Galapagos' GLPG3667 Meets Primary Endpoint In Dermatomyositis Study, Shows Mixed Results In Lupus Phase 3-Enabling Trials; Galapagos Will Evaluate All Strategic Alternatives, Including Resumption Of Its Partnering Process, To Accelerate Further Development Of GLPG3667 In Dermatomyositis And Potentially Other Severe Auto-Immune Indications

GLPG3667 met primary endpoint in dermatomyositis study, demonstrating a statistically significant clinical benefit and meaningful improvements on secondary measures of disease activity compared to placebo

In the systemic lupus erythematosus study, GLPG3667 delivered numerical improvements on several secondary endpoints compared to placebo but did not achieve statistical significance in primary endpoint analysis

The safety profile was consistent with previous studies with GLPG3667

Galapagos will evaluate all strategic alternatives, including resumption of its partnering process, to accelerate further development of GLPG3667 in dermatomyositis and potentially other severe auto-immune indications

Mechelen, Belgium; December 18, 2025, 22:01 CET; regulated information – inside information – Galapagos NV ((Euronext &, NASDAQ:GLPG) today announced the topline results from two Phase 3-enabling studies evaluating the efficacy and safety of GLPG3667, a selective TYK2 inhibitor, in patients with dermatomyositis (DM) (GALARISSO study) and active systemic lupus erythematosus (SLE) (GALACELA study).

The GALARISSO DM study met its primary endpoint, showing that GLPG3667, administered once daily at 150 mg (N=21) in addition to standard-of-care therapy, achieved a statistically significant clinical benefit in the Total Improvement Score (TIS)1 at Week 24 (p=0.0848; Δ: 14.26), compared to placebo (N=19). The pre-specified threshold of statistical significance was set at 10% (α=0.1). GLPG3667 also showed meaningful clinical improvements compared to placebo on several secondary endpoints of disease activity, including TIS20, TIS40, TIS60 and m-CDASI-A2. GLPG3667 demonstrated a favorable safety and tolerability profile throughout the 24-week treatment period.