A randomized, double-blind phase III study to demonstrate the clinical similarity of biosimilar SCT630 to reference adalimumab in Chinese patients with moderate to severe plaque psoriasis

•Phase III study was conducted in moderate-to-severity plaque psoriasis patients.•SCT630 and adalimumab showed equivalences in efficacy and similar safety.•Switching from adalimumab to SCT630 did not impact safety or efficacy. This phase III study aimed to compare the efficacy, safety, and immunogenicity of SCT630 with the reference adalimumab. A total of 367 Chinese patients with moderate-to-severe plaque psoriasis were randomly assigned to receive 80 mg of SCT630 or adalimumab subcutaneously at week 1, 40 mg at week 2, then 40 mg biweekly. At week 16, those with 50 % or more improvement in psoriasis area and severity index (PASI) were eligible to enter an extension period up to week 52. Patients on SCT630 continued the same treatment, whereas patients receiving adalimumab were re-randomized at a ratio of 1:1 to adalimumab or SCT630 group. The primary endpoint was percentage improvement in PASI at week 16. Other endpoints included PASI 50/75/90/100, Physician’s Global Assessment, Dermatology Life Quality Index, safety, and immunogenicity. PASI improvement at week 16 was 85.07 % for SCT630 and 84.82 % for adalimumab. The mean difference (3.10 %, 95 % CI: −1.875 %, 8.066 %) was within the equivalence interval. Other efficacy endpoints, safety and immunogenicity profiles were similar across the two groups. There were no safety or immunogenicity difference between switched/continued groups. This phase III study demonstrated the equivalences in efficacy, safety and immunogenicity of SCT630 to adalimumab in patients with moderate to severe psoriasis.