Epoetin alfa and zeta biosimilars

Recombinant human erythropoietin, a 165-amino-acid glycoprotein of about 30 kDa with three N-linked and one O-linked glycan, produced in Chinese hamster ovary cells. Epoetin alfa and epoetin zeta share the amino acid sequence and differ only in glycosylation profile, which is why the EU gave the Stada and Hospira product its own INN.

Binds the erythropoietin receptor on erythroid progenitors in the marrow, stimulating their proliferation and differentiation into red cells. The sialic acid content of its glycans determines its half-life and therefore its potency in vivo, which is why glycosylation is the critical quality attribute in every comparability exercise.

Subcutaneous bioavailability about 20 to 40%, peak concentrations at 12 to 18 hours and a half-life of about 24 hours subcutaneously and 4 to 13 hours intravenously. Dosing is one to three times weekly, titrated to haemoglobin.

50 to 150 IU/kg one to three times weekly, adjusted to a haemoglobin target, in pre-filled syringes and vials from 1,000 to 40,000 IU. The unit system and the target-haemoglobin restrictions introduced after cardiovascular safety findings are common to all products.

• Anaemia of chronic kidney disease, in dialysis and pre-dialysis patients
• Chemotherapy-induced anaemia in non-myeloid malignancies
• Reduction of allogeneic transfusion in elective surgery
• Anaemia of prematurity (EU) and of HIV treatment with zidovudine (United States)

Antibodies to epoetin can neutralise endogenous erythropoietin and cause pure red cell aplasia, a rare but serious event that shaped biosimilar requirements: the EU asked for immunogenicity data in the subcutaneous route in renal patients before allowing it. Comparative programmes use analytical similarity with emphasis on glycosylation, pharmacokinetic and pharmacodynamic studies in healthy volunteers using reticulocyte and haemoglobin response, and comparative efficacy in renal anaemia by both routes.

Epogen was licensed by FDA on 1 June 1989 (BLA 103234), with Procrit as the same product under a different name; Eprex was approved nationally in EU member states from 1988 and has no centralised number. Sandoz's Binocrit, with the Hexal and Medice brands, became the first EU epoetin biosimilar in August 2007, and Stada's Silapo and Hospira's Retacrit, as epoetin zeta, followed in December 2007. Retacrit reached the US in May 2018. India's first epoetins, from Wockhardt (2001) and Intas and Shantha (2005), predate the published CDSCO lists.

Sources: Purple Book (S016), EMA medicines data (S017), CDSCO lists (S011 to S014); Indian launch history from company and press reports.

Epoetin is where biosimilar regulation was invented: the first EU biosimilar guidelines were written around it, and the pure red cell aplasia episode with a reformulated Eprex in 2002 taught every regulator that small process changes matter. It is also the deepest Indian segment in this register, with more than a dozen firms holding manufacturing or import permissions, and Binocrit is registered in the UAE alongside Eprex.