Quanterix CTO exercises 130 RSUs, 39 shares withheld

Quanterix Chief Technology Officer Michael Francis Miller reported the vesting of 130 restricted stock units, which converted into the same number of common shares on May 31, 2026.

Rhea-AI Filing Summary

Quanterix Chief Technology Officer Michael Francis Miller reported the vesting of 130 restricted stock units, which converted into the same number of common shares on May 31, 2026. 39 of these shares were withheld at $3.06 per share to cover tax obligations, and he now directly holds 33,795 Quanterix common shares. The restricted stock units are part of a 6,278-unit grant from September 23, 2022 that vests 25% after one year and the remaining 75% in 36 equal monthly installments.

Insider Trade Summary

130 shares exercised/converted

Exercise 3 txns

Insider Miller Michael Francis

Role Chief Technology Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit	130	$0.00	$0.00
Exercise	Common Stock	130	$0.00	$0.00
Exercise Price or Tax Liability	Common Stock	39	$3.06	$119.34

Holdings After Transaction: Restricted Stock Unit — 419 contracts (Direct); Common Stock — 33,795 shares (Direct)

Footnotes (2)

1. F1. Restricted stock units convert into common stock on a one-for-one basis.
2. F2. On September 23, 2022, the reporting person was granted 6,278 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 last day of each month thereafter.

Key Figures

RSUs converted to common stock: 130.0000 Shares withheld for taxes: 39.0000 Tax withholding price per share: 3.0600 +4 more

7 metrics

RSUs converted to common stock 130.0000 Restricted stock units converted into common stock on May 31, 2026

Shares withheld for taxes 39.0000 Common shares withheld at $3.06 per share to cover tax obligations

Tax withholding price per share 3.0600 Per-share value used for the 39-share tax-withholding disposition

Post-transaction common stock holdings 33,795 Directly held Quanterix common shares after the reported transactions

Original RSU grant size 6,278 Restricted stock units granted on September 23, 2022

Initial vesting percentage 25% Portion of the RSU grant that vests on the first anniversary of the grant date

Remaining vesting percentage 75% Portion of the RSU grant vesting in 36 equal monthly installments

Key Terms

Restricted Stock Unit, tax-withholding disposition, derivative security

3 terms

Restricted Stock Unit financial

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

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.

tax-withholding disposition financial

"Payment of exercise price or tax liability by delivering securities"

A tax-withholding disposition is an event or transaction—such as selling or transferring securities, exercising options, or receiving compensation—that triggers a requirement to hold back part of the payment and remit it to tax authorities. It matters to investors because it reduces the cash they receive immediately and can change the timing and amount of taxable income, like a cashier taking a portion of your sale proceeds to pay taxes before you get the rest.

derivative security financial

"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.

FAQ

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

What insider transaction did Quanterix (QTRX) report for its CTO?

Quanterix CTO Michael Francis Miller converted 130 restricted stock units into common stock on May 31, 2026. 39 of the resulting shares were withheld at $3.06 per share to satisfy tax obligations, and he now directly holds 33,795 Quanterix shares.

How many Quanterix (QTRX) shares does the CTO hold after this Form 4?

After these transactions, CTO Michael Francis Miller directly holds 33,795 shares of Quanterix common stock. This balance reflects the 130 shares issued from vested restricted stock units and the 39 shares withheld to cover tax liabilities on the vesting.

How many Quanterix (QTRX) shares were withheld for taxes in this Form 4?

A total of 39 Quanterix common shares were withheld to cover tax obligations. These shares were valued at $3.06 per share and relate to the vesting and conversion of 130 restricted stock units into common stock for CTO Michael Francis Miller.

What was the size and vesting schedule of the CTO’s RSU grant at Quanterix (QTRX)?

Michael Francis Miller received a grant of 6,278 restricted stock units on September 23, 2022. 25% vests on the first anniversary of the grant date, with the remaining 75% vesting in 36 equal monthly installments on the last day of each month thereafter.

How do the Quanterix (QTRX) restricted stock units convert into shares?

The restricted stock units reported convert into Quanterix common stock on a one-for-one basis. In this Form 4, 130 restricted stock units converted into 130 common shares, with some of those shares withheld to satisfy the CTO’s tax obligations.

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

Form 4 Insider Transactions: What Each Field Means →

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Accepted by SEC EDGAR 06/01/2026 - 04:06 PM EDT 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)
05/31/2026

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	05/31/2026		M		130	A	(1)	33,834	D
Common Stock	05/31/2026		F		39	D	$3.06	33,795	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	05/31/2026		M			130	(2)	(2)	Common Stock	130	$0.00	419	D

Explanation of Responses:

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

2. On September 23, 2022, the reporting person was granted 6,278 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 last day of each month thereafter.

Remarks:

	/s/ Meghan Shevlin, Attorney-in-Fact	06/01/2026
	** 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)