Miami Intl Hldg SEC Filings

Miami International Holdings (MIAX) announced its financial results for the quarter ended September 30, 2025. The company furnished a press release as Exhibit 99.1 under Item 2.02 to provide the details. The disclosure is being furnished to the SEC and is not deemed “filed” under the Exchange Act.

Miami International Holdings, Inc. announced that director Jamil Nazarali notified the company he will resign effective October 3, 2025. The notice says the resignation is to "pursue other professional opportunities" and was not the result of any dispute or disagreement with the company, its management, or its board. The filing does not state any replacement director, transition plan, or additional details about Mr. Nazarali's future roles. This is a director-level governance change affecting board composition effective on a specific in 2025.

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.

Insider purchase and holdings disclosed. Murray Stahl and Horizon Kinetics Asset Management LLC reported acquisitions and existing derivative holdings in Miami International Holdings, Inc. (MIAX). On 09/26/2025 a purchase (code P) of Common Stock at $41.76 was reported, leaving 4,557,923 shares beneficially owned indirectly by Horizon Kinetics. The filing also lists vested, exercisable stock options awarded 08/13/2025 (totaling 34,831 options across four strike prices: $16.14, $25.98, $19.84) held directly, and multiple warrants held indirectly by Horizon Kinetics (totaling 137,636 warrants across various strikes and expiration dates). Murray Stahl is identified as Chairman, CEO, and CIO of HKAM and disclaims direct investment discretion over the managed accounts' holdings.

Murray Stahl and Horizon Kinetics Asset Management LLC reported insider transactions in Miami International Holdings, Inc. (MIAX). On 08/28/2025 a Form 4 shows a purchase of 34,470 shares of MIAX common stock at $36.10 per share. After the reported transaction, the filing shows beneficial ownership of 4,557,919 shares held indirectly by Horizon Kinetics. The filing also lists several vested stock options held directly by Mr. Stahl (totaling 43,131 options across multiple grant exercise prices and expirations) and multiple vested warrants held indirectly by Horizon Kinetics (totaling 137,656 warrants across different strikes and expiration dates). The filing clarifies Mr. Stahls roles at Horizon Kinetics and disclaims direct beneficial ownership except for any pecuniary interest.

John Smollen, EVP Traded Products & Relation of Miami International Holdings, Inc. (MIAX), reported option exercises on 09/11/2025 and subsequent net settlement for tax withholding. The filing shows two nonqualified stock option exercises of 125,001 and 24,999 shares at an exercise price of $12 per share, and the surrender of 52,054 shares to satisfy tax-withholding obligations at an indicated price of $37.39 per share. The options were fully vested and exercisable on 09/17/2025. Following the transactions the reporting person beneficially owned 166,119 shares directly. The form is signed by an attorney-in-fact on 09/15/2025.

Miami International Holdings insider Edward Deitzel completed option exercises and share purchases in September 2025, increasing his direct holdings. On 09/09/2025 he exercised 62,500 nonqualified options with a $12 exercise price and acquired 62,500 common shares via that exercise. The same day 38,090 shares were surrendered to the company to satisfy tax withholding related to the net settlement of those exercises; this surrender is not a sale. On 09/10/2025 he exercised 16,666 incentive stock options at $12, and on 09/11/2025 he purchased 16,666 shares at $12. Following these transactions his reported beneficial ownership totaled 122,963 shares. All options exercised were fully vested.

Jayabalan Harish, EVP, CISO and CRO of Miami International Holdings, Inc. (MIAX), reported option exercises and resulting share ownership changes on 09/09/2025. He exercised 21,999 incentive stock options and 3,001 nonqualified stock options at a $12 exercise price, resulting in 25,000 shares acquired that day. The filing shows 72,384 shares beneficially owned after the first reported acquisition line and 75,385 after the second; a separate line records a net disposition of 1,980 shares at $37.30 representing shares surrendered to satisfy tax withholding on the net settlement of exercised options (not a sale). The reporting was signed by an attorney-in-fact on 09/11/2025.

Shelly Brown, EVP of Strategic Planning & Business Development at Miami International Holdings, Inc. (MIAX), reported a disposition of 16,283 shares of MIAX common stock on 09/10/2025 at a reported price of $36.81 per share. After the transaction, she beneficially owns 311,699 shares, held directly.

The filing explains these shares were surrendered to the company to satisfy tax withholding in connection with the net settlement of restricted stock awards and explicitly states this was not a sale by the reporting person. The Form 4 was submitted by an attorney-in-fact on behalf of the reporting person.