What is clinical genomics?
Clinical genomics is a new and rapidly-changing field. Knowledge of the human genome is far from complete, but there are already uses for genetic and genomic information in the clinic.
Genome sequencing is expected to have the most impact in: characterising and diagnosing genetic disease; stratifying (better categorising) patients for appropriate cancer treatment; and providing information about an individual’s likely response to treatment to reduce adverse drug reactions.
Characterising and diagnosing inherited disease
Every baby born in Australia is offered screening for approximately 30 genetic conditions (the Guthrie test) and more than 300 tests for genetic disorders are available through the healthcare system.
Clinicians worldwide are beginning to embrace genome sequencing to search for variants implicated in undiagnosed genetic diseases and using this information to guide treatment. In one of the most dramatic cases, a young boy underwent a risky, but seemingly successful, bone marrow transplant that was proposed in response to molecular data.
Stratifying cancer for better treatment
A major focus of genomic medicine is cancer diagnosis and therapy. Clinicians are beginning to use genomic information to predict how a person's cancer will respond to drug therapy or surgery. In some cases, clinicians will profile the DNA and RNA of tumour cells to guide the use of existing treatments or focus on more targeted treatments.
At this stage, some patients have been spared costly and complex procedures based on a molecular diagnosis. Tumour development in a few patients has been stabilised – for a time, at least – by targeting specific molecules or pathways in the tumour cells.
Within Australia, useful information is being compiled by the Australian Pancreatic Cancer Genome Initiative (APGI), the Australian arm of an international consortium formed to catalogue the genetic changes of the 50 most common cancers.
Predicting drug response and reducing adverse drug reactions
In Australia, the Therapeutic Goods Administration received 14,200 cases of severe adverse drug reaction in 2010. Up to 80% of adverse reactions are of unknown origin – thought to be mostly due to genetic differences in either the targets of the drugs or in the enzymes involved in their breakdown.
Currently, only a handful of DNA tests for variants implicated in drug metabolism have been recommended for use in Australia. The first of these approved in Australia was for the drug abacavir, which is used to treat HIV infection, but causes a potentially life-threatening allergic reaction in 5-8% of patients. There are many more applications for pharmacogenomic tests for prescribing drugs such as antidepressants, painkillers, and anticoagulants. The number of recommended tests is expected to rise, as the US Food and Drug Administration list contains more than 100 drugs that are labelled with information about markers that may change the way an individual responds.
Other expected uses of genomic information in the clinic
In the near future, researchers expect to gather a broad range of variants that will be clinically useful. Interestingly, the application of genomic medicine may not be limited to typically genetic conditions.
Almost every disease has a genetic component: different people react differently to parasites, viruses and bacteria according to the information encoded in their genome. Comprehensive profiles of an individual’s genetic data, integrated with common clinical markers, are expected to provide new insights into genetic and infectious disease.
Additional references and commentaries:
Dinger M, Terrill BN (2016). A user’s guide to the human genome (PDF). O&G Magazine.
Gaff C. and Waring P (2014) Cheap genome tests to predict future illness? Don’t hold your breath. The Conversation.
Somogyi A (2013). Pharmacogenomics explains why some medicines may not work for you. The Conversation.
Check Hayden E (2011). Genome study solves twins' mystery condition. Nature. doi:10.1038/news.2011.368.
Johnson M, Gallagher K (2010). One in a Billion: A Boy's Life, A Medical Mystery. JSOnline: Milkwaukee Wisconsin Journal Sentinel.
National Health and Medical Research Council (2011). Clinical Utility of Personalised Medicine. (PS0001). Australian Government.
Maher B (2011). Human genetics: Genomes on prescription. [News Feature]. Nature 478:22-24. doi: 10.1038/478022a.
Mardis ER (2010). The $1,000 genome, the $100,000 analysis? Genome Medicine 2:84.