Amongst the various therapeutic targets mentioned earlier mRNA i.e. 'sense strand' is the earliest target, which can be thought of to prevent the disease. Antisense technology is a novel drug discovery method. Antisense drugs work at the genetic level to interrupt the process by which disease-causing proteins are produced. Proteins play a central role in virtually every aspect of human metabolism. Almost all human diseases are the result of inappropriate protein production (or disordered protein performance). This is true of both host diseases (such as cancer) and infectious diseases (such as AIDS).

Antisense drugs can be designed to treat a wide range of diseases including infectious, inflammatory and cardiovascular diseases and cancer and have the potential to be more selective and, as a result, more effective and less toxic than traditional drugs.

Specific genes contain information to produce specific proteins. The information required for the human body to produce all proteins is contained in the human genome and its collection of more than 100,000 genes. Genes are made up of DNA, which contains information about when, and how much of which protein to produce, depending upon what function is to be performed.

The DNA molecule is a double helix – a duplex of entwined strands. During transcription of information from DNA into mRNA, the two complementary strands of the DNA partly uncoil. The 'sense' strand separates from the 'antisense' strand. The 'antisense' strand of DNA is used as a template for transcribing enzymes, which assemble mRNA – a process called 'transcription'. Then, using encoded information in mRNA amino acids are joined together to form specific proteins. This process is called 'translation'.

Antisense drugs are complementary strands of small segments of mRNA. To create antisense drugs, nucleotides are linked together in short chains (called oligonucleotides). Each antisense drug is designed to bind to a specific sequence of nucleotides in its mRNA target to inhibit production of the protein encoded by the target mRNA.

There are some basic differences between traditional drugs and antisense drugs in their designing and action. These become the advantages of antisense drugs over traditional drugs.

The design of antisense drugs is rapid and less complex. Rational drug design usually begins by characterising the three-dimensional structure of the protein target in order to design a prototype drug to interact with the target. Proteins, however, are complex molecules whose structure is difficult to predict. In contrast, antisense compounds are designed to bind to mRNA whose structures are more easily understood and predicted. Once the receptor sequence on the mRNA is identified, the three-dimensional structure of the receptor site can be defined, and the prototype antisense drugs can be designed.

Isis Pharmaceuticals, Inc. is the leader in the discovery and development of this exciting new class of therapeutic compounds based on antisense oligonucleotides. Isis has initiated programs to discover and develop antisense drugs active against a wide range of infectious, inflammatory and immune-mediated diseases and cancer. Isis' proprietary technology to discover and characterise novel oligonucleotide analogues has enabled its scientists to modify the properties of its oligonucleotide analog drug candidates for optimal use with particular targets and thus to produce a broad proprietary portfolio of compounds applicable to many disease targets.

The effectiveness of the antisense mechanism continues to be proven in the laboratory, in animal studies, and in human trials. To date, Isis has five antisense compounds in clinical trials and a rich pipeline of preclinical compounds.