HS patients on biosimilar adalimumab lose response faster than those on the original drug

Patients with hidradenitis suppurativa (HS) who started on or switched to biosimilar adalimumab experienced lower treatment success and lost response more quickly, according to an Australian study published in JAAD International in October.

HS is a chronic, painful skin condition that causes nodules, abscesses, tunnels and scarring, typically in areas with sweat glands. Those with moderate to severe cases are usually treated with biologics such as adalimumab, sometimes alongside surgery, but the high cost of these drugs can limit access.

Biosimilars are medications designed to match the original biologic in safety and effectiveness while offering a more affordable option.

However, formal studies of adalimumab biosimilars in HS are limited. Approvals are usually based on research in psoriasis, and early reports suggest response rates of 40% to 50% in patients who haven’t previously used biologics.

Small differences in how the drug is created can affect immune responses, and switching between originator and biosimilar adalimumab could reduce effectiveness or adherence. In this study, “originator adalimumab” likely refers to Humira, while “biosimilar adalimumab” could include one of the Humira biosimilars used in Australia, such as Amgevita, Hyrimoz, Hulio, Idacio or Imraldi, although the study didn’t specify the brand used.

Researchers from The Skin Hospital and the University of New South Wales in Australia conducted the real-world, multicenter study to examine clinical response, loss of response and time-to-event outcomes in HS patients using either originator or biosimilar adalimumab, including the effects of nonmedical switching.

The study included patients treated at three Australian clinics between April 2021 and December 2024. Two groups were examined. The first group, called the bio-naïve cohort, included patients who had never received biologics and started on either originator or biosimilar adalimumab. The second group, the switched cohort, included patients who initially responded to originator adalimumab after 16 weeks and were then switched to a biosimilar due to formulary changes. Patients in the switched cohort were matched by age, sex, BMI and smoking status with those who stayed on the original drug.

All patients followed standard dosing of 160 mg at week 0, followed by 80 mg every two weeks and could continue other treatments. Clinical response was measured using HiSCR-50, HiSCR-75 and IHS4 scores. Time-to-event and regression analyses were used to compare response rates and factors affecting treatment outcomes between groups.

In the study, the bio-naïve cohort included 313 patients. At week 16, both groups had similar rates of partial response (HiSCR-50), but more patients on originator adalimumab achieved a stronger response (HiSCR-75). By week 52, the originator group showed better results across all measures, including HiSCR-50, HiSCR-75 and IHS4-55. Patients on biosimilars lost their response faster, with a median time to loss of 52 weeks compared with 100 weeks for the originator. Biosimilar use was associated with a 77% higher chance of losing response.

The switched cohort included 71 patients who moved from originator to biosimilar after 16 weeks. Compared with 71 matched patients who stayed on originator therapy, those who switched lost response sooner, with a median time of 50 weeks versus 87 weeks. Switching to a biosimilar increased the odds of losing response by 181%.

Based on the study methods and layout, study strengths include the real-world data from multiple clinics, making the findings more reliable. Comparing patients who switched with matched patients who stayed on the originator provided a clear framework for analysis. The study also accounted for factors such as disease severity, BMI and presence of tunnels to reduce bias. Study limitations include the small sample size and short follow-up.

The authors suggest larger prospective studies with more diverse patient populations and longer observation periods. They also recommend careful evaluation before switching stable HS patients to biosimilars due to the higher risk of losing clinical response and possible reduced treatment effectiveness.