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

Yes. A footnote explains at least one transaction was effected under a previously established Rule 10b5-1 trading plan adopted on December 29, 2025. Such plans pre-schedule trades, making the timing more routine rather than discretionary.

MIAMI INTERNATIONAL (NASDAQ: MIAX) CEO entity sells 224K shares after option exercise

Filing Impact

(Very High)

Filing Sentiment

(Very Negative)

Form Type

Rhea-AI Filing Summary

MIAMI INTERNATIONAL HOLDINGS, INC. Chairman & CEO Thomas P. Gallagher, through Gallagher Investments, LLC, exercised 70,001 nonqualified stock options for Common Stock at $12.00 per share, then sold a total of 224,025 Common shares in open-market transactions on April 15, 2026.

The sales by Gallagher Investments, LLC occurred at prices including $43.36 and $43.68 per share, with a disclosed intraday range from $42.57 to $44.41, under a previously established Rule 10b5-1 trading plan. After these trades, indirect holdings via Gallagher Investments, LLC were 1,723,275 shares, and direct holdings were 485,963 shares, which include 12,000 shares held jointly with his spouse.

Insider Trade Summary 10b5-1

Net Seller: 224,025 shares ($9,729,692)

Net Sell 5 txns

Insider Gallagher Thomas P.

Role Chairman & CEO

Sold 224,025 shs ($9.73M)

Type	Security	Shares	Price	Value
Exercise	Nonqualified Stock Option (Right to Buy)	70,001	$0.00	--
Exercise	Common Stock	70,001	$12.00	$840K
Sale	Common Stock	70,001	$43.36	$3.04M
Sale	Common Stock	104,124	$43.36	$4.51M
Sale	Common Stock	49,900	$43.68	$2.18M

Holdings After Transaction: Nonqualified Stock Option (Right to Buy) — 280,000 shares (Indirect, By Gallagher Investments, LLC); Common Stock — 1,897,400 shares (Indirect, By Gallagher Investments, LLC); Common Stock — 485,963 shares (Direct)

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 $42.57 to $44.41. 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. Includes 12,000 shares of common stock, which are held jointly with the Reporting Person's spouse with right of survival. The options are fully vested.

Key Figures

Options exercised: 70,001 options at $12.00 Shares sold total: 224,025 shares Key sale price: $43.36 per share +5 more

8 metrics

Options exercised 70,001 options at $12.00 Nonqualified stock option exercise on April 15, 2026

Shares sold total 224,025 shares Net open-market sales reported in this filing

Key sale price $43.36 per share Weighted average sale price for certain Common Stock sales

Additional sale price $43.68 per share Price for a separate Common Stock sale transaction

Indirect holdings after trades 1,723,275 shares MIAX Common Stock held via Gallagher Investments, LLC after transactions

Direct holdings after trades 485,963 shares MIAX Common Stock held directly after transactions, including joint holdings

Jointly held shares 12,000 shares Common Stock held jointly with spouse with right of survival

Intraday sale price range $42.57–$44.41 Price range for trades underlying the weighted average sale price

Key Terms

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

5 terms

Nonqualified Stock Option financial

"Nonqualified Stock Option (Right to Buy)"

Rule 10b5-1 Plan regulatory

"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.

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.

weighted average sale price financial

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

fully vested financial

"The options are fully vested"

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Form 4 Insider Transactions: What Each Field Means →

04/17/2026 - 04:17 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)
04/15/2026

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	04/15/2026		M⁽¹⁾		70,001	A	$12	1,897,400	I	By Gallagher Investments, LLC⁽²⁾
Common Stock	04/15/2026		S⁽¹⁾		70,001	D	$43.36⁽³⁾	1,827,399	I	By Gallagher Investments, LLC⁽²⁾
Common Stock	04/15/2026		S⁽¹⁾		104,124	D	$43.36⁽³⁾	1,723,275	I	By Gallagher Investments, LLC⁽²⁾
Common Stock	04/15/2026		S⁽¹⁾		49,900	D	$43.68⁽³⁾	485,963⁽⁴⁾	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)
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	04/15/2026		M⁽¹⁾			70,001	⁽⁵⁾	08/02/2026	Common Stock	70,001	$0	280,000	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 $42.57 to $44.41. 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. Includes 12,000 shares of common stock, which are held jointly with the Reporting Person's spouse with right of survival.

5. The options are fully vested.

Remarks:

	/s/Alessandra Maria Corona Henriques, Attorney-in-Fact	04/17/2026
	** 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)

Source: View Original Filing on SEC EDGAR

FAQ

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

Thomas Gallagher exercised 70,001 stock options at $12.00 per share and relatedly sold 224,025 shares of MIAX Common Stock in open-market transactions. These actions were reported as a combination of derivative exercise and subsequent sales.

How many MIAX shares did entities associated with Thomas Gallagher sell?

Entities associated with Thomas Gallagher sold 224,025 MIAX Common shares in total. This included sales by Gallagher Investments, LLC and additional direct sales, all executed in open-market transactions at prices generally around the low-to-mid $40 range.

At what prices were the MIAX shares sold in this Form 4?

Reported sale prices included $43.36 and $43.68 per MIAX share, with a footnote stating trades occurred between $42.57 and $44.41. The $43.36 figure reflects a weighted average sale price for multiple executions throughout the trading day.

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

After these transactions, Thomas Gallagher’s indirect holdings via Gallagher Investments, LLC were 1,723,275 MIAX shares. His direct holdings were 485,963 shares, which include 12,000 shares held jointly with his spouse with rights of survivorship.

What happened to the MIAX stock options reported in this Form 4?

Gallagher Investments, LLC exercised 70,001 nonqualified stock options for MIAX Common Stock at a $12.00 exercise price. A footnote notes the options are fully vested, and the corresponding Common shares were then partially or fully sold in open-market transactions.