
The filing lists pre-funded warrants exercisable for 3,391,164 shares and common warrants exercisable for 4,421,518 shares. Each warrant series contains a Beneficial Ownership Blocker limiting exercises above 9.99%.
What share count does the filing use to calculate the 9.99%?
The percentage is based on 19,618,032 shares outstanding as of March 23, 2026, plus a 1,030,354-share private placement closed March 26, 2026, and 161,559 shares issuable upon exercise of the Warrants, as stated in the filing.
Do the reporting persons claim to be a group under SEC rules?
No. The filing explicitly states the Reporting Persons "expressly disclaim status as a 'group'" and includes disclaimers about beneficial ownership attributions under Section 13(d).
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 per share
(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
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
2,078,913.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,078,913.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,078,913.00
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
2,078,913.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,078,913.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,078,913.00
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
2,078,913.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,078,913.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,078,913.00
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
2,078,913.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,078,913.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,078,913.00
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.
(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 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:
Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of shares of common stock of the Issuer beneficially owned by such Reporting Person 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 2,078,913 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 other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13G 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 is 9.99%. Such percentage is based upon the sum of (i) 19,618,032 shares of common stock outstanding as of March 23, 2026, as reported in the Issuer's Current Report on Form 8-K, filed with the Securities and Exchange Commission (the "SEC") on March 24, 2026; (ii) 1,030,354 shares of common stock issued in the private placement of equity securities by the Issuer that closed on March 26, 2026, as reported in the Issuer's Current Report on Form 8-K, filed with the SEC on March 24, 2026; and (iii) 161,559 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 sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person 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 sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person 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 sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person 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 sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person 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:
04/02/2026
Peter Kolchinsky
Signature:
/s/ Peter Kolchinsky
Name/Title:
Peter Kolchinsky
Date:
04/02/2026
Rajeev Shah
Signature:
/s/ Rajeev Shah
Name/Title:
Rajeev Shah
Date:
04/02/2026
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
