Monoclonal antibodies: what the "-mab" medicines are

Monoclonal antibodies (often abbreviated as mAbs) are laboratory-engineered molecules designed to mimic or enhance the immune system's natural defence mechanisms. Unlike traditional chemical drugs synthesised in laboratories, mAbs are complex biological medicines produced from living cells. They have become a cornerstone of modern therapeutics, used across a wide range of conditions from autoimmune disorders to various cancers. If you have ever noticed a medicine name ending in the letters "-mab", it belongs to this distinct class of biological therapies.

How monoclonal antibodies are made

The human immune system naturally produces antibodies to identify and neutralise foreign threats like bacteria and viruses. Monoclonal antibodies are designed to target a single, specific marker—known as an antigen—on a cell or pathogen. To create them, scientists first identify the specific antigen they want to target. They then expose an animal's immune system, historically a mouse, to this antigen to stimulate the production of the desired antibody. The antibody-producing white blood cells are harvested and fused with immortal tumour cells to create a continuously dividing cell line called a hybridoma. This hybridoma acts as a microscopic factory, churning out identical (monoclonal) copies of the antibody.

Modern techniques often use recombinant DNA technology to produce fully human or humanised antibodies in large bioreactors, which reduces the likelihood of the patient's immune system rejecting the treatment. Because they are large, complex proteins, mAbs cannot be absorbed intact from the digestive tract. Therefore, they cannot be taken as simple pills and are usually administered via injection or intravenous infusion directly into the bloodstream.

Decoding the "-mab" naming system

The names of monoclonal antibodies follow a specific formula established by the World Health Organization (WHO) for International Nonproprietary Names (INNs). The stem "-mab" at the end of a name always indicates a monoclonal antibody. The letter immediately preceding this stem indicates the source of the antibody: "-o-" for mouse, "-xi-" for chimeric (part mouse, part human), "-zu-" for humanised, and "-u-" for fully human.

Further towards the front of the word, an infix describes the medicine's target or the disease it addresses. For example, "-tu-" indicates a tumour target, "-li-" an immunomodulatory target, and "-vi-" a viral target. Breaking down a well-known medicine name like trastuzumab reveals "-mab" (monoclonal antibody), "-zu-" (humanised), and "-tu-" (tumour). This systematic naming provides clinicians and researchers with immediate clues about a medicine's biological composition and intended target.

Broad uses across disease areas

Monoclonal antibodies have transformed the management of numerous diseases. In oncology, they are used to bind to specific proteins on the surface of cancer cells, flagging them for destruction by the immune system or blocking signals that tell the tumour to grow. In autoimmune conditions, such as certain types of arthritis, mAbs can be designed to bind to and neutralise overactive inflammatory proteins, helping to quiet an immune system that is mistakenly attacking healthy tissue.

They are also increasingly used in infectious diseases; for example, some mAbs are designed to neutralise viruses like respiratory syncytial virus (RSV) or SARS-CoV-2. Because of their precision and clinical value, several monoclonal antibodies are included in the WHO Essential Medicines List (EML), which guides national governments on the most critical medicines required for a basic health system.

Why mAb medicines are costly

Despite their therapeutic value, monoclonal antibodies are generally among the most expensive medicines on the market. The cost stems largely from their highly complex manufacturing process. Unlike small-molecule chemical drugs that are synthesised in predictable batches, mAbs are grown in living cells. These cells require carefully controlled environments, specific nutrient broths, and constant monitoring. Furthermore, biological molecules are sensitive to temperature and handling, requiring an unbroken cold chain from the manufacturer to the patient.

Research and development for mAbs also involve lengthy and expensive clinical trials. In South Africa, all biological medicines, including mAbs, must be rigorously evaluated and registered by the South African Health Products Regulatory Authority (SAHPRA). Due to their production costs, they often carry a high Single Exit Price. However, as patents expire, the introduction of biosimilars—highly similar biological versions of the original product—is beginning to improve affordability and access globally. You can explore registered biological medicines and their pricing by using the search functions on HealthSA.