| 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 or Section 30(h) of the Investment Company Act of 1940 | 
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| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 | 2. Date of Event Requiring Statement
         (Month/Day/Year) 07/24/2013 | 3. Issuer Name and Ticker or Trading Symbol Conatus Pharmaceuticals Inc [ CNAT ] | |||||||||||||
| 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) 
 | 5. If Amendment, Date of Original Filed
         (Month/Day/Year) | ||||||||||||||
| 6. Individual or Joint/Group Filing (Check Applicable Line) 
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| 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) | 
| 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: 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 | ||||
| Series B Convertible Preferred Stock | (1) | (1) | Common Stock | 1,010,099 | (1) | I | See Footnote(2) | 
| Warrant to Purchase Series B Preferred Stock (Right to Buy) | 05/30/2013 | 05/30/2018 | Series B Preferred Stock | 265,837 | $0.9 | I | See Footnote(3) | 
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
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| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | ||||||||||||||||||||||||
| 1. Name and Address of Reporting Person* 
 
 
 (Street) 
 
 Relationship of Reporting Person(s) to Issuer 
 | 
| Explanation of Responses: | 
| 1. Each share of Series B Preferred Stock is convertible into 0.121212 of a share of Common Stock without payment of further consideration and will automatically convert into 0.121212 of a share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. The shares have no expiration date. | 
| 2. The shares (on an as-converted to Common Stock basis) are held as follows: 473,353 by MPM BioVentures IV-QP, L.P. ("BV IV QP"), 18,236 by MPM BioVentures IV GmbH & Co. Beteiligungs KG ("BV IV KG"), 13,460 by MPM Asset Management Investors BV4 LLC ("AM BV4"), 486,164 by MPM BioVentures V, L.P. ("BV V") and 18,886 by MPM Asset Management Investors BV5 LLC ("AM BV5"). MPM BioVentures IV GP LLC and MPM BioVentures IV LLC ("BV LLC") are the direct and indirect general partners of BV IV QP and BV IV KG and BV LLC is the manager of AM BV4. MPM BioVentures V GP LLC and MPM BioVentures V LLC ("BV V LLC") are the direct and indirect general partners of BV V and BV V LLC is the manager of AM BV5. Ansbert Gadicke, Luke Evnin, Vaughn M. Kailian,James Paul Scopa, Todd Foley and John Vander Vort are the members of BV LLC and BV V LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its respective pecuniary interest therein. | 
| 3. The warrants are held as follows: 124,577 by BV IV QP, 4,799 by BV IV KG, 3,542 by AM BV4, 127,948 by BV V and 4,971 by AM BV5. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its respective pecuniary interest therein. | 
| Remarks: | 
| See Form 3 for Luke Evnin for additional members of this joint filing. | 
| By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVentures IV GP LLC, the general partner of MPM BioVentures IV-QP, L.P. /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures IV LLC, the manager of MPM Asset Management Investors BV4 LLC /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures V LLC, the manager of MPM Asset Management Investors BV5 LLC /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVentures IV GP LLC, the managing limited partner of MPM BioVentures IV GmbH & Co. /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures IV LLC, the managing member of MPM BioVentures IV GP LLC /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures IV LLC /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures V LLC, the managing member of MPM BioVentures V GP LLC /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures V LLC, the managing member of MPM BioVentures V GP LLC, the General Partner of MPM BioVentures V, L.P. /s/ Luke Evnin | 07/24/2013 | |
| By Luke Evnin, member of MPM BioVentures V LLC /s/ Luke Evnin | 07/24/2013 | |
| ** Signature of Reporting Person | Date | |
| Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. | ||
| * 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). | ||
| Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure. | ||
| Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number. | ||