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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)*

HELICOS BIOSCIENCES CORPORATION

(Name of Issuer)

Common Stock
(Title of Class of Securities)

42326R 109
(CUSIP Number)

December 31, 2009
(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.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures III, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 2 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures III-QP, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 3 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures III Parallel Fund, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 4 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures III GmbH & Co. Beteiligungs KG


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Germany

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 5 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM Asset Management Investors 2003 BVIII LLC


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	OO

Page 6 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures III GP, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 7 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures III LLC


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	OO

Page 8 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Ansbert Gadicke


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 9 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Luke Evnin


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 10 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Nicholas Galakatos


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 11 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Michael Steinmetz


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 12 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Kurt Wheeler


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 13 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Nicholas Simon III


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 14 of 24


CUSIP No.		42326R 109


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Dennis Henner


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

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			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	0

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 15 of 24

Item 1.

(a)

Name of Issuer

Helicos BioSciences Corporation

(b)

Address of Issuer’s Principal Executive Offices

One Kendall Square
Building 700
Cambridge, MA 02139

Item 2.

(a)

Name of Person Filing

MPM BioVentures III, L.P.
MPM BioVentures III-QP, L.P.
MPM BioVentures III Parallel Fund, L.P.
MPM BioVentures III GmbH & Co. Beteiligungs KG
MPM Asset Management Investors 2003 BVIII LLC
MPM BioVentures III GP, L.P.
MPM BioVentures III LLC
Ansbert Gadicke
Luke Evnin
Nicholas Galakatos
Michael Steinmetz
Kurt Wheeler
Nicholas Simon III
Dennis Henner

(b)

Address of Principal Business Office or, if none, Residence

c/o MPM Capital L.P.
The John Hancock Tower
200 Clarendon Street, 54^th Floor
Boston, MA 02116

(c)

Citizenship

All entities were organized in Delaware, except MPM BioVentures III GmbH & Co. Beteiligungs KG which was organized in Germany. The individuals are United States citizens.

(d)

Title of Class of Securities

Common Stock

(e)

CUSIP Number

42326R 109

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

Page 16 of 24

Item 4. Ownership

(a)

Amount Beneficially Owned:


MPM BioVentures III, L.P.			0
MPM BioVentures III-QP, L.P.			0
MPM BioVentures III Parallel Fund, L.P.			0
MPM BioVentures III GmbH & Co. Beteiligungs KG			0
MPM Asset Management Investors 2003 BVIII LLC			0
MPM BioVentures III GP, L.P.			0
MPM BioVentures III LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0
Nicholas Simon III			0
Dennis Henner			0

Percent of Class:


MPM BioVentures III, L.P.	0	%
MPM BioVentures III-QP, L.P.	0	%
MPM BioVentures III Parallel Fund, L.P.	0	%
MPM BioVentures III GmbH & Co. Beteiligungs KG	0	%
MPM Asset Management Investors 2003 BVIII LLC	0	%
MPM BioVentures III GP, L.P.	0	%
MPM BioVentures III LLC	0	%
Ansbert Gadicke	0	%
Luke Evnin	0	%
Nicholas Galakatos	0	%
Michael Steinmetz	0	%
Kurt Wheeler	0	%
Nicholas Simon III	0	%
Dennis Henner	0	%

Page 17 of 24

(b)

Number of shares as to which the person has:

(i)

Sole power to vote or to direct the vote


MPM BioVentures III, L.P.			0
MPM BioVentures III-QP, L.P.			0
MPM BioVentures III Parallel Fund, L.P.			0
MPM BioVentures III GmbH & Co. Beteiligungs KG			0
MPM Asset Management Investors 2003 BVIII LLC			0
MPM BioVentures III GP, L.P.			0
MPM BioVentures III LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0
Nicholas Simon III			0
Dennis Henner			0

(ii)

Shared power to vote or to direct the vote


MPM BioVentures III, L.P.			0
MPM BioVentures III-QP, L.P.			0
MPM BioVentures III Parallel Fund, L.P.			0
MPM BioVentures III GmbH & Co. Beteiligungs KG			0
MPM Asset Management Investors 2003 BVIII LLC			0
MPM BioVentures III GP, L.P.			0
MPM BioVentures III LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0
Nicholas Simon III			0
Dennis Henner			0

Page 18 of 24

(iii)

Sole power to dispose or to direct the disposition of


MPM BioVentures III, L.P.			0
MPM BioVentures III-QP, L.P.			0
MPM BioVentures III Parallel Fund, L.P.			0
MPM BioVentures III GmbH & Co. Beteiligungs KG			0
MPM Asset Management Investors 2003 BVIII LLC			0
MPM BioVentures III GP, L.P.			0
MPM BioVentures III LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0
Nicholas Simon III			0
Dennis Henner			0

(iv)

Shared power to dispose or to direct the disposition of


MPM BioVentures III, L.P.			0
MPM BioVentures III-QP, L.P.			0
MPM BioVentures III Parallel Fund, L.P.			0
MPM BioVentures III GmbH & Co. Beteiligungs KG			0
MPM Asset Management Investors 2003 BVIII LLC			0
MPM BioVentures III GP, L.P.			0
MPM BioVentures III LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0
Nicholas Simon III			0
Dennis Henner			0

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 þ.

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 or Control Person.

Not Applicable

Item 8. Identification and Classification of Members of the Group

Not Applicable

Page 19 of 24

Item 9. Notice of Dissolution of a Group

Not Applicable

Item 10. Certification

Not Applicable

Page 20 of 24

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 11, 2010


MPM BIOVENTURES III, L.P.		MPM BIOVENTURES III-QP, L.P.

By:	MPM BioVentures III GP, L.P.,	By:	MPM BioVentures III GP, L.P.,
	its General Partner		its General Partner

By:	MPM BioVentures III LLC,	By:	MPM BioVentures III LLC,
	its General Partner		its General Partner

By:	/s/ Luke Evnin	By:	/s/ Luke Evnin

	Name: Luke Evnin		Name: Luke Evnin
	Title: Series A Member		Title: Series A Member


MPM BIOVENTURES III PARALLEL FUND, L.P.		MPM BIOVENTURES III GMBH & CO. BETEILIGUNGS KG
By:	MPM BioVentures III GP, L.P.,
	its General Partner	By:	MPM BioVentures III GP, L.P.,
			in its capacity as the Managing Limited Partner
By:	MPM BioVentures III LLC,
	its General Partner	By:	MPM BioVentures III LLC,
			its General Partner
By:	/s/ Luke Evnin

	Name: Luke Evnin	By:	/s/ Luke Evnin

	Title: Series A Member		Name: Luke Evnin
			Title: Series A Member

MPM ASSET MANAGEMENT INVESTORS 2003 BVIII LLC

MPM BIOVENTURES III GP, L.P.

By:

MPM BioVentures III LLC,

its General Partner

By:

/s/ Luke Evnin

Name: Luke Evnin

Title: Manager

By:

/s/ Luke Evnin

Name:

Luke Evnin

Title:

Series A Member


MPM BIOVENTURES III LLC

By:	/s/ Luke Evnin	/s/ Ansbert Gadicke

Name:	Luke Evnin	Ansbert Gadicke
Title:	Series A Member

Page 21 of 24


/s/ Luke Evnin				/s/ Nicholas Galakatos

Luke Evnin				Nicholas Galakatos

/s/ Michael Steinmetz				/s/ Kurt Wheeler

Michael Steinmetz				Kurt Wheeler

/s/ Nicholas Simon III				/s/ Dennis Henner

Nicholas Simon III				Dennis Henner

EXHIBITS

A: Joint Filing Agreement

Page 22 of 24

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 amendments thereto) with respect to the Common Stock of Helicos BioSciences Corporation and further agree that this agreement be included as an exhibit to such filing. Each party to the agreement expressly authorizes each other party to file on its behalf any and all amendments to such statement. Each party to this agreement agrees that this joint filing agreement may be signed in counterparts.

In evidence whereof, the undersigned have caused this Agreement to be executed on their behalf this 11^th day of February, 2010.


MPM BIOVENTURES III, L.P.		MPM BIOVENTURES III-QP, L.P.

By:	MPM BioVentures III GP, L.P.,	By:	MPM BioVentures III GP, L.P.,
	its General Partner		its General Partner

By:	MPM BioVentures III LLC,	By:	MPM BioVentures III LLC,
	its General Partner		its General Partner

By:	/s/ Luke Evnin	By:	/s/ Luke Evnin

	Name: Luke Evnin		Name: Luke Evnin
	Title: Series A Member		Title: Series A Member


MPM BIOVENTURES III PARALLEL FUND, L.P.		MPM BIOVENTURES III GMBH & CO. BETEILIGUNGS KG
By:	MPM BioVentures III GP, L.P.,
	its General Partner	By:	MPM BioVentures III GP, L.P.,
			in its capacity as the Managing Limited Partner
By:	MPM BioVentures III LLC,
	its General Partner	By:	MPM BioVentures III LLC,
			its General Partner
By:	/s/ Luke Evnin

	Name: Luke Evnin	By:	/s/ Luke Evnin

	Title: Series A Member		Name: Luke Evnin
			Title: Series A Member

MPM ASSET MANAGEMENT INVESTORS 2003
BVIII LLC

MPM BIOVENTURES III GP, L.P.

By:

MPM BioVentures III LLC,

its General Partner

By:

/s/ Luke Evnin

Name: Luke Evnin

Title: Manager

By:

/s/ Luke Evnin

Name:

Luke Evnin

Title:

Series A Member


MPM BIOVENTURES III LLC

By:	/s/ Luke Evnin	/s/ Ansbert Gadicke

Name:	Luke Evnin	Ansbert Gadicke
Title:	Series A Member

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/s/ Luke Evnin				/s/ Nicholas Galakatos

Luke Evnin				Nicholas Galakatos

/s/ Michael Steinmetz				/s/ Kurt Wheeler

Michael Steinmetz				Kurt Wheeler

/s/ Nicholas Simon III				/s/ Dennis Henner

Nicholas Simon III				Dennis Henner

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