Promising Phase 3 Trial Results for Ixekizumab for the Treatment of Psoriatic Arthritis

Patients in the SPIRIT-P1 trial with active psoriatic arthritis treated with ixekizumab achieved significant improvement as measured by ACR20 compared to patients who received placebo.

Eli Lilly recently announced that results from the phase 3 SPIRIT-P1 trial show that ixekizumab was statistically superior to placebo in the treatment of patients with active psoriatic arthritis.

During the 24-week, phase 3 study patients who had not previously been treated with biologic disease-modifying antirheumatic drugs received one of two different ixekizumab dosing regimens or placebo. According to Eli Lilly, “in both dosing regimens, ixekizumab-treated patients demonstrated significant improvements versus placebo in signs and symptoms” of active psoriatic arthritis.

Researchers reported that the incidence of treatment-emergent adverse events was more frequent with ixekizumab compared with placebo, and said the most common adverse events observed “were consistent with the Phase 3 studies of ixekizumab for the treatment of moderate-to-severe plaque psoriasis.” The treatment groups and placebo group experienced similar rates of serious adverse events. Discontinuation rates due to adverse events were also similar between treatment groups.

The company reported that ixekizumab is a monoclonal antibody “with high affinity and specificity that binds to and neutralizes the pro-inflammatory cytokine interleukin-17A (IL-17A), which research has shown can contribute to autoimmune diseases,” including psoriatic arthritis and psoriasis.

Ixekizumab does not bind to other IL-17 cytokines and is administered via subcutaneous injection. Ixekizumab is also in clinical development for the treatment of moderate-to-severe plaque psoriasis.

The news release from Eli Lilly noted that the patients participating in the SPIRIT-P1 trial were required to have an established diagnosis of psoriatic arthritis and active disease for at least six months prior to enrollment. Patients in the treatment arm of the study received an initial dose of subcutaneous 160 mg ixekizumab, and then were assigned to receive either 80 mg subcutaneous ixekizumab once every two weeks or 80 mg subcutaneous ixekizumab once every four weeks.

Subcutaneous adalimumab 40 mg every other week was used as the active control for comparison with placebo. The SPIRIT-P1 study will also evaluate the long-term efficacy and safety of ixekizumab in psoriatic arthritis for up to three years.