SynAct Pharma to present new resomelagon preclinical data on Phase 3-ready RA therapeutic candidate at the 17th World Congress of Inflammation 2026

• Preclinical data support broad efficacy and potential for resomelagon’s distinct pro-resolution mechanism of action
• First study supports resomelagon development to treat osteoarthritis
• Second study in pseudomonas supports resomelagon development as additive effect to antibiotics for hard-to-treat bacterial infections

SynAct Pharma AB (publ) (”SynAct”) (Nasdaq Stockholm: SYNACT), a clinical-stage biotechnological company focused on treating inflammation through a novel therapeutic approach called “pro-resolution”, today announces two poster presentations supporting the differentiated therapeutic potential of resomelagon (AP1189), the Company’s lead Phase 3-ready candidate at the 17th World Congress of Inflammation, to be held in Foz do Iguaçu, Brazil, from September 8–12, 2026.

The data further reinforce growing evidence on the role of pro-resolution mechanisms in treating inflammatory and infectious diseases, including osteoarthritis (OA) and hard-to-treat bacterial infections. Inflammation in OA and in infection can be related through shared innate immune pathways, cytokines, and signaling hubs, even though innate immune activation in OA is predominantly sterile while infection is driven by microbes. As a selective MC1R/MC3R agonist, resomelagon represents a novel approach to modulating inflammation and restoring tissue homeostasis, with potential applications across multiple therapeutic areas.

“SynAct’s focus on the pro-resolution mechanism sets us apart in the field of anti-inflammatory therapeutics,” said Thomas Jonassen, Chief Scientific Officer of SynAct Pharma. “These data further outline how resomelagon activates pro-resolution pathways to reduce inflammation and biomarkers, and its potential as a novel therapy for osteoarthritis and severe bacterial infections by resolving inflammation without broad immunosuppression.”

Resolution is the active, receptor-mediated termination of inflammation — a distinct biological program comprising cessation of neutrophil influx, efferocytosis of apoptotic cells, macrophage reprogramming toward a reparative phenotype, and restoration of tissue architecture. SynAct's resomelagon, an orally available, once-daily biased agonist of the MC1 and MC3 melanocortin receptors, was designed to engage this program directly, offering the potential to control inflammation both in resolution-deficient autoimmunity such as rheumatoid arthritis and in host-damaging responses to infection, without the immunosuppression that limits current standards of care.

Details of the presentations

Effects of MC1R/MC3R Melanocortin Receptor Agonism on Osteoarthritis Inflammation, Joint Damage, and Pain
Time: September 11, 2026, 18:30–19:30
Location: Poster Session

The first poster outlines how activation of specific melanocortin receptors engages pro-resolution pathways, tamping down inflammation and associated biomarkers. In short, resomelagon, offers a promising novel therapeutic approach for halting osteoarthritis progression and alleviating associated pain, without compromising the immune system, the way marketed therapies do.

This study, led by researchers from the Federal University of Minas Gerais (UFMG) and SynAct, investigates the effects of resomelagon in a murine model of OA induced by destabilization of the medial meniscus (DMM). Preliminary results demonstrate that resomelagon exerts a potential therapeutic effect by modulating the inflammatory profile and preventing the progression of experimental OA. Data showed it reduces cellular infiltration, modulates pro-inflammatory cytokines such as IL-1β and TGF-β, and prevents histopathological changes associated with OA progression. Notably, treated animals did not develop OA-like alterations, suggesting a potential disease-modifying effect.

OA is a highly prevalent joint disorder affecting 595 million people globally[1] characterized by chronic pain and functional impairment. Increasing evidence indicates that sustained low‑grade inflammation contributes to disease progression and structural joint damage.


Study of the Therapeutic Potential of a Biased Melanocortin Receptor Agonist (MRA) Against Pseudomonas aeruginosa-Induced Pneumonia in Mice
Time: September 9, 2026, 18:00–19:30
Location: Poster Session

The second poster demonstrates how resomelagon promotes a pro-resolving inflammatory milieu, without broad immunosuppression, and thus addresses a critical gap in the treatment of severe bacterial infections. Inflammation in response to bacterial infection plays an important role, orchestrating the recruitment of immune cells to contain and clear the pathogen — however, when excessive or dysregulated, it can drive collateral tissue damage, sepsis, and chronic disease.

Resomelagon was evaluated as both a monotherapy and in combination with the antibiotic imipenem in a murine model of P. aeruginosa-induced pneumonia. Treatment with resomelagon reduced mortality, lung histopathology scores, and intra-alveolar neutrophil accumulation, while trending toward a reduction in pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and an increase in the anti-inflammatory cytokine IL-10. The results underscore the potential of melanocortin receptor agonism to modulate, rather than suppress, the inflammatory response, thereby improving survival and limiting tissue damage.

[1] Lancet Rheumatol 2023; 5: e508–22