Amgen and Allergan plc announced positive top-line results from a Phase 1/Phase 3 study evaluating the pharmacokinetics, efficacy and safety of biosimilar candidate ABP 798, a biosimilar candidate to RITUXAN® (rituximab), compared to rituximab in patients with moderate-to-severe rheumatoid arthritis. The results demonstrate that the study met its primary endpoint of pharmacokinetic (PK) similarity. Additionally, equivalent efficacy was established and a similar safety profile was demonstrated.

The primary objective of the study was PK similarity comparing ABP 798 to rituximab. The PK endpoints of the study were area under the serum concentration–time curve (AUC) and maximum serum concentration (Cmax), both of which were within the pre-specified equivalence margin. The pre-specified equivalence in efficacy endpoint was measured by Disease Activity Score 28-joint count C reactive protein (DAS28-CRP) change from baseline at week 24.

Overall, safety and immunogenicity of ABP 798 were comparable to rituximab. This is the first of two studies intended to form the basis for global regulatory submissions for ABP 798. The second study is being conducted in patients with non-Hodgkin's lymphoma.

ABP 798 is being developed as a biosimilar candidate to rituximab, a CD20-directed cytolytic antibody that is approved in many regions for the treatment of adult patients with moderate-to-severe rheumatoid arthritis, non-Hodgkin's lymphoma, chronic lymphocytic leukemia, pemphigus vulgaris, granulomatosis with polyangiitis and microscopic polyangiitis. Amgen has a total of 10 biosimilars in its portfolio, including two that are approved in the United States (U.S.) and three that are approved in the European Union (EU). The referenced Phase 1/Phase 3 study was a randomized, double-blind trial (study number NCT02792699) that evaluated the PK, efficacy and safety of ABP 798 compared to rituximab in patients with moderate-to-severe rheumatoid arthritis. There were 311 patients enrolled and randomized (1:1:1) to receive either ABP 798, rituximab sourced from the U.S., or rituximab sourced from the EU, administered as an intravenous (IV) infusion at baseline and again at week 24.

Among them, 104 patients were randomized to the ABP 798 group, 103 patients were randomized to the rituximab (U.S.) group and 104 patients were randomized to the rituximab (EU) group. The primary PK endpoints of the study were AUC and Cmax. The pre-specified equivalence in efficacy endpoint was measured by DAS28-CRP change from baseline at week 24, and the overall study duration was 48 weeks. Additionally, the study included a single transition for subjects on rituximab (U.S.) to ABP 798.