Miami International exec sells 21K shares at $39

MIAX’s EVP and Chief Strategy Officer Shelly Brown sold 21,217 shares under a pre-arranged Rule 10b5-1 trading plan and now directly holds 316,490 shares.

Rhea-AI Filing Summary

MIAMI INTERNATIONAL HOLDINGS, INC. (MIAX) reported that executive vice president and chief strategy officer Shelly Brown sold 21,217 shares of Common Stock on September 16, 2026 in an open-market transaction at a weighted average price of $38.61 per share, with individual trades ranging from $37.84 to $39.56.

The sale was effected pursuant to a previously established Rule 10b5-1 Plan adopted by Shelly Brown on December 22, 2025. Following this transaction, Shelly Brown directly holds 316,490 shares of MIAX Common Stock.

Insider Trade Summary 10b5-1

Net Seller: 21,217 shares

Net Sell 1 txn

Insider Brown Shelly

Role EVP, Chief Strategy Officer

Sold 21,217 shs ($819K)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F2	21,217	$38.61	$819K

Holdings After Transaction: Common Stock — 316,490 shares (Direct)

Footnotes (2)

1. F1. This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 22, 2025.
2. F2. This transaction was executed in multiple trades throughout the day at prices ranging from $37.84 to $39.56. The price reported above reflects the weighted average sales price. The Reporting Person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer, full information regarding the number of shares and prices at which the transaction was effected.

Key Figures

Shares sold: 21,217 shares Weighted average sale price: $38.61 per share Sale price range: $37.84–$39.56 per share +2 more

5 metrics

Shares sold 21,217 shares Common Stock sale on September 16, 2026 by Shelly Brown

Weighted average sale price $38.61 per share Open-market sale of MIAX Common Stock on September 16, 2026

Sale price range $37.84–$39.56 per share Multiple trades executed throughout the day on September 16, 2026

Shares held after transaction 316,490 shares Direct holdings of Shelly Brown after the September 16, 2026 sale

Rule 10b5-1 Plan adoption date December 22, 2025 Plan under which the September 16, 2026 sale was effected

Key Terms

Rule 10b5-1 Plan, weighted average sales price, open market or private transaction

3 terms

Rule 10b5-1 Plan regulatory

"This transaction was effected pursuant to a previously established Rule 10b5-1 Plan"

A Rule 10b5-1 plan is a prearranged, written schedule that lets corporate insiders buy or sell company stock at set times or amounts, even if they later learn material nonpublic information. Think of it like setting an automatic thermostat for trades: it creates a clear record that trades were planned in advance, reducing the risk of insider-trading accusations and helping investors trust that insider transactions are routine rather than based on secret information.

weighted average sales price financial

"The price reported above reflects the weighted average sales price"

open market or private transaction financial

"Sale in open market or private transaction"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did MIAX report for Shelly Brown?

MIAMI INTERNATIONAL HOLDINGS, INC. reported that Shelly Brown sold 21,217 shares of Common Stock on September 16, 2026 in an open-market transaction at a weighted average price of $38.61 per share, with trade prices between $37.84 and $39.56.

How many MIAX (MIAX) shares does Shelly Brown hold after this transaction?

After the reported sale, Shelly Brown directly holds 316,490 shares of MIAMI INTERNATIONAL HOLDINGS, INC. Common Stock, as disclosed in the Form 4 filing for the September 16, 2026 transaction.

Was Shelly Brown’s MIAX stock sale made under a Rule 10b5-1 plan?

Yes. The filing states the sale was effected pursuant to a previously established Rule 10b5-1 Plan adopted by Shelly Brown on December 22, 2025, and the Form 4 affirms transactions under such a trading plan.

What price range did Shelly Brown’s MIAX shares sell for in this Form 4?

The filing explains that the 21,217 shares were sold in multiple trades at prices ranging from $37.84 to $39.56 per share. The reported $38.61 reflects the weighted average sales price for the September 16, 2026 transactions.

What is Shelly Brown’s role at MIAMI INTERNATIONAL HOLDINGS, INC.?

Shelly Brown is identified in the Form 4 as an officer of MIAMI INTERNATIONAL HOLDINGS, INC., serving as EVP, Chief Strategy Officer at the time of the reported stock sale.

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

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Available on EDGAR 09/17/2026 - 04:44 PM Accepted by SEC EDGAR 09/17/2026 - 04:43 PM Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Brown Shelly

(Last) (First) (Middle)

C/O MIAMI INTERNATIONAL HOLDINGS, INC.

7 ROSZEL ROAD, SUITE 1A

(Street)

PRINCETON NEW JERSEY 08540

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MIAMI INTERNATIONAL HOLDINGS, INC. [ MIAX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	EVP, Chief Strategy Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/16/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/16/2026		S(1)		21,217	D	$38.61(2)	316,490	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 22, 2025.

2. This transaction was executed in multiple trades throughout the day at prices ranging from $37.84 to $39.56. The price reported above reflects the weighted average sales price. The Reporting Person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the Issuer or a security holder of the Issuer, full information regarding the number of shares and prices at which the transaction was effected.

Remarks:

	/s/Alessandra Maria Corona Henriques, Attorney-in-Fact	09/17/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)