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Monoclonal antibodies are one of the most fastly developing areas of specific therapy for cancer, infectious, autoimmune and demyelinating diseases. The main targets of monoclonal antibodies in autoimmune and demyelinating diseases are T and B-lymphocytes, cytokines, complement, and adhesion molecules. In the field of neurodegenerative diseases, the largest number of studies has been carried out in patients with Alzheimer's disease, in which monoclonal antibodies are targeted to brain aggregates of beta-amyloid. This review presents new therapeutic approaches to the use of antibody fragments, with a focus of their new class, nanobodies. A special attention is paid to new anti-CD20 and anti-CD19 monoclonal antibody drugs in multiple sclerosis (ocrelizumab, ofatumumab) and neuromyelitis optica (inebilizumab). Ocrelizumab is the first medication that proved to be effective in primary progressive multiple sclerosis. There have been significant advances in the treatment of neuromyelitis optica: the first multicenter study of Inebilizumab (MEDI-551) is currently underway.

Countering the spread of new respiratory infections and reducing the damage they cause to society requires efficient strategies for rapidly developing of targeted therapeutics, such as monoclonal antibodies. Nanobodies, defined as variable fragments of heavy-chain camelid antibodies, have a set of characteristics that make them particularly convenient for this purpose. The speed at which the SARS-CoV-2 pandemic spread confirmed that the key factor in the development of therapeutics is obtaining highly effective blocking agents as soon as possible, as well as the diversity of epitopes to which these agents bind. We have optimized the selection process of blocking nanobodies from the genetic material of camelids and obtained a panel of nanobody structures with affinity to Spike protein in the lower nanomolar and picomolar ranges and with high binding specificity. The subset of nanobodies that demonstrate the ability to block the interaction between the Spike protein and the cellular ACE2 receptor was selected in experiments in vitro and in vivo. It has been established that the epitopes bound by the nanobodies are located in the RBD domain of the Spike protein and have little overlap. The diversity of binding regions may allow a mixture of nanobodies to retain potential therapeutic efficacy towards new Spike protein variants. Furthermore, the structural features of nanobodies, particularly their compact size and high stability, indicate the possibility of their utilization in the form of aerosols.