Miami International GC sells 44K shares at $40.49

MIAMI INTERNATIONAL HOLDINGS, INC.

Rhea-AI Filing Summary

MIAMI INTERNATIONAL HOLDINGS, INC. (MIAX) reported that executive vice president, general counsel and corporate secretary Barbara J. Comly exercised options for 44,445 shares of common stock at an exercise price of $12.00 per share on September 2, 2026, and sold the same number of shares at a weighted average price of $40.49 per share, pursuant to a previously established Rule 10b5-1 trading plan.

The option exercise reduced her position in the related option grant by 44,445 options, leaving 44,444 options of that grant outstanding and fully vested, with an expiration date of May 28, 2028.

Insider Trade Summary 10b5-1

Exercise and Sale: 44,445 shares ($1.27M approx. pre-tax spread)

Exercise and Sale 3 txns

Insider Comly Barbara J.

Role EVP, GC & Corporate Secretary

Sold 44,445 shs ($1.80M)

Approx. gross sale proceeds $1.80M

Approx. exercise cost $533K

Approx. pre-tax spread $1.27M

Type	Security	Shares	Price	Value
Exercise	Nonqualified Stock Option (Right to Buy) F1, F3	44,445	$0.00	$0.00
Exercise	Common Stock F1	44,445	$12.00	$533K
Sale	Common Stock F1, F2	44,445	$40.49	$1.80M

Holdings After Transaction: Nonqualified Stock Option (Right to Buy) — 44,444 contracts (Direct); Common Stock — 839,564 shares (Direct)

Footnotes (3)

1. F1. This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 18, 2025.
2. F2. This transaction was executed in multiple trades throughout the day at prices ranging from $39.66 to $41.80. 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.
3. F3. The options are fully vested.

Key Figures

Shares underlying options exercised: 44,445 shares Option exercise price: $12.00 per share Shares of common stock sold: 44,445 shares +5 more

8 metrics

Shares underlying options exercised 44,445 shares Nonqualified stock options for MIAX common stock exercised on September 2, 2026

Option exercise price $12.00 per share Exercise price for 44,445 nonqualified stock options exercised on September 2, 2026

Shares of common stock sold 44,445 shares MIAX common shares sold on September 2, 2026 after option exercise

Weighted average sale price $40.49 per share Weighted average price for 44,445 MIAX shares sold in multiple trades on September 2, 2026

Sale price range $39.66 to $41.80 per share Price range of multiple trades comprising the 44,445-share sale on September 2, 2026

Options remaining from this grant 44,444 options Nonqualified stock options reported as held directly after the exercise on September 2, 2026

Option expiration date May 28, 2028 Expiration date for the nonqualified stock options related to the reported exercise

Rule 10b5-1 plan adoption date December 18, 2025 Date Barbara J. Comly adopted the trading plan governing these transactions

Key Terms

Nonqualified Stock Option, Rule 10b5-1 Plan, weighted average sales price

3 terms

Nonqualified Stock Option financial

"The filing reports the exercise of a Nonqualified Stock Option to buy MIAX common stock."

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.

Rule 10b5-1 Plan regulatory

"A footnote states the trades were effected under 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.

weighted average sales price financial

"The price reported reflects the weighted average sales price for the shares sold."

FAQ

What did MIAX executive Barbara J. Comly report in this Form 4 for MIAX?

She reported exercising 44,445 options for MIAX common stock at $12.00 per share and selling 44,445 shares at a weighted average price of $40.49 per share on September 2, 2026, under a previously adopted Rule 10b5-1 trading plan.

How many MIAX shares did Barbara J. Comly sell and at what price?

She sold 44,445 shares of MIAX common stock on September 2, 2026 at a weighted average price of $40.49 per share, with individual trade prices ranging from $39.66 to $41.80, as disclosed in the Form 4 footnote.

What options did Barbara J. Comly exercise in this MIAX Form 4 filing?

She exercised 44,445 nonqualified stock options to buy MIAX common stock at an exercise price of $12.00 per share on September 2, 2026. The options are reported as fully vested and are scheduled to expire on May 28, 2028.

Were Barbara J. Comly’s MIAX transactions under a Rule 10b5-1 plan?

Yes. A footnote states that the reported transactions on September 2, 2026 were effected pursuant to a previously established Rule 10b5-1 Plan adopted by Barbara J. Comly on December 18, 2025.

How many MIAX options from this grant does Barbara J. Comly hold after these transactions?

After exercising 44,445 options from this grant, she is reported as holding 44,444 options of the same nonqualified stock option grant directly, with those options fully vested and expiring on May 28, 2028.

Does the Form 4 state how the MIAX sale price range was determined?

Yes. The filing explains that the sale was executed in multiple trades at prices ranging from $39.66 to $41.80, and that the reported $40.49 figure is the weighted average sales price for the reported 44,445 shares.

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Available on EDGAR 09/04/2026 - 04:31 PM Accepted by SEC EDGAR 09/04/2026 - 04:31 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^*

Comly Barbara J.

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	EVP, GC & Corporate Secretary

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/02/2026

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	09/02/2026		M(1)		44,445	A	$12	884,009	D
Common Stock	09/02/2026		S(1)		44,445	D	$40.49(2)	839,564	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Nonqualified Stock Option (Right to Buy)	$12	09/02/2026		M(1)			44,445	(3)	05/28/2028	Common Stock	44,445	$0	44,444	D

Explanation of Responses:

1. This transaction was effected pursuant to a previously established Rule 10b5-1 Plan adopted by the Reporting Person on December 18, 2025.

2. This transaction was executed in multiple trades throughout the day at prices ranging from $39.66 to $41.80. 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.

3. The options are fully vested.

Remarks:

	/s/Alessandra Maria Corona Henriques, Attorney-in-Fact	09/04/2026
	** 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)