Form 4 Filing for Yu Jonathan Yen-Wen

Yu Jonathan Yen-Wen, Chief Operating Officer of Disc Medicine, Inc., executed a series of transactions on June 16, 2026, under a Rule 10b5-1 trading plan. These transactions involved both the acquisition and disposition of common stock, as well as the exercise of stock options. Specifically, Mr. Yen-Wen acquired a total of 18,612 shares of common stock at a price of $9.86 per share. Concurrently, he disposed of 18,612 shares of common stock in two tranches. The first tranche of 11,651 shares was sold at a weighted average price of $68.76, with prices ranging from $68.37 to $69.36. The second tranche of 6,961 shares was sold at a weighted average price of $69.92, with prices ranging from $69.40 to $70.19. Additionally, Mr. Yen-Wen exercised stock options to acquire 18,612 shares of common stock. Following these transactions, his post-transaction share ownership is reported. Footnote 1 indicates these transactions were made pursuant to a pre-arranged trading plan.