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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(AMENDMENT NO 1)*

ARCA BIOPHARMA, INC.
(Name of Issuer)
Common Stock
(Title of Class of Securities)
00211Y100
(CUSIP Number)
December 31, 2010
(Date of Event which Requires Filing of this Statement)

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

     o Rule 13d-1(b)

     o Rule 13d-1(c)

     þ 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 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.
  
00211Y100 
 13G  
 
      
Page 2 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

InterWest Partners IX, LP

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  California
       
  5   SOLE VOTING POWER
     
NUMBER OF   521,904
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   0
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   521,904
       
8   SHARED DISPOSITIVE POWER
     
    0
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  PN

Page 2 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 3 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

InterWest Management Partners IX, LLC (the General Partner of InterWest Partners IX, LP)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  California
       
  5   SOLE VOTING POWER
     
NUMBER OF   521,904
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   0
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   521,904
       
8   SHARED DISPOSITIVE POWER
     
    0
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  OO

Page 3 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 4 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Harvey B. Cash (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Harvey B. Cash that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 4 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 5 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Bruce A. Cleveland (a Venture Member of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Bruce A. Cleveland that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 5 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 6 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Christopher B. Ehrlich (a Venture Member of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Christopher B. Ehrlich that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 6 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 7 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Philip T. Gianos (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Philip T. Gianos that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 7 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 8 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Linda S. Grais (a Venture Member of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   11,000
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   11,000
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  532,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  6.0%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Linda S. Grais that she is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 8 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 9 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

W. Stephen Holmes III (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by W. Stephen Holmes III that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 9 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 10 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Nina S. Kjellson (a Venture Member of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Nina S. Kjellson that she is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 10 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 11 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Gilbert H. Kliman (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Gilbert H. Kliman that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 11 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 12 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Khaled A. Nasr (a Venture Member of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Khaled A. Nasr that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 12 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 13 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Arnold L. Oronsky (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Arnold L. Oronsky that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 13 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 14 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Douglas A. Pepper (a Venture Member of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Douglas A. Pepper that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 14 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 15 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Thomas L. Rosch (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Thomas L. Rosch that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 15 of 21 Pages

 

                     
CUSIP No.
  
00211Y100 
 13G  
 
      
Page 16 of 21 Pages 

 

           
1   NAME OF REPORTING PERSONS

Michael B. Sweeney (a Managing Director of InterWest Management Partners IX, LLC)

I.R.S. IDENTIFICATION NO(S). OF ABOVE PERSON(S) (ENTITIES ONLY)
     
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
  (a)   o
  (b)   o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  United States
       
  5   SOLE VOTING POWER
     
NUMBER OF   0
       
SHARES 6   SHARED VOTING POWER
BENEFICIALLY    
OWNED BY   521,904
       
REPORTING 7   SOLE DISPOSITIVE POWER
PERSON    
WITH   0
       
8   SHARED DISPOSITIVE POWER
     
    521,904
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  521,904
     
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES:
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  5.9%
     
12   TYPE OF REPORTING PERSON
   
  IN
Neither the filing of this statement on Schedule 13G nor any of its contents shall be deemed to constitute an admission by Michael B. Sweeney that he is the beneficial owner of any of the Common Stock referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose, and such beneficial ownership is expressly disclaimed, except to the extent of his pecuniary interest.

Page 16 of 21 Pages

 

ITEM 1.
(a)   NAME OF ISSUER : ARCA biopharma, Inc.
 
(b)   ADDRESS OF ISSUER’S PRINCIPAL EXECUTIVE OFFICE:
 
    8001 Arista Place, Suite 200, Broomfield, CO 80021
ITEM 2.
(a)   NAME OF PERSON(S) FILING:
InterWest Partners IX, LP (“IWP IX”)
InterWest Management Partners IX, LLC (“IMP IX”)
Harvey B. Cash (“Cash”)
Bruce A. Cleveland (“Cleveland”)
Christopher B. Ehrlich (“Ehrlich”)
Philip T. Gianos (“Gianos”)
Linda S. Grais (“Grais”)
W. Stephen Holmes III (“Holmes”)
Nina S. Kjellson (“Kjellson”)
Gilbert H. Kliman (“Kliman”)
Khaled A. Nasr (“Nasr”)
Arnold L. Oronsky (“Oronsky”)
Douglas A. Pepper (“Pepper”)
Thomas L. Rosch (“Rosch”)
Michael B. Sweeney (“Sweeney”)
(b)   ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:
 
    2710 Sand Hill Road, Second Floor, Menlo Park, CA 94025
 
(c)   CITIZENSHIP/PLACE OF ORGANIZATION:
     
IWP IX:
  California
IMP IX:
  California
Cash:
  United States
Cleveland:
  United States
Ehrlich:
  United States
Gianos:
  United States
Grais:
  United States
Holmes:
  United States
Kjellson:
  United States
Kliman:
  United States
Nasr:
  United States
Oronsky:
  United States
Pepper:
  United States
Rosch:
  United States
Sweeney:
  United States
Page 17 of 21 Pages

 

 

(d)   TITLE OF CLASS OF SECURITIES: Common Stock
 
(e)   CUSIP NUMBER: 00211Y100
ITEM 3. NOT APPLICABLE.
ITEM 4. OWNERSHIP.
                                         
    IWP IX   IMP IX (1)   Cash (2)   Cleveland (2)   Ehrlich (2)
Beneficial Ownership
     521,904       521,904       521,904       521,904       521,904  
Percentage of Class
     5.9 %     5.9 %     5.9 %     5.9 %     5.9 %
Sole Voting Power
     521,904       521,904       0       0       0  
Shared Voting Power
     0       0       521,904       521,904       521,904  
Sole Dispositive Power
     521,904       521,904       0       0       0  
Shared Dispositive Power
     0       0       521,904       521,904       521,904  
                                 
    Gianos (2)   Grais (2) **   Holmes (2)   Kjellson (2)
Beneficial Ownership
     521,904       532,904       521,904       521,904  
Percentage of Class
     5.9 %     6.0 %     5.9 %     5.9 %
Sole Voting Power
     0       11,000       0       0  
Shared Voting Power
     521,904       521,904       521,904       521,904  
Sole Dispositive Power
     0       11,000       0       0  
Shared Dispositive Power
     521,904       521,904       521,904       521,904  
                         
    Kliman (2)   Nasr (2)   Oronsky (2)
Beneficial Ownership
     521,904       521,904       521,904  
Percentage of Class
     5.9 %     5.9 %     5.9 %
Sole Voting Power
     0       0       0  
Shared Voting Power
     521,904       521,904       521,904  
Sole Dispositive Power
     0       0       0  
Shared Dispositive Power
     521,904       521,904       521,904  
                         
    Pepper (2)   Rosch (2)   Sweeney (2)
Beneficial Ownership
     521,904       521,904       521,904  
Percentage of Class
     5.9 %     5.9 %     5.9 %
Sole Voting Power
     0       0       0  
Shared Voting Power
     521,904       521,904       521,904  
Sole Dispositive Power
     0       0       0  
Shared Dispositive Power
     521,904       521,904       521,904  
 
**   Includes 11,000 shares issuable to Grais pursuant to outstanding options exercisable within 60 days of December 31, 2010.
 
(1)   IMP IX is the general partner of IWP IX.
 
(2)   Cash, Gianos, Holmes, Kliman, Oronsky, Rosch, and Sweeney are Managing Directors of IMP IX. Cleveland, Ehrlich, Grais, Kjellson, Nasr, and Pepper are Venture Members of IMP IX.
Page 18 of 21 Pages

 

 

ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.
Not applicable.
ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON.
Under certain circumstances set forth in the limited liability company operating agreement of IMP IX, the members of such limited liability company have the right to receive dividends from, or the proceeds from the sale of, the common stock of Issuer beneficially owned by such limited liability company.
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.
No reporting person is a member of a group as defined in section 240.13d-1(b)(1)(iii)(H) of the Act.
ITEM 9. NOTICE OF DISSOLUTION OF THE GROUP.
Not applicable.
ITEM 10. CERTIFICATION.
Not applicable.
EXHIBITS
Joint Filing Statement attached as Exhibit A.
Page 19 of 21 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.
Date: February 4, 2011

         
     
By:   /s/ Harvey B. Cash      
  Name:   Harvey B. Cash     
     
By:   /s/ Bruce A. Cleveland      
  Name:   Bruce A. Cleveland     
     
By:   /s/ Christopher B. Ehrlich      
  Name:   Christopher B. Ehrlich     
     
By:   /s/ Philip T. Gianos      
  Name:   Philip T. Gianos     
     
By:   /s/ Linda S. Grais      
  Name:   Linda S. Grais     
     
By:   /s/ W. Stephen Holmes      
  Name:   W. Stephen Holmes     
     
By:   /s/ Nina S. Kjellson      
  Name:   Nina S. Kjellson     
     
By:   /s/ Gilbert H. Kliman      
  Name:   Gilbert H. Kliman     
     
By:   /s/ Khaled A. Nasr      
  Name:   Khaled A. Nasr     
     
By:   /s/ Arnold L. Oronsky      
  Name:   Arnold L. Oronsky     
       
 
         
INTERWEST PARTNERS IX, LP
 		    
By:   InterWest Management Partners IX, LLC      
its General Partner     
     
By:   /s/ W. Stephen Holmes      
  Managing Director     
     
INTERWEST MANAGEMENT PARTNERS IX, LLC
 		    
By:   /s/ W. Stephen Holmes      
  Managing Director     
     
By:   /s/ Douglas A. Pepper      
  Name:   Douglas A. Pepper     
     
By:   /s/ Thomas L. Rosch      
  Name:   Thomas L. Rosch     
     
By:   /s/ Michael B. Sweeney      
  Name:   Michael B. Sweeney     
       
 


Page 20 of 21 Pages

 

 

EXHIBIT A
Joint Filing Statement
We, the undersigned, hereby express our agreement that the attached Schedule 13G is filed on behalf of each of us.
Date: February 4, 2011

         
     
By:   /s/ Harvey B. Cash      
  Name:   Harvey B. Cash     
     
By:   /s/ Bruce A. Cleveland      
  Name:   Bruce A. Cleveland     
     
By:   /s/ Christopher B. Ehrlich      
  Name:   Christopher B. Ehrlich     
     
By:   /s/ Philip T. Gianos      
  Name:   Philip T. Gianos     
     
By:   /s/ Linda S. Grais      
  Name:   Linda S. Grais       
     
By:   /s/ W. Stephen Holmes      
  Name:   W. Stephen Holmes     
     
By:   /s/ Nina S. Kjellson      
  Name:   Nina S. Kjellson     
     
By:   /s/ Gilbert H. Kliman      
  Name:   Gilbert H. Kliman     
     
By:   /s/ Khaled A. Nasr      
  Name:   Khaled A. Nasr     
     
By:   /s/ Arnold L. Oronsky      
  Name:   Arnold L. Oronsky     
       
 
         
INTERWEST PARTNERS IX, LP
 		    
By:   InterWest Management Partners IX, LLC      
its General Partner     
     
By:   /s/ W. Stephen Holmes      
  Managing Director     
     
INTERWEST MANAGEMENT PARTNERS IX, LLC
 		    
By:   /s/ W. Stephen Holmes      
  Managing Director     
     
By:   /s/ Douglas A. Pepper      
  Name:   Douglas A. Pepper     
     
By:   /s/ Thomas L. Rosch      
  Name:   Thomas L. Rosch     
     
By:   /s/ Michael B. Sweeney      
  Name:   Michael B. Sweeney     
       
 


Page 21 of 21 Pages