Biopharmaceutical Assignment On Rituxan Production, Structure And Uses

Introduction

Both pharmaceuticals and biological products are heavily dependent on in modern society. However, with advancements in technology and resources, scientists are focusing more and more on the importance of bio-pharmaceuticals. These products are typically large molecular weight & extremely complex molecules that are derived from living organisms. The coding DNA for these complex molecules can be isolated and extracted from one organism and inserted and expressed in another. These are known as transgenic organisms and can produce a biological product that can exhibit therapeutic effects. Biotechnology involves multiple pathways for biologics to serve a purpose through the use of gene therapy, hybridoma technology, recombinant DNA and more.

The use of these complex technologies has allowed bio-pharmaceutical companies such as Roche, Pfizer and Sanofi to manufacture lifesaving drugs and dominate the pharmaceutical industry as a whole. Roche has 4 of the top 10 biologicals in the world in 2017. They have generated over 25 billion dollars in revenue from these 4 drugs in 2017 alone. This demonstrates the importance of new age drugs in the world today. One of the drugs they produce is called Rituxan.

Rituxan backround

Rituximab (trade name) or Rituxan (generic name) is a genetically engineered chimeric monoclonal antibody manufactured and sold by a Roche subsidiary known as Genentech. It was approved for usage in the US by the FDA in 1997. The patent expired in 2015 & now there are a couple of biosimilar products available. Nabil Hanna who worked at Biogen was the primary researcher on this antibody and is accredited for its discovery. The drug is currently on the “World health organization’s list of essential medicines”. Rituximab is a very complex molecule that has been genetically engineered using Chinese Hamster Ovaries (CHOs). It has a molecular weight of 145kD.

FDA approval

The biopharmaceutical drug Rituxan was approved by Jay P. Siegel, M. D of the Food and Drug administration on the 26th November 1997 via an FDA approval letter. The letter was addressed to Dr. MacFarlane of Genentech Inc. The letter stated that the manufacturer Genentech were” authorized to manufacture and ship for sale, barter or exchange in interstate and foreign commerce Rituximab under department of Health and Human services biologics licence No. 1048”. The letter from the FDA essentially authorized Genentech to formularize, manufacture and sell their commercial biologic via 10ml and 50ml vials. The letter also states that all promotional claims must be consistent with the approved labelling and packaging. ProductionRituximab is a chimeric antibody meaning that it contains both human and mouse antibodies. It is produced in a laboratory using genetically engineered clones of B cells. The antigen that Rituxan has an affinity for is CD20 which is found on the surface of matured B cells. The region located on the tip of the Y branch are derived from mouse antibodies and the rest of the antibody comes from a human sequence. The human element helps reduce the immune response. Rituximab is produced by means of recombinant DNA technology. The DNA of interest is inserted into mammalian CHO cells, known as the host organism. The cells are suspended in a nutrient culture media along with the antibiotic Gentamicin. This antibody is not detectable in the final product. The CHO cells are placed in a huge bioreactor and undergo a fermentation process in order to increase the biomass and in turn the total amount of viable cells. As biomass increases, the CHO cells produce and secrete the product meaning that the liquid contains the product of interest.

The actual production of this impure product falls under the category of upstream processing. After a number of days or cell life cycles, the liquid is removed and purified using a number of chromatographic techniques such as Ion exchange chromatography and Diafiltration. These two techniques separate substances based on their charge and size. Once the product is of sufficient purity and is deemed safe it is then packaged and stored. This whole process requires an extremely high level of sterility to ensure the product is safe and effective. As of 2018 the drug is sold via 10ml vials with a concentration of 10mg/ml. A single dose of Rituxan can cost upwards of $13,000! Figure 1: represents the production process of Rituximab.

Structure

Rituximab has a chimeric antibody structure meaning that it is comprised of a human IgG1 and kappa chain constant regions as well as a variable light and heavy chain from a murine antibody. The murine part of the antibody is responsible for binding selectively to CD20 antigen. Rituxan has a molecular weight of 145 Kilo Daltons. Mechanism of action Rituxan is highly specific to CD20 antigen on B-cells. CD20 is a transmembrane protein found on B-cells. CD20 is said to help regulate the influx and efflux of Ca2+ ions across cell membranes and allow the activation of b lymphocytes. Rituxan attracts complement proteins that cause cell destruction by lysis and phagocytosis. The drug recruits macrophages which releases inflammatory and cytotixic mediators that promote phagocytosis. Rituxan also causes natural killer cells (NK) to latch onto the membrane proteins and cause cell lysis. This can aid in the destruction of malignant cells caused by ailments such as Non-Hodgkin’s Lymphoma.

The safe use of Rituxan can lead to elimination of B cells (destroying cancerous cells in the process) and allow newer, healthier sets of B cells to develop. This is a form of anti CD20 therapy and can result in the regression of malignancies. It is also believed that the use of Rituxan can increase the patient’s sensitivity to other forms of treatment such as chemotherapy.

Diseases associated with Rituxan

Non-Hodgkin’s lymphoma (NHL) is a type of cancer that develops from lymphocytes. Lymphomas affect the body’s lymphatic system which is a part of the overall immune system. The immune system is the body’s defence against pathogens and foreign substances. Lymphomas can originate in multiple places in the body such as lymph nodes, spleen, bone marrow etc.

Symptoms of NHL include fever, weight loss, bone pain, tiredness and enlarged lymph nodes. Potential causes of NHL include exposure to infectious agents such as HIV, Epstein barr virus, exposure to chemicals like polychlorinated biphenyls and autoimmune diseases such as Lupus and Rheumatoid arthritis. Rheumatoid arthritis (RA) is an autoimmune disease which affects joints. Causes of this autoimmune disease are unclear but genic and environmental factors are said to play a key role. Symptoms of this disease include painful, swollen, stiff joints usually on the hands and wrists. The body’s own immune system attacks the joints causing the synovial fluid in joints to inflame and thicken. RA can be diagnosed using X-rays along with presence of certain symptoms.