Blisibimod (formerly AMG623) is a small protein that targets B-cell activating factor (BAFF), which is abnormally high in some B-cell mediated autoimmune diseases. BAFF is part of a group of proteins that are very important for the development, maintenance, and survival of B-cells, a type of white blood cells that make antibodies.

Blisibimod is currently being developed by Anthera for the treatment of IgA nephropathy, also known as Berger’s disease. Researchers believe it may also help treat ANCA vasculitis, an autoimmune disease characterized by the destruction and inflammation of small blood vessels.

How blisibimod works

Autoimmune diseases are characterized by an excessive production of B-cells, leading to the destruction of healthy tissue.

Blisibimod is a neutralizing therapeutic agent produced in bacteria that works by binding to BAFF that exists both in the cell membranes and in soluble form, inhibiting its interaction with its receptors. When BAFF is blocked, the number of B-cells decrease, producing fewer autoantibodies.

The advantage of blisibimod compared to similar molecules is that it has a unique structure, with four BAFF-binding sites. However, one limitation is that being completely synthetic, it may trigger an immune reaction where a neutralizing antibody response develops, reducing the potency of blisibimod.

Blisibimod research

Blisibimod has never been tested in people with ANCA vasculitis, but other BAFF blockers have, and blisimod is currently in clinical trials for other autoimmune diseases, including IgA nephropathy and systemic lupus erythematosus (SLE).

The unique structure of blisibimod showed a good safety and tolerability profile in people with SLE in Phase 1 and 2 studies (NCT02443506), (NCT02411136) and (NCT01162681). A Phase 3 study in people with SLE with higher disease activity (NCT01395745) has been completed, although it did not achieve its primary objective, based upon the SLE responder index-6 at 52 weeks.

A Phase 2/3 trial (NCT02062684) in people with IgA nephropathy is ongoing but not currently recruiting participants.

If the results of these trials are positive, this may suggest that blisimod may also be effective in people with ANCA vasculitis, but this remains to be tested.

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