X0306 4 2019-08-29 0 0001711279 Krystal Biotech, Inc. KRYS 0001198325 JANNEY DANIEL 2100 WHARTON STREET SUITE 701 PITTSBURGH PA 15203 1 0 0 0 Common Stock 2019-08-29 4 S 0 55794 46.61 D 399252 I See footnotes Common Stock 2019-08-29 4 S 0 700 47.50 D 398552 I See footnotes Common Stock 2019-08-30 4 S 0 32190 46.18 D 366362 I See footnotes This transaction was executed in multiple trades ranging from $46.43 to $47.42. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price within the range set forth herein. Directly beneficially owned by Alta Bioequities, L.P. Alta Bioequities Management, LLC is the general partner of Alta Bioequities, L.P. and may be deemed to have sole voting and investment power over the shares beneficially owned by Alta Bioequities, L.P. The reporting person is the Managing Director of Alta Bioequities Management, LLC. The reporting person disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein. This transaction was executed in multiple trades ranging from $47.43 to $47.69. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price within the range set forth herein. This transaction was executed in multiple trades ranging from $46.03 to $46.60. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price within the range set forth herein. /s/ Daniel S. Janney 2019-09-03