UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

Amendment No. 2

PTC Therapeutics, Inc.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

69366J200

(CUSIP Number)

December 31, 2015

(Date of Event Which Requires Filing of this Statement)

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

¨ Rule 13d-1(b)

¨ Rule 13d-1(c)

x 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).

13G—AMENDMENT NO. 2

CUSIP No. 69366J200 Page 2 of 10 Pages

1	NAMES OF REPORTING PERSONS/I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Paul G. Allen
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)  ¨        (b)  x(1)
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION     U.S.
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER     261,562 (2)
		6	SHARED VOTING POWER     0
		7	SOLE DISPOSITIVE POWER     261,562 (2)
		8	SHARED DISPOSITIVE POWER     0
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON     261,562 (2)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES    ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)     Less than 5% (3)
12	TYPE OF REPORTING PERSON     IN

(1) This Schedule 13G is filed by Paul G. Allen, Vulcan Ventures Incorporated (“VVI”), Cougar Investment Holdings LLC (“Cougar”), VCVC Management III LLC (“VCVC Management III”) and VCVC III LLC (“VCVC III” and, together with Paul G. Allen, VVI, Cougar and VCVC Management III, the “Reporting Persons”). The Reporting Persons expressly disclaim status as a “group” for purposes of this Schedule 13G.

(2) Mr. Allen has sole voting and dispositive power over the aggregate 261,562 shares (the “Shares”), including (a) the 101,562 shares held of record by VVI (the “VVI Shares”) and (b) the 160,000 shares held of record by VCVC III (the “VCVC III Shares”). Mr. Allen is not a holder of record of any of the Shares, and disclaims all beneficial ownership in the shares held by VVI and VCVC III, except to the extent of his pecuniary interest therein.

(3) Based upon 34,271,694 shares of common stock of the Company outstanding as of November 5, 2015, as reported by the Company in its Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (the “SEC”) on November 9, 2015.

13G—AMENDMENT NO. 2

CUSIP No. 69366J200 Page 3 of 10 Pages

1	NAMES OF REPORTING PERSONS/I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Vulcan Ventures Incorporated (“VVI”)
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)  ¨        (b)  x
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION     Washington
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     0
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON     101,562 (1)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES    ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)     Less than 5% (2)
12	TYPE OF REPORTING PERSON     CO

(1) VVI is the record holder of the 101,562 VVI Shares. Paul G. Allen is the sole owner of VVI, and has sole voting and dispositive power over the VVI Shares.

(2) Based upon 34,271,694 shares of common stock of the Company outstanding as of November 5, 2015, as reported by the Company in its Quarterly Report on Form 10-Q filed with the SEC on November 9, 2015.

13G—AMENDMENT NO. 2

CUSIP No. 69366J200 Page 4 of 10 Pages

1	NAMES OF REPORTING PERSONS/I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) Cougar Investment Holdings LLC (“Cougar”)
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)  ¨        (b)  x
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION     Delaware
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     0
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON     160,000 (1)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES    ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)     Less than 5% (2)
12	TYPE OF REPORTING PERSON     OO

(1) Cougar is the managing member of VCVC Management III, which is the manager of VCVC III, which is the record holder of the 160,000 VCVC III Shares. Cougar is not a record holder of the VCVC III Shares and disclaims all beneficial ownership in the VCVC III Shares, except to the extent of its pecuniary interest therein. Paul G. Allen is the sole owner of Cougar and has sole voting and dispositive power over the VCVC III Shares.

(2) Based upon 34,271,694 shares of common stock of the Company outstanding as of November 5, 2015, as reported by the Company in its Quarterly Report on Form 10-Q filed with the SEC on November 9, 2015.

13G—AMENDMENT NO. 2

CUSIP No. 69366J200 Page 5 of 10 Pages

1	NAMES OF REPORTING PERSONS/I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) VCVC Management III LLC (“VCVC Management III”)
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)  ¨        (b)  x
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION     Delaware
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     0
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON     160,000 (1)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES    ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)     Less than 5% (2)
12	TYPE OF REPORTING PERSON     OO

(1) VCVC Management III is the manager of VCVC III, which is the record holder of the 160,000 VCVC III Shares. VCVC Management III is not a record holder of the VCVC III Shares and disclaims all beneficial ownership in the VCVC III Shares, except to the extent of its pecuniary interest therein. Paul G. Allen is the sole owner of Cougar, which is the managing member of VCVC Management III, and has sole voting and dispositive power over the VCVC III Shares.

(2) Based upon 34,271,694 shares of common stock of the Company outstanding as of November 5, 2015, as reported by the Company in its Quarterly Report on Form 10-Q filed with the SEC on November 9, 2015.

13G—AMENDMENT NO. 2

CUSIP No. 69366J200 Page 6 of 10 Pages

1	NAMES OF REPORTING PERSONS/I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) VCVC III LLC (“VCVC III”)
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a)  ¨        (b)  x
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION     Delaware
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     0
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON     160,000 (1)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES    ¨
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)     Less than 5% (2)
12	TYPE OF REPORTING PERSON     OO

(1) VCVC III is the record holder of the 160,000 VCVC III Shares. VCVC III is managed by VCVC Management III, which in turn in managed by Cougar. Mr. Allen, who is the sole owner of Cougar, has sole voting and dispositive power over the VCVC III Shares. Mr. Allen, Cougar and VCVC Management III are not the record holders of the VCVC III Shares and disclaim all beneficial ownership in the VCVC III Shares, except to the extent of their respective pecuniary interest therein.

(2) Based upon 34,271,694 shares of common stock of the Company outstanding as of November 5, 2015, as reported by the Company in its Quarterly Report on Form 10-Q filed with the SEC on November 9, 2015.

	13G—AMENDMENT NO. 2
CUSIP No. 69366J200		Page 7 of 10 Pages

Item 1(a) Name of Issuer:

PTC Therapeutics, Inc.

Item 1(b) Address of Issuer’s Principal Executive Offices:

100 Corporate Court, South Plainfield, NJ 07080

Item 2(a) Name of Person Filing:

(i) Paul G. Allen;

(ii) Vulcan Ventures Incorporated (“VVI”);

(iii) Cougar Investment Holdings LLC (“Cougar”);

(iv) VCVC Management III LLC (“VCVC Management III”);

(v) VCVC III LLC (“VCVC III”).

The foregoing persons hereinafter sometimes collectively are referred to as the “Reporting Persons.” Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party. The Reporting Persons’ agreement in writing to file this statement on behalf of each of them is attached as Exhibit 99.1 hereto.

Item 2(b) Address of Principal Business Office or, If None, Residence

(i) 505 Fifth Avenue South, Suite 900, Seattle, WA 98104

(ii) 505 Fifth Avenue South, Suite 900, Seattle, WA 98104

(iii) 505 Fifth Avenue South, Suite 900, Seattle, WA 98104

(iv) 505 Fifth Avenue South, Suite 900, Seattle, WA 98104

(v) 505 Fifth Avenue South, Suite 900, Seattle, WA 98104

Item 2(c) Citizenship:

(i) U.S.

(ii) Washington

(iii) Delaware

(iv) Delaware

(v) Delaware

Item 2(d) Title of Class of Securities:

Common Stock, $0.001 par value per share

Item 2(e) CUSIP Number:

69366J200

	13G—AMENDMENT NO. 2
CUSIP No. 69366J200		Page 8 of 10 Pages

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);

(k) ¨ Group, in accordance with 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with §240.13d–1(b)(1)(ii)(J), please specify the type of institution:             

Not applicable.

Item 4. Ownership

Reporting Person	Sole Voting Power		Shared Voting Power		Sole Dispositive Power		Shared Dispositive Power		Beneficial Ownership		Percentage of Class*
Paul G. Allen		261,562		0		261,552		0		261,562		Less than 5	%
VVI		0		0		0		0		101,562		Less than 5	%
Cougar		0		0		0		0		160,000		Less than 5	%
VCVC Management III		0		0		0		0		160,000		Less than 5	%
VCVC III		0		0		0		0		160,000		Less than 5	%

Paul G. Allen, who is the sole owner of VVI and Cougar, has sole voting and dispositive power over the aggregate 261,562 shares, including the 101,562 shares held of record by VVI and the 160,000 shares held of record by VCVC III. Cougar is the managing member of VCVC Management III, which is the manager of VCVC III. Mr. Allen, Cougar and VCVC Management III disclaim all beneficial ownership in the shares held by VCVC III, except to the extent of their respective pecuniary interest therein.

* Based upon 34,271,694 shares of common stock of the Company outstanding as of November 5, 2015, as reported by the Company in its Quarterly Report on Form 10-Q filed with the SEC on November 9, 2015.

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 person has ceased to be the beneficial owner or more than five percent of the class of securities, check the following box:  x

Item 6. Ownership of More Than Five Percent on Behalf of Another Person

Not applicable.

	13G—AMENDMENT NO. 2
CUSIP No. 69366J200		Page 9 of 10 Pages

Item 7. Identification and Classification of Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person

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. Certifications

Not applicable.

	13G—AMENDMENT NO. 2
CUSIP No. 69366J200		Page 10 of 10 Pages

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.

Dated: February 8, 2016	PAUL G. ALLEN
	By:	/s/ DAVID R. STEWART
	Name:	David R. Stewart
	Title:	Attorney-in-fact for Paul G. Allen
Dated: February 8, 2016	VULCAN VENTURES INCORPORATED
	By:	/s/ DAVID R. STEWART
	Name:	David R. Stewart
	Title:	Vice President
Dated: February 8, 2016	COUGAR INVESTMENT HOLDINGS LLC
	By:	/s/ DAVID R. STEWART
	Name:	David R. Stewart
	Title:	Vice President
Dated: February 8, 2016	VCVC MANAGEMENT III LLC
	By	Cougar Investment Holdings LLC, its Managing Member
	By:	/s/ DAVID R. STEWART
	Name:	David R. Stewart
	Title:	Vice President
Dated: February 8, 2016	VCVC III LLC
	By	VCVC Management III LLC, its Manager
	By	Cougar Investment Holdings LLC, its Managing Member
	By:	/s/ DAVID R. STEWART
	Name:	David R. Stewart
	Title:	Vice President

EXHIBIT INDEX

Exhibit	Title
99.1	Joint Filing Agreement dated February 8, 2016 among the Reporting Persons
99.2	Power of Attorney