As of November 6, 2026, 4 holders' latest Schedule 13D or 13G filings report owning 5% or more of Quanterix Corp. The largest reported stake is Ameriprise Financial, Inc.'s, at 7.5%. 12 filings are on record since July 15, 2025 (Schedule 13G/A, May 15, 2026).
Sell to companies like Quanterix Corp? Enter your website and see 10 with a filed reason to buy from you this month. Free.
Opens in a new tab. No signup.
Key facts
- · Reporting person: Portolan Capital Management, LLC · Sole voting: 1,899,308 · Shared voting: 0 · Sole dispositive: 1,899,308 · Shared dispositive: 0 · SCHEDULE 13G/A, 2026-08-14
- · Reporting person: First Eagle Investment Management, LLC · Sole voting: 2,753,165 · Shared voting: 0 · Sole dispositive: 2,753,165 · Shared dispositive: 0 · SCHEDULE 13G, 2026-08-06
- · Holder: Portolan Capital Management, LLC · Percent: 6.25% · SCHEDULE 13G/A
- · Holder: Ameriprise Financial, Inc. · Percent: 7.5% · SCHEDULE 13G/A
- · Holder: Ameriprise Financial, Inc. · Percent: 2.1% · SCHEDULE 13G/A
Quanterix Corp has 12 Schedule 13D or 13G filings on record since 2025-07-15. 4 holders' latest filing reports 5% or more of common stock, $0.001 par value per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| Ameriprise Financial, Inc. | 7.5% | 3,542,374 | SCHEDULE 13G/A, 2026-05-15 | 2026-03-31 |
| BlackRock, Inc. | 7.3% | 2,843,760 | SCHEDULE 13G/A, 2025-07-17 | 2025-06-30 |
| First Eagle Investment Management, LLC | 5.8% | 2,753,165 | SCHEDULE 13G, 2026-08-06 | 2026-06-30 |
| Telegraph Hill Partners III, L.P. | 5.4% | 2,504,648 | SCHEDULE 13G, 2025-11-19 | 2025-09-30 |
| Kent Lake PR LLC | 4.5% | 2,089,500 | SCHEDULE 13D/A, 2025-07-15 | 2025-07-11 |
| Portolan Capital Management, LLC | 4.02% | 1,899,308 | SCHEDULE 13G/A, 2026-08-14 | 2026-06-30 |
| The Vanguard Group | 0% | 0 | SCHEDULE 13G/A, 2026-03-27 | 2026-03-13 |
Holding shares or following this stake? See who's behind Quanterix Corp and the warning signs.
Free to see. No signup.
Keep reading
More on Quanterix Corp and the records around it.
Quanterix Corp elsewhere on the record
- Leadership changes Jun 2026
- Who owns it
Companies that share a holder
- Kent Lake Partners LP also filed stake reports on 1 other company: UNIVERSAL ELECTRONICS INC (Nov 2025)
- Portolan Capital Management, LLC also filed stake reports on 13 other companies: LANTRONIX, INC. (Oct 2026), SILICOM LTD. (Sep 2026), Real Brokerage Inc (Aug 2026)
- First Eagle Investment Management, LLC also filed stake reports on 16 other companies: AMTECH SYSTEMS INC (Aug 2026), DENTSPLY SIRONA Inc. (Aug 2026), Warrior Met Coal Inc (Aug 2026)
Watch Quanterix Corp
Get an email when Quanterix Corp files again: a new raise, a leadership change, a layoff or an IPO filing. One email first to confirm; nothing else until you click it. At most one a day, one click to stop. Free for up to 3 companies.
Want the whole picture on Quanterix Corp?
Example from a real report (our sample on Target): “In March 2026, Target announced a planned incremental $1 billion operating investment” Source: Target Corporation (press release)
A Full Report on Quanterix Corp: verified, sourced, every claim cited, ready in a few minutes. See pricing.
What the Full Report on Quanterix Corp covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
Sources
15 cited sources found
Plus the sections for what you are deciding, which you pick after ordering.
A real finished report, first screen. Opens in a new tab.
Not ready to order yet? Keep this snapshot.
Sends this preview to you once; we won't add you to any list
Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| First Eagle Investment Management, LLC | 2,753,165 | 0 | 2,753,165 | 0 | SCHEDULE 13G, 2026-08-06 |
| First Eagle Small Cap Opportunity Fund | 2,421,533 | 0 | 2,421,533 | 0 | SCHEDULE 13G, 2026-08-06 |
| Portolan Capital Management, LLC | 1,899,308 | 0 | 1,899,308 | 0 | SCHEDULE 13G/A, 2026-08-14 |
| George McCabe | 1,899,308 | 0 | 1,899,308 | 0 | SCHEDULE 13G/A, 2026-08-14 |
The latest filing identifies Quanterix Corp by CUSIP 74766Q101 and gives its principal executive office as 900 Middlesex Turnpike, Billerica, MA 01821 (SCHEDULE 13G/A, 2026-08-14).
Purpose of Transaction (Item 4)
Kent Lake PR LLC
Item 4 is hereby amended to add the following: As previously disclosed in Amendment No. 1 to the Schedule 13D, on February 28, 2025, Kent Lake delivered a letter to the Issuer nominating Alexander G. Dickinson, Bruce Felt and Hakan Sakul (the "Nominees") for election to the Board of Directors of the Issuer (the "Board") at the 2025 annual meeting of stockholders (the "Annual Meeting"). On July 11, 2025, Kent Lake resubmitted its nomination of the Nominees for election to the Board at the Annual Meeting following the Issuer's disclosure that the Annual Meeting will now be held on September 23, 2025.Item 4 of the SCHEDULE 13D/A filed 2025-07-15
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-07-15 | Kent Lake PR LLC | 4.5% | SCHEDULE 13D/A |
| 2025-07-17 | BlackRock, Inc. | 7.3% | SCHEDULE 13G/A |
| 2025-08-13 | Portolan Capital Management, LLC | 9.36% | SCHEDULE 13G/A |
| 2025-11-14 | Ameriprise Financial, Inc. | 9.1% | SCHEDULE 13G/A |
| 2025-11-19 | Telegraph Hill Partners III, L.P. | 5.4% | SCHEDULE 13G |
| 2026-02-17 | Ameriprise Financial, Inc. | 10.7% | SCHEDULE 13G/A |
| 2026-03-27 | The Vanguard Group | 0% | SCHEDULE 13G/A |
| 2026-05-07 | Ameriprise Financial, Inc. | 2.1% | SCHEDULE 13G/A |
| 2026-05-15 | Portolan Capital Management, LLC | 6.25% | SCHEDULE 13G/A |
| 2026-05-15 | Ameriprise Financial, Inc. | 7.5% | SCHEDULE 13G/A |
| 2026-08-06 | First Eagle Investment Management, LLC | 5.8% | SCHEDULE 13G |
| 2026-08-14 | Portolan Capital Management, LLC | 4.02% | SCHEDULE 13G/A |
Questions about who owns Quanterix Corp
Who owns Quanterix Corp?
On this page, 4 holders' latest ownership filings report 5% or more of Quanterix Corp: Ameriprise Financial, Inc. (7.5%, Schedule 13G/A, filed 2026-05-15), BlackRock, Inc. (7.3%, Schedule 13G/A, filed 2025-07-17), First Eagle Investment Management, LLC (5.8%, Schedule 13G, filed 2026-08-06) and Telegraph Hill Partners III, L.P. (5.4%, Schedule 13G, filed 2025-11-19).
Who are the largest shareholders of Quanterix Corp?
By the share each holder's latest filing reports, the largest holders of Quanterix Corp on this page are Ameriprise Financial, Inc. (7.5%), BlackRock, Inc. (7.3%) and First Eagle Investment Management, LLC (5.8%).
When did Ameriprise Financial, Inc. buy into Quanterix Corp?
The filings give report dates, not purchase dates. The earliest filing from Ameriprise Financial, Inc. on this page is the Schedule 13G/A, filed 2025-11-14, reporting 9.1%; its latest, Schedule 13G/A filed 2026-05-15, reports 7.5%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 12 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Also on the record for Quanterix Corp
| Date | Record | Figure | Our page | Source |
|---|---|---|---|---|
| June 9, 2026 | Leadership change: Jason Faessler appointed, Chief Financial Officer | — | Leadership changes | Source |
| May 26, 2026 | Leadership change: Anthony Catalano appointed, Chief Operating Officer | — | Leadership changes | Source |
| May 12, 2026 | Leadership change filing (Form 8-K, Item 5.02) | — | Leadership changes | Source |
Tools for this story
Each opens in a new tab, filled in for Quanterix Corp. With no account yet, you sign up free and land on the result.
Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.