In 2015 Barack Obama announced that the American government would invest hundreds of millions of dollars in a “precision medicine initiative”. Although doctors and scientists were thrilled at such a forward-thinking programme, patients could be forgiven for wondering why modern medicine, with all its clever science, isn’t precise already. The problem is that humans are as individual and varied as their fingerprints. Sometimes this wonderful variation does not matter and the drugs that doctors prescribe, such as antibiotics, painkillers and statins, work nicely. At other times this variation matters a great deal. It can mean the difference between success or failure in treating a disease, and it can lead to dangerous, or even fatal, side-effects.
It is this sort of human variation—which might come from underlying genetic differences, or subtleties in the metabolites found inside cells—that precision (or “personalised”) medicine hopes to tackle in order to cure diseases more effectively. Although Mr Obama’s initiative is just getting started, there has been plenty of progress and there is plenty more to expect. Personalised medicine is already having a huge impact on oncology. These days cancer is seen less as a disease of specific organs. Rather, doctors are now classifying it according to molecular mechanisms caused by the mutation of specific genes. So drugs that have been created for colorectal cancer, say, may turn out to be useful for an entirely different part of the body, such as the breast.
What all this means is that genetic and molecular information is fast becoming essential to the way cancers are monitored and treated. It is already quite common to do genetic tests on cancer biopsies. The range and scope of these tests are growing with every month, as is understanding of their results and potential applications. For example, one new test can identify when women who have been diagnosed with breast cancer might be safe to skip the gruelling process of chemotherapy. The test looks at the activity of genes that control the growth and spread of cancer, and can identify women with a low risk of recurrence of cancer and little to gain from chemotherapy.
DNA tests such as Oncotype DX and MammaPrint are among the advances which will help doctors pick treatments. A recent trial found that in one in five patients with advanced cancer, DNA tests could identify therapies that slowed down their tumours. Similarly it now looks likely that genetic testing will help identify those with advanced prostate cancer whose disease is caused by mutations in DNA-repair genes, in which case a different kind of drug could be called for. Personalised medicine also looks promising in deciding who might benefit from some of the powerful but expensive new immuno-oncology drugs, which seem to work only in a subset of patients.
Many companies are developing “liquid biopsies”—blood tests that seek to monitor the way that cancers respond to treatment. Unlike a conventional biopsy, they can be done frequently without harm to the patient. With multiple companies such as Foundation Medicine, Qiagen, Genomic Health and Myriad Genetics all developing liquid biopsies, patients can expect to see them arriving in the clinic in the next year or two.
The design of drugs, too, is getting more personalised. Researchers are getting excited about a new generation of CAR-T drugs. T-cells (special immune cells) are extracted from cancer patients and implanted with new genes by a custom-built virus. When the t-cells are reintroduced into the patient, this causes them to home in on the patient’s particular cancer. It is a highly personalised and very potent treatment, and not without risk. But Kite Pharma, a biotech company, is hoping to bring its drug KTE-c19—for refractory, aggressive non-Hodgkin lymphoma—to market in 2017.
Medicine has a long way to go before the genetic basis of cancer is fully unravelled. The meaning of some of the genomic variations that can be detected is not yet understood; some genetic tests will reveal variation that a doctor has no way of interpreting. Nonetheless, the ability to do a blood test for cancer opens up the possibility of using this to detect tumours before symptoms are even apparent, rather than just monitoring existing cancers in order to tailor treatments. The biggest manufacturer of DNA-sequencing machines, Illumina, has formed a company called Grail to develop such tests. Using “ultra-deep sequencing” to read DNA in a sample many tens of thousands of times, it hopes to pick up the hard-to-spot signals that might arise from a fragment of tumour circulating in the blood.
Decades from now, historians may look back and see 2017 as the year that precision medicine blossomed. Today 29% of health-care providers in America use it, according to HIMSS Analytics, a research firm. One day all doctors will, as the approach moves into areas beyond oncology. Neurology, for example, is crying out for a switch from disease types based on clusters of similar symptoms to ones based on genetic and molecular changes. Eventually, all medicine will be precision.