(Amendment No. __)*
Check the appropriate box to designate the rule pursuant to
which this Schedule is filed:
*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 the disclosures provided in a prior cover page.
The information required in 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).
CUSIP No. 74373B109
|
13G
|
Page
2
of 15Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
HealthCare Ventures VIII, L.P.
|
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
Delaware
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
PN
|
1
This Schedule 13G is being filed jointly by the
Reporting Persons, as hereinafter defined. Such Reporting Persons expressly disclaim status as a “group” for purposes
of this Schedule 13G.
CUSIP No. 74373B109
|
13G
|
Page
3
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
HealthCare Partners VIII, L.P.
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
Delaware
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
PN
|
CUSIP No. 74373B109
|
13G
|
Page
4
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
HealthCare Partners VIII, LLC
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
Delaware
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
OO
|
CUSIP No. 74373B109
|
13G
|
Page
5
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
James H. Cavanaugh, Ph.D.
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
United States
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
IN
|
CUSIP No. 74373B109
|
13G
|
Page
6
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
Christopher Mirabelli, Ph.D.
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
United States
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
IN
|
CUSIP No. 74373B109
|
13G
|
Page
7
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
Harold R. Werner
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
United States
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
IN
|
CUSIP No. 74373B109
|
13G
|
Page
8
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
John W. Littlechild
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
United States
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
IN
|
CUSIP No. 74373B109
|
13G
|
Page
9
of 15 Pages
|
1
|
NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
Augustine Lawlor
|
2
|
CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a)
¨
(b)
x
See Footnote 1
|
3
|
SEC USE ONLY
|
4
|
CITIZENSHIP OR PLACE OF ORGANIZATION
United States
|
NUMBER OF
|
5
|
SOLE VOTING POWER
|
SHARES
BENEFICIALLY
OWNED BY
|
6
|
SHARED VOTING POWER
2,164,095 (See Items 2 and 4 herein)
|
EACH
REPORTING
PERSON
|
7
|
SOLE DISPOSITIVE POWER
|
WITH
|
8
|
SHARED DISPOSITIVE POWER
2,164,095 (See Items 2 and 4 herein)
|
9
|
AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,164,095 (See Items 2 and 4 herein)
|
10
|
CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
¨
|
11
|
PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
8.7%
|
12
|
TYPE OF REPORTING PERSON*
IN
|
CUSIP No. 74373B109
|
13G
|
Page
10
of 15 Pages
|
Item 1.
Proteostasis Therapeutics, Inc.
|
(b)
|
Address of Issuer’s Principal Executive Offices
|
200 Technology Square, 4
th
Floor
Cambridge, Massachusetts 02139
Item 2.
|
(a)
|
Name of Person Filing
|
HealthCare Ventures VIII, L.P.
(“HCVVIII”)
HealthCare Partners VIII, L.P.
(“HCPVIII”)
HealthCare Partners VIII, LLC
(“HCP VIII LLC”)
James H. Cavanaugh, Ph.D. (“Cavanaugh”)
Christopher Mirabelli, Ph.D. (“Mirabelli”)
Harold R. Werner (“Werner”)
John W. Littlechild (“Littlechild”)
Augustine Lawlor (“Lawlor”)
See attached Exhibit A,
which is a copy of their agreement in writing to file this statement on behalf of each of them.
1
|
(b)
|
Address of Principal Business Office or, if none, Residence
|
The business address for HCVVIII,
HCPVIII, HCP VIII LLC, Drs. Cavanaugh and Mirabelli and Messrs. Werner, Littlechild and Lawlor is 47 Thorndike Street, Suite B1-1,
Cambridge, Massachusetts 02141.
HCVVIII and HCPVIII are limited
partnerships organized under the laws of the State of Delaware. HCP VIII LLC is a limited liability company organized under the
laws of the State of Delaware. Drs. Cavanaugh and Mirabelli and Messrs. Werner, Littlechild, and Lawlor are each United States
citizens.
1
Drs.
Cavanaugh and Mirabelli and Messrs. Werner, Littlechild and Lawlor are the Managing Directors of HCP VIII LLC. HCP VIII LLC is
the General Partner of HCPVIII, which is the General Partner of HCVVIII, the record holder of the securities.
CUSIP No. 74373B109
|
13G
|
Page
11
of 15 Pages
|
|
(d)
|
Title of Class of Securities
|
Common Stock, $0.001 par value
per share (the “Common Stock”)
74373B109
|
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:
NOT APPLICABLE.
|
(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:________________
.
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:
|
As of December 31, 2016: HCVVIII
beneficially owns 2,164,095 shares of the Issuer’s Common Stock consisting of (i) 2,149,295 shares of Common Stock, and (ii)
Warrants to purchase 14,800 shares of Common Stock. HCPVIII, as the general partner of HCVVIII, HCPVIII LLC, as the general partner
of HCPVIII, and each of Drs. Cavanaugh and Mirabelli and Messrs. Werner, Littlechild and Lawlor may be deemed to indirectly beneficially
own the shares of Common Stock and the warrants to purchase Common Stock owned by HCVVIII.
CUSIP No. 74373B109
|
13G
|
Page
12
of 15 Pages
|
|
(b)
|
Percent of class: (based on 24,960,243 shares of the Issuer’s Common Stock issued and outstanding as of November 8, 2016
as reported in the Issuer’s Form 10-Q for the period ended September 30, 2016 and filed with the Securities and Exchange
Commission on November 10, 2016 and Warrants to purchase 14,800 shares of Common Stock owned by the Reporting Persons).
|
As of December 31, 2016: The 2,164,095
shares of the Issuer’s Common Stock owned by HCVVIII (and which may be deemed beneficially owned by HCPVIII, HCP VIII LLC,
Drs. Cavanaugh and Mirabelli and Messrs. Werner, Littlechild and Lawlor) constituted 8.7% of the shares outstanding.
|
(c)
|
Number of shares as to which the person has:
|
|
(i)
|
Sole power to vote or to direct the vote –
Not Applicable.
|
|
(ii)
|
Shared power to vote or to direct the vote –
|
HCVVIII, HCPVIII, HCP VIII LLC,
Drs. Cavanaugh and Mirabelli and Messrs. Werner, Littlechild and Lawlor share the power to vote or direct the vote of those shares
owned by HCVVIII.
|
(iii)
|
Sole power to dispose or to direct the disposition of –
Not Applicable.
|
|
(iv)
|
Shared power to dispose or to direct the disposition of –
|
HCVVIII, HCPVIII, HCP VIII LLC,
Drs. Cavanaugh and Mirabelli and Messrs. Werner, Littlechild and Lawlor share the power to dispose of or direct the disposition
of those shares owned by HCVVIII.
Instruction
. For computations regarding securities which
represent a right to acquire an underlying security see §240.13d-3(d)(1).
|
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 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
CUSIP No. 74373B109
|
13G
|
Page
13
of 15 Pages
|
Not Applicable.
CUSIP No. 74373B109
|
13G
|
Page
14
of 15 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.
January 19, 2017
|
HealthCare Ventures VIII,
L.P.
|
|
By: its General Partner,
HealthCare Partners VIII, L.P.
|
|
By: its
General Partner, HealthCare Partners VIII, LLC
|
|
|
|
|
By:
|
/s/
Jeffrey Steinberg
|
|
|
Jeffrey Steinberg,
Administrative Officer
|
|
HealthCare Partners VIII,
L.P.
|
|
By: its General Partner,
HealthCare Partners VIII, LLC
|
|
|
|
January 19, 2017
|
By:
|
/s/
Jeffrey Steinberg
|
|
|
Jeffrey Steinberg,
Administrative Officer
|
|
HealthCare Partners VIII,
LLC
|
|
|
|
|
By:
|
/s/Jeffrey
Steinberg
|
January 19, 2017
|
|
Jeffrey Steinberg,
Administrative Officer
|
|
|
|
January
19, 2017
|
/s/Jeffery
Steinberg, Attorney-in-Fact
|
|
James H. Cavanaugh, Ph.D.
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
Christopher Mirabelli, Ph.D.
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
Harold R. Werner
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
John W. Littlechild
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
Augustine Lawlor
|
CUSIP No. 74373B109
|
13G
|
Page
15
of 15 Pages
|
EXHIBIT
A
AGREEMENT
JOINT
FILING OF SCHEDULE 13G
The undersigned hereby agree to jointly prepare and file with
regulatory authorities a Schedule 13G and any future amendments thereto reporting each of the undersigned’s ownership of
securities of Proteostasis Therapeutics, Inc. and hereby affirm that such Schedule 13G is being filed on behalf of each of the
undersigned.
January 19, 2017
|
HealthCare Ventures VIII,
L.P.
|
|
By: its General Partner,
HealthCare Partners VIII, L.P.
|
|
By: its General Partner,
HealthCare Partners VIII, LLC
|
|
|
|
|
By:
|
/s/ Jeffrey
Steinberg
|
|
|
Jeffrey Steinberg, Administrative Officer
|
|
HealthCare Partners VIII,
L.P.
|
|
By: its General Partner,
HealthCare Partners VIII, LLC
|
|
|
|
January 19, 2017
|
By:
|
/s/ Jeffrey
Steinberg
|
|
|
Jeffrey Steinberg, Administrative Officer
|
|
HealthCare Partners VIII,
LLC
|
|
|
|
January 19, 2017
|
By:
|
/s/Jeffrey
Steinberg
|
|
|
Jeffrey Steinberg, Administrative Officer
|
|
|
|
January 19, 2017
|
/s/Jeffery
Steinberg, Attorney-in-Fact
|
|
James H. Cavanaugh, Ph.D.
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
Christopher Mirabelli, Ph.D.
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
Harold R. Werner
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
John W. Littlechild
|
|
|
January 19, 2017
|
/s/Jeffrey
Steinberg, Attorney-in-Fact
|
|
Augustine Lawlor
|