Sec Form 4 Filing - Cormorant Asset Management, LLC @ PROTEOSTASIS THERAPEUTICS, INC. - 2016-11-09

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, 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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1. Name and Address of Reporting Person Cormorant Asset Management, LLC 2. Issuer Name and Ticker or Trading Symbol PROTEOSTASIS THERAPEUTICS, INC. [ PTI] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 200 CLARENDON STREET, 52ND FLOOR, 3. Date of Earliest Transaction (MM/DD/YY) 11/09/2016 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 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 Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 11/09/2016 P 12,100 A $ 9.6794 ( 3 ) 2,770,682 I See Footnotes ( 1 ) ( 2 ) ( 3 ) Common Stock 11/10/2016 P 216,700 A $ 11.0687 ( 4 ) 2,987,382 I See Footnotes ( 1 ) ( 2 ) ( 4 ) Common Stock 11/11/2016 P 21,200 A $ 11.4611 ( 5 ) 3,008,582 I See Footnotes ( 1 ) ( 2 ) ( 5 ) Common Stock 11/14/2016 P 9,500 A $ 11.4754 ( 6 ) 3,018,082 I See Footnotes ( 1 ) ( 2 ) ( 6 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Cormorant Asset Management, LLC 200 CLARENDON STREET, 52ND FLOOR BOSTON, MA02116 X Chen Bihua C/O CORMORANT ASSET MANAGEMENT, LLC 200 CLARENDON STREET, 52ND FLOOR BOSTON, MA02116 X X Cormorant Global Healthcare GP, LLC 200 CLARENDON STREET, 52ND FLOOR BOSTON, MA02116 X Cormorant Global Healthcare Master Fund, LP 200 CLARENDON STREET, 52ND FLOOR BOSTON, MA02116 X Signatures /s/ CORMORANT GLOBAL HEALTHCARE GP, LLC By: Bihua Chen, Managing Member 11/14/2016 Signature of Reporting Person Date /s/ CORMORANT ASSET MANAGEMENT, LLC By: Bihua Chen, Managing Member 11/14/2016 Signature of Reporting Person Date /s/ CORMORANT GLOBAL HEALTHCARE MASTER FUND, LP By: Cormorant Global Healthcare GP, LLC, its General Partner By: Bihua Chen, Managing Member 11/14/2016 Signature of Reporting Person Date /s/ Bihua Chen 11/14/2016 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares reported herein are held by Cormorant Global Healthcare Master Fund, LP (the "Master Fund") and by a managed account (the "Account"). Cormorant Asset Management, LLC ("Cormorant") serves as the investment manager of the Master Fund and the Account. Cormorant Global Healthcare GP, LLC ("GP LLC") serves as General Partner of the Master Fund. Bihua Chen serves as manager of Cormorant and GP LLC. GP LLC may be deemed to beneficially own the shares held by the Master Fund, and Cormorant and Ms. Chen may be deemed to beneficially own the shares held by the Master Fund and the Account. ( 2 )Each of the Reporting Persons disclaims beneficial ownership of the shares reported herein except to the extent of its or her pecuniary interest therein, and the filing of this Form 4 shall not be construed as an admission that any of the Reporting Persons is the beneficial owner of any such shares for purposes of Section 16(a) of the Securities Exchange Act of 1934 or for any other purpose. ( 3 )Represents the weighted average purchase price of shares purchased in a series of open market transactions on the transaction date at prices ranging from $9.57 to $9.75 per share. The Reporting Persons undertake to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased at each price. Of these shares, 10,061 were purchased for the Master Fund and 2,039 shares were purchased for the Account. As of November 9, 2016, the Master Fund held 2,310,774 shares, and the Account held 459,908 shares. ( 4 )Represents the weighted average purchase price of shares purchased in a series of open market transactions on the transaction date at prices ranging from $10.59 to $11.50 per share. The Reporting Persons undertake to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased at each price. Of these shares, 180,187 were purchased for the Master Fund and 36,513 shares were purchased for the Account. As of November 10, 2016, the Master Fund held 2,490,961 shares, and the Account held 496,421 shares. ( 5 )Represents the weighted average purchase price of shares purchased in a series of open market transactions on the transaction date at prices ranging from $11.39 to $11.50 per share. The Reporting Persons undertake to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased at each price. Of these shares, 17,627 were purchased for the Master Fund and 3,573 shares were purchased for the Account. As of November 11, 2016, the Master Fund held 2,508,588 shares, and the Account held 499,994 shares. ( 6 )Represents the weighted average purchase price of shares purchased in a series of open market transactions on the transaction date at prices ranging from $11.44 to $11.50 per share. The Reporting Persons undertake to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased at each price. Of these shares, 7,899 were purchased for the Master Fund and 1,601 shares were purchased for the Account. As of November 14, 2016, the Master Fund held 2,516,487 shares, and the Account held 501,595 shares.

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