Miami International CEO sells 15,771 shares

Rhea-AI Filing Summary

Miami International Holdings reported that Chairman & CEO Thomas P. Gallagher, through Gallagher Investments, LLC, exercised nonqualified stock options for 15,771 shares at $12 and sold 15,771 common shares at a weighted average $47.92 under a Rule 10b5-1 plan, and now indirectly holds 1,723,275 common shares.

Insider Trade Summary 10b5-1

Exercise and Sale: 15,771 shares ($566K approx. pre-tax spread)

Exercise and Sale 3 txns

Insider Gallagher Thomas P.

Role Chairman & CEO

Sold 15,771 shs ($756K)

Approx. gross sale proceeds $756K

Approx. exercise cost $189K

Approx. pre-tax spread $566K

Type	Security	Shares	Price	Value
Exercise	Nonqualified Stock Option (Right to Buy)	15,771	$0.00	$0.00
Exercise	Common Stock	15,771	$12.00	$189K
Sale	Common Stock	15,771	$47.92	$756K

Holdings After Transaction: Nonqualified Stock Option (Right to Buy) — 210,000 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 $47.13 to $48.35. The price reported above reflects the weighted average sale 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: 15,771 shares Weighted average sale price: $47.92 per share Sale price range: $47.13–$48.35 per share +3 more

6 metrics

Shares sold 15,771 shares Common stock sold indirectly by Gallagher Investments, LLC on 2026-05-05

Weighted average sale price $47.92 per share Weighted average price for the 15,771-share sale on 2026-05-05

Sale price range $47.13–$48.35 per share Intraday range of prices for the reported sale trades

Option strike price $12.00 per share Exercise price of the nonqualified stock options exercised

Options exercised 15,771 shares Underlying common shares from nonqualified stock options exercised on 2026-05-05

Post-transaction indirect holding 1,723,275 Indirect MIAX common shares held through Gallagher Investments, LLC after the transactions

Key Terms

Rule 10b5-1 Plan, Nonqualified Stock Option, beneficial ownership, weighted average sale price, +1 more

5 terms

Rule 10b5-1 Plan financial

"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 financial

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

A nonqualified stock option (NQSO) is a company grant that gives an individual the right to buy shares at a set price but does not meet special tax rules for incentive stock options; when exercised the difference between the market price and the exercise price is treated as ordinary income for the recipient and as a tax-deductible expense for the company. It matters to investors because NQSOs affect an employee’s after-tax proceeds, the company’s reported expenses, and potential share dilution—think of it like a cash bonus that converts into stock but is taxed as regular pay when you take it.

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 sale price financial

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

dispositive and voting control financial

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

FAQ

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

What insider transaction did MIAX report for Thomas P. Gallagher?

Thomas P. Gallagher, via Gallagher Investments, LLC, exercised nonqualified stock options for 15,771 shares at $12 and then sold 15,771 common shares on May 5, 2026, in a planned Rule 10b5-1 transaction.

How many MIAX shares did Gallagher sell and at what price?

An entity controlled by Thomas P. Gallagher sold 15,771 MIAX common shares at a weighted average price of $47.92 per share, with individual trade prices ranging between $47.13 and $48.35 during the day.

Were the MIAX (MIAX) insider transactions under a Rule 10b5-1 plan?

Yes, the reported transactions were effected under a previously established Rule 10b5-1 Plan adopted by Thomas P. Gallagher on December 29, 2025, as disclosed, and the Form 4’s 10b5-1 checkbox is marked as affirmed.

What is Gallagher’s remaining MIAX ownership after this Form 4?

After these transactions, an entity controlled by Thomas P. Gallagher, Gallagher Investments, LLC, indirectly holds 1,723,275 MIAX common shares. He maintains beneficial ownership with dispositive and voting control over this LLC-held position.

What options did Gallagher exercise in the MIAX Form 4 filing?

Gallagher, through his LLC, exercised nonqualified stock options covering 15,771 shares of MIAX common stock at a $12.00 strike price. The options are fully vested and carried an expiration date of August 2, 2026 before exercise.

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

Form 4 Insider Transactions: What Each Field Means →

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Accepted by SEC EDGAR 05/07/2026 - 04:07 PM EDT 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)
05/05/2026

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	05/05/2026		M(1)		15,771	A	$12	1,739,046	I	By Gallagher Investments, LLC(2)
Common Stock	05/05/2026		S(1)		15,771	D	$47.92(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	05/05/2026		M(1)			15,771	(4)	08/02/2026	Common Stock	15,771	$0	210,000	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 $47.13 to $48.35. The price reported above reflects the weighted average sale 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	05/07/2026
	** 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)