US regulators have issued a green light for the first biosimilar of AbbVie's biologic Humira, the world second best-selling drug.

Amgen's Amjevita has been cleared for all eligible indications of its reference product, including moderate-to-severe rheumatoid arthritis, moderate-to-severe polyarticular juvenile idiopathic arthritis, psoriatic arthritis, ankylosing spondylitis, moderate-to-severe chronic plaque psoriasis, adult moderate-to-severe Crohn's disease and moderate-to-severe ulcerative colitis.

The approval follows analytical, nonclinical, pharmacokinetic and clinical data showing biosimilarity between Amjevita and Humira, including results from two Phase III studies conducted in moderate-to-severe plaque psoriasis and moderate-to-severe rheumatoid arthritis patients which met their primary endpoint showing clinical and safety equivalence.

Humira, an anti-TNF monoclonal antibody, pulls in annual sales of nearly $15 billion across its range of indications for inflammatory diseases. While pricing data aren't yet available, Amgen's offering is expected to be significantly cheaper and thus has the potential to generate substantial savings for healthcare providers.

However, the company may not be able to launch its drug until 2022, because AbbVie is claiming that Amjevita infringes patent protection on Humira that is valid until 2022. The firms are currently battling the issue in the US Court for the District of Delaware.

According to AbbVie, "whereas AbbVie has spent decades of research and vast resources on the development of Humira [adalimumab], Amgen seeks to copy AbbVie's work and ignore AbbVie's patents", and "while the Biosimilar Price Competition and Innovation Act gives Amgen an abbreviated regulatory pathway for its biosimilar version of Humira, it does not give Amgen license to infringe AbbVie's patents."