The zebrafish are native to rivers in India and Bangladesh. They have been quite popular as ornamental fish in USA. At the National University of Singapore in the late 1990s, Dr. Zhiyuan Gong and his associates extracted a protein from a jellyfish and inserted the gene into the zebrafish genome. The idea was to make them fluoresce in the presence of toxins. The GM (genetically modified) zebra fish was being developed as a tool to detect pollutants and toxins in water. However, Yorktown Technologies, Austin, Texas, USA dubbed the fish ‘Glofish’ and marketed them as tropical aquarium fish for ornamental purposes. Thus, Glofish became the first genetically engineered pet!
Technology platforms are the springboards for creating new products that provide marketing successes. For e.g., capsule technology has created many pharmaceutical formulations of various drugs, and big businesses are built on the capsule technology platform. Today, the most robust futuristic technology platform for mega business prospects is rDNA technology. The market is still not crowded, there are hefty margins. There is no commoditization in this field like chemical or natural ingredient based pharmaceuticals or healthcare products. rDNA tech is still a mysterious tech.
DNA, fundamental molecule of life
DNA is the name of a molecule that occurs in the nuclei of cells. It also occurs in viruses (that do not have nuclei). DNA is the fundamental molecule of life. It has information in the form of codes for all the characteristics or traits of an organism. For e.g.., actress Aishwarya Rai has a DNA code in her cell for her beautiful eyes!
DNA molecules combine with certain proteins to become chromosomes. The chromosomes are stained easily by certain dyes and stand out when seen through microscope. The 46 chromosomes (i.e., 23 pairs) in the human cell refers to the 3 billion base pairs of DNA. Chromosomes are made up of DNA. The no. of chromosomes is fixed for a species. For e.g., human cells have 23 pairs or 46 chromosomes. Potato cells have 48 chromosomes. Rabbit has 44 chromosomes.
Similarly, genes are parts of the DNA molecule. A gene is a sequence of the DNA molecule. Normally, a single gene codes for a specific trait. So, to summarize:
DNA - the basic information molecule with a double helical structure in humans, makes up the chromosomes. Genes are parts of the DNA molecule.
So each portion of a DNA molecule codes for something - a trait or a process in the cell. If you identify and isolate a portion of the DNA molecule responsible for say producing insulin and introduce it in to the genetic structure of a compatible bacterium or yeast cell, then it is possible that the host bacterium or yeast cell will start manufacturing insulin and express it in large quantities out of the cell in to the fluid outside. Or the insulin may remain in the cytoplasm of the host cell.
The insulin thus manufactured by the yeast or bacterial cell can then be extracted out, isolated, purified, suitably formulated, and administered to patients. This is crudely the rDNA tech process...
The rDNA concept
The word recombinant in rDNA refers to an organism or cell in which genetic recombination (new genetic combination) has been occurred. New genetic combinations (recombination) occur naturally during reproduction in the offspring. The offspring has new genetic combinations that are not present in the parents. So, genetic recombination does occur in nature through reproduction.
Today, scientists use rDNA technology to do what nature does - i.e....., create new genetic combinations in cells. rDNA technology creates new genetic combinations usually in yeasts like Saccharomyces cerevisiae or bacteria like Escherichia coli using certain genetic engineering techniques. Thus, an alteration in genetic structure of the yeast cell or bacterium is done using rDNA technology.
Why alteration is done using rDNA technology?
In the pharmaceutical field, this genetic modification is done, to use the 'new yeast cells' or the 'new bacterium' to manufacture large quantities of therapeutic chemicals - usually proteins - that have health and commercial value. These therapeutic proteins expressed by the genetically modified yeast cells or bacteria are extracted, formulated usually in ampoules for injections and marketed to doctors for administration to suitable patients.
Role of enzymes in creating rDNA products
Enzymes (all enzymes are proteins) are important chemical reactants or accelerators of chemical reactions that are used in large quantities to manufacture the rDNA tech products. The types of enzymes used are mainly restriction enzymes (that scissor DNA strands at specific points), and ligases (that restitch the DNA). Thus, the rDNA tech is an interplay of DNA and enzymes.
To put the rDNA concept in an over simplified form, the required DNA sequence (that codes for say manufacturing insulin, the peptide hormone) is cut out and stitched in to the DNA of a compatible yeast cell or bacterium. This genetically modified yeast or bacterial cell then starts manufacturing the protein of pharmaceutical interest (for e.g., insulin the peptide hormone).
Recombinant insulin and recombinant erythropoietin are two popular rDNA tech products:
rDNA human insulin is manufactured usually using Escherichia coli (a gram negative bacterium) or sometimes yeast. The manufacturing is through a complex process utilizing DNA synthesizers, fermenter tanks, centrifuges etc. In 2007, the worldwide market for human insulin products was US $ 10.2 billion.
rDNA erythropoietin is used to stimulate production of red blood cells in the management of anaemia due to chronic kidney disease and cancer chemotherapy. In 2007 the market for this product (erythropoietin stimulating agents market) was $ 11.7 billion. The rDNA based pharma products enjoy a worldwide multi billion dollar market.
There are many types of rDNA products - they are mainly proteins such as hormones and blood factors.
DNA synthesizers
DNA synthesizers have their origin in the human genome project. This was the international scientific project that mapped the entire human genetic information. The human genome project determined the complete structure of the human DNA molecule and the functions. rDNA technology has its roots in the methods used in the human genome project. DNA synthesizers too are based on the methods used by scientists of the human genome project.
DNA synthesizers are machines that use a strand of DNA as a blueprint and they manufacture required DNA strands in large quantities that are in turn used in rDNA tech product manufacture.
Tech application in agriculture
Bt cotton and Bt brinjal are important rDNA tech based agri products. Bt crops contain nonplant genes in plants. Bt stands for Bacillus thuringiensis. This bacterium produces crystal proteins that are lethal to insect larvae. Thus, Bt crystal protein genes (i.e.., bacterial genes) have been transferred to cotton, soya, brinjal, and corn using rDNA techniques so that these plants can produce the crystal proteins to protect themselves from pests like American boll worm and European corn borer. Hence, Bt cotton and Bt brinjal are described as pest resistant plants. These are exceptional plants that contain bacterial genes for pest resistance.
Hence, Bt brinjal is called a GM food (genetically modified food). The commercial marketeers of Bt brinjal claim it to be safe. rDNA tech based pharmaceutical products have to undergo a battery of preclinical and clinical trials, and continue to have a long term phase 4 postmarketing surveillance clinical study to monitor safety and efficacy.
Endnote
Whether one likes or dislikes, technological change is a part of modern society. rDNA tech products are making their sure entry into the pens of prescribers. rDNA tech - based products are high value products with high growth. They address the medical management needs of clinicians not addressed earlier. So it is important that the Indian pharma industry continues appreciating the rDNA tech platform to power ahead in the field of biosimilars and biotech products.
-The author is manager –marketing and training, Juggat Pharma
(Pharma Division of Jagdale Industries Ltd), Bangalore