[Form 4] Quanterix Corporation Insider Trading Activity

Rhea-AI Filing Summary

Toloue Masoud, President & CEO and director of Quanterix Corporation (QTRX), reported a transaction dated 08/15/2025 showing a disposition of 1,242 shares of common stock at a price of $4.57 per share under transaction code F. The filing explains those shares were withheld by the company to cover tax obligations related to the vesting of 3,722 restricted stock units (RSUs). After the reported transaction, the reporting person beneficially owns 514,688 shares, which the filing notes includes 228,813 restricted stock units. The form was signed by an attorney-in-fact on 08/19/2025.

Insights

Financial Analyst

TL;DR: Routine insider tax-withholding on RSU vesting; no change to strategic ownership.

The Form 4 documents a small disposition of 1,242 shares at $4.57 to satisfy tax withholding tied to the vesting of 3,722 RSUs. This is a common administrative step that converts part of equity compensation into cash to meet tax obligations and does not indicate a cash-sale decision beyond withholding. The remaining beneficial ownership of 514,688 shares, including 228,813 RSUs, suggests continued substantial insider alignment with shareholder value. There are no other purchases, exercises, or derivative transactions disclosed.

Corporate Governance Expert

TL;DR: Disclosure is standard and compliant; withholding reduces outstanding vested shares but preserves long-term alignment.

The filing clearly identifies the reporting person, relationship to the issuer, and the nature of the disposition as tax-related withholding from vested RSUs. Use of an attorney-in-fact signature is noted and dated. From a governance perspective, the transaction is routine, transparently documented, and does not reflect a change in executive control or a material shift in ownership structure based on the presented figures.

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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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 for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Toloue Masoud

(Last) (First) (Middle)

C/O QUANTERIX CORPORATION

900 MIDDLESEX TURNPIKE

(Street)

BILLERICA MA 01821

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Quanterix Corp [ QTRX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	President & CEO

3. Date of Earliest Transaction (Month/Day/Year)
08/15/2025

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	08/15/2025		F		1,242(1)	D	$4.57	514,688(2)	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

Explanation of Responses:

1. Shares withheld by Quanterix Corporation solely to cover tax obligations upon the vesting of 3,722 RSUs.

2. Includes 228,813 restricted stock units.

Remarks:

	/s/ Brian Keane, as Attorney-in-Fact	08/19/2025
	** 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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What transaction did Toloue Masoud report on Form 4 for QTRX?

The report shows a disposition of 1,242 shares of common stock on 08/15/2025 at $4.57 per share under transaction code F.

Why were shares disposed in this Form 4 filing for QTRX?

The filing states 1,242 shares were withheld by Quanterix solely to cover tax obligations upon the vesting of 3,722 RSUs.

How many shares does the reporting person beneficially own after the transaction?

Following the reported transaction, the reporting person beneficially owns 514,688 shares, which includes 228,813 restricted stock units.

What is Toloue Masoud's role at Quanterix as listed on the form?

The form lists Toloue Masoud as a Director and as an Officer with the title President & CEO.

When was the Form 4 signed and by whom?

The signature block shows the form was signed by Brian Keane, as Attorney-in-Fact on 08/19/2025.