MIAX insider filing: 4.56M indirect shares; vested warrants/options

Rhea-AI Filing Summary

Murray Stahl and Horizon Kinetics Asset Management LLC reported coordinated Section 16 transactions in Miami International Holdings, Inc. (MIAX). On 10/03/2025 a purchase (code P) of 2 shares of common stock was executed at $41.97, leaving 4,557,925 shares beneficially owned indirectly through Horizon Kinetics. The filing discloses multiple vested stock options (totaling 44,831 options across various strike prices) and vested, presently exercisable warrants (totaling 137,656 warrants) with exercise prices between $15.00 and $20.50 and expirations through 05/31/2031 to 02/05/2027 and beyond. Disclosure states Mr. Stahl is Chairman, CEO and CIO of Horizon Kinetics, that the reported ownership is indirect, and that certain preferred and non-voting shares converted one-for-one to common stock upon the company's IPO.

Positive

• Significant indirect stake of 4,557,925 shares held by Horizon Kinetics suggests sustained investor interest
• Options and warrants are vested and exercisable, enabling structured alignment of management/manager incentives with shareholder outcomes

Negative

• Potential future dilution from 44,831 options and 137,656 warrants if exercised
• Ownership held indirectly through an asset manager, with the reporting person disclaiming direct investment discretion

Insights

Corporate Governance Expert

Minor direct purchase; material indirect stake held by investment manager.

The filing shows a small direct purchase of 2 common shares at $41.97 alongside a large indirect stake of 4,557,925 shares held through Horizon Kinetics Asset Management LLC. The report clarifies that Murray Stahl is Chairman, CEO and CIO of the asset manager and disclaims direct investment discretion over the managed accounts' holdings.

This structure means voting and economic exposure are held through an investment adviser vehicle rather than personally. Investors should note the distinction when assessing insider alignment; any change in the asset manager's mandate or ownership could affect these holdings over time.

Securities/Equity Analyst

Multiple vested derivatives increase potential future common dilution/exposure.

The Form 4 lists vested options totaling 44,831 and vested, exercisable warrants totaling 137,656 with strike prices from $15.00 to $25.98 and expiration dates spanning 04/08/2026 to 03/26/2033. These instruments, if exercised, would convert into additional common shares and increase outstanding share count.

Key near-term items to monitor are warrant expiration dates in 2026 and option exercise windows beginning as early as 08/13/2025, which determine potential dilution timing and cash inflows if exercised.

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^*

STAHL MURRAY

(Last) (First) (Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK NY 10016

(City) (State) (Zip)

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
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
10/03/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

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	10/03/2025		P		2	A	$41.97	4,557,925(1)(2)	I	Horizon Kinetics Asset Management LLC

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
OPTIONS	$16.14(3)							08/13/2025	05/31/2031	Miami International Holdings Inc	2,500		2,500	D
OPTIONS	$16.14(3)							08/13/2025	07/31/2031	Miami International Holdings Inc	7,500		7,500	D
OPTIONS	$25.98(3)							08/13/2025	06/30/2032	Miami International Holdings Inc	10,000		10,000	D
OPTIONS	$19.84(3)							08/13/2025	03/26/2033	Miami International Holdings Inc	14,331		14,331	D
Warrants	$20.5(1)(4)							08/13/2025	11/15/2026	Miami International Holdings Inc	24,878		24,878	I	Horizon Kinetics Asset Management LLC
Warrants	$20.5(1)(4)							08/13/2025	02/05/2027	Miami International Holdings Inc	27,561		27,561	I	Horizon Kinetics Asset Management LLC
Warrants	$15(1)(4)							08/13/2025	04/08/2026	Miami International Holdings Inc	21,290		21,290	I	Horizon Kinetics Asset Management LLC
Warrants	$20.5(1)(4)							08/13/2025	10/17/2026	Miami International Holdings Inc	38,927		38,927	I	Horizon Kinetics Asset Management LLC

1. Name and Address of Reporting Person^*

STAHL MURRAY

(Last) (First) (Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK NY 10016

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

HORIZON KINETICS ASSET MANAGEMENT LLC

(Last) (First) (Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK NY 10016

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. Murray Stahl serves as Chairman, Chief Executive Officer, and Chief Investment Officer of Horizon Kinetics Asset Management LLC ("HKAM"), which manages funds and accounts (the "Managed Accounts") that hold securities of the Issuer. Mr. Stahl does not exercise investment discretion with respect to the securities of the Issuer that are beneficially owned by the Managed Accounts. Mr. Stahl disclaims beneficial ownership over the securities reported, except to the extent of his pecuniary interest therein, if any. The filing of this Form shall not be deemed an admission that the Mr. Stahl is the beneficial owner of such securities for purposes of Section 16 or any other purpose.

2. Includes 5,000 shares of Series B Preferred Stock that have been converted into Common Stock on a one-for-one basis upon the closing of the Company's initial public offering and which have no expiration date and 14,998 shares of Non-Voting Common Stock that have been converted into shares of Common Stock on a one-for-one basis upon the closing of the Company's IPO and which have no expiration date.

3. The Options given to Mr. Stahl are fully vested.

4. The Warrants are currently vested and presently exercisable until the expiration date show.

	/s/ Jay Kesslen, attorney-in-fact	10/06/2025
	** 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.

FAQ

What transactions were reported for MIAX on the Form 4?

The filing reports a purchase of 2 common shares at $41.97 on 10/03/2025 and disclosures of vested options and vested, exercisable warrants.

How many MIAX shares are beneficially owned by Horizon Kinetics?

The filing shows 4,557,925 shares beneficially owned indirectly through Horizon Kinetics Asset Management LLC.

Are the reported options and warrants exercisable?

Yes. The Form 4 states the listed options are fully vested and the warrants are currently vested and presently exercisable with various expiration dates through 03/26/2033.

What are the exercise prices for the reported derivatives?

Strike prices listed include $16.14, $25.98, $19.84, and warrants at $20.50 and $15.00.

What relationship does Murray Stahl have to Horizon Kinetics?

Murray Stahl serves as Chairman, Chief Executive Officer, and Chief Investment Officer of Horizon Kinetics Asset Management LLC, per the filing.