SCHEDULE: BlackRock Discloses 5.5% Stake in Tourmaline Bio

BlackRock, Inc. has reported a 5.5% beneficial ownership stake in Tourmaline Bio, Inc., holding 1,411,832 shares of common stock as of September 30, 2025.

Summary

• BlackRock, Inc. reported beneficial ownership of 1,411,832 shares of Tourmaline Bio, Inc. common stock.
• This represents 5.5% of the total class of securities.
• The event requiring this filing occurred on September 30, 2025.
• The Schedule 13G Amendment No. 1 was filed on October 17, 2025.
• BlackRock holds sole voting power over 1,364,933 shares and sole dispositive power over 1,411,832 shares.
• No shared voting or dispositive power was reported.
• The securities were acquired and are held in the ordinary course of business, not for the purpose of changing or influencing control of Tourmaline Bio, Inc.
• Several BlackRock subsidiaries, including BlackRock Advisors, LLC, BlackRock Asset Management Canada Limited, and BlackRock Fund Advisors, are identified as potentially holding 5% or greater beneficial ownership.

Sentiment

Score: 5

Explanation: The filing is a factual disclosure of beneficial ownership and does not contain information that would inherently indicate positive or negative sentiment regarding the issuer's performance or prospects.

Positives

• BlackRock, a major institutional investor, has taken a significant 5.5% stake in Tourmaline Bio, Inc., which can be viewed as a vote of confidence in the company.
• The acquisition of shares was made in the ordinary course of business, indicating a standard investment rather than an activist position.

Future Outlook

This filing is a disclosure of beneficial ownership and does not contain any forward-looking statements or guidance regarding Tourmaline Bio, Inc.'s future performance or strategic direction.

Management Comments

• 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.
• After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Industry Context

BlackRock, Inc. is one of the world's largest asset managers, and its disclosure of a significant stake in Tourmaline Bio, Inc. reflects its ongoing strategy of investing in publicly traded companies across various sectors. Such filings are standard for institutional investors crossing ownership thresholds and provide transparency into major holdings.

Stakeholder Impact

• Shareholders: The disclosure of a significant stake by a major institutional investor like BlackRock could be perceived positively, potentially boosting investor confidence and market liquidity for Tourmaline Bio, Inc.

Key Dates

Keywords

BlackRock, Tourmaline Bio, Common Stock, Beneficial Ownership, Institutional Investor, Schedule 13G, Equity Stake, Investment Management