Atlas Venture Fund VIII, L.P. - 23 Dec 2025 Form 4 Insider Report for INTEGRAL AD SCIENCE HOLDING CORP. (IAS)

Role: 10%+ Owner
Signature: Atlas Venture Fund VIII, L.P., By: Atlas Venture Associates VIII, L.P., its general partner, By: Atlas Venture Associates VIII, Inc., its general partner, By: Frank Castellucci, General Counsel and Secretary /s/ Frank Castellucci
Issuer symbol: IAS
Transactions as of: 23 Dec 2025
Net transactions value: -$234,044,531
Form type: 4
Filing time: 23 Dec 2025, 20:35:54 UTC
Previous filing: 29 Jun 2021
SEC: View on sec.gov

Reporting Owners (3)

Name	Relationship	Address	Signature	Signature date	CIK
Atlas Venture Fund VIII, L.P.	10%+ Owner	56 WAREHAM STREET, FLOOR 3, BOSTON	Atlas Venture Fund VIII, L.P., By: Atlas Venture Associates VIII, L.P., its general partner, By: Atlas Venture Associates VIII, Inc., its general partner, By: Frank Castellucci, General Counsel and Secretary /s/ Frank Castellucci	23 Dec 2025	0001451626
Atlas Venture Associates VIII, L.P.	10%+ Owner	56 WAREHAM STREET, FLOOR 3, BOSTON	Atlas Venture Associates VIII, L.P. By: Atlas Venture Associates VIII, Inc., its general partner, By: Frank Castellucci, General Counsel and Secretary /s/ Frank Castellucci	23 Dec 2025	0001451625
Atlas Venture Associates VIII, Inc.	10%+ Owner	56 WAREHAM STREET, FLOOR 3, BOSTON	Atlas Venture Associates VIII, Inc, By: Frank Castellucci, General Counsel and Secretary /s/ Frank Castellucci	23 Dec 2025	0001451624

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	IAS	Common stock, $0.001 par value	Other	$234,044,531	-22,722,770	-100%	$10.30	0	23 Dec 2025	See Footnote	F1, F2

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Atlas Venture Fund VIII, L.P. is no longer subject to Section 16 filing requirements. Form 4 or Form 5 obligations may continue.

Explanation of Responses:

Id	Content
F1	This Form 4 reports securities disposed pursuant to the Agreement and Plan of Merger, dated as of September 24, 2025 (the "Merger Agreement") by and among the Issuer, Igloo Group Parent, Inc., a Delaware corporation ("Parent"), and Igloo Group Acquisition Company, Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"). Pursuant to the Merger Agreement, on December 23, 2025 (the "Effective Time"), Merger Sub merged with and into the Issuer, with the Issuer surviving as a wholly owned subsidiary of Parent. At the Effective Time, each share of common stock of the Issuer owned by the reporting persons immediately prior to the Effective Time was automatically cancelled, extinguished and converted into the right to receive $10.30 in cash, without interest thereon.
F2	Shares held directly by Atlas Venture Fund VIII, L.P. ("Atlas VIII"). Atlas Venture Associates VIII, L.P. ("AVA VIII LP") is the sole general partner of Atlas VIII. Atlas Venture Associates VIII, Inc. ("AVA VIII Inc.") is the sole general partner of AVA VIII LP. Each of Atlas VIII, AVA VIII LP and AVA VIII Inc. disclaim beneficial ownership of all shares except to the extent of its pecuniary interest, if any, therein. This report shall not be deemed to be an admission that the reporting persons are the beneficial owners of such securities for purposes of Section 16 or for any other purpose.

Content

This Form 4 reports securities disposed pursuant to the Agreement and Plan of Merger, dated as of September 24, 2025 (the "Merger Agreement") by and among the Issuer, Igloo Group Parent, Inc., a Delaware corporation ("Parent"), and Igloo Group Acquisition Company, Inc., a Delaware corporation and a wholly owned subsidiary of Parent ("Merger Sub"). Pursuant to the Merger Agreement, on December 23, 2025 (the "Effective Time"), Merger Sub merged with and into the Issuer, with the Issuer surviving as a wholly owned subsidiary of Parent. At the Effective Time, each share of common stock of the Issuer owned by the reporting persons immediately prior to the Effective Time was automatically cancelled, extinguished and converted into the right to receive $10.30 in cash, without interest thereon.

Shares held directly by Atlas Venture Fund VIII, L.P. ("Atlas VIII"). Atlas Venture Associates VIII, L.P. ("AVA VIII LP") is the sole general partner of Atlas VIII. Atlas Venture Associates VIII, Inc. ("AVA VIII Inc.") is the sole general partner of AVA VIII LP. Each of Atlas VIII, AVA VIII LP and AVA VIII Inc. disclaim beneficial ownership of all shares except to the extent of its pecuniary interest, if any, therein. This report shall not be deemed to be an admission that the reporting persons are the beneficial owners of such securities for purposes of Section 16 or for any other purpose.