X0306 4 2019-07-29 0 0001447362 CASTLE BIOSCIENCES INC CSTL 0001783205 Cook Joseph C. III C/O CASTLE BIOSCIENCES, INC. 820 S. FRIENDSWOOD DRIVE, SUITE 201 FRIENDSWOOD TX 77546 1 0 1 0 Common Stock 2019-07-29 4 C 0 1336927 A 1336927 I See footnotes Common Stock 2019-07-29 4 C 0 97428 12.80 A 1434355 I See footnotes Common Stock 2019-07-29 4 P 0 312500 16.00 A 1746855 I See footnotes Common Stock 2019-07-29 4 C 0 169086 A 169086 D Common Stock 2019-07-29 4 C 0 16722 12.80 A 185808 D Common Stock 2019-07-29 4 P 0 22245 16.00 A 208053 D Series A Preferred Stock 2019-07-29 4 C 0 19524 D Common Stock 16015 0 I See footnotes Series B Preferred Stock 2019-07-29 4 C 0 122158 D Common Stock 100210 0 D Series D Preferred Stock 2019-07-29 4 C 0 15918 D Common Stock 13058 0 D Series D Preferred Stock 2019-07-29 4 C 0 337754 D Common Stock 277074 0 I See footnotes Series E-1 Preferred Stock 2019-07-29 4 C 0 463453 D Common Stock 380190 0 I See footnotes Series E-2 Preferred Stock 2019-07-29 4 C 0 5461 D Common Stock 4479 0 D Series E-2 Preferred Stock 2019-07-29 4 C 0 158379 D Common Stock 129925 0 I See footnotes Series E-3 Preferred Stock 2019-07-29 4 C 0 4681 D Common Stock 3840 0 D Series E-3 Preferred Stock 2019-07-29 4 C 0 142843 D Common Stock 117180 0 I See footnotes. Series F Preferred Stock 2019-07-29 4 C 0 57899 D Common Stock 47495 0 D Series F Preferred Stock 2019-07-29 4 C 0 507762 D Common Stock 416537 0 I See footnotes Convertible Promissory Note 12.80 2019-07-29 4 C 0 205970.51 D Common Stock 16722 0 D Convertible Promissory Note 12.80 2019-07-29 4 C 0 1200000.00 D Common Stock 97428 0 I See footnotes The shares of Common Stock issued upon conversion of the Preferred Stock were calculated by first aggregating all series of Preferred Stock held by the Reporting Person, in accordance with the terms of the Company's then-effective Certificate of Incorporation. Every 1.219 outstanding shares of Preferred Stock automatically converted into 1 share of Common Stock immediately prior to the closing of the Issuer's initial public offering (the "IPO"), for no additional consideration, with cash paid for any fractional shares. The Preferred Stock had no expiration date. Held by MGC Venture Partners 2013, L.P. ("MGC 2013 LP"). MGC Venture Partners 2013 GP, LLC ("MGC 2013 GP") is the general partner of MGC 2013 LP. The Reporting Person is a managing director of MGC 2013 GP and a managing partner of MGC Venture Partners 2018 GP, LLC ("MGC 2018 GP"), and shares voting and investment power over the shares held by MGC 2013 LP, MGC Venture Partners 2018, L.P. ("MGC 2018 LP") and MGC Venture Partners QP 2018, L.P. ("MGC QP 2018 LP"). The Reporting Person disclaims beneficial ownership of the shares held by MGC 2013 GP, MGC 2018 GP, MGC 2013 LP, MGC 2018 LP and MGC QP 2018 LP as reported herein, except to the extent of his pecuniary interest therein, and this report shall not be deemed an admission that the Reporting Person is the beneficial owners of such securities for purposes of Section 16 or for any other purposes. The principal amount of the Convertible Promissory Note held by the designated Reporting Person was $1,200,000.00. Upon closing of the IPO, all unpaid principal and accrued interest outstanding on the Convertible Promissory Note (the "Conversion Amount") automatically converted into the number of shares of Common Stock equal to the Conversion Amount as of the date immediately prior to the closing date divided by 80% of the IPO price per share of $16.00 per share. Represents a purchase from the underwriters in the Issuer's IPO. Held by MGC 2013 LP, MGC 2018 LP and MGC QP 2018 LP. MGC 2018 GP is the general partner of MGC 2018 LP and MGC QP 2018 LP. The principal amount of the Convertible Promissory Note held by the designated Reporting Person was $205,970.51. Upon closing of the IPO, the Conversion Amount automatically converted into the number of shares of Common Stock equal to the Conversion Amount as of the date immediately prior to the closing date divided by 80% of the IPO price per share of $16.00 per share. /s/ Greg Acosta, Attorney-in-fact 2019-07-31