# EDGAR Filing Document

**Accession Number:** 0001503274
**File Stem:** 0001104659-25-114078
**Filing Date:** 2025-11
**Character Count:** 19003
**Document Hash:** fc8286fed866139952e2099f0ef9efb6
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-114078.hdr.sgml**: 20251119

**ACCESSION NUMBER**: 0001104659-25-114078

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13G

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20251119

**DATE AS OF CHANGE**: 20251119

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Quanterix Corp
- **CENTRAL INDEX KEY:** 0001503274
- **STANDARD INDUSTRIAL CLASSIFICATION:** LABORATORY ANALYTICAL INSTRUMENTS [3826]
- **ORGANIZATION NAME:** 08 Industrial Applications and Services
- **EIN:** 208957988
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-90285
- **FILM NUMBER:** 251499273

**BUSINESS ADDRESS:**
- **STREET 1:** 900 MIDDLESEX TURNPIKE
- **CITY:** BILLERICA
- **STATE:** MA
- **ZIP:** 01821
- **BUSINESS PHONE:** 617-301-9400

**MAIL ADDRESS:**
- **STREET 1:** 900 MIDDLESEX TURNPIKE
- **CITY:** BILLERICA
- **STATE:** MA
- **ZIP:** 01821
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Telegraph Hill Partners III, L.P.
- **CENTRAL INDEX KEY:** 0001555119

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G

**BUSINESS ADDRESS:**
- **STREET 1:** 360 POST STREET, SUITE 601
- **CITY:** SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94108
- **BUSINESS PHONE:** 415-765-6980

**MAIL ADDRESS:**
- **STREET 1:** 360 POST STREET, SUITE 601
- **CITY:** SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94108

## Ex-99.A

**EXHIBIT A**

**JOINT FILING AGREEMENT**

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto) with respect to the shares of common stock, $0.001 par value per share, of Quanterix Corporation, and further agree that this Joint Filing Agreement shall be included as an exhibit to such joint filings.

The undersigned further agree that each party hereto is responsible for the timely filing of such Statement on Schedule 13G and any amendments thereto, and for the accuracy and completeness of the information concerning such party contained therein; provided, however, that no party is responsible for the accuracy or completeness of the information concerning any other party, unless such party knows or has reason to believe that such information is inaccurate.

This Joint Filing Agreement may be signed in counterparts with the same effect as if the signature on each counterpart were upon the same instrument.

IN WITNESS WHEREOF, the undersigned have executed this Agreement as of November 17, 2025.

---

| | |
|:---|:---|
| **Telegraph Hill Partners III, L.P.** | **Telegraph Hill Partners III, L.P.** |
| a Delaware limited partnership | a Delaware limited partnership |
| By: | /s/ Rob Hart |
| Name: | Rob Hart |
| Title: | Partner |
| **THP III Affiliates Fund, LLC** | **THP III Affiliates Fund, LLC** |
| a Delaware limited liability company | a Delaware limited liability company |
| By: | /s/ Rob Hart |
| Name: | Rob Hart |
| Title: | Partner |
| **Telegraph Hill Partners III Investment Management, LLC** | **Telegraph Hill Partners III Investment Management, LLC** |
| a Delaware limited liability company | a Delaware limited liability company |
| By: | /s/ Rob Hart |
| Name: | Rob Hart |
| Title: | Partner |
| **Telegraph Hill Partners Management Company, LLC** | **Telegraph Hill Partners Management Company, LLC** |
| a Delaware limited liability company | a Delaware limited liability company |
| By: | /s/ Rob Hart |
| Name: | Rob Hart |
| Title: | Partner |

---

## Ex-99.B

**Exhibit B**

Due to the relationships between them, the reporting persons hereunder may be deemed to constitute a "group" with one another for purposes of Section 13(d)(3) of the Securities Exchange Act of 1934.

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13G

### Under the Securities Exchange Act of 1934

**Issuer:** Quanterix Corp

**Title of Class of Securities:** Common Stock, par value $0.001

**CUSIP Number:** 74766Q101

**Date of Event Which Requires Filing of this Statement:** 09/30/2025

**Check the appropriate box to designate the rule pursuant to which this Schedule is filed:**

- [ ] Rule 13d-1(b)

- [x] Rule 13d-1(c)

- [ ] Rule 13d-1(d)

---

| 1. | Names of Reporting Persons<br>Telegraph Hill Partners III, L.P. | Names of Reporting Persons<br>Telegraph Hill Partners III, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2504648.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2504648.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>5.4% | Percent of Class Represented by Amount in Row (9)<br>5.4% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

**Comment for Type of Reporting Person:** Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC.
Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer.

---

| 1. | Names of Reporting Persons<br>THP III Affiliates Fund, LLC | Names of Reporting Persons<br>THP III Affiliates Fund, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2504648.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2504648.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>5.4% | Percent of Class Represented by Amount in Row (9)<br>5.4% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

**Comment for Type of Reporting Person:** Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC.
Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer.

---

| 1. | Names of Reporting Persons<br>Telegraph Hill Partners III Investment Management, LLC | Names of Reporting Persons<br>Telegraph Hill Partners III Investment Management, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2504648.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2504648.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>5.4% | Percent of Class Represented by Amount in Row (9)<br>5.4% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

**Comment for Type of Reporting Person:** Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC.
Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer.

---

| 1. | Names of Reporting Persons<br>Telegraph Hill Partners Management Company, LLC | Names of Reporting Persons<br>Telegraph Hill Partners Management Company, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [x] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2504648.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0.00 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2504648.00 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2504648.00 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>5.4% | Percent of Class Represented by Amount in Row (9)<br>5.4% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

**Comment for Type of Reporting Person:** Row 6, 8, 9 and 11: Includes (i) 2,258,408 shares of common stock held by Telegraph Hill Partners III, L.P. and (ii) 246,240 shares of common stock held by THP III Affiliates Fund, LLC.
Row 11: Consists of 46,710,797 shares of Common Stock of the Issuer outstanding on November 4, 2025, based on information publicly disclosed by the Issuer.

---

**Item 1(a). Name of Issuer:**
Quanterix Corp

**Item 1(b). Address of Issuer's Principal Executive Offices:**
1900 Middlesex Turnpike Billerica, MA, 01821

**Item 2(a). Name of Person Filing:**
This Statement is filed on behalf of each of the following persons (collectively, the "Reporting Persons"):
(i) Telegraph Hill Partners III, L.P.
(ii) THP III Affiliates Fund, LLC
(iii) Telegraph Hill Partners III Investment Management, LLC
(iv) Telegraph Hill Partners Management Company, LLC

**Item 2(b). Address of Principal Business Office:**
The address of the principal business and principal office of each of the Reporting Persons is 300 Montgomery Street, Suite 1130, San Francisco, California 94104.

**Item 2(c). Citizenship:**
(i) Telegraph Hill Partners III, L.P. is a Delaware limited partnership.
(ii) THP III Affiliates Fund, LLC is a Delaware limited liability company.
(iii) Telegraph Hill Partners III Investment Management, LLC is a Delaware limited liability company.
(iv) Telegraph Hill Partners Management Company, LLC is a Delaware limited liability company.

**Item 2(d). Title of Class of Securities:**
Common Stock, par value $0.001

**Item 2(e). CUSIP Number:**
74766Q101

**Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:**

(a) [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c) [ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d) [ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e) [ ] An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f) [ ] An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g) [ ] A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h) [ ] A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i) [ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j) [ ] A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), if filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

(k) [ ] Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

**Item 4. Ownership:**

**(a) Amount beneficially owned:**

Telegraph Hill Partners III, L.P.
2,258,408 shares of common stock are held of record by Telegraph Hill Partners III, L.P. ("THP III"). Telegraph Hill Partners III Investment Management, LLC ("THP IM") is the general partner of THP III. Telegraph Hill Partners Management Company, LLC ("THPMC") is the manager of THP IM.
THP III Affiliates Fund, LLC
246,240 shares of common stock are held of record by THP III Affiliates Fund, LLC ("THP III AFF"). THP IM is the manager of THP III AFF. THPMC is the manager of THP IM.

**(b) Percent of class:**

The information required by Item 4(b) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.

**(c) Number of shares as to which the person has:**

**(i) Sole power to vote or to direct the vote:**

The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.

**(ii) Shared power to vote or to direct the vote:**

The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.

**(iii) Sole power to dispose or to direct the disposition of:**

The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.

**(iv) Shared power to dispose or to direct the disposition of:**

The information required by Item 4(c) is set forth in Rows (5)-(9) and (11) of the cover page for each Reporting Person hereto and is incorporated herein by reference for each Reporting Person.

**Item 5. Ownership of Five Percent or Less of a Class.**

[x] If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.

**Item 6. Ownership of More than 5 Percent on Behalf of Another Person.**

Not Applicable

**Item 7. Identification and Classification of the Subsidiary**

Not Applicable

**Item 8. Identification and Classification of Members of the Group**

Not Applicable

**Item 9. Notice of Dissolution of Group**

Not Applicable

**Item 10. Certification:**

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Telegraph Hill Partners III, L.P.**

**Date:** 11/17/2025

**By:** /s/ Rob Hart

**Name & Title:** Rob Hart/Partner, Telegraph Hill Partners III Investment Management, LLC, Its: General Partner, Telegraph Hill Partners Mgmt Company LLC, Its: Manager

**THP III Affiliates Fund, LLC**

**Date:** 11/17/2025

**By:** /s/ Rob Hart

**Name & Title:** Rob Hart/Partner, Telegraph Hill Partners III Investment Management, LLC, Its: Manager, Telegraph Hill Partners Management Company LLC, Its: Manager

**Telegraph Hill Partners III Investment Management, LLC**

**Date:** 11/17/2025

**By:** /s/ Rob Hart

**Name & Title:** Rob Hart/Partner, Telegraph Hill Partners Management Company LLC, Its: Manager

**Telegraph Hill Partners Management Company, LLC**

**Date:** 11/17/2025

**By:** /s/ Rob Hart

**Name & Title:** Rob Hart/Partner