Filgrastim biosimilars

Non-glycosylated recombinant methionyl human granulocyte colony-stimulating factor of 175 amino acids and about 18.8 kDa, produced in Escherichia coli. It differs from the native protein by an N-terminal methionine and the absence of O-glycosylation.

Binds the G-CSF receptor on committed myeloid progenitors and mature neutrophils, driving proliferation, differentiation and release of neutrophils from the marrow and enhancing their function. It also mobilises CD34+ haematopoietic stem cells into peripheral blood, the basis of its use before stem cell collection.

Given subcutaneously or intravenously; peak concentrations two to eight hours after subcutaneous injection and a half-life of about 3.5 hours, so it is dosed daily until neutrophil recovery. Clearance is largely neutrophil-mediated and falls during neutropenia.

5 micrograms per kg daily by subcutaneous injection during chemotherapy-induced neutropenia, 10 micrograms per kg daily for stem cell mobilisation, in 300 microgram and 480 microgram pre-filled syringes or vials.

• Reduction in the duration of neutropenia and the incidence of febrile neutropenia in cytotoxic chemotherapy
• Reduction in the duration of neutropenia after myeloablative therapy and bone marrow transplantation
• Mobilisation of peripheral blood progenitor cells
• Severe chronic neutropenia
• Persistent neutropenia in advanced HIV infection (EU)
• Hematopoietic subsyndrome of acute radiation syndrome (United States)

Anti-filgrastim antibodies are rare and neutralising antibodies have not been reported. Comparative programmes rely on analytical similarity, pharmacokinetic and pharmacodynamic equivalence in healthy volunteers using absolute neutrophil count and CD34+ cells, and comparative safety and immunogenicity in breast cancer patients; a comparative efficacy study is no longer expected by FDA or EMA.

Neupogen was licensed by FDA on 20 February 1991 (BLA 103353) and approved in EU member states nationally from 1991. Because it predates the centralised procedure it has no EMA product number, though its biosimilars do. The first G-CSF biosimilars, Ratiograstim, Tevagrastim and Biograstim, were authorised in the EU in September 2008, and Zarxio became the first biosimilar of any molecule approved in the United States on 6 March 2015. India's first filgrastim biosimilars, from Intas and Reliance, reached the market in 2004 and 2007, before the published CDSCO lists begin.

Sources: Purple Book (S016), EMA medicines data (S017), CDSCO lists (S013, S014); Indian launch history from company and press reports.

Filgrastim is the origin story of biosimilars: the first EU G-CSF biosimilars in 2008, the first US biosimilar of any kind in 2015, and a mature market where PK/PD data now carry the approval. For an Indian developer it is the most crowded domestic segment after insulin, with dozens of brands and import permissions dating back to 2008, and margins that reward manufacturing scale rather than clinical differentiation. In the UAE two EU-sourced products, Zarzio and TevaGrastim, sit alongside Neupogen.