Upstream Bio Inc., a Waltham, Massachusetts-based biotech company, had a successful initial public offering (IPO), raising $255 million by selling 15 million shares at $17 each, surpassing its initial plan of 12.5 million shares. The company's shares surged 26% to $21.50 in early trading on the Nasdaq, valuing the firm at approximately $1.05 billion. Upstream Bio focuses on developing treatments for severe respiratory disorders, with its lead experimental drug, verekitug, in mid-stage studies for treating severe asthma and chronic rhinosinusitis with nasal polyps. The IPO was underwritten by J.P. Morgan, TD Cowen, Piper Sandler, and William Blair. This IPO is part of a broader trend of strong investor interest in the biotech sector, following a busy month for healthcare IPOs.