[Form 4] Y-mAbs Therapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Y-mAbs director Laura Hamill reported that pursuant to a merger transaction on 09/16/2025 she disposed of all her company equity for cash consideration of $8.60 per share. The Form 4 shows 5,825 common shares tendered and 25,080 RSUs converted into cash, leaving 0 shares beneficially owned. Outstanding stock options were also cancelled or cashed out: several options were converted into cash based on the difference between the $8.60 merger price and their exercise prices, while any option with an exercise price equal to or above $8.60 was cancelled for no consideration. The reporting person’s position in Y-mAbs is fully eliminated as a result of the merger.

Positive

• All equity converted to cash at a stated merger consideration of $8.60 per share, providing immediate liquidity to the reporting person
• RSUs and in-the-money options were settled for cash under the merger agreement, ensuring value realization for vested/unvested awards

Negative

• Several stock options with exercise prices ≥ $8.60 were cancelled for no consideration, resulting in loss of potential upside for those awards
• Reporting person’s beneficial ownership reduced to zero, meaning no ongoing public-equity alignment with remaining shareholders post-merger

Insights

Securities Analyst

TL;DR: Director fully exited equity post-merger, receiving $8.60 per share and cash settlements for vested/unvested awards.

The Form 4 documents a corporate-control transaction that converted all equity holdings into cash at $8.60 per share as part of a completed merger. The reporting person surrendered 5,825 shares and had 25,080 RSUs converted to cash, with multiple stock options either cashed out for the spread or cancelled if their exercise price met or exceeded $8.60. For investors, this is an insider disposition driven by deal terms rather than voluntary market sales; it reflects transactional liquidity rather than a trading signal about company fundamentals.

Corporate Governance Expert

TL;DR: Insider holdings were eliminated under merger terms; treatment of awards follows standard change-of-control provisions.

The filing shows standard merger consideration mechanics: shares tendered for $8.60 cash, RSUs converted pro rata to cash and options net-settled based on spread, with in-the-money options receiving cash and out-of-the-money or at‑the‑money options cancelled where exercise price >= consideration. The disclosure is complete regarding the mechanics and outcomes for each award class and confirms the director no longer holds equity in the surviving private entity.

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

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X

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

Hamill Laura

(Last) (First) (Middle)

C/O Y-MABS THERAPEUTICS, INC.

230 PARK AVENUE, SUITE 3350

(Street)

NEW YORK NY 10169

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Y-mAbs Therapeutics, Inc. [ YMAB ]

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)
09/16/2025

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

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

X	Form filed by One Reporting Person
	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	09/16/2025(1)		U		5,825	D	$8.6(2)	0	D
Common Stock	09/16/2025(1)		D		25,080(3)	D	(4)	0	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
Employee Stock Option (right to buy)	$48.67	09/16/2025(1)		D			27,000	(5)	06/23/2030	Common Stock	27,000	(5)	0	D
Employee Stock Option (right to buy)	$37.53	09/16/2025(1)		D			11,000	(5)	06/10/2031	Common Stock	11,000	(5)	0	D
Employee Stock Option (right to buy)	$16.64	09/16/2025(1)		D			16,000	(5)	07/15/2032	Common Stock	16,000	(5)	0	D
Employee Stock Option (right to buy)	$8.13	09/16/2025(1)		D			13,950	(5)	06/08/2033	Common Stock	13,950	(5)	0	D
Employee Stock Option (right to buy)	$12.01	09/16/2025(1)		D			14,545	(5)	06/11/2034	Common Stock	14,545	(5)	0	D
Employee Stock Option (right to buy)	$4.51	09/16/2025(1)		D			33,450	(5)	06/30/2035	Common Stock	33,450	(5)	0	D

Explanation of Responses:

1. Pursuant to the Agreement and Plan of Merger (the "Merger Agreement"), dated as of August 4, 2025, by and among Y-mAbs Therapeutics, Inc. (the "Issuer"), Yosemite Merger Sub, Inc. ("Purchaser"), Perseus BidCo US, Inc., a Delaware corporation ("Parent"), and Stark International Lux, a Luxembourg private limited liability company ("Ultimate Parent"), on September 16, 2025, Purchaser completed a tender offer for shares of common stock of the Issuer (each, a "Share") and thereafter merged with and into the Issuer, with the Issuer continuing as the surviving corporation and an indirect wholly owned subsidiary of Parent (the "Merger").

2. Pursuant to the terms of the Merger Agreement, the Shares were tendered at the Offer Acceptance Time (as defined in the Merger Agreement) in exchange for the right to receive $8.60 per Share, in cash, without interest, subject to any applicable withholding of taxes (the "Merger Consideration"). At the effective time of the Merger (being such date and at such time as the certificate of merger in respect of the Merger was duly filed with the Secretary of State of the State of Delaware in accordance with the DGCL) (the "Effective Time"), each issued and outstanding Share was cancelled in exchange for the Merger Consideration.

3. Represents restricted stock units ("RSUs") granted to the Reporting Person pursuant to the Issuer's 2018 Equity Incentive Plan. Each RSU represents a contingent right to receive one share of Common Stock on the vesting dates of the RSU.

4. At the Effective Time, pursuant to the Merger Agreement, each RSU award outstanding as of immediately prior to the Effective Time, whether vested or unvested, was cancelled and converted into the right to receive an amount in cash, without interest, equal to the product of (a) the total number of Shares issuable in settlement of such RSU award immediately prior to the Effective Time, multiplied by (b) the Merger Consideration.

5. At the Effective Time, pursuant to the Merger Agreement, each stock option ("Option") outstanding as of immediately prior to the Effective Time, whether vested or unvested, was cancelled and converted into the right to receive cash, without interest, equal to the product of (a) the total number of Shares subject to such Option immediately prior to the Effective Time, multiplied by (b) the excess of the Merger Consideration over the exercise price payable per Share under such Option. Any Options with an exercise price equal to or in excess of the Merger Consideration were cancelled for no consideration.

Remarks:

The foregoing descriptions in the footnotes to this Form 4 are qualified in their entirety by reference to the terms of the Merger Agreement. In the event of any conflict between the descriptions above and the terms set forth in the Merger Agreement, the terms set forth in the Merger Agreement shall control.

	/s/ John LaRocca, Attorney-in-Fact	09/18/2025
	** 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).
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FAQ

What did Laura Hamill receive per YMAB share in the merger?

The filing states a merger consideration of $8.60 per Share paid in cash.

How many ordinary shares did the reporting person tender in the YMAB transaction?

The Form 4 reports 5,825 common shares tendered and disposed of on 09/16/2025.

What happened to RSUs and options held by the reporting person in YMAB?

RSUs (25,080) were converted into the right to receive cash equal to the number of shares times $8.60; options were either cashed out based on the spread or cancelled if their exercise price was equal to or above $8.60.

Does Laura Hamill retain any YMAB shares after the merger?

No. The Form 4 shows 0 shares beneficially owned following the reported transactions.

Was the disposition a market sale or merger-related?

The filing explains the dispositions occurred pursuant to a merger agreement and related tender offer completed on 09/16/2025.