SC 13G/A 1 tm215780d8_sc13ga.htm SC 13G/A

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

(RULE 13d - 102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2

(Amendment No. 2)*

Quanterix Corporation

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

74766Q101

(CUSIP Number)

December 31, 2020

(Date of Event which Requires Filing of this Statement)

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

x Rule 13d-1(b)

¨ Rule 13d-1(c)

¨ Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(Page 1 of 5 Pages)

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CUSIP No. 74766Q101

1	NAME OF REPORTING PERSON Gilder, Gagnon, Howe & Co. LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP		(a) ¨ (b) ¨
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION New York

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH	5	SOLE VOTING POWER 0
	6	SHARED VOTING POWER 0
	7	SOLE DISPOSITIVE POWER 0
	8	SHARED DISPOSITIVE POWER 3,075,251
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 3,075,251
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 9.71%
12	TYPE OF REPORTING PERSON BD

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ITEM 1(a).

Name of Issuer:

Quanterix Corporation

Item 1(b).

Address of Issuer's Principal Executive Offices:

900 Middlesex Turnpike

Billerica, MA 01821

Item 2(a).

Name of Persons Filing:

Gilder, Gagnon, Howe & Co. LLC

Item 2(b).

Address of Principal Business Office or, if None, Residence:

475 10th Avenue

New York, NY 10018

Item 2(c).

Citizenship:

New York

Item 2(d).

Title of Class of Securities

Common Stock

Item 2(e).

CUSIP Number:

74766Q101

ITEM 3.

IF THIS STATEMENT IS FILED PURSUANT TO RULE 13d-1(b), OR 13d-2(b) OR (c), CHECK WHETHER THE PERSON FILING IS A:

(a)

x 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 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 Rule 13d-1(b)(1)(ii)(E).

(f)

¨ An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F).

(g)

¨ A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G).

(h)

¨ A savings association 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)

(k)

¨ Group, in accordance with Rule 13d-1(b)(1)(ii)(K).

Page 4 of 5

Item 4.

Ownership.

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

(a) Amount beneficially owned: 3,075,251

(b) Percent of class: 9.71%%

(i)

Sole power to vote or direct the vote: 0

(ii)

Shared power to vote or direct the vote: 0

(iii)

Sole power to dispose or direct the disposition: 0

(iv)

Shared power to dispose or direct the disposition: 3,075,251

The shares reported include 3,075,251shares held in customer accounts over which partners and/or employees of the Reporting Person have discretionary authority to dispose of or direct the disposition of the shares.

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the Reporting Persons have 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 Five Percent on Behalf of Another Person.

Not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company.

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 the undersigned certifies that, to the best of its knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and 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.

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SIGNATURES

After reasonable inquiry and to the best of the undersigned’s knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated: February 16, 2021

	GILDER, GAGNON, HOWE & CO. LLC


	By:	/s/ Laura Esposito
	Name:	Laura Esposito
	Title:	Chief Compliance Officer

SEC Form SC 13G/A filed