Analysis
TRexBio, a South San Francisco biotech focused on tissue regulatory T cell (Treg) biology, closed its initial public offering on Oct. 13, selling 8,333,334 shares at $14.00 each for gross proceeds of about $116.7 million, according to a release carried by FinancialContent. The stock, which trades on the Nasdaq Global Select Market under TRXB, began trading Oct. 9 after pricing at the bottom of its marketed range. J.P. Morgan, Evercore ISI, Cantor and Stifel served as joint bookrunners, and underwriters hold a 30-day option to buy up to 1.25 million additional shares, which could add roughly $17.5 million if fully exercised.
Why Eli Lilly is the real story here
Eli Lilly is TRexBio's largest shareholder and has indicated interest in increasing its stake to 19.9% of outstanding stock following the IPO. The relationship runs deeper than an investment: Lilly previously exercised an option on three of TRexBio's immune-mediated disease candidates -- TRB-031, TRB-041 and TRB-051 -- paying $55 million upfront with up to $1.1 billion in potential milestones for an exclusive license. TRexBio's current lead candidate, TRB-061, a TNFR2 agonist, is entering early clinical proof-of-concept testing under the company's own control.
“TRexBio's current lead candidate, TRB-061, a TNFR2 agonist, is entering early clinical proof-of-concept testing under the company's own control.”
Before this IPO, TRexBio had raised a $59 million Series A, closed in 2021 with Lilly, SV Health, Johnson & Johnson Innovation, Pfizer Ventures and Alexandria Venture Investments as investors, and an $84 million Series B in 2024 led by Delos Capital with the same group plus Polaris Partners. That puts disclosed private funding near $143 million before the public offering.
A measured debut in a selective IPO window
Pulse has tracked a broader pattern this month: just days after Nvidia-backed Firmus withdrew a roughly $31 billion-valuation IPO citing market turbulence, TRexBio and fellow biotech Retension Pharmaceuticals priced their own, far smaller IPOs anyway, together raising about $161.7 million. TRexBio's Treg-biology approach puts it alongside Sonoma Biotherapeutics and Abata Therapeutics as newer entrants racing to turn regulatory T cell science into approved medicines -- none of which has yet delivered a pivotal trial readout. Pricing at the low end of the range suggests investors wanted exposure to the Lilly relationship without paying up for it; whether Lilly actually moves toward that 19.9% stake is the clearer signal to watch than the stock's first-day pop.
