US immunology biotech Zenas BioPharma files $100m IPO

Just a few months after raising $200 million in third-round financing, immunology specialist Zenas BioPharma has filed an initial public offering in the US seeking to add another $100 million to the pot.

The five-year-old Waltham, Massachusetts-based company is developing a bifunctional monoclonal antibody targeting CD19 and FcγRIIb, called obexelimab, which is in a phase 3 trial as a treatment for IgG4-related disease (IgG4-RD), phase 2/3 in warm autoimmune haemolytic anaemia (wAIHA), and phase 2 in multiple sclerosis (MS) and systemic lupus erythematosus (SLE).

Zenas acquired worldwide rights to obexelimab from its original developer Xencor in a $480 million deal agreed in 2021. The drug was a flagship project at Xencor until it failed a phase 2 trial in SLE in 2018, albeit with a trend towards efficacy that the company said warranted further investigation.

The company is now waiting for the results of the INDIGO trial in IgG4-RD in 2025, aiming to become the first FDA-approved treatment for the progressive, fibroinflammatory disease, which can cause damage to organs throughout the body and affect 1 to 5 out of every 100,000 people in the US and is more common in men.

It has some rivals in its push to the IgG4-RD market, notably Amgen which reported positive topline results from a phase 3 trial of its CD19-directed antibody Uplizna (inebilizumab), acquired as part of its $27.8 billion takeover of Horizon Therapeutics last year.

Last year, Zenas licensed certain rights to the drug in Asia to Bristol-Myers Squibb for $50 million upfront plus undisclosed milestones.

According to a prospectus on the IPO, Zenas ended the second quarter with around $184 million in cash and has earmarked most of the IPO proceeds for obexelimab's clinical trials programme, although its pipeline also includes several other clinical-stage programmes targeting a range of immunological pathways.

IPO tracker Renaissance Capital said the $100 million figure cited by Zenas in its prospectus is likely a placeholder and it is really hoping to raise "$150 million or more."

The company – which plans to list on the Nasdaq under the symbol ZBIO – raised $200 million in a Series C in May and $118 million in a Series B that closed in 2022.

The IPO comes amid a stuttering acceleration in the number of biotech companies seeking public listings after a two-year lull, with a pick-up in the first quarter of 2024 that lost some momentum in the second quarter.