Our TYK2 program: GLPG3667

GLPG3667 is an investigational reversible and selective TYK2 kinase domain inhibitor that was discovered by us and evaluated in a Phase 1 healthy volunteer study in 2020. The Phase 1 study was a randomized, double-blind, placebo-controlled dose escalation study evaluating safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of single and multiple ascending oral doses of GLPG3667 for 13 days.

Blood was drawn at multiple time points on Day 1 and on Day 10 and stimulated ex vivo with several cytokines, including IFNα, to analyze the level of inhibition of inflammation, including the effect on phosphorylated signal transducer and activator of transcription (pSTAT) signaling as well as hematological parameters, lipids and creatine-phosphokinase (CPK) (see graphs below).

'3667 is a potent, selective TYK2 inhibitor

No effect on hematological parameters, lipids and CPK

Following these results, we initiated a randomized, placebo-controlled, double-blind Phase 1b study in 31 patients with moderate to severe plaque psoriasis. Patients were randomized in a 1:1:1 ratio to a daily oral dose of GLPG3667 (low dose or high dose) or placebo, for a total of 4 weeks.

In July 2021, we announced positive topline results demonstrating that GLPG3667 was generally well tolerated with a positive response signal at Week 4 (see graph below):

• At Week 4, four out of 10 patients in the high dose group had a Psoriasis Area and Severity Index (PASI)50 response, defined as at least a 50% improvement in PASI from baseline, compared to one out of 10 subjects on placebo. There were no subjects with a PASI 50 response on the low dose of GLPG3667. The 4 responders in the high dose group of GLPG3667 achieved a 52%, 65%, 74% and 81% improvement respectively in their PASI scores from baseline, while the subject randomized to placebo improved by 52%. Positive efficacy signals were also observed with the high dose for other endpoints, including affected Body Surface Area and physician and patient global assessment, versus placebo at Week 4.

GLPG3667: clinical activity in Psoriasis at Week 4

Phase 1b psoriasis study with '3667

Clinical activity at 4 weeks with once daily dosing

• One subject in the low dose group interrupted participation in the study for one day due to exacerbation of psoriasis. The majority of treatment related adverse events (AEs) were mild in nature and transient. There were no deaths or serious adverse events (SAEs) in this 4-week study.

Following these results, in 2022, we initiated the preparations for the Phase 2 studies with GLPG3667 in dermatomyositis (DM) and systemic lupus erythematosus (SLE). 

DM is the most common form of idiopathic inflammatory myopathies (IIM) and is characterized by inflammatory and degenerative changes of the muscles and skin. IIMs are a heterogenous group of rare autoimmune disorders primarily affecting the proximal muscles. They are characterized by severe muscle weakness, muscle enzyme elevations, inflammation on muscle biopsy, and extra-muscular manifestations. The quality of life of patients with DM is impaired due to muscle weakness and pain, and skin disease activity.¹⁴ The overall mortality ratio in DM patients also remains three times higher compared to the general population, with cancer, lung, and cardiac complications and infections being the most common causes of death.

The Phase 2 studies in DM and SLE are expected to start later in 2023.