Immunology research continues to draw investment for new ways to suppress excessive immune responses. TRexBio takes a different approach, tapping into the body’s built-in way of keeping the immune system in balance. A TRex-discovered molecule is progressing in the clinic in the hands of partner Eli Lilly. Now the biotech has $116.7 million in IPO cash to support clinical development of its wholly owned assets.
Late Thursday, TRex priced 8.33 million shares at $14 each, which was the low end of the preliminary price range it had set earlier in the week. Those shares began trading on the Nasdaq Friday under the stock symbol “TRXB.”
The research of South San Francisco-based TRex focuses on regulatory T cells, or Tregs. While the activity of immune cells leads to inflammation, the body counterbalances that with Tregs, which tamp down excessive immune responses and stop the immune system from attacking healthy tissue.
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There are some biotech companies developing Treg cell therapies made by harvesting and engineering a patient’s own Tregs or working with Tregs sourced from healthy donors. While there’s evidence that these approaches can work, the commercialization of T cell therapies for cancer shows the logistical hurdles of engineering cells into living medicines. There’s one FDA-approved Treg so far, a blood cancer treatment developed by Orca Bio. It’s made by shipping a sample of patient blood to an Orca facility that isolates Tregs. Those cells are then shipped back for infusion into the patient. The complexity, cost, and time for manufacturing Treg cell therapies likely limits its use in large autoimmune disease populations, TRex said in its IPO filing.
Rather than working with directly with Tregs, TRex aims to leverage Tregs already in the patient’s body. Its drugs are fusion proteins designed to activate and expand Tregs that are in inflamed tissue as a way of restoring immune balance. The company says its drugs can do so selectively, without also activating proinflammatory immune cells. These drugs come from a TRex platform technology that gleans immunology insights by analyzing a database of healthy and diseased tissue samples.
“Our approach is designed to address disease at its source — in the tissue — by developing medicines focused on tissue immune homeostasis that we believe have the potential to provide a durable clinical benefit,” TRex said in the filing.
TRex formed in 2018. In 2021, Lilly participated in the biotech’s Series A financing. Two years later, the pharma company paid $55 million up front to begin a research collaboration. The alliance produced TRB-051, which is designed to modulate immune effector cells. In June, TRex said Lilly plans to advance TRB-051 to Phase 2a testing in lupus with cutaneous involvement.
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TRex’s most advanced wholly owned program is TRB-061, which is designed to activate tumor necrosis factor receptor 2 (TNFR2), expanding and activating Tregs in inflamed tissues. In August, TRex reported Phase 1a results showing activation and expansion of Tregs in the tissue of healthy volunteers. The study drug was also well tolerated and no serious adverse events were reported. The results supported dose selection for a Phase 1b test in patients with moderate-to-severe atopic dermatitis; preliminary data are expected in mid-2027. TRex also describes alopecia areata as a “priority indication,” pointing to published studies supporting the role of Tregs in mediating the hair follicle cycle and hair regrowth.
A second TRex drug candidate, TRB-071, is designed to activate the protein CD30 to augment tissue Tregs and block immune system inflammatory signaling. In the filing, TRex points to genetic studies supporting the involvement of CD30 and its ligand in inflammatory bowel disease. The company plans to start a Phase 1 test in the first half of next year.
In its history as a private company, TRex said it had raised about $220 million. Lilly paid TRex a $15 million milestone payment in 2024 and the biotech is eligible to receive up to $577.5 million more in additional milestone payments, according to the filing. TRex last raised money early this year, a $50 million financing.
A 2021 collaboration agreement with a Johnson & Johnson affiliate was terminated last year, according to the filing. But the document also shows Johnson & Johnson Innovation—JJDC owns a 4.6% post-IPO stake. Lilly is TRex’s largest shareholder with a 16.8% stake after the IPO, followed by the 14.1% owned by SV Health Investors. TRex said Lilly has expressed an interest in purchasing additional shares at the IPO price in an amount not to exceed 19.9% of the company, but there is no binding commitment for the stock purchase.
As of the end of the second quarter of this year, TRex reported its cash position was $90.9 million. Combined with the IPO proceeds, TRex plans to spend about $90 million to bring TRB-016 through the readout of topline Phase 2 data in atopic dermatitis and alopecia areata and $10 million for the start and completion of TRB-071’s Phase 1 test in healthy volunteers. The company estimates its capital will last into the second half of 2029.
Retension Pharma Reels In $45M for Next-Gen Hypertension Drug
Retension Pharmaceuticals joined the public markets with an IPO that raised $45 million for a drug in clinical development for uncontrolled hypertension.
Retension’s RTN-001 is a small molecule inhibitor of an enzyme called PDE-5. In its IPO filing, the company notes that first-generation PDE-5 inhibitors, such as the sexual dysfunction drug Viagra, were initially studied in cardiovascular indications such as hypertension and angina. Retension contends these drugs did not offer adequate bioavailability and tissue penetration to address cardiac tissue, leading to their failure as blood pressure medications.
Falls Church, Virginia-based Retension describes RTN-001 as a next-generation PDE-5 inhibitor engineered for better bioavailability and increased distribution to places such as the aorta and its branches. In two Phase 2 pilot trials, the company said the once-daily pill led to clinically meaningful placebo-adjusted reductions in blood pressure.
“We believe RTN-001 has the potential to be an effective treatment for hypertension with a favorable safety profile and thus be part of an anti-hypertensive treatment approach,” Retension said in its IPO filing.
The molecule that is now RTN-001 was originally developed by a company called Surface Logix. It has changed hands several times; in 2023, Retension licensed all rights to the molecule from Redux Therapeutics. As of the end of June, Retension reported its cash position was about $13.5 million. That capital along with the IPO proceeds will go toward clinical development of RTN-001, Retension’s only drug candidate.
The company plans to spend about $18 million to complete an ongoing Phase 2b test of RTN-001 in uncontrolled hypertension. Preliminary data are expected in the first half of 2027. Another $10 million is budgeted for preparing for a planned Phase 3 test in this indication.
Retension offered 3.75 million shares priced at $12 each, which was the midpoint of the price range the biotech set in preliminary financial terms earlier in the week. Those shares began trading on the Nasdaq Friday under the stock symbol “RTSN.”
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