Upstream Bio, Inc. — Insider Transactions

Form 4 filings by directors, officers, and 10%+ shareholders

SEC rules require corporate insiders — including directors, executive officers, and any shareholder owning more than 10% of a company's shares — to report changes in their ownership within two business days of a transaction. These disclosures are filed as Form 4. Open-market purchases (code P) are generally considered the most meaningful signal, as insiders are spending their own money.