Eli Lilly’s best-selling weight loss drug, Zepbound (tirzepatide), has scored again, this time in a late-stage trial alongside the company’s plaque psoriasis drug, Taltz (ixekizumab).
During the Phase IIIb TOGETHER-PsA study (NCT06588296), the concomitant use of Zepbound-Taltz significantly increased the percentage of patients (31.7%) exhibiting at least a 50% improvement in psoriatic arthritis (PsA) activity and a 10% reduction in body weight compared with Taltz alone (0.8%) – meeting its primary endpoint.
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Measures of PsA activity were categorised through the American College of Rheumatology 50 (ACR50) system, which is used to determine if a patient with PsA has had a clinically significant response to a disease-modifying therapy (DMT) such as Taltz.
The trial also met its secondary endpoint, as Taltz-Zepbound prompted an ACR50 response in 33.5% of patients – a 64% relative increase over the 20.4% who achieved this milestone in the Taltz monotherapy group. This suggests that the drugs can work in synergy to reduce PsA activity.
Treatment-emergent adverse events (TEAEs) associated with Zepbound-Taltz also aligned with the respective safety profile of each therapy, with the most common AEs being nausea, diarrhoea, constipation and injection site reactions.
Taltz acts through the interleukin-17 (IL-17) cytokine, inhibiting its interaction with the IL-17 receptor. The therapy first gained US approval for the treatment of plaque psoriasis in adults in 2016 and has since been given the green light for use in children over six years of age.
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By GlobalDataCombating the Taltz patent cliff
Since its market debut, Taltz has been a strong seller for Eli Lilly, bringing in $3.2bn for the company in 2024 alone. According to a forecast from GlobalData, parent company of Clinical Trials Arena, the blockbuster therapy’s sales will continue to grow until 2029 – reaching a peak of $4bn by the end of the year.
However, Taltz’s sales could soon drop as its US patent is set to expire in 2028.
According to Lilly, the TOGETHER-PsA trial is the first controlled study to establish the benefit of combining an incretin therapy with a PsA biologic for treating psoriatic arthritis. This is notable as obesity is a common comorbidity associated with PsA, with researchers estimating that 65% of US patients with the disease are also obese or overweight.
According to Mark Genovese, senior VP of Lilly Immunology, the results of this study demonstrate the potential of an integrated treatment approach in treating PsA, which could “improve the standard of care (SoC) in a compelling and comprehensive way”.
By combining Zepbound and Taltz to establish a new treatment paradigm, Eli Lilly could potentially mitigate the impacts of the upcoming Taltz patent cliff while further establishing its presence in the PsA market.
