Castle Biosciences, Inc. announced today the pricing of its initial public offering of 4,000,000 shares of its common stock at a price to the public of $16.00 per share. The gross proceeds to Castle Biosciences from the offering, before deducting the underwriting discounts and commissions and offering expenses, are expected to be $64.0 million. The shares are expected to begin trading on The Nasdaq Global Market on July 25, 2019 under the symbol "CSTL." All of the common stock in the offering is being offered by Castle Biosciences. The offering is expected to close on July 29, 2019, subject to customary closing conditions. In addition, Castle Biosciences has granted the underwriters a 30-day option to purchase up to an additional 600,000 shares of common stock.

SVB Leerink and Baird are acting as joint book-running managers for the offering and as representatives of the underwriters. Canaccord Genuity and BTIG are acting as co-managers for the offering.

Registration statements relating to these securities have been filed with the Securities and Exchange Commission and became effective on July 24, 2019. The offering is being made only by means of a prospectus. Copies of the final prospectus related to the offering, when available, may be obtained from: SVB Leerink LLC, Attention: Syndicate Department, One Federal Street, 37th Floor, Boston, MA 02110, by telephone: (800) 808‐7525, ext. 6132, or by e‐mail: syndicate@svbleerink.com; or Robert W. Baird & Co. Incorporated, Attention: Syndicate Department, 777 East Wisconsin Ave., Milwaukee, WI 53202, by telephone: (800) 792-2473, or by email: syndicate@rwbaird.com.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Castle Biosciences

Castle Biosciences is a commercial-stage dermatological cancer company focused on providing physicians and their patients with personalized, clinically actionable genomic information to make more accurate treatment decisions.