MIAX CEO exercises options, sells 70K shares

MIAMI INTERNATIONAL HOLDINGS, INC.

Rhea-AI Filing Summary

MIAMI INTERNATIONAL HOLDINGS, INC. Chairman & CEO Thomas P. Gallagher, through Gallagher Investments, LLC, completed a paired option exercise and share sale in MIAX common stock. On July 6–7, 2026, Gallagher Investments exercised nonqualified stock options for a total of 70,000 shares at an exercise price of $12.00 per share and sold the same 70,000 shares in open-market transactions at weighted average prices of $42.09 and $42.27 per share.

All reported transactions were executed under a previously established Rule 10b5-1 Plan adopted on December 29, 2025, indicating they were pre-scheduled. Following these transactions, Gallagher Investments holds 1,723,275 shares of MIAX common stock indirectly for Gallagher, who maintains voting and dispositive control.

Insider Trade Summary 10b5-1

Exercise and Sale: 70,000 shares ($2.11M approx. pre-tax spread)

Exercise and Sale 6 txns

Insider Gallagher Thomas P.

Role Chairman & CEO

Sold 70,000 shs ($2.95M)

Approx. gross sale proceeds $2.95M

Approx. exercise cost $840K

Approx. pre-tax spread $2.11M

Type	Security	Shares	Price	Value
Exercise	Nonqualified Stock Option (Right to Buy)	28,228	$0.00	$0.00
Exercise	Common Stock	28,228	$12.00	$339K
Sale	Common Stock	28,228	$42.27	$1.19M
Exercise	Nonqualified Stock Option (Right to Buy)	41,772	$0.00	$0.00
Exercise	Common Stock	41,772	$12.00	$501K
Sale	Common Stock	41,772	$42.09	$1.76M

Holdings After Transaction: Nonqualified Stock Option (Right to Buy) — 70,000 contracts (Indirect, By Gallagher Investments, LLC); Common Stock — 1,723,275 shares (Indirect, By Gallagher Investments, LLC)

Footnotes (5)

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 $42.32. 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. This transaction was executed in multiple trades throughout the day at prices ranging from $42.00 to $42.50. 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.
5. F5. The options are fully vested.

Key Figures

Shares sold: 70,000 shares Sale prices July 6: $42.09 per share Sale prices July 7: $42.27 per share +3 more

6 metrics

Shares sold 70,000 shares Open-market sales of MIAX common stock

Sale prices July 6 $42.09 per share Weighted average sale price on July 6, 2026

Sale prices July 7 $42.27 per share Weighted average sale price on July 7, 2026

Option exercise price $12.00 per share Nonqualified stock option exercise price

Shares acquired via exercise 70,000 shares Common shares from option exercises

Post-transaction holdings 1,723,275 shares Indirect MIAX holdings via Gallagher Investments, LLC

Key Terms

Rule 10b5-1 Plan, Nonqualified Stock Option (Right to Buy), beneficial ownership, open-market sale, +1 more

5 terms

Rule 10b5-1 Plan regulatory

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

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)" with an exercise price of $12.0000."

beneficial ownership financial

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

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.

open-market sale financial

"transaction_action: "open-market sale" for MIAX common stock transactions coded S."

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

derivative exercise/conversion financial

"transaction_action: "derivative exercise/conversion" for option exercises coded M."

FAQ

What did MIAX Chairman & CEO Thomas Gallagher do in this Form 4 filing?

Thomas Gallagher’s affiliated entity exercised options for 70,000 MIAX shares at $12.00 and sold the same 70,000 shares around $42. The transactions reflect an exercise-and-sell pattern rather than a simple open-market purchase or sale.

How many MIAX shares did Thomas Gallagher sell in this Form 4?

Gallagher’s affiliated LLC sold 70,000 MIAX common shares in open-market trades at weighted average prices of $42.09 and $42.27. These sales matched the 70,000 shares acquired from exercising nonqualified stock options at $12.00 per share.

What option exercise price is disclosed for Thomas Gallagher’s MIAX options?

The filing shows Gallagher’s affiliated entity exercised nonqualified stock options with a conversion or exercise price of $12.00 per share. Those options converted into 70,000 MIAX common shares, which were then sold in the open market at prices around $42 per share.

How many MIAX shares does Thomas Gallagher hold after these transactions?

After the reported transactions, Gallagher Investments, LLC holds 1,723,275 MIAX shares indirectly for Thomas Gallagher. He maintains beneficial ownership, including voting and dispositive control, over this LLC, according to the disclosure language in the filing’s footnotes.

Were Thomas Gallagher’s MIAX share sales made under a Rule 10b5-1 plan?

Yes. The filing states the transactions were effected under a previously established Rule 10b5-1 plan adopted on December 29, 2025. Such plans pre-schedule trades, indicating these sales followed a preset trading arrangement rather than discretionary timing decisions.

How are Thomas Gallagher’s MIAX holdings structured according to the Form 4 footnotes?

The shares are held indirectly through Gallagher Investments, LLC, which is listed as the owner for the transactions. The footnotes state Gallagher maintains beneficial ownership with both voting and dispositive control over this LLC’s MIAX common stock holdings.

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Available on EDGAR 07/07/2026 - 05:03 PM Accepted by SEC EDGAR 07/07/2026 - 05:03 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)
07/06/2026

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	07/06/2026		M(1)		41,772	A	$12	1,765,047	I	By Gallagher Investments, LLC(2)
Common Stock	07/06/2026		S(1)		41,772	D	$42.09(3)	1,723,275	I	By Gallagher Investments, LLC(2)
Common Stock	07/07/2026		M(1)		28,228	A	$12	1,751,503	I	By Gallagher Investments, LLC(2)
Common Stock	07/07/2026		S(1)		28,228	D	$42.27(4)	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	07/06/2026		M(1)			41,772	(5)	08/02/2026	Common Stock	41,772	$0	98,228	I	By Gallagher Investments, LLC(2)
Nonqualified Stock Option (Right to Buy)	$12	07/07/2026		M(1)			28,228	(5)	08/02/2026	Common Stock	28,228	$0	70,000	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 $42.32. 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. This transaction was executed in multiple trades throughout the day at prices ranging from $42.00 to $42.50. 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.

5. The options are fully vested.

Remarks:

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