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By Emily Burke, Ph.D., Director of Instruction,  |  Oct 14, 2015

Personalized Medicine & Companion Diagnostics: What You Need to Know

Personalized medicine – also referred to as precision or stratified medicine – is already changing the way we diagnose and treat disease. As our ability to obtain and analyze large amounts of genetic data increases, so too will the range and power of these personalized tools.

Emily Burke,

Emily Burke,

The idea of personalized medicine is not new. Physicians have long known that patients vary in their responses to medicine, and have sought to optimize individual responses. The father of medicine, Hippocrates, writing more than two millennia ago, said “It is more important to know what sort of person has a disease,” wrote Hippocrates, “than to know what sort of disease a person has.”  But today, for the first time in human history, we have the tools available to make it personalized medicine a reality.

Twenty years ago, there were only four medicines on the market with genomic information on their label. Today, there are more than 100. These breakthroughs were made possible first by the completion of the Human Genome Project in 2003, and accelerated by advances in technology that have made sequencing individual patient genomes a realistic possibility. These new medicines and their accompanying diagnostics have increased both safety and efficacy by targeting specific patient populations most likely to benefit.

In this Real World Health Care series, we’ll examine specific examples of personalized medicines and diagnostics, and explain the technology that has made them possible.

Helpful Terms

Companion Diagnostic: A companion diagnostic is the test or measurement intended to assist physicians in making treatment decisions for their patients, usually by determining the efficacy and/or safety of a specific drug for a targeted patient group. For a list of all FDA-approved companion diagnostics, click here.

DNA Sequencing: Determines the order of every single base pair in a given gene (gene sequencing) or in an entire genome (whole genome sequencing).

Epidermal Growth Factor Receptors (EGFR): EGFR is found on the cell surface and is activated by growth factor binding. Once activated, EGFR activates enzymes inside the cell that drive the cell forward into cell division. EGFR overexpression is associated with a number of cancers, including lung cancer, anal cancers, and glioblastoma multiforme.

Gene Expression: The process cells use to read genetic information to make proteins. Because each cell in our body has the same genetic information, it is the differences in gene expression that determine what proteins a cell will end up producing. Gene expression differences are also associated with disease. For example, a type of cell or tissue may make too much or too little of a particular protein, which is the basis for many genetic disorders.

Monogenic Diseases: Changes in one gene cause the disease. Examples: sickle cell anemia, cystic fibrosis, and Huntington’s disease.

Personalized Medicine: Implies the development of medicines for an individual, based on their unique genetic, metabolic, microbiomic and other “signatures.”

Pharmacodynamics (PD): How a drug affects the body.

Pharmacokinetics (PK): How the body affects a drug.

Polygenic Disease: Caused by the interactions of many different genes. Examples: cancer, heart disease, Alzheimer’s disease and Parkinson’s disease. Polygenic diseases often have susceptibility genes associated with them, which increase the likelihood of the person developing the disease, but do not absolutely predict its development.

Precision Medicine: Dividing patient groups into specific populations and designing new drugs for those subtypes.

Prodrug: A drug given to patients in an inactive or less than fully active form.

Single Nucleotide Polymorphism (SNP): A one base difference in the DNA sequence of a gene when compared to the sequence found in the majority of the population. Many SNPs have no significant impact on an individual’s health, but others are associated with disease susceptibility.

Check back soon for the next article in our series on personalized medicine and companion diagnostics: an interview with Joshua P. Cohen, Ph.D., Research Associate Professor, Tufts Center for the Study of Drug Development.

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