13G Filing: Cormorant Global Healthcare Master Fund and Proteostasis Therapeutics, Inc. (PTI)

1

Names of Reporting Persons.

I.R.S. Identification Nos. of above persons (entities only)

Cormorant Global Healthcare GP, LLC

2

Check the Appropriate Box if a Member of a Group (See Instructions)

3

SEC Use Only

4

Citizenship or Place of Organization.

Delaware

Number

of Shares

Beneficially

Owned by

Each

Reporting

Person With

0 shares

1,450,825 shares (1,466,734 shares as of February 26, 2016)

Refer to Item 4 below.

0 shares

1,450,825 shares (1,466,734 shares as of February 26, 2016)

Refer to Item 4 below.

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,450,825 shares (1,466,734 shares as of February 26, 2016)

Refer to Item 4 below.

10

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)     [ ] N/A

11

Percent of Class Represented by Amount in Row (9)*

7.6% (7.7% as of February 26, 2016)

Refer to Item 4 below.

12

Type of Reporting Person (See Instructions)

OO (Limited Liability Company)