TRexBio and Retension Raise a Combined $161.7 Million in IPOs as Biotech Listings Reach 29 for the Year

What happened

Two biotech companies priced initial public offerings on Oct. 8 and were set to begin trading on Friday, Oct. 9. According to BioSpace, TRexBio raised $116.7 million and Retension Pharmaceuticals raised $45 million, for a combined $161.7 million. The listings bring the number of biotech IPOs in 2026 to 29.

Renaissance Capital lists TRexBio under the ticker TRXB and Retension under RTSN.

Offering details

TRexBio

• 8.3 million shares at $14, the low end of its $14 to $16 range.
• Gross proceeds of $116.7 million.
• Underwriters have a 30-day option to buy 1.25 million additional shares.
• Eli Lilly reported direct holdings of 5.4 million TRexBio shares.

Retension Pharmaceuticals

• 3.75 million shares at $12, the midpoint of its expected range.
• Gross proceeds of $45 million.
• Underwriters have a 30-day option to buy up to 562,500 additional shares.

Company details

TRexBio’s pipeline includes TRB-061, an early-stage fusion protein for atopic dermatitis with a topline Phase 1b readout expected in mid-2027, and TRB-071, a preclinical CD30 agonist, according to BioSpace.

Retension, a Virginia-based cardiovascular company, is developing RTN-001, a daily oral small-molecule PDE-5 blocker for hypertension. The drug is in Phase 2b, and the company plans to advance it to Phase 3.

The IPO queue

BioSpace reported that two more companies set terms the same week. City Therapeutics, an RNA interference company, expects to raise about $158.3 million at an assumed $18 per share, with planned allocations to CITY-FXI for thrombosis, CITY-RBP4 for Stargardt disease and geographic atrophy, CITY-TFR2 for anemia associated with myelofibrosis and platform work. Iambic Therapeutics set a $15 to $17 range for an expected $135 million IPO and plans to direct $75 million to IAM1363, an oral HER2 inhibitor in Phase 1/1b for HER2-altered solid tumors.

Why it matters for the sector

The pricing outcomes illustrate the selectivity in the 2026 IPO market. TRexBio’s pricing at the low end of its range suggests investors pushed back on valuation even as demand was sufficient to complete the deal. Retension’s smaller raise at the midpoint reflects the more modest size typical of companies with a single lead asset.

The steady pace of listings, now 29 for the year according to BioSpace, marks a significant improvement over the previous several years, when the biotech IPO window was largely closed. Large offerings earlier in the year by Parabilis, Kailera and ADARx drew attention, but the market has also supported smaller deals.

Lilly’s stake in TRexBio is another example of large pharma investing in emerging immunology companies ahead of or alongside public listings, a pattern that can lend credibility to an IPO.

Hypertension remains one of the most common chronic conditions, but new mechanisms have been limited for years. Retension’s PDE-5 approach will need to show meaningful blood pressure reductions in later trials to compete with inexpensive generic therapies.

The underwriters’ options to buy additional shares, if exercised, would add to the proceeds of both offerings. Exercise usually depends on how the stocks trade in the first weeks after listing.

The combination of a sizable immunology listing and a small cardiovascular IPO in the same week shows the range of companies currently accessing public markets, from venture-backed platforms with pharma shareholders to single-asset developers seeking capital for late-stage trials.

What to watch

• First-day and early trading performance for TRXB and RTSN.
• Pricing of the City Therapeutics and Iambic IPOs.
• TRexBio’s Phase 1b readout for TRB-061 in mid-2027.
• Retension’s plans for a Phase 3 hypertension trial.

This article is for information only and is not investment advice.

Sources: BioSpace, Renaissance Capital

Reading Where an IPO Prices Within Its Range

Before an IPO, a company and its underwriters publish an expected price range based on early conversations with investors. Where the final price lands relative to that range is one of the first signals the market sends about a new listing.

• Above the range. Demand significantly exceeded the shares available, allowing the company to raise more per share. Often accompanied by an increase in share count.
• At the midpoint. Demand met expectations. The company raised roughly what it planned.
• At the low end. Investors were willing to participate but pushed for a lower valuation, and the company chose to complete the deal rather than wait.
• Below the range. Demand fell short at the expected valuation, and the company accepted a meaningful discount to get the deal done.

None of these outcomes predicts long-term performance by itself. Companies that price at the low end can trade well later if clinical results are strong, and the reverse is also true.

The Science in Brief

Fusion proteins

A fusion protein is an engineered molecule that joins parts of two or more proteins into one. In immunology, a common design links a biologically active segment to the Fc region of an antibody, which can extend how long the molecule stays in the bloodstream. Fusion proteins allow developers to combine functions, such as targeting and signaling, that do not exist together naturally.

Agonists

An agonist activates a receptor, as opposed to an antagonist or blocker that prevents activation. In immunology, agonists are being explored as a way to strengthen the body’s own regulatory pathways, which act to calm excessive immune responses.

PDE-5 inhibition and blood pressure

Phosphodiesterase-5 is an enzyme that breaks down cGMP, a signaling molecule that helps relax the smooth muscle in blood vessel walls. Blocking PDE-5 allows cGMP to persist, which can widen blood vessels. Drugs in this class are already used for erectile dysfunction and pulmonary arterial hypertension. Applying the mechanism to everyday high blood pressure requires showing consistent, meaningful reductions with acceptable side effects over long-term daily use.

What Phase 2b and Phase 3 Mean

Phase 2 trials test whether a drug works in patients and help choose doses. A Phase 2b study is typically larger and more rigorous than an early Phase 2a study, often comparing several doses against placebo. Phase 3 trials enroll many more patients over longer periods to confirm effectiveness and safety, producing the evidence regulators require for approval. For a common condition such as hypertension, Phase 3 programs can be large because the drug must perform well against inexpensive established treatments.

Questions Readers Ask

Why would a pharma company hold IPO shares?

A large shareholding can reflect an earlier investment or partnership and gives the pharma company insight into a field of interest. It does not guarantee a future acquisition or deal.

What is Stargardt disease?

An inherited eye disease that damages the central retina, typically causing progressive loss of central vision beginning in childhood or young adulthood.

What is a ticker symbol?

The short code used to identify a company’s shares on an exchange, such as TRXB or RTSN.

This article is for general information only and is not medical or investment advice. Readers should consult their own physicians and financial professionals.