Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES 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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1. Name and Address of Reporting Person * VEP Group, LLC 2. Issuer Name and Ticker or Trading Symbol INTEGRAL AD SCIENCE HOLDING CORP. [IAS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O VISTA EQUITY PARTNERS, 4 EMBARCADERO CENTER, 20TH FL. 3. Date of Earliest Transaction (Month/Day/Year) 12/23/2025 (Street) SAN FRANCISCO, CA 94111 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) 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, $0.001 par value 12/23/2025 J(1) 65,010,001(2) D $10.3 0 I See Footnotes(3)(4)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 Underlying Securities (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 of Derivative Security: 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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
VEP Group, LLC C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
Vista Equity Partners Fund VI, L.P. C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
Vista Equity Partners Fund VI-A, L.P. C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
VEPF VI FAF, L.P. C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
Vista Equity Partners Fund VI GP, L.P. C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
VEPF VI GP. Ltd. C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
VEPF MANAGEMENT, L.P. C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
VISTA EQUITY PARTNERS MANAGEMENT, LLC C/O VISTA EQUITY PARTNERS 4 EMBARCADERO CENTER, 20TH FL. SAN FRANCISCO, CA 94111		X
SMITH ROBERT F C/O VISTA EQUITY PARTNERS 401 CONGRESS DRIVE, SUITE 3100 AUSTIN, TX 78701		X

Signatures

/s/ Robert F. Smith, Managing Member of VEP Group, LLC		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Director of the General Partner of the General Partner of Vista Equity Partners Fund VI, L.P.		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Director of the General Partner of the General Partner of Vista Equity Partners Fund VI-A, L.P.		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Director of the General Partner of the General Partner of VEPF VI FAF, L.P.		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Director of the General Partner of Vista Equity Partners Fund VI GP, L.P.		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Director of VEPF VI GP, Ltd.		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Managing Member of the General Partner of VEPF Management, L.P.		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith, Managing Member of the Managing Member of Vista Equity Partners Management, LLC		12/29/2025
**Signature of Reporting Person		Date
/s/ Robert F. Smith		12/29/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Pursuant to the Agreement and Plan of Merger, dated as of September 24, 2025, by and among the Issuer, Igloo Group Parent, Inc. ("Parent") and Igloo Group Acquisition Company, Inc. ("Merger Sub"), Merger Sub merged with and into the Issuer (the "Merger"), with the Issuer surviving as a wholly owned subsidiary of Parent. At the effective time of the Merger, each issued and outstanding share of the Issuer's common stock, par value $0.001 per share ("Common Stock"), owned by the reporting persons immediately prior to the Effective Time was automatically cancelled, extinguished and converted into the right to receive $10.30 per share in cash, without interest thereon.
(2)	Consisted of (i) 40,222,196 shares of Common Stock held by Vista Equity Partners Fund VI, L.P. ("VEPF VI"), (ii) 24,298,354 shares of Common Stock held by Vista Equity Partners Fund VI-A, L.P. ("VEPF VI-A") and (iii) 489,451 shares of Common Stock held by VEPF VI FAF, L.P. ("VEPF FAF" and, collectively with VEPF VI and VEPF VI-A, the "Vista Funds").
(3)	Vista Equity Partners Fund VI GP, L.P. ("Fund VI GP") is the sole general partner of each of the Vista Funds. Fund VI GP's sole general partner is VEPF VI GP, Ltd. ("Fund VI UGP"). Robert F. Smith is the sole director and one of 11 members of Fund VI UGP. VEPF Management, L.P. ("Management Company") is the sole management company of each of the Vista Funds. The Management Company's sole general partner is VEP Group, LLC ("VEP Group"), and the Management Company's sole limited partner is Vista Equity Partners Management, LLC ("VEPM"). VEP Group is the Senior Managing Member of VEPM. Robert F. Smith is the sole Managing Member of VEP Group. Consequently, Mr. Smith, Fund VI GP, Fund VI UGP, the Management Company, VEPM and VEP Group may be deemed the beneficial owners of the shares held by the Vista Funds.
(4)	Each of the Vista Funds, Fund VI GP, Fund VI UGP, the Management Company, VEP Group, VEPM and Mr. Smith expressly disclaim beneficial ownership except to the extent of its or his pecuniary interest and the inclusion of the reported securities in this report shall not be deemed an admission by any of the foregoing of beneficial ownership of any or all of the reported securities for purposes of Section 16 or for any other purpose.

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