Quanterix Form 4 Filings

Quanterix Corp (QTRX) director Jeffrey Thomas Elliott reported an exercise and conversion of restricted stock units (RSUs) into common stock. On August 19, 2026, 3,955 RSUs were converted into 3,955 shares of common stock on a one-for-one basis. Following the transactions, Elliott directly held 15,345 shares of common stock and 4,075 RSUs. The RSUs relate to a prior grant of 11,985 RSUs, vesting 33%, 33%, and 34% on the first, second, and third anniversaries of the August 19, 2024 grant date, respectively.

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.

Quanterix Corp’s Chief Technology Officer, Michael Francis Miller, reported multiple equity compensation transactions on August 15, 2026. He exercised or converted restricted stock units into 1,558 shares of common stock, with the RSUs converting into common stock on a one-for-one basis. In related transactions, 467 common shares were delivered or withheld at $2.59 per share for payment of exercise price or tax liability. The mix of RSU conversions and share withholdings results in a largely administrative change in Miller’s reported holdings rather than a market purchase or sale.

Quanterix Corp director William P. Donnelly, through trusts established by him and his spouse, reported two indirect open-market purchases of common stock. On August 12, 2026, the trusts acquired 27,155 shares at a weighted average price of $2.75 per share, in multiple trades between $2.58 and $2.95. On August 13, 2026, they acquired an additional 72,245 shares at a weighted average price of $2.93 per share, in trades between $2.85 and $3.13. In total, the trusts purchased 99,400 shares of Quanterix common stock in these transactions.

Quanterix Corp Chief Technology Officer Michael Francis Miller reported the conversion of 130 restricted stock units into an equal number of common shares on July 31, 2026, from a 6,278-unit grant awarded September 23, 2022. In a related transaction, 39 common shares were disposed of at $3.48 per share as payment of exercise price or tax liability. The filing does not affirm these transactions as made under a Rule 10b5-1 trading plan.

Quanterix Corp Chief Technology Officer Michael Francis Miller reported compensation-related equity activity. On July 15, 2026 he converted 1,558 restricted stock units into common stock and had 467 shares withheld to satisfy tax obligations. After these non–open-market transactions, he directly owns 36,068 Quanterix common shares and continues to hold multiple unvested RSU awards.

Quanterix Corp granted its Chief Financial Officer, Jason F. Faessler, 141,820 restricted stock units on July 15, 2026. These RSUs convert into common stock and vest in four equal annual installments on each of the first four anniversaries of the grant date, contingent on his continued employment. Following this award, he reports direct beneficial ownership of 141,820

Quanterix Corp director Scott Mendel reported an equity compensation event. On July 8, 2026, he converted 8,073 restricted stock units into an equal number of common shares at no cost, reflecting routine vesting. After this conversion, he directly holds 24,056 common shares and 16,391 restricted stock units. The RSUs relate to a 24,464-unit grant made on July 8, 2025, which vests 33%, 33%, and 34% on the first three anniversaries of the grant date.

Quanterix Corp director Myla Lai-Goldman exercised restricted stock units into common shares. She converted 8,073 restricted stock units into 8,073 shares of Common Stock at a reported price of $0.00 per share, increasing her direct common stock holdings to 15,041 shares.

Following this transaction, she also holds 16,391 restricted stock units, which convert into common stock on a one-for-one basis. These units come from a prior grant of 24,464 restricted stock units awarded on July 8, 2025, vesting 33%, 33%, and 34% over three years.

Mendel Scott reported acquisition or exercise transactions in this Form 4 filing.

Quanterix Corp director Scott Mendel received a stock grant as board compensation. He was awarded 3,456 shares of Common Stock at a reference price of $4.34 per share, issued in lieu of cash fees for his service on the Board and its committees for the second quarter of 2026. Following this grant, he holds 16,837 common shares directly.

DONNELLY WILLIAM P reported acquisition or exercise transactions in this Form 4 filing.

Quanterix Corp director William P. Donnelly received 5,472 shares of Common Stock as a grant, valued at $4.34 per share. The award was granted in lieu of cash fees for his service on the company’s Board of Directors and its committees for the second quarter of 2026. After this compensation-related stock grant, he directly holds a total of 160,305 Quanterix common shares.

Quanterix Corp Chief Technology Officer Michael Francis Miller reported routine equity compensation activity involving restricted stock units. He exercised RSUs that converted into 130 shares of common stock on a one-for-one basis and a portion of the resulting shares, 39 in total, was disposed of to cover tax obligations. These transactions did not involve any open-market buying or selling and reflect standard mechanisms for settling equity awards and related taxes.

Quanterix Corp Chief Financial Officer Vandana Sriram reported routine equity compensation activity involving restricted stock units. On June 15, 2026, restricted stock units converted into 1,833 shares of common stock, and 548 shares were withheld at $3.10 per share to cover tax obligations.

These transactions reflect RSU vesting and related tax-withholding dispositions, not open-market trades. Following the transactions, Sriram directly owns 31,283 shares of Quanterix common stock. Footnotes state RSUs convert one-for-one into common stock and describe multi-year vesting schedules for prior RSU grants.

Quanterix Corp Chief Technology Officer Michael Francis Miller reported routine equity compensation activity on June 15, 2026. He exercised derivative awards for a total of 1,558 common shares and used 467 shares, valued at $3.10 each, to cover tax obligations. Following these transactions, he directly holds 33,851 shares of common stock, and restricted stock units continue to vest over time under previously granted awards.

Quanterix Corp Chief Commercial Officer Benjamin Meadows reported an open-market purchase of company stock. On May 12, 2026, he bought 3,500 shares of Common Stock at a price of $2.77 per share. Following this transaction, he directly holds 3,500 shares of Quanterix common stock.

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.

Quanterix Corp Chief Financial Officer Vandana Sriram reported routine equity compensation activity involving restricted stock units (RSUs). On May 15, 2026, RSUs converted into common stock in several tranches, including 1,056, 514, and 263 shares, reflecting scheduled vesting.

To cover tax obligations, the filing shows share dispositions of 315, 154, and 79 shares of common stock at $2.75 per share, characterized as tax-withholding transactions rather than open-market sales. Following these transactions, the CFO directly held 28,897 shares of Quanterix common stock, while additional RSUs remain outstanding and continue to vest over time.

Quanterix Corp Chief Technology Officer Michael Francis Miller reported routine equity compensation activity. On May 15, 2026, restricted stock units vested and were converted into 1,558 shares of Common Stock, while 467 shares were withheld at $2.75 per share to cover tax obligations. After these transactions, he directly owned 32,694 Common shares and 760 restricted stock units that may vest later.

Quanterix Corp Chief Operating Officer Michael Francis Miller reported routine equity compensation activity. He exercised 130 restricted stock units that converted into 130 shares of common stock on a one-for-one basis. To cover tax obligations, 39 common shares were disposed of through a tax-withholding transaction, not an open-market sale.

Following these transactions, Miller directly holds 32,613 shares of common stock and 549 restricted stock units that remain outstanding from a prior grant of 6,278 RSUs made on September 23, 2022.

Quanterix Corp Chief Operating Officer Michael Francis Miller exercised restricted stock units into common stock and had shares withheld to cover taxes. On April 15, 2026, he acquired a total of 1,558 shares of common stock through multiple RSU conversions, all at a stated price of $0.00 per share.

To satisfy tax obligations related to these vesting events, 467 shares of common stock were disposed of at $3.60 per share in tax-withholding transactions. Following these transactions, Miller directly held 32,522 shares of Quanterix common stock.

Quanterix Corp Chief Financial Officer Sriram Vandana reported routine equity compensation activity involving restricted stock units that converted into common stock. On April 15, 2026, restricted stock units converted into common stock on a one-for-one basis, delivering 263, 514 and 1,056 shares in separate tranches.

Related common stock entries show 263, 514 and 1,056-share acquisitions at a price of $0.00 per share. To satisfy tax obligations, 79, 154 and 315 shares of common stock were withheld at $3.60 per share as tax-withholding dispositions, rather than open-market sales.

Following these transactions, the filing shows Sriram Vandana directly holding 28,713 shares of Quanterix common stock. The derivative section lists no remaining restricted stock units tied to these specific conversions, underscoring that the reported activity reflects compensation vesting and associated tax withholding.

DONNELLY WILLIAM P reported acquisition or exercise transactions in this Form 4 filing.

Quanterix Corp Executive Chair William P. Donnelly received 6,178 shares of Common Stock as a stock grant. The shares were awarded at a stated price of $0.00 per share as a grant or award transaction, rather than an open-market purchase or sale.

According to the disclosure, this stock was granted in lieu of cash fees for Donnelly’s service on Quanterix’s Board of Directors and its committees for the first quarter of 2026. Following this award, Donnelly directly holds a total of 154,127 shares of Quanterix Common Stock.

Mendel Scott reported acquisition or exercise transactions in this Form 4 filing.

Quanterix Corp director Scott Mendel received a grant of 4,310 shares of common stock as compensation. The shares were granted in lieu of cash fees for his service on the company’s Board of Directors and its committees for the first quarter of 2026. Following this award, he directly holds 12,527 shares.

Quanterix Corp Chief Operating Officer Michael Francis Miller exercised restricted stock units into common shares and had a portion withheld for taxes. On March 31, 2026, he converted 229 restricted stock units, which convert to common stock on a one-for-one basis, into the same number of common shares at a stated price of $0.00 per share.

To cover tax obligations, 69 common shares were disposed of through tax-withholding transactions at $3.52 per share, leaving him with a net increase of 160 common shares. Following these transactions, Miller directly owned 31,431 shares of Quanterix common stock. The restricted stock units exercised were part of prior grants from April 7, 2022 and September 23, 2022 that vest over time.

Quanterix Corp’s Chief Operating Officer Michael Francis Miller reported routine equity compensation activity. On March 15, 2026, multiple restricted stock unit awards converted into common stock, with derivative exercises totaling 1,558 shares according to the filing’s transaction summary.

To cover related tax obligations, 549 common shares were withheld at a price of $4.72 per share under code F transactions, which are tax-withholding dispositions rather than market sales. Following these transactions, Miller directly holds 31,271 shares of Quanterix common stock.

Quanterix Corp Chief Financial Officer Vandana Sriram reported routine equity compensation activity involving restricted stock units that convert into common stock on a one-for-one basis. On March 15, 2026, she exercised RSUs covering 1,833 common shares in total through derivative exercises.

To satisfy tax obligations, 645 common shares were withheld and disposed of at $4.72 per share, with the remaining shares added to her direct holdings. Following these transactions, she directly owned 27,428 shares of Quanterix common stock. The RSUs stem from prior grants of 12,624 units on August 21, 2023, 24,675 units on February 2, 2024, and 50,712 units on February 4, 2025, each vesting over time with an initial 25% cliff and subsequent monthly installments.

Quanterix Corp’s chief financial officer, Vandana Sriram, reported equity award and related tax transactions. The CFO received grants of 74,905 performance stock units and 74,905 restricted stock units at a stated price of $0 per unit. Footnotes explain that PSUs vest based on performance conditions and then in four equal annual installments starting on the first anniversary of the grant date, while the new RSU award also vests in four equal annual installments.

The filing also shows exercises of previously granted restricted stock units into common stock, along with share dispositions to cover tax obligations. Specifically, 514 and 263 RSUs were converted into common stock, and 179 and 92 common shares were withheld at $5.74 per share to satisfy tax liabilities. After these transactions, the CFO directly held 26,240 shares of Quanterix common stock.

Quanterix Corporation’s Chief Financial Officer, Sriram Vandana, reported a routine tax-related share withholding. On February 4, 2026, 4,395 shares of common stock were withheld by Quanterix to cover tax obligations from the vesting of 12,678 restricted stock units (RSUs).

After this transaction, the CFO beneficially owned 81,618 shares of Quanterix common stock, which includes 55,884 RSUs. This filing reflects a non-open-market transaction coded "F," indicating shares retained for taxes rather than a discretionary sale into the market.

Quanterix CorpEverett CunninghamJanuary 19, 2026813,750 performance-based restricted stock units (RSUs)1,070,000 time-based RSUs

The performance-based RSUs vest only if the volume-weighted average price of Quanterix stock meets specified thresholds within a four-year period, as outlined in his January 8, 2026 employment agreement. The time-based RSUs vest in four equal annual installments on January 19, 2027, 2028, 2029, and 20301,883,750 derivative securities$0

Quanterix Corporation’s Chief Financial Officer, Sriram Vandana, reported an automatic share withholding related to equity compensation. On 01/15/2026, 274 shares of Quanterix common stock were withheld by the company at a price of $7.95 per share solely to cover tax obligations upon the vesting of 777 restricted stock units (RSUs).

Following this tax withholding, Vandana beneficially owned 86,013 shares of Quanterix common stock, which includes 68,562 RSUs. The company’s year-end reconciliation identified a variance of 310 shares, and the corrected balance is reflected in the reported holdings.

Quanterix Corp President & CEO Masoud Toloue reported a routine tax-related share withholding in company stock. On 01/15/2026, 1,817 shares of Quanterix common stock were withheld by the company at a price of $7.95 per share to cover tax obligations arising from the vesting of 3,722 restricted stock units (RSUs). After this transaction, Toloue beneficially owned 507,310 shares of common stock, which the filing notes include 206,398 RSUs. A year-end reconciliation by Quanterix identified a variance of 681 shares, and the corrected ownership balance is reflected in this filing.

Quanterix Corp director Paul M. Meister reported a stock-based board fee grant. On 01/02/2026, he acquired 3,974 shares of Quanterix common stock at a stated price of $0.00 per share as stock granted in lieu of cash fees for service on the company's Board of Directors and its committees for the third and fourth quarter of 2025. After this grant, he beneficially owned 313,253 shares of Quanterix common stock held directly.

Quanterix Corporation director Ivana Magovcevic-Liebisch received an equity grant of 23,372 restricted stock units (RSUs) of common stock on January 2, 2026. The RSUs were granted at a price of $0.00 per unit under the company’s Amended and Restated Non-Employee Director Compensation Policy.

The RSUs vest as to 100% of the shares on January 2, 2027, meaning they convert into common shares on that date if vesting conditions are met. Following this grant, she beneficially owns 43,607 RSUs, each representing the right to receive one share of Quanterix common stock.

Quanterix Corporation director Elliott Jeffrey Thomas reported a stock-based award from the company. On January 2, 2026, he received 23,372 shares of Quanterix common stock in the form of restricted stock units at a price of $0.00 per share under the Amended and Restated Non-Employee Director Compensation Policy.

These restricted stock units vest as to 100% of the shares on January 2, 2027, and each unit represents the right to receive one share of common stock. Following this grant, Thomas beneficially owned a total of 42,792 shares of Quanterix common stock, which includes 31,402 restricted stock units.

Quanterix Corporation director David R. Walt received 1,215 shares of common stock on 01/02/2026, reported at a price of $0.00 per share. According to the filing, this stock was granted in lieu of cash fees for his service on the company’s Board of Directors and its committees for the fourth quarter of 2025.

After this grant, Walt beneficially owned 1,872,890 shares of Quanterix common stock, held directly. The transaction was reported on a Form 4 as an acquisition of non-derivative securities.

Quanterix Corp director Myla Lai-Goldman reported new equity awards in the company’s common stock. On January 2, 2026, she received 23,372 restricted stock units that will vest in full on January 2, 2027 under Quanterix’s Amended and Restated Non-Employee Director Compensation Policy, with each unit representing one share of common stock. The same day, she was also granted 1,944 shares of common stock issued in lieu of cash fees for serving on the board and its committees for the fourth quarter of 2025. Both awards were recorded at a price of $0.00 per share. After these transactions, she directly beneficially owned 54,804 shares of Quanterix common stock, which the filing notes include 47,836 restricted stock units.

Quanterix Corp director Scott Mendel reported new equity awards in the company’s stock. On 01/02/2026, he received 23,372 restricted stock units that will vest in full on January 2, 2027 under the Quanterix Corporation Amended and Restated Non-Employee Director Compensation Policy, with each unit representing one share of common stock. On the same date, he was also granted 1,944 shares of common stock issued in lieu of cash fees for his Board and committee service for the fourth quarter of 2025. Following these awards, he beneficially owned 56,053 shares of Quanterix common stock, including 47,836 restricted stock units, all reported as directly held.

Quanterix Corporation’s Chief Financial Officer reported a routine share adjustment related to equity compensation. On 12/15/2025, 229 shares of common stock were withheld by Quanterix at a price of $7.41 per share to cover tax obligations that arose when 777 restricted stock units (RSUs) vested. After this tax withholding, the officer beneficially owns 85,977 shares of Quanterix common stock, which includes 84,652 RSUs. This filing reflects administrative handling of taxes on vested stock awards rather than an open-market purchase or sale.

Quanterix Corp reported an insider equity transaction by its President & CEO and Director on 12/15/2025. The filing shows that 1,242 shares of common stock were withheld by Quanterix solely to cover tax obligations that arose when 3,722 restricted stock units (RSUs) vested. This is recorded as a disposition at a price of $7.41 per share for reporting purposes.

Following this tax withholding event, the reporting person beneficially owned 508,704 shares of Quanterix common stock, which includes 212,123 RSUs. The transaction was filed as a Form 4 for a single reporting person in their roles as both Director and President & CEO.

Quanterix Corp (QTRX) reported a new equity award to one of its directors. On November 20, 2025, the director acquired 46,727 shares of common stock through a grant of restricted stock units (RSUs), reported as an acquisition in a Form 4 filing. Following this grant, the director beneficially owns 46,727 shares directly.

The RSUs vest in three equal installments. One-third of the total shares vest on each of November 20, 2026, November 20, 2027 and November 20, 2028, provided the director continues to provide service to Quanterix on each vesting date. This filing reflects routine director equity compensation rather than an open‑market purchase or sale.

Quanterix Corporation (QTRX) reported a new stock option grant to its Executive Chair and Director. On 11/20/2025, the insider acquired stock options to purchase 70,091 shares of Quanterix common stock at an exercise price of $5.91 per share. These options expire on 11/20/2035.

The options vest monthly over two years in 24 equal installments, as long as the Executive Chair continues providing service to Quanterix on each vesting date. Following this transaction, the reporting person beneficially owns 70,091 derivative securities directly.

Quanterix Corporation’s Chief Financial Officer reported a routine equity transaction on Form 4. On 11/15/2025, 229 shares of common stock were withheld by Quanterix solely to cover tax obligations when 777 restricted stock units vested. After this tax withholding, the reporting person beneficially owns 86,206 shares of Quanterix common stock, which includes 85,429 restricted stock units that may convert into shares over time.

Quanterix Corp (QTRX) reported an insider equity transaction by its President & CEO, who is also a director. On 11/15/2025, 1,242 shares of common stock were withheld under transaction code "F", meaning the shares were retained by the company solely to cover tax obligations triggered by the vesting of 2,480 restricted stock units (RSUs). Following this tax withholding, the reporting person beneficially owns 510,200 shares of Quanterix common stock, which includes 216,606 RSUs.

Quanterix (QTRX) reported an insider tax-withholding event by its President & CEO and Director. On October 31, 2025, 254 shares of common stock were withheld at $5.34 to cover taxes upon vesting of 761 RSUs.

After this transaction, the insider beneficially owns 511,442 shares, which includes 219,086 RSUs. The filing reflects routine administration of equity compensation rather than an open‑market sale.

Quanterix (QTRX) insider update: The Chief Financial Officer reported a tax-withholding transaction on 10/15/2025. Code F indicates 229 shares of common stock were withheld at $5.78 per share to satisfy taxes upon vesting of 777 restricted stock units.

Following this non‑open‑market event, the officer beneficially owns 86,742 shares, which includes 70,893 RSUs.

Quanterix Corp (QTRX) disclosed an insider transaction by its President & CEO and Director on 10/15/2025. The filing shows 1,242 shares of common stock were withheld (code F) at $5.78 per share to cover taxes upon the vesting of 3,722 RSUs.

Following this tax-withholding transaction, the reporting person beneficially owns 511,696 shares, which includes 219,847 RSUs. This is an administrative, non‑open market event tied to equity award vesting.

Quanterix Corp (QTRX) disclosed that a director acquired common stock through board compensation. On 10/01/2025, the director received 2,084 shares of common stock granted in lieu of cash fees for service on the Board and its committees for the third quarter of 2025. The grant was valued at the $5.54 closing price on the Nasdaq Global Market on that date.

Following this transaction, the director’s beneficial ownership was 29,488 shares, held directly, which includes 24,464 restricted stock units.

Quanterix Corporation director William P. Donnelly received 5,076 shares of common stock on 10/01/2025 as compensation in lieu of cash for board and committee service for the third quarter of 2025. The shares were recorded at the closing price of $5.54 on the Nasdaq Global Market for that date. Following the grant, Mr. Donnelly beneficially owns 148,374 shares, which include 12,955 restricted stock units. The Form 4 was filed individually and signed via attorney-in-fact on behalf of the reporting person.

Mendel Scott, a director of Quanterix Corp (QTRX), received 2,084 shares of common stock on 10/01/2025 as stock issued in lieu of cash board fees for Q3 2025 at a closing price of $5.54. Following the issuance, Mr. Scott beneficially owns 30,737 shares, which include 24,464 restricted stock units. The Form 4 was signed on behalf of the reporting person by Brian Keane, Attorney-in-Fact. The filing discloses no derivative transactions, option grants, or other cash purchases in this report.