AV-1101 is an analogue of phenbutazone, a non-steroidal anti-inflammatory that was tested in the late 1980s as an AIDS treatment in France. It has an immunosuppressive effect. It is being developed by A-VIRAL, a Norwegian biotechnology company.

AV-1101 is thought to have two modes of action:

• a direct effect on HIV replication (target site unknown)

• an effect on CD4 cell proliferation by means of preventing lymphocyte activation

Dr Frank Miedema, an immunologist who has published extensively on the mechanisms of CD4 cell loss in HIV disease, has proposed that AV-1101 may be a useful treatment for its ability to remove CD4+RO (memory) cells from the circulation. Miedema has hypothesised that the preponderance of memory cells over naﶥ cells suppresses the production of naive cells; if this block is removed by a period of immunosuppressive treatment which can specifically target lymphocytes, naﶥ cell production from the bone marrow can be resumed.

In vitro studies suggest a tendency towards neutropenia at doses above 10mg/kg.