Schedule 13G/A: Acorn entities disclose stakes in Y-mAbs, Hove holds 6.2%

Rhea-AI Filing Summary

Acorn-related investors disclosed beneficial ownership positions in Y-mAbs Therapeutics (YMAB). The filing shows Acorn Bioventures, L.P. and Acorn Capital Advisors GP, LLC each report shared voting and dispositive power over 1,175,686 shares (2.6% of the class). Acorn Bioventures 2, L.P. and its GP report shared voting and dispositive power over 1,620,611 shares (3.6%). Individually, Anders Hove is reported with shared voting and dispositive power over 2,796,297 shares, representing 6.2% of the outstanding common stock. The percentages are calculated using 45,438,420 shares outstanding as of August 4, 2025. All reporting persons are organized in Delaware except Anders Hove, a U.S. citizen. The filers certify the holdings were not acquired to influence control of the issuer.

Positive

• Anders Hove is reported as beneficially owning 2,796,297 shares, equal to 6.2% of outstanding common stock, a material disclosure above the 5% threshold
• Filing specifies share counts and voting/dispositive power for each reporting person, enabling transparent ownership tracking
• Percentages are calculated using a disclosed share base of 45,438,420 shares outstanding as of August 4, 2025

Negative

• None.

Insights

Financial Analyst

TL;DR: A key insider and affiliated Acorn entities report meaningful stakes; Anders Hove holds a >5% position.

The Schedule 13G/A discloses that affiliated Acorn investment vehicles collectively report material holdings in YMAB, with specific positions of 2.6% and 3.6% reported by individual funds. Notably, Anders Hove is reported with a 6.2% beneficial interest based on 45,438,420 shares outstanding, which crosses the common 5% reporting threshold and can be material for shareholder composition analysis. The filing states shared voting and dispositive power for these positions and includes the standard certification that the holdings are not intended to change control. For investors, this updates ownership concentration and insider-affiliated exposure without indicating activist intent or control-seeking activity.

Corporate Governance Expert

TL;DR: Ownership disclosure shows a >5% beneficial owner and affiliated GP relationships; no group or control assertion.

The filing identifies structure: two Acorn limited partnerships and their GP entities, with Anders Hove as manager, resulting in reported shared voting and dispositive power across holdings. The 13G/A classification and the signed certification indicate a passive reporting status rather than an active Section 13(d) control filing. The document lists no group formation, no ownership exclusions, and reaffirms the passive intent statement. This is important for governance review because a 6.2% reported stake by an individual associated with the funds is material for ownership tables and may affect proxy dynamics, though the filer disclaims any change-of-control purpose.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 3)

Y-mAbs Therapeutics, Inc.

(Name of Issuer)

Common stock, par value $0.0001 per share

(Title of Class of Securities)

984241109

(CUSIP Number)

08/19/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 984241109

1

Names of Reporting Persons

ACORN BIOVENTURES, L.P.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,175,686.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,175,686.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,175,686.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 984241109

1

Names of Reporting Persons

ACORN CAPITAL ADVISORS GP, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,175,686.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,175,686.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,175,686.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

2.6 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

CUSIP No. 984241109

1

Names of Reporting Persons

ACORN BIOVENTURES 2, L.P.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,620,611.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,620,611.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,620,611.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.6 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

CUSIP No. 984241109

1

Names of Reporting Persons

Acorn Capital Advisors GP 2, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,620,611.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,620,611.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,620,611.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

3.6 %

12

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13G

CUSIP No. 984241109

1

Names of Reporting Persons

Anders Hove

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 2,796,297.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 2,796,297.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,796,297.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.2 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Y-mAbs Therapeutics, Inc.
(b)	Address of issuer's principal executive offices: 202 CARNEGIE CENTER, SUITE 301, PRINCETON, NEW JERSEY, 08540.
Item 2.
(a)	Name of person filing: Acorn Bioventures, L.P. Acorn Capital Advisors GP, LLC Acorn Bioventures 2, L.P. Acorn Capital Advisors GP 2, LLC Anders Hove
(b)	Address or principal business office or, if none, residence: 420 Lexington Avenue, Suite 2626, New York, New York 10170
(c)	Citizenship: Acorn Bioventures, L.P. and Acorn Bioventures 2 L.P. are both Delaware limited partnerships. Acorn Capital Advisors GP, LLC and Acorn Capital Advisors GP 2, LLC are both Delaware limited liability companies. Anders Hove is a citizen of the United States of America.
(d)	Title of class of securities: Common stock, par value $0.0001 per share
(e)	CUSIP No.: 984241109
Item 4.	Ownership
(a)	Amount beneficially owned: The information required by Items 4(a) - (c) is set forth in Rows (5) - (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.
(b)	Percent of class: The percentages set forth herein are calculated based upon 45,438,420 shares of Common Stock outstanding as of August 4, 2025 as reported in the Issuer's Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2025 filed with the Securities and Exchange Commission on August 8, 2025.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Acorn Capital Advisors GP, LLC is the General Partner of Acorn Bioventures, LP and may be deemed to beneficially own the shares of Common Stock beneficially owned by Acorn Bioventures, LP. Acorn Capital Advisors GP 2, LLC is the General Partner of Acorn Bioventures 2, L.P. and may be deemed to beneficially own the shares of Common Stock beneficially owned by Acorn Bioventures 2, L.P.
	(ii) Shared power to vote or to direct the vote: Anders Hove, in his capacity as Manager of each of Acorn Capital Advisors GP, LLC and Acorn Capital Advisors GP 2, LLC, may be deemed to beneficially own the shares beneficially owned by each of Acorn Capital Advisors GP, LLC and Acorn Capital Advisors GP 2, LLC.
	(iii) Sole power to dispose or to direct the disposition of:
	(iv) Shared power to dispose or to direct the disposition of:
Item 5.	Ownership of 5 Percent or Less of a Class.
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

ACORN BIOVENTURES, L.P.

Signature:	Anders Hove
Name/Title:	Manager of General Partner
Date:	08/20/2025

ACORN CAPITAL ADVISORS GP, LLC

Signature:	Anders Hove
Name/Title:	Manager
Date:	08/20/2025

ACORN BIOVENTURES 2, L.P.

Signature:	Anders Hove
Name/Title:	Manager of General Partner
Date:	08/20/2025

Acorn Capital Advisors GP 2, LLC

Signature:	Anders Hove
Name/Title:	Manager
Date:	08/20/2025

Anders Hove

Signature:	Anders Hove
Name/Title:	Individually
Date:	08/20/2025

FAQ

Who filed the Schedule 13G/A for YMAB?

The filing was made by Acorn Bioventures, L.P.; Acorn Capital Advisors GP, LLC; Acorn Bioventures 2, L.P.; Acorn Capital Advisors GP 2, LLC; and Anders Hove.

How many YMAB shares does Anders Hove beneficially own?

Anders Hove is reported with shared voting and dispositive power over 2,796,297 shares, representing 6.2% of the class.

What percentages of YMAB do the Acorn entities report?

Acorn Bioventures, L.P. and Acorn Capital Advisors GP, LLC each report 1,175,686 shares (2.6%); Acorn Bioventures 2, L.P. and its GP report 1,620,611 shares (3.6%).

What share count was used to calculate percentages in the filing?

Percentages are based on 45,438,420 shares outstanding as of August 4, 2025, per the issuer's quarterly report.

Does the filing indicate an intent to change or influence control of Y-mAbs?

No. The filers certify the securities were not acquired and are not held to change or influence control and are reported under Schedule 13G/A.