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  4. [Form 4] MIAMI INTERNATIONAL HOLDINGS, INC. Insider Trading Activity

Miami International Holdings (MIAX) CEO sells 70K pre-planned shares

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

MIAMI INTERNATIONAL HOLDINGS, INC. Chairman & CEO Thomas P. Gallagher, through Gallagher Investments, LLC, exercised options for 70,000 shares of common stock at $12.00 per share and sold 70,000 shares at a weighted average of $42.36 on June 2, 2026.

The sales were made in open-market transactions under a previously established Rule 10b5-1 Plan adopted on December 29, 2025. Following these transactions, Gallagher Investments, LLC holds 1,723,275 shares of common stock indirectly controlled by Mr. Gallagher.

Positive

  • None.

Negative

  • None.
Insider Gallagher Thomas P.
Role Chairman & CEO
Sold 70,000 shs ($2.97M)
Type Security Shares Price Value
Exercise Nonqualified Stock Option (Right to Buy) 70,000 $0.00 --
Exercise Common Stock 70,000 $12.00 $840K
Sale Common Stock 70,000 $42.36 $2.97M
Holdings After Transaction: Nonqualified Stock Option (Right to Buy) — 140,000 shares (Indirect, By Gallagher Investments, LLC); Common Stock — 1,793,275 shares (Indirect, By Gallagher Investments, LLC)
Footnotes (1)
  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 $42.00 to $45.73. 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. The options are fully vested.
Shares sold 70,000 shares Open-market sale of common stock on June 2, 2026
Weighted average sale price $42.36 per share Common stock sales on June 2, 2026
Sale price range $42.00–$45.73 per share Price range for June 2, 2026 trades
Options exercised 70,000 options Nonqualified stock options converted to common stock
Option exercise price $12.00 per share Conversion price for nonqualified stock options
Shares held after transactions 1,723,275 shares Indirect holdings via Gallagher Investments, LLC after June 2, 2026
Rule 10b5-1 plan adoption date December 29, 2025 Plan governing June 2, 2026 share sales
Option expiration date August 2, 2026 Expiration of exercised nonqualified stock options
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 $12.00 per share."
open-market sale financial
"Transaction action: open-market sale of 70,000 shares of common stock."
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.
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.
derivative security financial
"Transaction code description: Exercise or conversion of derivative security."
A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.
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Form 4 Insider Transactions: What Each Field Means →
SEC Form 4
FORM 4UNITED 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)
XDirector10% Owner
XOfficer (give title below)Other (specify below)
Chairman & CEO
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
06/02/2026		6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Common Stock06/02/2026M(1)70,000A$121,793,275IBy Gallagher Investments, LLC(2)
Common Stock06/02/2026S(1)70,000D$42.36(3)1,723,275IBy 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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Nonqualified Stock Option (Right to Buy)$1206/02/2026M(1)70,000 (4)08/02/2026Common Stock70,000$0140,000IBy 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 $45.73. 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-Fact06/04/2026
** Signature of Reporting PersonDate
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 insider transactions did MIAX Chairman & CEO Thomas P. Gallagher report?

Thomas P. Gallagher, via Gallagher Investments, LLC, reported exercising options for 70,000 MIAX common shares at $12.00 and selling 70,000 shares at a weighted average price of $42.36 on June 2, 2026, under a pre-established trading plan.

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

Gallagher Investments, LLC sold 70,000 shares of MIAX common stock. The open-market sales occurred on June 2, 2026 at prices ranging from $42.00 to $45.73, with a reported weighted average price of $42.36 per share.

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

Gallagher exercised 70,000 nonqualified stock options into MIAX common stock at a conversion price of $12.00 per share. These options were fully vested, and the exercise was paired with same-day open-market sales of the acquired shares.

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

After the reported transactions, Gallagher Investments, LLC holds 1,723,275 MIAX common shares. Mr. Gallagher maintains beneficial ownership with voting and dispositive control over this entity, so these shares represent his indirect ownership position following the June 2, 2026 trades.

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

Yes. The filing states the 70,000-share sale was executed pursuant to a previously established Rule 10b5-1 Plan adopted by Mr. Gallagher on December 29, 2025, indicating the sales were pre-planned rather than discretionary market-timing decisions.

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

Gallagher exercised 70,000 nonqualified stock options (right to buy) in MIAX with an exercise price of $12.00 per share. These options were fully vested and were scheduled to expire on August 2, 2026, leading to the acquisition of 70,000 common shares.