Zenas BioPharma (NASDAQ: ZBIO) has announced significant progress with its investigational drug, obexelimab, during a presentation at the Guggenheim Emerging Outlook Biotech Summit 2026. Chief Executive Officer Lonnie Moulder focused on the promising results from the INDIGO Phase 3 study targeting IgG4-related disease (IgG4-RD) and outlined plans for regulatory filings anticipated in the coming months.
Positive Phase 3 Results and Durability Insights
Moulder highlighted the positive top-line results from the INDIGO Phase 3 study, which evaluated obexelimab in patients experiencing flare-ups of IgG4-RD. The trial employed a design previously accepted by regulators, involving patient enrollment during flares, treatment with steroids to achieve remission, and subsequent randomization off steroids. The primary analysis indicated that obexelimab achieved a 56% risk reduction in time to disease flare, with a hazard ratio of approximately 0.4.
He noted that about 75% of participants remained flare-free, and all key secondary endpoints were achieved with high statistical significance. Initial data from the open-label extension of the study revealed that of the 141 patients who entered this phase, nearly half were evaluable at six months, with a remarkable 92% remaining flare-free.
Moulder also addressed safety concerns, stating that serious adverse events were comparable to those seen in placebo groups. The study showed that infection-related issues, including upper respiratory and urinary tract infections, were “positioned really well,” which is crucial given that patients with IgG4-RD are often older and at higher risk for complications.
Market Research Insights and Future Plans
Zenas conducted a market research survey involving 80 participants, primarily rheumatologists and gastroenterologists. The survey revealed that 64% of clinicians indicated a likelihood to prescribe obexelimab based on its Phase 3 profile. Participants projected a 47% market share for obexelimab compared to existing therapies like Uplizna and rituximab.
In discussing treatment preferences, Moulder noted that approximately 40% of clinicians expressed a strong preference for weekly subcutaneous administration over an intravenous regimen administered every six months. This preference was echoed in a separate survey of 20 IgG4-RD patients, where 75% favored the subcutaneous option.
Moulder explained that the inhibitory approach of obexelimab is appealing due to safety considerations, especially for older patients with existing health conditions. He contrasted this with B-cell depletion therapies, which can lead to long-term side effects and complicate the management of comorbidities.
The company estimates there are around 20,000 diagnosed IgG4-RD patients in the U.S. and Europe, with a potential total of 30,000–40,000 in the U.S. alone. Moulder suggested that educational initiatives could further increase diagnosis rates, ultimately expanding the treatable population.
Financially, Moulder projected a market opportunity of $3 billion to $4 billion in the U.S. for obexelimab, anticipating that it could exceed $1 billion in annual sales for Zenas. The company plans to submit a Biologics License Application (BLA) in the U.S. during the second quarter of 2026, followed by a European filing in the latter half of the year.
Zenas BioPharma is also preparing for market entry with a focused commercialization strategy. Moulder mentioned that the initial launch would utilize prefilled syringes, with the introduction of an autoinjector expected within a year of approval. The U.S. commercial team could consist of around 70 personnel, while initial European efforts will target Germany, followed by Italy and France.
In addition to obexelimab, Zenas is engaged in various other clinical programs. Moulder noted that the company’s lupus study is expected to report results in the fourth quarter of this year, and they are advancing multiple candidates in the oncology and infectious disease spaces.
Founded in 2021 and headquartered in Cambridge, Massachusetts, Zenas BioPharma aims to streamline drug discovery through innovative approaches to treatment development, particularly for areas where current therapies are limited by efficacy or safety concerns.
