Quanterix director logs 2,802-share RSU vesting

Quanterix Corp (QTRX) director William P. Donnelly reported the vesting and conversion of restricted stock units into common stock.

Rhea-AI Filing Summary

Quanterix Corp (QTRX) director William P. Donnelly reported the vesting and conversion of restricted stock units into common stock. On 2026-08-17, 2,802 restricted stock units converted into 2,802 shares of common stock on a one-for-one basis, eliminating that RSU position. Following this transaction, Donnelly directly holds 162,401 shares of Quanterix common stock.

Insider Trade Summary

2,802 shares exercised/converted

Exercise 2 txns

Insider DONNELLY WILLIAM P

Role Director

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit F2	2,802	$0.00	$0.00
Exercise	Common Stock F1	2,802	--	--

Holdings After Transaction: Restricted Stock Unit — 0 contracts (Direct); Common Stock — 162,401 shares (Direct)

Footnotes (2)

1. F1. Restricted stock units convert into common stock on a one-for-one basis.
2. F2. On August 17, 2023, the reporting person was granted 8,238 restricted stock units, vesting 33%, 33%, and 34% on the first, second, and third anniversaries of the grant date, respectively.

Key Figures

RSUs converted: 2,802 restricted stock units Common shares received: 2,802 shares of common stock Shares owned after transaction: 162,401 shares +1 more

4 metrics

RSUs converted 2,802 restricted stock units RSUs converting into common stock on 2026-08-17

Common shares received 2,802 shares of common stock Shares issued upon RSU conversion on 2026-08-17

Shares owned after transaction 162,401 shares Directly owned Quanterix common stock following the reported transactions

Original RSU grant 8,238 restricted stock units Granted on August 17, 2023 with 33%/33%/34% annual vesting schedule

Key Terms

Restricted stock units, derivative security, one-for-one basis

3 terms

Restricted stock units financial

"On August 17, 2023, the reporting person was granted 8,238 restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

derivative security financial

"transaction_code_description": "Exercise or conversion of derivative security"

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

one-for-one basis financial

"Restricted stock units convert into common stock on a one-for-one basis"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did William P. Donnelly report for Quanterix Corp (QTRX)?

William P. Donnelly reported the vesting and conversion of 2,802 restricted stock units into 2,802 shares of Quanterix common stock on 2026-08-17, reflecting an equity award settlement rather than an open-market trade.

How many Quanterix (QTRX) shares does William P. Donnelly own after this Form 4 transaction?

After the 2026-08-17 RSU conversion, William P. Donnelly directly owns 162,401 shares of Quanterix common stock. This figure reflects his reported direct holdings following the settlement of 2,802 restricted stock units.

What happened to the 2,802 restricted stock units in the Quanterix (QTRX) Form 4?

The 2,802 restricted stock units were reported as disposed of as derivatives because they converted one-for-one into 2,802 shares of Quanterix common stock on 2026-08-17, eliminating that specific RSU position.

When were the restricted stock units in this Quanterix (QTRX) filing originally granted?

The filing states that on August 17, 2023, the reporting person was granted 8,238 restricted stock units, vesting 33%, 33%, and 34% on the first, second, and third anniversaries of the grant date, respectively, providing the source for the 2026 vesting event.

What does one-for-one RSU conversion mean in the Quanterix (QTRX) Form 4?

The filing explains that the restricted stock units convert into common stock on a one-for-one basis, meaning each RSU delivers one share of Quanterix common stock upon vesting or settlement, as occurred with the 2,802-unit conversion.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/19/2026 - 06:38 AM Accepted by SEC EDGAR 08/19/2026 - 06:37 AM Learn about SEC filing dates

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

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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^*

DONNELLY WILLIAM P

(Last) (First) (Middle)

C/O QUANTERIX CORPORATION

900 MIDDLESEX TURNPIKE

(Street)

BILLERICA MASSACHUSETTS 01821

(City) (State) (Zip)

UNITED STATES

(Country)

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
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/17/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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	08/17/2026		M		2,802	A	(1)	162,401	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
Restricted Stock Unit	$0.00	08/17/2026		M			2,802	(2)	(2)	Common Stock	2,802	$0.00	0.00	D

Explanation of Responses:

1. Restricted stock units convert into common stock on a one-for-one basis.

2. On August 17, 2023, the reporting person was granted 8,238 restricted stock units, vesting 33%, 33%, and 34% on the first, second, and third anniversaries of the grant date, respectively.

Remarks:

	/s/ Meghan Shevlin, Attorney-in-Fact	08/19/2026
	** 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.
* Form 4: SEC 1474 (03-26)