Sobi (Nasdaq Stockholm: SOBI) will present four posters on its antibody Gamifant (emapalumab) at the Histiocyte Society’s 2026 annual meeting in Rotterdam, which runs September 26 to 29. The company announced the lineup in a September 24 press release. What it did not announce was a single result.

That gap matters for investors. Gamifant is one of the drugs Sobi counts on for growth, and the headline poster, a pooled look at survival before and after stem cell transplant, is the analysis Sobi itself flags as new. For now, it is a title and a time slot.

What Sobi Is Presenting

All four posters go up on September 29, from 3:45 to 5:00 p.m. local time.

The new one pools pre- and post-transplant survival across three prospective trials: NI-0501-04, the pivotal study behind Gamifant’s 2018 U.S. approval; NI-0501-05, its long-term follow-up; and NI-0501-09. Sobi says the abstract ranked among the meeting’s ten highest-scoring posters and was nominated for the Robert J. Arceci Prize for Best Poster. The prize itself has not been awarded.

Two others are encore presentations, meaning data already shown at an earlier meeting. The fourth covers a post-authorization study, Sobi.EMAPALUMAB-104, in Chinese patients who had already been treated for the disease.

A Quick Primer on Primary HLH

Primary hemophagocytic lymphohistiocytosis (HLH) is an ultra-rare, inherited immune disorder that usually strikes in infancy. The immune system switches on and fails to switch off. A signaling protein called interferon gamma floods the body, and the resulting inflammation can shut down organs.

A stem cell transplant is the only potentially curative option. Getting there is the hard part. Patients need their inflammation under control first, and that bridge is where Gamifant comes in. It is a monoclonal antibody, a lab-made protein that binds interferon gamma and neutralizes it, given as a one-hour IV infusion.

A Preview From Last Year’s Data

The two encore titles closely match abstracts published in the journal Blood for the American Society of Hematology’s (ASH) 2025 meeting. Those abstracts give a reasonable preview of what Rotterdam attendees will see.

The first pooled 80 children from the same three trials. Median age was under one year. By week 8 or end of treatment, 84% of evaluable patients (57 of 68) had responded, based on the treating investigator’s overall judgment. The first response came at a median of 16 days.

Some 81% (57 of 70) reached what the authors call bridging-success survival. Of those, 51 went on to transplant and six were alive at least three months after treatment without one. By end of treatment, 79% had cut their steroid dose by at least half.

Those numbers need context. The analysis was post hoc, meaning it was designed after the trials ended. There was no comparison arm. It used a looser response definition than the trials’ own protocols, which the authors argued better reflects real-world practice. Safety was not re-analyzed. Five of the seven authors are Sobi employees or consultants.

The second abstract split the same pool by prior treatment and by central nervous system involvement, which affected 31% of patients. Its authors concluded that benefit held across subgroups, though complete responses arrived more slowly when the disease had reached the brain or spinal cord.

For reference, the pivotal NI-0501-04 trial, published in the New England Journal of Medicine in 2020, reported a 63% response rate in previously treated patients under strict protocol criteria. Its authors cited physician-assessed two-month response rates of 59% and 51% from the Histiocyte Society’s earlier HLH-94 and HLH-2004 studies in newly diagnosed patients. Those are different populations, eras and definitions. It is a cross-trial comparison, not a head-to-head result.

What the Release Leaves Out

No survival figures for the new pooled analysis. No patient counts. Nothing on transplant outcomes or safety from the Chinese study. The release also omits Gamifant’s regulatory history outside the U.S., and never mentions that Sobi shares trade in the U.S. over the counter under BIOVF. Investors will have to wait until September 29 for the posters themselves.

Where Gamifant Stands

Gamifant holds two U.S. approvals. The first, in 2018, covers primary HLH that is refractory, recurrent or progressive, or where patients cannot tolerate conventional therapy. The second, in June 2025, covers HLH/macrophage activation syndrome (MAS) in known or suspected Still’s disease, a rare autoinflammatory condition. China approved it for primary HLH in March 2022.

Europe is a different story. The European Medicines Agency refused authorization for primary HLH in children in 2020 and upheld that decision on re-examination. Sobi’s second-quarter 2026 report says it now expects a European decision on the Still’s disease MAS indication in 2027, with a Japanese decision due in the second half of 2026.

Sales are climbing. Gamifant brought in SEK 794 million in the second quarter, up 29% at constant exchange rates, driven mainly by new U.S. patients with MAS in Still’s disease. Full-year 2025 sales were SEK 2.71 billion.

Sobi calls Gamifant the only approved anti-interferon gamma monoclonal antibody. BioTech Stocks Daily found no approved rival in that class. Conventional primary HLH care still leans on steroids and chemotherapy, which Sobi notes are not specifically approved for the disease.

Sobi reports third-quarter results on October 27. This article covers conference data and is not medical or investment advice.

Sources

• Sobi: Sobi to Present Clinical Data on Gamifant at Histiocyte Society 2026 in Rotterdam, PR Newswire, September 24, 2026. Primary source release.
• Blood (ASH 2025 abstract): Emapalumab Induces Rapid, Durable Responses and Reliable Bridging to Curative HSCT in Patients With Primary HLH, cited for the prior pooled response, bridging-success, steroid-tapering data, author disclosures and study limitations.
• Blood (ASH 2025 abstract): Use of Emapalumab Is Associated With Rapid and Sustained Benefits in Primary HLH Subgroups, cited for the subgroup analysis by CNS involvement and prior treatment.
• New England Journal of Medicine: Emapalumab in Children With Primary Hemophagocytic Lymphohistiocytosis, cited for the pivotal NI-0501-04 response rate and the historical HLH-94/HLH-2004 benchmarks.
• Sobi Q2 2026 Interim Report, cited for Gamifant sales, the Europe and Japan regulatory timelines, and the Q3 reporting date.
• Sobi: FDA Approves Gamifant as First-Ever Treatment for Adults and Children With MAS in Still’s Disease, cited for the June 2025 U.S. approval.
• Sobi: Gamifant Approved in China for the Treatment of Primary HLH, cited for the March 2022 Chinese approval.
• Sobi: Gamifant Recommended for Approval in China, cited for Sobi’s statement that conventional steroid and chemotherapy regimens are not specifically approved for primary HLH.
• European Medicines Agency: Gamifant (Refused), cited for the 2020 EU refusal and re-examination outcome.
• TradingView: Swedish Orphan Biovitrum AB (OTC: BIOVF), cited for Sobi’s U.S. over-the-counter listing, which the release did not mention.

Editorial Disclosure

This article reports on a press release issued by Swedish Orphan Biovitrum AB (publ) (Sobi) on September 24, 2026, announcing clinical data presentations on Gamifant (emapalumab) at the 2026 Annual Meeting of the Histiocyte Society (HS2026) in Rotterdam. Securities discussed: Swedish Orphan Biovitrum AB (Nasdaq Stockholm: SOBI; OTC: BIOVF). Prior pooled efficacy data, regulatory history outside the United States, product sales figures, and the company’s U.S. over-the-counter listing were drawn from independent sources cited above, since the original release did not address them. BioTech Stocks Daily has not received, nor will it accept, any compensation, direct or indirect, from Sobi or any other corporate or third-party sponsor for the preparation or publication of this coverage. No staff member, principal, or affiliate of BioTech Stocks Daily holds a position, option, or financial interest in any of the securities mentioned as of the date of publication. Statements regarding the content of upcoming poster presentations, pending regulatory decisions in Europe and Japan, future sales performance, and the outcome of the Robert J. Arceci Prize nomination are forward-looking statements. They involve substantial risks, regulatory uncertainties, and scientific variables; actual clinical outcomes, regulatory decisions, and commercial results may differ materially. Biotechnology and pharmaceutical investments carry a high degree of financial risk. Drug development and commercialization are subject to clinical failure, regulatory rejection, and market competition, which can result in the loss of invested capital. This article is published strictly for independent news reporting, market context, and educational purposes only. It does not constitute an investment recommendation, endorsement, or professional financial, legal, or tax advice. Furthermore, this content is not medical advice; patients and healthcare providers should consult appropriate clinical professionals for medical guidance.

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