SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* BB BIOVENTURES L P (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol IDENIX PHARMACEUTICALS INC [ IDIX ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 07/27/2004
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	07/27/2004		S		508,371(1)	D	$14	4,797,991	I	See Footnote(2)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* BB BIOVENTURES L P (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BAB BIO VENTURES LLP (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BAB BIO VENTURES NV (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MPM ASSET MANAGEMENT INVESTORS 1998 LLC/MA (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MPM BIO VENTURES PARALLEL FUND L P (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MPM BIO VENTURES I LP (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MPM BIO VENTURES I LLC (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* MPM ASSET MANAGEMENT LLC (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* STEINMETZ MICHAEL (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* EVNIN LUKE (Last) (First) (Middle) 111 HUNTINGTON AVENUE 31ST FLOOR (Street) BOSTON MA 02199 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. The shares were sold as follows 462,317 by BB BioVentures, L.P. ("BB BioVentures"), 40,208 by MPM BioVentures Parallel Fund, L.P. ("MPM Parallel") and 5,846 by MPM Asset Management Investors 1998 LLC ("MPM Investors").

2. The shares are held as follows 4,292,188 by BB BioVentures, 373,298 by MPM Parallel, 54,277 by MPM Investors and 78,228 by MPM Asset Management LLC ("MPM Asset"). BB BioVentures is under common control with MPM Parallel and MPM Investors. BAB BioVentures L.P. ("BAB BV"), BAB BioVentures NV and MPM BioVentures I LLC ("BioVentures LLC") are the direct and indirect general partners of BB BioVentures. MPM BioVentures I L.P. ("BioVentures LP") and BioVentures LLC are the direct and indirect general partners of MPM Parallel. Luke Evnin, Ansbert Gadicke and Michael Steinmetz are the managers of MPM Investors and BioVentures LLC and Luke Evnin and Ansbert Gadicke are the managers of MPM Asset. Each member of the group disclaims beneficial ownership of the securities except to the extent of its pecuniary interest therein.

	By Ansbert Gadicke, managing director of BAB BioVentures NV, the general partner of BAB BioVentures L.P., the general partner of BB BioVentures L.P. /s/ Ansbert Gadicke	07/27/2004
	By Ansbert Gadicke, managing director of BAB BioVentures NV, the general partner of BAB BioVentures L.P. /s/ Ansbert Gadicke	07/27/2004
	By Ansbert Gadicke, managing director of BAB BioVentures NV /s/ Ansbert Gadicke	07/27/2004
	By Luke Evnin, manager of MPM Asset Management Investors 1998 LLC /s/ Luke Evnin	07/27/2004
	By Luke Evnin, manager of MPM BioVentures I LLC, the general partner of MPM BioVentures I L.P., the general partner of MPM BioVentures Parallel Fund, L.P. /s/ Luke Evnin	07/27/2004
	By Luke Evnin, manager of MPM BioVentures I LLC, the general partner of MPM BioVentures I L.P. /s/ Luke Evnin	07/27/2004
	By Luke Evnin, manager of MPM BioVentures I LLC /s/ Luke Evnin	07/27/2004
	By Luke Evnin, manager of MPM Asset Management LLC /s/ Luke Evnin	07/27/2004
	/s/ Michael Steinmetz	07/27/2004
	/s/ Luke Evnin	07/27/2004
	** Signature of Reporting Person	Date
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* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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