The phase III, randomized, double-blind, parallel group, multicentre study was designed to compare the efficacy and safety of candidate etanercept biosimilar (ABP 501) versus Humira (adalimumab) in subjects with moderate to severe rheumatoid arthritis who have an inadequate response to methotrexate. The trial, which was carried out in Bulgaria, Canada, Czech Republic, Germany, Hungary, Mexico, Poland, Romania, Russia, Spain, the UK and the US was planned to be completed in November 2014.

The study consisted of a screening period of four weeks and a treatment period of 22 weeks. Patients were randomized to receive either 40 mg ABP 501 subcutaneous injection (SC) every two weeks (n = 264) or 40 mg SC Humira every two weeks (n = 262) until week 22. The study completed at week 24, followed by a safety follow-up period through to week 26.

The detailed phase III results for ABP 501 were presented at the 2015 Annual Meeting of the American College of Rheumatology (ACR) and the Association for Rheumatology Health Professionals (ARHP), which was held in San Francisco, USA on 6–11 November 2015.

Amgen claims that the study met the primary endpoint, which was an achievement of ACR20 (20% or greater improvement in American College of Rheumatology assessment) at week 24. At week 24, 74.6% of patients in the ABP 501 group and 72.4% in the adalimumab group met the ACR20 response criteria. The risk ratio of ACR20 was 1.039 with the two-sided 90% confidence interval (CI) of 0.954–1.133, which fell within the predefined equivalence margin.

Secondary endpoints, including ACR50, ACR70 and change from baseline in DAS28-CRP (Disease Activity Score examining 28 joints in the body as measured by C-reactive protein in the blood), were also ‘achieved’, according to Amgen. At week 24, patients treated with ABP 501 compared with those treated with adalimumab achieved ACR50 (49.2% vs. 52.0%) and ACR70 (26.0% vs. 22.9%), respectively.

Safety parameters, such as treatment-emergent adverse events (TEAEs) (50% vs. 55%), serious adverse events (3.8% vs. 5.0%) and serious infections (0.8% vs. 1.1%) were similar in the ABP 501 and adalimumab groups, respectively. By the end of week 24, binding antibodies (38.3% vs. 38.2%) and neutralizing antibodies were identified (9.1% vs. 11.1%) in patients treated with ABP 501 and adalimumab, respectively.

Amgen is carrying out a long-term open-label, single-arm extension study in rheumatoid arthritis patients. The company is also carrying out a phase III clinical trial of its biosimilar adalimumab in patients suffering from plaque psoriasis [1].

Editor’s comment
It should be noted that data of the study presented in this article were published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

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Reference
1.    GaBI Online - Generics and Biosimilars Initiative. Amgen starts another phase III trial for biosimilar adalimumab [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2015 Dec 4]. Available from: www.gabionline.net/Biosimilars/News/Amgen-starts-another-phase-III-trial-for-biosimilar-adalimumab

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