YMAB Merger: Director’s Shares, RSUs and Options Converted to Cash

Rhea-AI Filing Summary

Y-mAbs Therapeutics director and 10% owner Johan Wedell-Wedellsborg reported multiple disposals tied to a completed merger. On September 16, 2025, Purchaser completed a tender offer and merged Y-mAbs into an indirect wholly owned subsidiary of Perseus BidCo US, Inc., with each outstanding share cancelled for $8.60 cash per share. The reporting person’s direct and indirect common shares, restricted stock units and stock options were cancelled and converted into cash payments under the Merger Agreement: ordinary shares and RSUs were exchanged for $8.60 per share, while options were cashed out for the excess of $8.60 over each exercise price; options with exercise prices at or above $8.60 were cancelled without consideration. The Form 4 reflects zero continuing share ownership.

Positive

• Completed change of control with a defined cash consideration of $8.60 per share, providing immediate liquidity to holders
• All outstanding equity awards addressed: RSUs and options were converted per agreement terms, removing settlement uncertainty

Negative

• Insider ownership eliminated—the reporting person shows zero direct or indirect shares following the Merger, removing public alignment
• Out-of-the-money options cancelled without consideration, resulting in no recovery for holders of options with exercise prices ≥ $8.60

Insights

Financial Analyst

TL;DR Director’s holdings were fully cashed out at $8.60 per share as part of a controlling-merger, removing insider equity exposure.

The transaction is material for equity holders because it represents a change of control and a cash-out of all outstanding equity and equity-based awards at a fixed price. The Merger consideration of $8.60 per share determined both common stock cash-outs and the option settlement formulas, meaning holders received value only to the extent options were in-the-money. The Form 4 shows no remaining direct or indirect beneficial ownership by the reporting person, indicating a complete exit by this insider from public equity exposure.

Corporate Governance Expert

TL;DR Governance impact: change of control completed and legacy equity awards extinguished, consistent with standard merger treatment.

The Merger Agreement converted all outstanding RSUs and options into cash payments and cancelled shares, which is a routine control outcome but significant governance-wise because it ends public minority governance rights. The disclosure clarifies treatment of in-the-money options and cancellation of out-of-the-money options, and notes the reporting person’s indirect ownership via WG Biotech ApS prior to the Effective Time. The Form 4 is consistent with Section 16 reporting of insider holdings following a definitive liquidity event.

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^*

Wedell-Wedellsborg Johan

(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	X	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
Common Stock	09/16/2025(1)		U		4,559,233	D	$8.6(2)	0	I	By WG Biotech ApS(5)

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)	$4.38	09/16/2025(1)		D			36,000	(6)	10/21/2026	Common Stock	36,000	(6)	0	D
Employee Stock Option (right to buy)	$11.16	09/16/2025(1)		D			32,000	(6)	04/24/2028	Common Stock	32,000	(6)	0	D
Employee Stock Option (right to buy)	$21.45	09/16/2025(1)		D			16,000	(6)	06/12/2029	Common Stock	16,000	(6)	0	D
Employee Stock Option (right to buy)	$48.67	09/16/2025(1)		D			11,000	(6)	06/23/2030	Common Stock	11,000	(6)	0	D
Employee Stock Option (right to buy)	$37.53	09/16/2025(1)		D			11,000	(6)	06/10/2031	Common Stock	11,000	(6)	0	D
Employee Stock Option (right to buy)	$16.64	09/16/2025(1)		D			16,000	(6)	07/15/2032	Common Stock	16,000	(6)	0	D
Employee Stock Option (right to buy)	$8.13	09/16/2025(1)		D			13,950	(6)	06/08/2033	Common Stock	13,950	(6)	0	D
Employee Stock Option (right to buy)	$12.01	09/16/2025(1)		D			14,545	(6)	06/11/2034	Common Stock	14,545	(6)	0	D
Employee Stock Option (right to buy)	$4.51	09/16/2025(1)		D			33,450	(6)	06/30/2035	Common Stock	33,450	(6)	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. Reporting Person is the majority owner of WG Biotech ApS and as such has sole voting and dispositive power with respect to such shares.

6. 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
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FAQ

What did the Form 4 filed for YMAB disclose about Johan Wedell-Wedellsborg’s holdings?

The Form 4 shows the reporting person’s common shares, RSUs and options were cancelled or cashed out in connection with the merger, leaving 0 shares beneficially owned.

How much cash was paid per Y-mAbs share in the merger?

The Merger Consideration paid was $8.60 per share in cash, without interest, subject to tax withholding.

How were stock options treated in the Y-mAbs merger?

Each outstanding option was converted into a cash payment equal to the number of shares times the excess of $8.60 over the option exercise price; options with exercise prices ≥ $8.60 were cancelled for no consideration.

Were restricted stock units (RSUs) affected by the merger?

Yes. Each RSU, vested or unvested, was cancelled and converted into the right to receive cash equal to the number of shares issuable times $8.60.

Does the Form 4 indicate any remaining indirect ownership through WG Biotech ApS?

No. The Form 4 reports 0 shares beneficially owned following the reported transactions; the filing notes the reporting person was majority owner of WG Biotech ApS prior to the Effective Time.