Matisse Pharmaceuticals has closed a €14 million Series A financing round to fund a Phase 2 trial of isupartob sodium, a drug designed to neutralize the histones that sepsis releases into the bloodstream. The Geleen, Netherlands company announced the round on 17 September 2026, three months after FDA granted the drug Fast Track designation and ten months after the World Health Organization recognized it as the first drug in a new class.
Isupartob sodium’s path in four numbers
Figures from Matisse’s public announcements and The Lancet’s 2020 global sepsis burden study.
A disease that kills one in five people, worldwide
Sepsis is not a niche indication. A Global Burden of Disease analysis published in The Lancet estimated 48.9 million sepsis cases and 11 million sepsis-related deaths in 2017 alone — about 19.7% of all deaths worldwide that year, a toll the World Health Organization has since cited in calling for global action on the condition. Despite that scale, sepsis treatment remains largely supportive: antibiotics, fluids and organ support, with no approved drug that directly targets the runaway inflammatory cascade histones are thought to drive.
Sepsis therapeutics, two forecasts to 2030
$3.95B → $5.65B
Global sepsis therapeutics market, 2024 to 2030, per Grand View Research; The Business Research Company separately forecasts $6.92B by 2030.
Sources: Grand View Research, Sepsis Therapeutics Market Size, Share & Trends Analysis Report · The Business Research Company, Sepsis Therapeutics Global Market Report 2026
Regulatory News outlook
We expect any approved histone-targeting therapy to enter as an add-on to existing supportive care rather than a replacement for it, so its addressable slice of the sepsis-therapeutics market will track how many patients a Phase 2 trial shows benefit for, not the market total.
How we got here: The two published forecasts already bracket a range — $5.65 billion to $6.92 billion by 2030 — without any histone-targeting drug approved yet; we treat that gap, about $1.3 billion, as the rough ceiling a first-in-class entrant could add if later trials support broad use.
Isupartob sodium against sepsis’s other experimental approaches
| Candidate | Mechanism | Stage | Sponsor |
|---|---|---|---|
| Isupartob sodium (Matisse) | Neutralizes extracellular histones released during sepsis | Phase 1 complete; Phase 2 funded, not yet started | Matisse Pharmaceuticals |
| Nangibotide | TREM-1 inhibitory peptide; dampens an overactive inflammatory response | Phase 3 (ACCURATE) planned after a Phase 2b subgroup signal | Inotrem |
| ATX101 | Targets loss of vascular integrity in septic shock | Phase 1 complete; preparing Phase 2 | AUROBAC Therapeutics |
| STC3141 | Carbohydrate-based agent that dampens a NETosis-linked immune reaction | Phase 2 complete with positive results | Academic-led (Griffith University / Australian National University) |
From each program’s own announcements and public trial records; not a head-to-head clinical comparison.
Neutralizing the histones, not just the infection
Matisse’s drug targets a specific step in sepsis’s downward spiral: as cells die and the innate immune system responds, histones — proteins normally used to package DNA inside the nucleus — are released into the bloodstream. Outside the cell, histones are toxic to cell membranes and can trigger further cell death, more histone release, endothelial injury and organ failure, a self-reinforcing cascade independent of the original infection. Isupartob sodium is a highly negatively charged, low-anticoagulant heparin derivative built to bind those positively charged extracellular histones and interrupt that cascade.
In December 2025, the World Health Organization assigned the drug the international nonproprietary name isupartob sodium, creating ‘-partob’ as a new suffix for histone-binding heparin derivatives — a naming decision Matisse frames as recognition that no other approved or investigational drug shares its exact mechanism.
What Matisse is betting proceeds on
A first-in-class mechanism, on the WHO’s own terms
The WHO’s December 2025 INN assignment created a new drug-class suffix specifically for isupartob sodium’s mechanism, rather than filing it under an existing heparin category.
Two completed Phase 1 studies, not zero
A 120-hour healthy-volunteer infusion study and a 10-patient critically ill sepsis study at Amsterdam UMC both reported favorable safety and near dose-proportional pharmacokinetics before this raise.
FDA already engaged
The company received FDA IND clearance in May 2026 and Fast Track designation in June 2026, both ahead of the Phase 2 trial this financing is meant to fund.
What €14 million buys before a Phase 2 readout
Matisse says the round’s proceeds will “primarily be used to execute the Phase 2 clinical trial of isupartob sodium, a key value-inflection milestone for the company, while supporting regulatory, manufacturing and operational activities.” As of publication, the company had not registered the Phase 2 trial on ClinicalTrials.gov or the EU’s Clinical Trials Information System, and had not disclosed a start date; its own release describes plans to submit regulatory dossiers for the study in the U.S., Europe and Asia.
“This financing represents an important milestone for Matisse. We are grateful for the continued commitment of our existing shareholders and are pleased to welcome new investors who share our long-term vision. Their support enables us to focus on what matters most: successfully completing our Phase 2 clinical trial in sepsis patients and generating the clinical data needed to unlock the next stage of the company’s development.” Marcel Jacobs, Chief Executive Officer, Matisse Pharmaceuticals — 17 September 2026 announcement
From a Chemelot lab to a third capital raise
Matisse’s twelve years to a Phase 2-ready raise
- 2014
Matisse Pharmaceuticals founded
Founded at the Brightlands Chemelot Campus in Geleen, the Netherlands.
- January 2024
Marcel Jacobs named CEO
Appointed effective 1 January 2024.
- Early 2024
€3.6 million financing round
Closed with Brightlands Venture Partners and other investors, extending an earlier relationship.
- December 2025
WHO grants the INN ‘isupartob sodium’
A new drug-class suffix, ‘-partob,’ is created for histone-binding heparin derivatives.
- May 2026
FDA IND clearance
Clears the way for U.S. clinical development of isupartob sodium.
- June 2026
FDA Fast Track designation
Granted for isupartob sodium in sepsis.
- 17 September 2026
€14 million Series A closes
Proceeds earmarked primarily for the Phase 2 trial.
- Not yet dated
Phase 2 trial start
No registered trial entry or start date disclosed as of publication.
The gap between this raise and a dosed Phase 2 patient is the milestone that will actually test isupartob sodium’s promise: the completed Phase 1 work showed the drug was safe and moved the biomarkers Matisse expected, but a randomized, adequately powered Phase 2 trial in sepsis patients — a population where many past investigational drugs have failed to move survival — is the study that will determine whether history is different this time.
- Investors: Brightlands Venture Partners and LIOF led the institutional participation, alongside private investors and Matisse’s own management.
- Prior funding: a €3.6 million round in early 2024 and a €524,000 non-dilutive Eurostars grant in 2025, alongside an earlier, undisclosed-amount round for the Phase I/IIa trial.
- Not yet public: Matisse has not disclosed the Phase 2 trial’s planned enrollment, primary endpoint, or start date, nor a post-money valuation for this round.
Sources & further reading
- Matisse Pharmaceuticals, “Matisse Pharmaceuticals Closed Series A Financing Round to Advance Isupartob Sodium Through Phase 2 Clinical Development,” press release, 17 September 2026. globenewswire.com
- “Matisse Raises €14M for Phase 2 Sepsis Trial,” European Biotechnology Magazine, September 2026. european-biotechnology.com
- ClinicalTrials.gov, “A Study in Healthy Subjects to Assess the Safety and Tolerability of a 120-hour Continuous Infusion of M6229,” NCT07285603. clinicaltrials.gov
- “A phase I trial evaluating the safety, tolerability, pharmacokinetics and pharmacodynamics of intravenously administered low-anticoagulant heparin (M6229) in critically ill sepsis patients,” peer-reviewed article, PMC. ncbi.nlm.nih.gov
- Matisse Pharmaceuticals, “Matisse Pharmaceuticals Receives INN ‘Isupartob Sodium’, Recognizing First-in-Class Drug Status for M6229,” press release, 11 December 2025. globenewswire.com
- Matisse Pharmaceuticals, “Matisse Pharmaceuticals Receives FDA Fast Track Designation for Isupartob Sodium in Sepsis,” press release, 9 June 2026. globenewswire.com
- Rudd et al., “Global, regional, and national sepsis incidence and mortality, 1990-2017: analysis for the Global Burden of Disease Study,” The Lancet, 2020. thelancet.com
- Grand View Research, “Sepsis Therapeutics Market Size, Share & Trends Analysis Report.” grandviewresearch.com
Regulatory News reports on public regulatory documents. It is not legal advice, and the primary sources above govern. If we have made an error, we will say so in public: see corrections.
Frequently asked questions
How much did Matisse Pharmaceuticals raise, and for what?
€14 million, announced 17 September 2026, from existing and new institutional investors including Brightlands Venture Partners and LIOF, plus private investors and management. The company says proceeds will primarily fund a Phase 2 trial of isupartob sodium in sepsis patients, alongside regulatory, manufacturing and operational costs.
What is isupartob sodium?
Also known as M6229, it is a low-anticoagulant heparin derivative designed to neutralize extracellular histones — proteins released into the bloodstream during sepsis that damage cell membranes and drive organ failure. The World Health Organization assigned it the international nonproprietary name ‘isupartob sodium’ in December 2025, creating a new drug-class suffix, ‘-partob,’ for histone-binding heparin derivatives.
Has isupartob sodium been tested in patients?
Yes. Two completed Phase 1 studies — a 120-hour continuous-infusion safety study in healthy volunteers, and a 10-patient study in critically ill sepsis patients at Amsterdam UMC — both reported favorable safety, tolerability and close to dose-proportional pharmacokinetics. FDA cleared the drug’s IND in May 2026 and granted it Fast Track designation in June 2026.
Is this Matisse's first funding round?
No. The company, founded in 2014, previously closed a €3.6 million round in early 2024 and an earlier round to fund its Phase I/IIa trial, plus a €524,000 non-dilutive Eurostars grant in 2025. This Series A is its largest disclosed round to date.
