RTW Investments, LP Increases Stake in Castle Biosciences, Inc. to 9.3%

On May 15, 2026, RTW Investments, LP, along with Managing Partner Roderick Wong, M.D., filed a Schedule 13G/A regarding their holdings in Castle Biosciences, Inc. (CSTL). The filing reports that as of the event date on March 31, 2026, the reporting persons beneficially own 2,758,335 shares of common stock, representing a 9.3% ownership stake in the company. This represents an increase from a previously reported 0% position, based on the 29,731,198 shares outstanding as of February 19, 2026. RTW Investments serves as the investment adviser to various funds that directly hold the shares, while Dr. Wong exercises shared voting and dispositive power over the securities. The filing indicates that the shares were acquired in the ordinary course of business and not for the purpose of influencing or changing control of the issuer. The reporting persons maintain their principal business office in New York.