X0206 3 2016-02-10 0 0001445283 PROTEOSTASIS THERAPEUTICS, INC. PTI 0001297709 Novartis Bioventures Ltd 131 FRONT STREET HAMILTON D0 HM12 BERMUDA 0 0 1 0 0001114448 NOVARTIS AG LICHTSTRASSE 35 CH-4056 BASEL V8 SWITZERLAND 0 0 1 0 Series A Convertible Redeemable Preferred Stock Common Stock 1318932 D Series B Convertible Redeemable Preferred Stock Common Stock 179859 D The Series A Convertible Redeemable Preferred Stock (the "Series A Shares") are convertible on a 10.8102-to-1 basis into the Issuer's Common Stock at any time at the election of the Reporting Person and will automatically convert, together with the accrued but unpaid dividends, upon the closing of the Issuer's initial public offering into the number of shares of the Issuer's Common Stock shown in column 3. The Series A Shares do not have an expiration date. These securities are held directly by Novartis Bioventures Ltd. ("Novartis Bioventures"). Novartis Bioventures is a corporation organized under the laws of Bermuda and is an indirect wholly-owned subsidiary of Novartis AG. Novartis AG is a corporation organized under the laws of Switzerland and is the publicly owned parent of Novartis Bioventures Ltd. The Series B Convertible Redeemable Preferred Stock (the "Series B Shares") are convertible on a 10.8102-to-1 basis into the number of shares of the Issuer's Common Stock as shown in column 3 at any time at the election of the Reporting Person and will automatically convert upon the closing of the Issuer's initial public offering. The Series B Shares do not have an expiration date. /s/ Simon Zivi, Chairman 2016-02-10 /s/ Laurieann Chaikowsky, Authorized Signatory 2016-02-10