MIAX CEO exercises options, sells 70,000 shares

Rhea-AI Filing Summary

Miami International Holdings, Inc. Chairman & CEO Thomas P. Gallagher, through Gallagher Investments, LLC, exercised nonqualified stock options to acquire 70,000 shares of common stock at an exercise price of $12.00 per share and sold 70,000 shares in open-market transactions at a weighted average price of $42.52 per share, within a range of $42.00 to $43.49. The sale was effected under a previously established Rule 10b5-1 Plan, and following these transactions, Gallagher Investments, LLC held 1,723,275 shares of common stock indirectly beneficially owned by Mr. Gallagher. The options exercised were fully vested and this option grant now has no remaining balance.

Insider Trade Summary 10b5-1

Exercise and Sale: 70,000 shares ($2.14M approx. pre-tax spread)

Exercise and Sale 3 txns

Insider Gallagher Thomas P.

Role Chairman & CEO

Sold 70,000 shs ($2.98M)

Approx. gross sale proceeds $2.98M

Approx. exercise cost $840K

Approx. pre-tax spread $2.14M

Type	Security	Shares	Price	Value
Exercise	Nonqualified Stock Option (Right to Buy) F1, F4, F2	70,000	$0.00	$0.00
Exercise	Common Stock F1, F2	70,000	$12.00	$840K
Sale	Common Stock F1, F3, F2	70,000	$42.52	$2.98M

Holdings After Transaction: Nonqualified Stock Option (Right to Buy) — 0 contracts (Indirect, By Gallagher Investments, LLC); Common Stock — 1,723,275 shares (Indirect, By Gallagher Investments, LLC)

Footnotes (4)

1. F1. This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 29, 2025.
2. F2. Mr. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC.
3. F3. This transaction was executed in multiple trades throughout the day at prices ranging from $42.00 to $43.49. 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.
4. F4. The options are fully vested.

Key Figures

Shares sold: 70,000 shares Weighted average sale price: $42.52 per share Shares acquired via option exercise: 70,000 shares +4 more

7 metrics

Shares sold 70,000 shares Open-market sale of common stock on July 13, 2026

Weighted average sale price $42.52 per share Average price for 70,000 shares sold within a $42.00–$43.49 range

Shares acquired via option exercise 70,000 shares Common stock obtained through exercise of nonqualified stock options

Option exercise price $12.00 per share Strike price of nonqualified stock options exercised for 70,000 shares

Indirect holdings after transactions 1,723,275 shares Common stock indirectly held through Gallagher Investments, LLC following transactions

Option expiration date 2026-08-02 Expiration date of the nonqualified stock option that was exercised

Sale price range $42.00–$43.49 per share Range of prices across multiple trades for the 70,000 shares sold

Key Terms

Rule 10b5-1 Plan, Nonqualified Stock Option (Right to Buy), beneficial ownership, weighted average sales price

4 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.

Nonqualified Stock Option (Right to Buy) financial

"security_title: Nonqualified Stock Option (Right to Buy)"

beneficial ownership financial

"Mr. Gallagher maintains beneficial ownership, including dispositive and voting control"

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.

weighted average sales price financial

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

FAQ

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

What did MIAX Chairman & CEO Thomas P. Gallagher report in this Form 4 transaction?

Thomas P. Gallagher reported exercising options for 70,000 shares of MIAX common stock at $12.00 per share and selling 70,000 shares in open-market trades at a weighted average price of $42.52 per share on July 13, 2026.

Was the MIAX (MIAX) insider sale by Thomas P. Gallagher pre-planned?

Yes. The 70,000-share sale of MIAX common stock was executed under a previously established Rule 10b5-1 Plan adopted by Thomas P. Gallagher on December 29, 2025, indicating the trades were pre-scheduled rather than discretionary.

What is Thomas P. Gallagher’s remaining indirect ownership in MIAX after these transactions?

After the reported transactions, Gallagher Investments, LLC held 1,723,275 shares of MIAX common stock, indirectly beneficially owned by Thomas P. Gallagher, who maintains voting and dispositive control over that entity according to the disclosure footnotes.

What type of derivative security did Thomas P. Gallagher exercise in this MIAX Form 4?

He exercised a Nonqualified Stock Option (Right to Buy) for 70,000 underlying shares of MIAX common stock at an exercise price of $12.00 per share. The options were fully vested and had an expiration date of August 2, 2026.

At what prices were the MIAX shares sold in Thomas P. Gallagher’s Form 4 transaction?

The 70,000 MIAX shares were sold at prices ranging from $42.00 to $43.49 per share. The reported $42.52 figure reflects the weighted average sales price across multiple trades executed throughout July 13, 2026.

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

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Accepted by SEC EDGAR 07/14/2026 - 04:04 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^*

Gallagher Thomas P.

(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)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chairman & CEO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
07/13/2026

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	07/13/2026		M(1)		70,000	A	$12	1,793,275	I	By Gallagher Investments, LLC(2)
Common Stock	07/13/2026		S(1)		70,000	D	$42.52(3)	1,723,275	I	By Gallagher Investments, LLC(2)

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
Nonqualified Stock Option (Right to Buy)	$12	07/13/2026		M(1)			70,000	(4)	08/02/2026	Common Stock	70,000	$0	0	I	By Gallagher Investments, LLC(2)

Explanation of Responses:

1. This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 29, 2025.

2. Mr. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC.

3. This transaction was executed in multiple trades throughout the day at prices ranging from $42.00 to $43.49. 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.

4. The options are fully vested.

Remarks:

	/s/Alessandra Maria Corona Henriques, Attorney-in-Fact	07/14/2026
	** 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)