Therapeutic proteins are engineered proteins used to treat or prevent diseases such as cancer, diabetes, and cardiovascular disorders by replacing missing proteins, enhancing existing pathways, or novel functions. Therapeutic proteins include haemostasis factors, thrombolytic agents, hormones, and recombinant vaccines. The development of chimeric and humanised antibodies, along with antibody fragments, has a crucial role in modern therapeutics by enhancing precision treatment and minimising immune rejection. It also emphasises microbial transformation processes and cell surface display technologies that enhance drug development and delivery mechanisms. Vaccine development includes DNA-based approaches, along with efficient ways to produce antibodies and enzymes on a large scale. Hence, DNA-based vaccines have become a valuable technique for protecting against infectious diseases. Current Good Manufacturing Practice (cGMP) and Good Laboratory Practice (GLP) guidelines ensure that research and production are done safely, correctly, and meet quality standards. This chapter highlights the in-depth knowledge about therapeutic proteins and their classes, biotechnology, microbiology, chimeric and humanised antibodies, and their therapeutic applications.