Boost Run Inc. Schedule 13G: a group of Citadel entities and Kenneth Griffin jointly report beneficial ownership of Class A common stock. Citadel Advisors LLC and related entities may be deemed to beneficially own 1,516,090 shares (4.8%). Citadel Securities LLC may be deemed to beneficially own 224,223 shares (0.7%). Kenneth Griffin may be deemed to beneficially own 1,740,313 shares (5.5%). The filing cites 31,895,656 Shares outstanding as of May 8, 2026 and notes holdings may include instruments exercisable for or convertible into Shares.
Positive
None.
Negative
None.
Insights
Citadel and affiliates report single‑digit stakes in Boost Run.
The filing lists 1,516,090 shares for Citadel Advisors and affiliates representing 4.8% of the class and 224,223 shares for Citadel Securities representing 0.7%. The percentages are calculated from an explicit outstanding share count of 31,895,656 as of May 8, 2026.
Holdings are reported as beneficial and may include convertible/exercisable instruments; cash‑flow treatment is not specified in the excerpt. Subsequent filings could show changes if instruments are exercised or dispositions occur.
Joint filing clarifies shared voting/dispositive power across multiple Citadel entities.
The statement attributes shared voting and dispositive power to Citadel Advisors, CAH and CGP over 1,516,090 shares and to Citadel Securities entities over 224,223 shares. Mr. Griffin is reported with aggregate shared power over 1,740,313 shares.
The text emphasizes that the filing "shall not be construed as an admission" of beneficial ownership beyond securities actually owned by each reporting person; governance implications depend on any future changes to voting arrangements or dispositions disclosed in later filings.
Key Figures
Shares outstanding:31,895,656 sharesCitadel Advisors ownership:1,516,090 sharesCitadel Advisors percent:4.8%+4 more
7 metrics
Shares outstanding31,895,656 sharesas of May 8, 2026
Kenneth Griffin percent5.5%percent of Class A common stock
Key Terms
beneficial ownership, shared dispositive power, instruments exercisable for or convertible
3 terms
beneficial ownershipregulatory
"may be deemed to beneficially own 1,516,090 Shares"
Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.
shared dispositive powerregulatory
"Shared Dispositive Power 1,516,090.00"
instruments exercisable for or convertiblefinancial
"holdings of the reporting persons reported in this are as of the opening... may include other instruments exercisable for or convertible into Shares"
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Boost Run Inc.
(Name of Issuer)
Class A Common Stock, par value $0.0001 per share (the "Shares")
(Title of Class of Securities)
09940T100
(CUSIP Number)
05/14/2026
(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):
09940T100
1
Names of Reporting Persons
Citadel Advisors LLC
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
1,516,090.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,516,090.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,516,090.00
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)
4.8 %
12
Type of Reporting Person (See Instructions)
IA, HC, OO
Comment for Type of Reporting Person: The percentages reported in this Schedule 13G are based upon 31,895,656 Shares outstanding as of May 8, 2026 (according to the issuer's Form 8-K as filed with the Securities and Exchange Commission on May 15, 2026). Except as described in the preceding sentence, all Shares for the holdings of the reporting persons reported in this Schedule 13G are as of the opening of the market on May 21, 2026.
SCHEDULE 13G
CUSIP Number(s):
09940T100
1
Names of Reporting Persons
Citadel Advisors Holdings 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
1,516,090.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,516,090.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,516,090.00
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)
4.8 %
12
Type of Reporting Person (See Instructions)
HC, PN
SCHEDULE 13G
CUSIP Number(s):
09940T100
1
Names of Reporting Persons
Citadel GP LLC
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
1,516,090.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,516,090.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,516,090.00
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)
4.8 %
12
Type of Reporting Person (See Instructions)
HC, OO
SCHEDULE 13G
CUSIP Number(s):
09940T100
1
Names of Reporting Persons
Citadel Securities LLC
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
224,223.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
224,223.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
224,223.00
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)
0.7 %
12
Type of Reporting Person (See Instructions)
BD, OO
SCHEDULE 13G
CUSIP Number(s):
09940T100
1
Names of Reporting Persons
Citadel Securities Group 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
224,223.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
224,223.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
224,223.00
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)
0.7 %
12
Type of Reporting Person (See Instructions)
HC, PN
SCHEDULE 13G
CUSIP Number(s):
09940T100
1
Names of Reporting Persons
Citadel Securities GP LLC
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
224,223.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
224,223.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
224,223.00
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)
0.7 %
12
Type of Reporting Person (See Instructions)
HC, OO
SCHEDULE 13G
CUSIP Number(s):
09940T100
1
Names of Reporting Persons
Kenneth Griffin
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
1,740,313.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
1,740,313.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
1,740,313.00
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)
5.5 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Boost Run Inc.
(b)
Address of issuer's principal executive offices:
5 Revere Drive, Suite 200, Northbrook, IL 60062
Item 2.
(a)
Name of person filing:
This Schedule 13G is being jointly filed by Citadel Advisors LLC ("Citadel Advisors"), Citadel Advisors Holdings LP ("CAH"), Citadel GP LLC ("CGP"), Citadel Securities LLC ("Citadel Securities"), Citadel Securities Group LP ("CALC4"), Citadel Securities GP LLC ("CSGP") and Mr. Kenneth Griffin (collectively with Citadel Advisors, CAH, CGP, Citadel Securities, CALC4 and CSGP, the "Reporting Persons") with respect to the Shares of the above-named issuer owned by Citadel Multi-Strategy Equities Master Fund Ltd., a Cayman Islands company ("CM"), and Citadel Securities. Such owned Shares may include other instruments exercisable for or convertible into Shares.
Citadel Advisors is the portfolio manager for CM. CAH is the sole member of Citadel Advisors. CGP is the general partner of CAH. CALC4 is the non-member manager of Citadel Securities. CSGP is the general partner of CALC4. Mr. Griffin is the President and Chief Executive Officer of CGP, and owns a controlling interest in CGP and CSGP.
The filing of this statement shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any securities covered by the statement other than the securities actually owned by such person (if any).
(b)
Address or principal business office or, if none, residence:
The address of each of the Reporting Persons is 830 Brickell Plaza, Miami, Florida 33131.
(c)
Citizenship:
Each of Citadel Advisors, CGP, Citadel Securities and CSGP is organized as a limited liability company under the laws of the State of Delaware. Each of CALC4 and CAH is organized as a limited partnership under the laws of the State of Delaware. Mr. Griffin is a U.S. citizen.
(d)
Title of class of securities:
Class A Common Stock, par value $0.0001 per share (the "Shares")
(e)
CUSIP Number(s):
09940T100
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:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own 1,516,090 Shares.
2. Citadel Securities LLC may be deemed to beneficially own 224,223 Shares.
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own 224,223 Shares.
4. Mr. Griffin may be deemed to beneficially own 1,740,313 Shares.
(b)
Percent of class:
1. The number of Shares that each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC may be deemed to beneficially own constitutes 4.8% of the Shares outstanding.
2. The number of Shares that Citadel Securities LLC may be deemed to beneficially own constitutes 0.7% of the Shares outstanding.
3. The number of Shares that each of Citadel Securities Group LP and Citadel Securities GP LLC may be deemed to beneficially own constitutes 0.7% of the Shares outstanding.
4. The number of Shares that Mr. Griffin may be deemed to beneficially own constitutes 5.5% of the Shares outstanding.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0
2. Citadel Securities LLC: 0
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0
4. Mr. Griffin: 0
(ii) Shared power to vote or to direct the vote:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 1,516,090
2. Citadel Securities LLC: 224,223
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 224,223
4. Mr. Griffin: 1,740,313
(iii) Sole power to dispose or to direct the disposition of:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 0
2. Citadel Securities LLC: 0
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 0
4. Mr. Griffin: 0
(iv) Shared power to dispose or to direct the disposition of:
1. Each of Citadel Advisors LLC, Citadel Advisors Holdings LP and Citadel GP LLC: 1,516,090
2. Citadel Securities LLC: 224,223
3. Each of Citadel Securities Group LP and Citadel Securities GP LLC: 224,223
4. Mr. Griffin: 1,740,313
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.
Citadel Advisors LLC
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, Authorized Signatory
Date:
05/21/2026
Citadel Advisors Holdings LP
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, Authorized Signatory
Date:
05/21/2026
Citadel GP LLC
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, Authorized Signatory
Date:
05/21/2026
Citadel Securities LLC
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, Authorized Signatory
Date:
05/21/2026
Citadel Securities Group LP
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, Authorized Signatory
Date:
05/21/2026
Citadel Securities GP LLC
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, Authorized Signatory
Date:
05/21/2026
Kenneth Griffin
Signature:
/s/ Seth Levy
Name/Title:
Seth Levy, attorney-in-fact*
Date:
05/21/2026
Comments accompanying signature: * Seth Levy is signing on behalf of Kenneth Griffin as attorney-in-fact pursuant to a power of attorney previously filed with the Securities and Exchange Commission, and hereby incorporated by reference herein. The power of attorney was filed as an attachment to a filing by Citadel Advisors LLC on Schedule 13G for Allakos Inc. on October 13, 2023.
What stake does Citadel report in Boost Run (BRUN)?
Citadel Advisors and related entities report beneficial ownership of 1,516,090 shares, representing 4.8% of Class A common stock. The percentage is calculated from 31,895,656 shares outstanding as of May 8, 2026.
How many shares does Kenneth Griffin report owning in BRUN?
Mr. Kenneth Griffin is reported as beneficially owning 1,740,313 shares, representing 5.5% of the Class A shares outstanding as stated in the filing.
Does the filing include convertible or exercisable instruments for BRUN?
Yes. The joint filing states holdings "may include other instruments exercisable for or convertible into Shares," indicating the reported counts can reflect such instruments when applicable.
What voting and dispositive power does Citadel claim over BRUN shares?
The filing shows 0 sole voting power and shared voting power of 1,516,090 shares for Citadel Advisors/affiliates, and shared voting power of 224,223 shares for Citadel Securities LLC, per the disclosure.
What outstanding share count does the BRUN filing use to compute percentages?
The percentages are based on an explicit outstanding share count of 31,895,656 Shares as of May 8, 2026, cited in the filing.
