TRexBio IPO: $116.7M Nasdaq Debut, and Why Eli Lilly Wants a Bigger Stake

TRexBio raised $116.7 million in its initial public offering, pricing 8.33 million shares at $14.00 each on October 8, 2026 — the low end of its marketed range — with the stock trading on the Nasdaq Global Select Market under the ticker TRXB since October 9.

TRexBio is a South San Francisco biotech working on tissue regulatory T cell (Treg) biology, and its IPO closed October 13, 2026, according to a release carried by FinancialContent, corroborated by IPO Scoop and RTTNews. The bigger story sitting underneath the pricing is TRexBio's relationship with Eli Lilly, already its largest shareholder, which has signaled interest in growing that position to 19.9% of outstanding stock.

TRexBio IPO at a Glance

How we counted: figures from TRexBio's IPO pricing and closing announcements, per FinancialContent, IPO Scoop, and RTTNews; October 2026; as of October 14, 2026.

Why Is Eli Lilly the Real Story Behind TRexBio's IPO?

Eli Lilly is TRexBio's largest shareholder, and its prospectus disclosed interest in increasing that stake to 19.9% of outstanding stock following the IPO. The relationship runs deeper than a cap-table line: 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 for atopic dermatitis under the company's own control, with topline Phase 1b data expected in mid-2027.

That structure means TRexBio enters public markets with two distinct value streams: potential milestone income tied to candidates Lilly now controls, and whatever TRB-061 and the rest of its Treg-biology pipeline are worth on their own. A pharma partner moving to nearly a fifth ownership is a stronger vote of confidence than most biotech IPOs carry at debut, since it signals Lilly's own scientists see enough in TRexBio's platform to want more exposure rather than simply licensing out the candidates it already optioned and walking away.

How Does TRexBio's $116.7M Raise Compare to Other 2026 Biotech IPOs?

TRexBio's raise sits in the smaller half of a busy 2026 biotech IPO class. ADARx Pharmaceuticals raised $446 million at a $1.81 billion valuation with AbbVie taking a stake, Iambic Therapeutics raised $150 million at a roughly $758 million valuation, and City Therapeutics raised $175 million — all larger than TRexBio's $116.7 million. Retension Pharmaceuticals priced the smallest of the group, at about $45 million, the same week as TRexBio.

How we counted: IPO sizes as priced, per Value Add VC's own coverage of each listing; 2026; as of October 14, 2026.

How Much Had TRexBio Raised Before Going Public?

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; an $84 million Series B in 2024 led by Delos Capital with the same group plus Polaris Partners; and a $50 million financing round in early 2026 at the same per-share price as the IPO. That puts disclosed private funding at roughly $193 million before the public offering, on top of the $116.7 million raised at IPO.

How Does TRexBio's Debut Fit Into This Month's IPO Window?

TRexBio's pricing came the same week as fellow biotech Retension Pharmaceuticals, which raised about $45 million in its own IPO — together, the two offerings raised roughly $161.7 million. That pairing came just days after Nvidia-backed Firmus withdrew a roughly $31 billion-valuation listing citing market turbulence, a sign that smaller, more conservatively priced biotech offerings found room to proceed even as a much larger tech IPO pulled back. 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, though none of the three has yet delivered a pivotal trial readout.

What the headline misses

Pricing at the bottom of the marketed range is a sign of measured rather than enthusiastic demand, not a triumphant debut — the same signal showed up in Retension Pharmaceuticals' IPO the same week. TRexBio also has no approved products and only one candidate, TRB-061, in its own early-stage pipeline; the rest of its near-term value proposition rests on milestone payments from Lilly's licensed candidates rather than on products TRexBio itself will bring to market. Whether Lilly actually exercises toward a 19.9% stake in the next two quarters is a more meaningful signal of confidence than the stock's first-day trading.