SCHEDULE: RTW Investments Discloses 7.2% Stake in Castle Biosciences

RTW Investments, LP and Roderick Wong, M.D. have disclosed a 7.2% beneficial ownership stake in Castle Biosciences, Inc. as of December 31, 2025.

Summary

• RTW Investments, LP and Roderick Wong, M.D. reported beneficial ownership of 2,115,237 shares of Castle Biosciences, Inc. common stock.
• This ownership represents 7.2% of Castle Biosciences' outstanding common stock.
• The shares were acquired and are held in the ordinary course of business, not for the purpose of changing or influencing control of the issuer.
• The percentage is calculated based on 29,188,659 shares outstanding as of October 27, 2025, as reported in the company's Quarterly Report on Form 10-Q filed on November 3, 2025.

Sentiment

Score: 7

Explanation: StockSavvy.ai views this as a moderately positive signal, as a reputable investment firm has taken a significant stake, suggesting confidence in Castle Biosciences' long-term prospects without indicating an activist intent.

Positives

• A significant institutional investor, RTW Investments, LP, has taken a 7.2% stake in Castle Biosciences, indicating potential confidence in the company's prospects.
• The investment is stated to be in the ordinary course of business, suggesting a long-term investment strategy rather than an activist play.

Negatives

• This beneficial ownership filing does not contain any negative information regarding Castle Biosciences' operations or financial performance.

Risks

• No specific risks related to Castle Biosciences, Inc. were mentioned in this beneficial ownership filing.

Future Outlook

This filing does not contain any forward-looking statements or guidance from Castle Biosciences, Inc. or the reporting persons regarding the issuer's future performance.

Management Comments

• The undersigned acknowledge and agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements.
• The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him or it contained herein and therein, but shall not be responsible for the completeness and accuracy of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information is inaccurate.
• By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under §§ 240.14a-11.

Industry Context

StockSavvy.ai notes that a significant stake (over 5%) by an investment adviser like RTW Investments, LP, often specializing in healthcare and life sciences, can signal a vote of confidence in Castle Biosciences' diagnostic and prognostic solutions within the dermatology and oncology sectors. This type of disclosure is common for institutional investors building positions in companies they believe have strong growth potential or undervalued assets.

Comparison to Industry Standards

• Direct comparisons to specific comparable companies, projects, or results are not applicable based on the content of this beneficial ownership filing, as it does not provide operational or financial performance data for Castle Biosciences. The filing solely discloses an ownership stake.

Stakeholder Impact

• Shareholders may view the disclosure of a significant institutional stake by RTW Investments, LP as a positive indicator, potentially boosting investor confidence and market perception of Castle Biosciences.

Next Steps

• The reporting persons will be responsible for timely filing of subsequent amendments to this Schedule 13G.

Key Dates

Recommendation

While the disclosure of a significant institutional stake by RTW Investments is a positive signal, this filing alone does not provide sufficient operational or financial data to warrant a 'buy' or 'strong buy' recommendation. It primarily indicates an institutional investor's confidence. A 'hold' recommendation is appropriate, suggesting investors monitor future company performance and further disclosures from RTW Investments for more comprehensive insights.

Keywords

Castle Biosciences, RTW Investments, Roderick Wong, Beneficial Ownership, Schedule 13G, Institutional Investment, Common Stock, Biotechnology, Healthcare, Investment Adviser