X0206 3 2016-02-10 0 0001445283 PROTEOSTASIS THERAPEUTICS, INC. PTI 0001661335 Lee Po Shun 200 TECHNOLOGY SQUARE, 4TH FLOOR CAMBRIDGE MA 02139 0 1 0 0 See Remarks Employee Stock Option (Right to Buy) 11.03 2025-06-29 Common Stock 24976 D Employee Stock Option (Right to Buy) 11.03 2025-06-29 Common Stock 27751 D These securities shall vest over a four-year period as follows: 25% on November 24, 2015 and 6.25% each quarter thereafter. These securities shall vest over a four-year period as follows: 25% on June 30, 2016 and 6.25% each quarter thereafter. Executive Vice President and Chief Medical Officer Exhibit List - Exhibit 24.1 - Power of Attorney /s/ Janet L. Smart, Attorney-in-Fact 2016-02-10