Were the MIAX share sales by Gallagher pre-planned under a Rule 10b5-1 plan?

Yes. The filing states the transaction was effected under a previously established Rule 10b5-1 Plan adopted on December 29, 2025. Such plans pre-schedule trades, indicating the timing was set in advance rather than decided on the trade date.

Miami International (MIAX) CEO trades 15,771 shares under 10b5-1 plan

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

Rhea-AI Filing Summary

Miami International Holdings Chairman & CEO Thomas P. Gallagher, through Gallagher Investments, LLC, exercised options and sold shares in a planned transaction. On May 5, 2026, Gallagher Investments sold 15,771 shares of common stock at a weighted average price of $47.92 per share, in open-market trades executed between $47.13 and $48.35, under a previously established Rule 10b5-1 Plan.

On the same date, Gallagher Investments exercised 15,771 nonqualified stock options at an exercise price of $12.00 per share, converting them into common stock. After these transactions, indirect holdings stood at 1,739,046 common shares, with 210,000 nonqualified stock options remaining outstanding, all indirectly held through Gallagher Investments, LLC, over which Mr. Gallagher has voting and dispositive control.

Insider Trade Summary 10b5-1

Net Seller: 15,771 shares ($755,746)

Net Sell 3 txns

Insider Gallagher Thomas P.

Role Chairman & CEO

Sold 15,771 shs ($756K)

Type	Security	Shares	Price	Value
Exercise	Nonqualified Stock Option (Right to Buy)	15,771	$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 shares (Indirect, By Gallagher Investments, LLC); Common Stock — 1,739,046 shares (Indirect, By Gallagher Investments, LLC)

Footnotes (1)

This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 29, 2025. Mr. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC. 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. The options are fully vested.

Key Figures

Shares sold: 15,771 shares Sale price (weighted average): $47.92 per share Sale price range: $47.13–$48.35 per share +4 more

7 metrics

Shares sold 15,771 shares Open-market sale of common stock on May 5, 2026

Sale price (weighted average) $47.92 per share Weighted average sale price for 15,771 shares

Sale price range $47.13–$48.35 per share Intraday price range for executed trades

Options exercised 15,771 options Nonqualified stock options exercised into common stock

Option exercise price $12.00 per share Exercise price of nonqualified stock options

Shares held after 1,739,046 shares Indirect common stock holdings after transactions

Options remaining 210,000 options Nonqualified stock options outstanding after exercise

Key Terms

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

4 terms

Rule 10b5-1 Plan regulatory

"This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person"

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

"Nonqualified Stock Option (Right to Buy)"

beneficial ownership regulatory

"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.

weighted average sale price financial

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

Form 4 Insider Transactions: What Each Field Means →

05/07/2026 - 04:07 PM

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).

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
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)

Source: View Original Filing on SEC EDGAR

FAQ

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

Thomas P. Gallagher, via Gallagher Investments, LLC, sold 15,771 MIAX common shares and exercised 15,771 nonqualified stock options. The transactions were reported as indirect holdings changes and completed under a previously adopted Rule 10b5-1 Plan.

How many MIAX shares did Gallagher Investments, LLC sell in the latest Form 4?

Gallagher Investments, LLC sold 15,771 MIAX common shares. These open-market transactions occurred on May 5, 2026 at a weighted average sale price of $47.92 per share, within an intraday range from $47.13 to $48.35.

At what price did Thomas P. Gallagher exercise MIAX stock options?

Gallagher, through Gallagher Investments, LLC, exercised 15,771 nonqualified stock options at an exercise price of $12.00 per share. These options were fully vested and converted into an equal number of MIAX common shares before the same-size open-market sale.

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

Following the reported transactions, Gallagher Investments, LLC indirectly holds 1,739,046 MIAX common shares. Mr. Gallagher maintains beneficial ownership, including voting and dispositive control, over Gallagher Investments, LLC as disclosed in the filing footnotes.

How many MIAX stock options remain for Gallagher after the Form 4 activity?

After exercising 15,771 nonqualified stock options, Gallagher Investments, LLC has 210,000 nonqualified stock options remaining. These options relate to MIAX common stock and were reported as indirectly owned through Gallagher Investments, LLC.