Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Clarus Lifesciences II, L.P.
 2. Date of Event Requiring Statement (Month/Day/Year)
08/13/2008		 3. Issuer Name and Ticker or Trading Symbol
ACHILLION PHARMACEUTICALS INC [ACHN]
(Last)
(First)
(Middle)
C/O CLARUS VENTURES, LLC, 101 MAIN STREET, SUITE 1210		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

CAMBRIDGE, MA 02142		 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 5,163,689 (1) (2)
D
 

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Common Stock Warrant (right to buy) 08/13/2008 08/13/2015 Common Stock 1,290,922 (1) (2) $ 3.53 D  
Unit Warrant 02/13/2009 08/13/2009 Common Stock (3) 2,216,313 $ (3) D  

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Clarus Lifesciences II, L.P.
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
Clarus Ventures II GP, L.P.
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
Clarus Ventures II, LLC
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
LIPTAK ROBERT
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
Simon Nicholas
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
HENNER DENNIS
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
GALAKATOS NICHOLAS
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
Leiden Jeffrey
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
WHEELER KURT
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    
STEINMETZ MICHAEL
C/O CLARUS VENTURES, LLC
101 MAIN STREET, SUITE 1210
CAMBRIDGE, MA 02142		     X    

Signatures

/s/ Robert Liptak, Manager of Clarus Ventures II, LLC, general partner of Clarus Ventures II GP, L.P., general partner of Clarus Lifesciences II, L.P. 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, Manager of Clarus Ventures II, LLC, general partner of Clarus Ventures II GP, L.P. 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, Manager of Clarus Ventures II, LLC 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, as attorney-in-fact for Nicholas Simon 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, as attorney-in-fact for Dennis Henner 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, as attorney-in-fact for Nicholas Galakatos 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, as attorney-in-fact for Jeffrey Leiden 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, as attorney-in-fact for Kurt Wheeler 08/20/2008
**Signature of Reporting Person Date
/s/ Robert Liptak, as attorney-in-fact for Michael Steinmetz 08/20/2008
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Securities held of record by Clarus Lifesciences II, L.P. ("Clarus"). Clarus Ventures II GP, L.P. (the "GPLP"), as the sole general partner of Clarus, may be deemed to beneficially own certain of the shares held of record by Clarus. The GPLP disclaims beneficial ownership of all shares held of record by Clarus in which the GPLP does not have an actual pecuniary interest. Clarus Ventures II, LLC (the "GPLLC"), as the sole general partner of the GPLP, may be deemed to beneficially own certain of the shares held of record by Clarus. The GPLLC disclaims beneficial ownership of all shares held of record by Clarus in which it does not have an actual pecuniary interest.
(2) Each of Messrs. Galakatos, Henner, Leiden, Liptak, Simon, Steinmetz and Wheeler, as individual Managing Directors of the GPLLC, may be deemed to beneficially own certain of the shares held of record by Clarus. Each of Messrs. Galakatos, Henner, Leiden, Liptak, Simon, Steinmetz and Wheeler disclaims beneficial ownership of all shares held of record by Clarus in which he does not have an actual pecuniary interest.
(3) The reported securities are included within a Unit Warrant purchased by Clarus for $95,124.13. Clarus has the right to purchase 1,773,050 Units. Each Unit consists of (i) one share of Common Stock, par value $0.001 per share of the Company and (ii) a warrant to purchase 0.25 shares of Common Stock. The exercise price of the Unit Warrant is $2.82 per Unit, and the exercise price of the warrant to purchase Common Stock underlying the Unit Warrant is $3.53 per share.

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