Here are the 424B prospectus supplements from Upstream Bio, Inc. (UPB) in our archive over the last 12 months, newest first, and each one links through to the document itself with the summary and the scores our analysis gives it.
A 424B covers the supplement that carries the terms of a priced offering, so if you follow UPB and want that one kind of document rather than the whole filing history, this is the page to keep. The company's other filings, of every form, are on the full UPB filings page.
Upstream Bio, Inc. has entered into a sales agreement with Leerink Partners LLC to offer and sell, from time to time, shares of its common stock in an at-the-market offering of up to $150,000,000. The sales agent may sell shares on Nasdaq consistent with market conditions and will receive compensation up to 3.0% of gross proceeds. An illustrative offering at the March 24, 2026 last reported sale price of $8.45 per share would equal $150.0 million or approximately 17,751,479 shares; shares outstanding were 54,237,750 as of December 31, 2025. The prospectus supplement highlights that proceeds treatment, timing and quantities will vary with market conditions, and that the sales agent will be deemed an underwriter for purposes of the Securities Act.