Quanterix CTO exercises 1,558 RSUs to stock

Quanterix’s CTO converted vested restricted stock units into common stock, with part of the shares withheld to cover the exercise price or taxes.

Rhea-AI Filing Summary

Quanterix Corp (QTRX) reported that Chief Technology Officer Michael Francis Miller exercised restricted stock units into common stock on September 15, 2026. A total of 1,558 restricted stock units converted into common shares on a one-for-one basis, and 467 common shares were delivered or withheld to pay the exercise price or related tax liability at $2.72 per share. No Rule 10b5-1 trading plan is indicated for these transactions.

Insider Trade Summary

1,558 shares exercised/converted

Exercise 15 txns

Insider Miller Michael Francis

Role Chief Technology Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit F2	81	$0.00	$0.00
Exercise	Restricted Stock Unit F3	136	$0.00	$0.00
Exercise	Restricted Stock Unit F4	135	$0.00	$0.00
Exercise	Restricted Stock Unit F5	372	$0.00	$0.00
Exercise	Restricted Stock Unit F6	834	$0.00	$0.00
Exercise	Common Stock F1	81	--	--
Exercise Price or Tax Liability	Common Stock	25	$2.72	$68.00
Exercise	Common Stock F1	136	--	--
Exercise Price or Tax Liability	Common Stock	41	$2.72	$111.52
Exercise	Common Stock F1	135	--	--
Exercise Price or Tax Liability	Common Stock	41	$2.72	$111.52
Exercise	Common Stock F1	372	--	--
Exercise Price or Tax Liability	Common Stock	111	$2.72	$301.92
Exercise	Common Stock F1	834	--	--
Exercise Price or Tax Liability	Common Stock	249	$2.72	$677.28

Holdings After Transaction: Restricted Stock Unit — 35,233 contracts (Direct); Common Stock — 38,452 shares (Direct)

Footnotes (6)

1. F1. Restricted stock units convert into common stock on a one-for-one basis.
2. F2. On February 6, 2023, the reporting person was granted 3,929 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.
3. F3. On March 15, 2023, the reporting person was granted 6,566 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.
4. F4. On February 2, 2024, the reporting person was granted 6,494 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.
5. F5. On May 21, 2024, the reporting person was granted 17,878 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.
6. F6. On February 4, 2025, the reporting person was granted 40,036 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.

Key Figures

Restricted stock units exercised: 1,558 units Shares delivered/withheld for exercise price or tax liability: 467 shares Per-share value for tax/exercise settlements: $2.72 per share +2 more

5 metrics

Restricted stock units exercised 1,558 units Total RSUs converted into common stock on September 15, 2026

Shares delivered/withheld for exercise price or tax liability 467 shares Total common shares used in code F transactions on September 15, 2026

Per-share value for tax/exercise settlements $2.72 per share Price applied to the 467 common shares in code F transactions

Number of RSU exercise events 5 transactions Derivative exercises (code M) reported for September 15, 2026

Number of tax/exercise settlement events 5 transactions Code F transactions delivering or withholding shares on September 15, 2026

Key Terms

Restricted Stock Unit, derivative security, Payment of exercise price or tax liability

3 terms

Restricted Stock Unit financial

"security title listed as Restricted Stock Unit for multiple transactions"

A restricted stock unit is a promise from a company to give an employee shares of stock after certain conditions are met, like staying with the company for a set amount of time. It’s like earning a bonus that turns into company stock once you’ve proven your commitment, making it a way to motivate and reward employees.

derivative security financial

"transaction code description refers to 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.

Payment of exercise price or tax liability financial

"transaction code description states Payment of exercise price or tax liability"

FAQ

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

What insider transactions did Quanterix (QTRX) report for its CTO on September 15, 2026?

Quanterix reported that its CTO, Michael Francis Miller, exercised 1,558 restricted stock units into common stock on September 15, 2026, with a portion of the resulting shares delivered or withheld to cover the exercise price or related tax liability.

How many Quanterix (QTRX) restricted stock units did the CTO exercise in this Form 4?

The CTO exercised 1,558 restricted stock units into Quanterix common stock. These were previously granted RSUs that vest over time and convert into common shares on a one-for-one basis according to the filed footnotes.

How many Quanterix (QTRX) shares were withheld or delivered for taxes or exercise price?

The filing shows 467 common shares were delivered or withheld as payment of the exercise price or related tax liability, consisting of transactions of 25, 41, 41, 111 and 249 shares, each at $2.72 per share.

At what price were Quanterix (QTRX) shares used to cover the CTO’s tax or exercise obligations?

Shares used to cover the CTO’s exercise price or tax obligations were valued at $2.72 per share for the code F transactions involving a total of 467 Quanterix common shares.

Were the Quanterix (QTRX) CTO’s transactions made under a Rule 10b5-1 trading plan?

No. The filing’s Rule 10b5-1 checkbox is not marked as affirmative, and there is no footnote stating that these transactions were made pursuant to a Rule 10b5-1 trading plan.

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

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Available on EDGAR 09/16/2026 - 04:59 PM Accepted by SEC EDGAR 09/16/2026 - 04:59 PM 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^*

Miller Michael Francis

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Technology Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/15/2026

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	09/15/2026		M		81	A	(1)	37,442	D
Common Stock	09/15/2026		F		25	D	$2.72	37,417	D
Common Stock	09/15/2026		M		136	A	(1)	37,553	D
Common Stock	09/15/2026		F		41	D	$2.72	37,512	D
Common Stock	09/15/2026		M		135	A	(1)	37,647	D
Common Stock	09/15/2026		F		41	D	$2.72	37,606	D
Common Stock	09/15/2026		M		372	A	(1)	37,978	D
Common Stock	09/15/2026		F		111	D	$2.72	37,867	D
Common Stock	09/15/2026		M		834	A	(1)	38,701	D
Common Stock	09/15/2026		F		249	D	$2.72	38,452	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	09/15/2026		M			81	(2)	(2)	Common Stock	81	$0.00	436	D
Restricted Stock Unit	$0.00	09/15/2026		M			136	(3)	(3)	Common Stock	136	$0.00	845	D
Restricted Stock Unit	$0.00	09/15/2026		M			135	(4)	(4)	Common Stock	135	$0.00	2,306	D
Restricted Stock Unit	$0.00	09/15/2026		M			372	(5)	(5)	Common Stock	372	$0.00	7,457	D
Restricted Stock Unit	$0.00	09/15/2026		M			834	(6)	(6)	Common Stock	834	$0.00	24,189	D

Explanation of Responses:

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

2. On February 6, 2023, the reporting person was granted 3,929 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.

3. On March 15, 2023, the reporting person was granted 6,566 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.

4. On February 2, 2024, the reporting person was granted 6,494 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.

5. On May 21, 2024, the reporting person was granted 17,878 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.

6. On February 4, 2025, the reporting person was granted 40,036 restricted stock units, vesting 25% on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the 15th day of each month thereafter.

Remarks:

	/s/ Michael Lanieri, Attorney-in-Fact	09/16/2026
	** 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)