Therapeutic proteins are biologically-derived molecules, such as enzymes, antibodies, cytokines, or hormones, that are used to treat various diseases and conditions. These proteins can be isolated from natural sources or produced using recombinant DNA technology, where the gene encoding the protein of interest is inserted into a host organism, such as bacteria, yeast, or mammalian cells, to express the protein.

Therapeutic proteins have a wide range of applications in medicine due to their high specificity, potency, and ability to modulate biological processes. Some examples of therapeutic proteins include:

1. Enzyme replacement therapy: In some genetic disorders, such as lysosomal storage diseases, enzyme deficiencies lead to the accumulation of toxic substances in cells. Therapeutic enzymes can be used to replace the missing or non-functional enzyme, helping to break down the accumulated substances. Examples include imiglucerase for Gaucher disease and agalsidase beta for Fabry disease.
2. Monoclonal antibodies: These proteins are engineered to specifically recognize and bind to target antigens on the surface of cells or other molecules. Monoclonal antibodies have diverse applications, such as targeting cancer cells, modulating immune responses, and neutralizing pathogens. Examples include trastuzumab for HER2-positive breast cancer, adalimumab for autoimmune diseases, and palivizumab for the prevention of respiratory syncytial virus (RSV) infection in high-risk infants.
3. Cytokines and growth factors: These proteins play critical roles in regulating immune responses, cell growth, and tissue repair. Therapeutic cytokines and growth factors can be used to boost the immune system, stimulate the production of blood cells, or promote wound healing. Examples include interferon-alpha for hepatitis C treatment, erythropoietin for anemia, and granulocyte colony-stimulating factor (G-CSF) for neutropenia.
4. Hormones: Hormone replacement therapy can be used to treat hormone deficiencies or imbalances. Examples include recombinant insulin for diabetes, human growth hormone for growth hormone deficiency, and follicle-stimulating hormone (FSH) for infertility treatment.
5. Blood clotting factors: Inherited bleeding disorders, such as hemophilia, can be treated with recombinant clotting factors. Examples include recombinant Factor VIII and Factor IX for hemophilia A and B, respectively.
6. Anticoagulants and thrombolytic agents: These proteins can be used to prevent or treat blood clots in various conditions, such as deep vein thrombosis, pulmonary embolism, or stroke. Examples include recombinant tissue plasminogen activator (tPA) for the treatment of acute ischemic stroke and recombinant antithrombin III for hereditary antithrombin deficiency.

Despite their advantages, therapeutic proteins also have some limitations, such as potential immunogenicity, a short half-life, and high production costs. Continued research and development in protein engineering, formulation, and delivery technologies are expected to improve the safety, efficacy, and accessibility of therapeutic proteins for a wide range of medical applications.