Riabni (rituximab arrx) is a biosimilar of Roche’s MabThera/Rituxan (rituximab), which had sales of CHF 7.3 billion (Euros 6.4 billion) in 2016, before the advent of biosimilars. The patents on MabThera/Rituxan expired in the US in September 2016 and in Europe in February 2013 [1].

Rituximab is a chimeric monoclonal antibody against the protein CD20, which is primarily found on the surface of immune system B cells. Rituximab destroys B cells and is therefore used to treat diseases that are characterized by excessive number of B cells, overactive B cells or dysfunctional B cells. This includes many lymphomas, leukaemias, transplant rejection and autoimmune disorders.

Riabni has been approved for the treatment of adult patients with non-Hodgkin’s lymphoma (NHL), chronic lymphocytic leukaemia (CLL), granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA).

FDA approval was based on the review of a data package, which, according to Amgen, demonstrated that Riabni was ‘highly similar to Rituxan based on a totality of evidence, which included comparative analytical, non-clinical and clinical data, with no clinically meaningful differences in safety or effectiveness’. Amgen submitted its application for approval of ABP 798 to FDA in December 2019 [2], stating at the time that the data package included analytical, pharmacokinetic (PK) and clinical data, as well as pharmacology and toxicology data generated in two clinical studies, one in rheumatoid arthritis [3] and one in CD20-positive B-cell non-Hodgkin's lymphoma (NHL) patients [4].

The randomized, double-blind, comparative clinical study evaluated the efficacy, pharmacokinetics, pharmacodynamics (PD), safety, tolerability and immunogenicity of Riabni compared to Rituxan in subjects with grade 1, 2 or 3a follicular B-cell NHL and low tumour burden. There were 256 patients enrolled and randomized (1:1) to receive 375 mg/m² intravenous infusion of either Riabni or Rituxan, once weekly for 4 weeks followed by dosing at Weeks 12 and 20. The primary endpoint, an assessment of overall response rate (ORR) by Week 28, was within the prespecified margin for Riabni compared to Rituxan, showing clinical equivalence. Based on these results Amgen concluded that the ‘PK, PD, safety and immunogenicity of Riabni were similar to Rituxan’.

Riabni has been approved as a biosimilar, not as an interchangeable product. According to the Biologics Price Competition and Innovation Act of 2009 (BPCI Act), only a biological that has been approved as interchangeable may be substituted for the reference product without the intervention of the healthcare provider who prescribed the reference product. To date, no biosimilar has been approved as interchangeable in the US.

Riabni will be available in the US at a Wholesale Acquisition Cost (WAC or list price) of US$716.80 per 100 mg and US$3,584.00 per 500 mg single-dose vial, making it 23.7% cheaper than the WAC for the originator Rituxan and matching the WAC for Ruxience (another rituximab biosimilar).

The approval of Riabni marks the fifth biosimilar from Amgen to be approved by FDA. Amjevita (adalimumab-atto) was approved in September 2016, Avsola (infliximab-axxq) in December 2019, Kanjinti (trastuzumab-anns) in June 2019 and Mvasi (bevacizumab-awwb) in September 2017 [5].

Amgen also has three biosimilars, Kanjinti (trastuzumab), Mvasi (bevacizumab) and Solymbic (adalimumab), approved in Europe [6].

Related article
Biosimilars of rituximab

References
1. Derbyshire M. Patent expiry dates for biologicals: 2018 update. Generics and Biosimilars Initiative Journal (GaBI Journal). 2019;8(1):24-31. doi:10.5639/gabij.2019.0801.003
2. GaBI Online - Generics and Biosimilars Initiative. Rituximab biosimilar ABP 798 submitted to FDA [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Jan 29]. Available from: www.gabionline.net/Biosimilars/News/Rituximab-biosimilar-ABP-798-submitted-to-FDA 
3. GaBI Online - Generics and Biosimilars Initiative. Positive phase III results for rituximab biosimilar ABP 798 [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Jan 29]. Available from: www.gabionline.net/Biosimilars/Research/Positive-phase-III-results-for-rituximab-biosimilar-ABP-798 
4. GaBI Online - Generics and Biosimilars Initiative. More positive phase III results for rituximab biosimilar ABP 798 [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Jan 29]. Available from: www.gabionline.net/Biosimilars/Research/More-positive-phase-III-results-for-rituximab-biosimilar-ABP-798 
5. GaBI Online - Generics and Biosimilars Initiative. Biosimilars approved in the US [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Jan 29]. Available from: www.gabionline.net/Biosimilars/General/Biosimilars-approved-in-the-US 
6. GaBI Online - Generics and Biosimilars Initiative. Biosimilars approved in Europe [www.gabionline.net]. Mol, Belgium: Pro Pharma Communications International; [cited 2021 Jan 29]. Available from: www.gabionline.net/Biosimilars/General/Biosimilars-approved-in-Europe

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