PERRIGO Co plc — Director's Dealing 2016

Feb 18, 2016

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: PROTEOSTASIS THERAPEUTICS, INC. (PTI)
CIK: 0001445283
Period of Report: 2016-02-10

Reporting Person: PERRIGO Co plc (10% Owner)
Reporting Person: PERRIGO HOLDINGS LTD. (10% Owner)
Reporting Person: ELAN PHARMA INTERNATIONAL LTD. (10% Owner)
Reporting Person: PERRIGO CORP LTD. (10% Owner)
Reporting Person: PERRIGO SCIENCE ONE LTD. (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2016-02-17	Common Stock	C	2416612	—	Acquired	2416612	Indirect
2016-02-17	Common Stock	C	366455	—	Acquired	2783067	Indirect
2016-02-17	Common Strock	P	125000	$8.00	Acquired	2908067	Indirect

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2016-02-17	Series A Convertible Redeemable Preferred Stock	$	C	20000000	Disposed		Common Stock (2416612)	Indirect
2016-02-17	Series B Convertible Redeemable Preferred Stock	$	C	3961459	Disposed		Common Stock (366455)	Indirect
2016-02-10	Stock Option (Right to Buy)	$8	A	45760	Acquired	2016-02-10	Common Stock (45760)	Indirect

Footnotes

F1: The Series A Convertible Redeemable Preferred Stock (the "Series A Shares") automatically converted on a 10.8102-to-1 basis into the Issuer's Common Stock, together with the accrued but unpaid dividends, upon closing of the Issuer's initial public offering into 2,416,612 shares of the Issuer's Common Stock. The Series A Shares did not have an expiration date.

F2: The Series B Convertible Redeemable Preferred Stock (the "Series B Shares") automatically converted on a 10.8102-to-1 basis into the Issuer's Common Stock upon closing of the Issuer's initial public offering into 366,455 shares of the Issuer's Common Stock. The Series B Shares did not have an expiration date.

F3: Perrigo Science One Ltd. ("Science") (formerly Elan Science One Ltd.) is the direct owner of these securities. Science is a direct or indirect, wholly-owned subsidiary of each of the other reporting persons.

F4: These securities were purchased in connection with the initial public offering of the Issuer.

F5: These securities shall vest and become exercisable in equal quarterly installments starting on February 10, 2016 until the option is fully vested and exercisable on February 10, 2019, subject to continued service.

F6: Perrigo Company plc ("Perrigo") and the other reporting persons named herein may be deemed to beneficially own the 45,760 options granted to Mr. Walshe in his capacity as a director of Proteostasis Therapeutics, Inc. (the "Company"). Mr. Walshe has an understanding with Perrigo pursuant to which he holds such securities for the benefit of Perrigo.