TRexBio prices $116.7M IPO for tissue-focused Treg drugs

TRexBio is developing medicines for autoimmune and inflammatory diseases that activate regulatory T cells already inside inflamed tissue. The clinical-stage biotech said it priced 8.33 million IPO shares at $14 each on October 8, for expected gross proceeds of $116.7 million. All the shares came from the company. Trading began on Nasdaq the next morning, while closing remains scheduled for October 13 subject to customary conditions.

Regulatory T cells, or Tregs, restrain excessive immune responses and help keep the immune system from attacking healthy tissue. Some experimental therapies require a patient’s cells to be collected, engineered and returned by infusion, a process that adds manufacturing and logistical demands. MedCity News reported that TRexBio instead designs fusion proteins to activate and expand Tregs already present in diseased tissue, without also stimulating inflammatory immune cells, according to the company.

TRexBio’s discovery platform analyzes healthy and diseased tissue samples to identify immune dysfunction and potential drug targets. Its most advanced wholly owned candidate, TRB-061, activates the TNFR2 receptor. The company reported that a Phase 1a study in healthy volunteers showed Treg activation and expansion in tissue, with no serious adverse events, though those findings don’t yet establish a benefit for patients.

The next study moves TRB-061 into people with moderate-to-severe atopic dermatitis, with preliminary Phase 1b data expected in mid-2027. TRexBio also identifies alopecia areata as a priority indication. A second owned candidate, TRB-071, targets CD30 to increase tissue Tregs and inhibit inflammatory signaling; the company plans to begin a Phase 1 study in the first half of 2027.

A separate program shows how TRexBio can pair its platform with a larger drugmaker. Eli Lilly paid $55 million upfront for a 2023 research collaboration that produced TRB-051, a candidate Lilly plans to advance into Phase 2a testing for lupus with skin involvement. According to MedCity’s account of the IPO filing, TRexBio could receive up to another $577.5 million in milestone payments under that alliance.

Before the IPO, TRexBio had raised approximately $220 million privately, including a $50 million financing early this year. It reported $90.9 million of cash at the end of the second quarter and estimates that its existing capital plus the offering proceeds will fund operations into the second half of 2029. That period includes the planned patient readout for TRB-061 and the initial clinical study of TRB-071.