Sundance Biosciences Presents Positive Phase 1 Data for SUN-627

SOUTH SAN FRANCISCO, Calif. — October 21, 2026

Phase 1 Study Demonstrates CNS Exposure and Favorable Tolerability

The randomized, double-blind, placebo-controlled Phase 1 trial evaluated the safety, tolerability and pharmacokinetics of oral, once-daily SUN-627 in healthy adult volunteers using single-ascending-dose and multiple-ascending-dose cohorts. A dedicated cohort assessed the drug’s pharmacokinetics in cerebrospinal fluid (CSF). According to Sundance, SUN-627 was well tolerated, with no serious adverse events reported and all treatment-related adverse events classified as Grade 1, or mild. The candidate achieved a CNS penetration ratio of 1, measured as the ratio of unbound SUN-627 in CSF to unbound SUN-627 in plasma. The study also showed greater than 90% reduction in key TYK2 pathway biomarkers over a 24-hour period with once-daily dosing. Based on the reported pharmacokinetic findings, steady-state CSF exposure is predicted to remain above the preclinically derived IC90 for induced pluripotent stem cell (iPSC)-derived microglia for approximately 24 hours at doses of 40 mg or higher once daily. These results characterize the candidate’s exposure and pathway activity in healthy volunteers; its safety and efficacy in people with MS require evaluation in patient studies.

Preclinical Findings Examine Neuroinflammation Mechanisms

Sundance also presented preclinical data from experimental autoimmune encephalomyelitis (EAE), a widely used rodent model of MS, and cell culture experiments. The findings indicated that brain-penetrant TYK2 inhibition affected interferon-enriched activated microglia and astrocytes, CNS-resident cell types associated with chronic active lesions in progressive MS. The company also reported that TYK2 inhibition impeded interferon-dependent dendritic cell differentiation and antigen-mediated T-cell activation, processes implicated in ongoing inflammatory activity in the central nervous system. In additional EAE studies, Sundance reported that brain-penetrant TYK2 inhibition reversed disease and reduced markers associated with neuroinflammation and neurodegeneration. Reported effects included dampened microglial and astrocytic activation, lower levels of downstream cytokines and chemokines, and reductions in markers of neurodegeneration and demyelination. These results provide a mechanistic rationale for further investigation of the approach, but findings from animal models and cell experiments do not establish clinical benefit in humans. The company believes CNS penetration may enable SUN-627 to affect inflammatory processes behind the blood-brain barrier that contribute to progressive disease.

SUN-627 Advances Sundance’s Neuroimmunology Pipeline

Sundance Chief Executive Officer Andrew Yost said the clinical and preclinical findings support continued development of SUN-627 for progressive MS, while Chief Scientific Officer Steve Wood highlighted the candidate’s CNS penetration and sustained TYK2 pathway inhibition. SUN-627 is designed to modulate immune signaling involving B cells, T cells, astrocytes and microglia, with the aim of regulating downstream inflammatory pathways associated with disease progression. The company also sees potential applications for brain-penetrant TYK2 inhibition in other neuroinflammatory conditions, including Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis (ALS), although these remain potential future research areas. Sundance’s pipeline also includes SUN-111, a Phase 2-ready, peripherally restricted TYK2 inhibitor being developed for immune-mediated diseases. SUN-627 remains investigational, and the Phase 1 findings in healthy volunteers do not demonstrate that the candidate improves symptoms or slows progression in patients with MS. Further clinical evaluation will be needed to determine its therapeutic potential, safety profile and appropriate dosing in people with progressive disease.

Source::Sundance Biosciences,,,,press release