Personalized Medicine

In this series of articles, medical students from across the country will discuss a range of topics from medical ethics to the NHS to public health to medical conditions to clinical governance.

Personalized medicine uses a person’s individual genetic makeup or genome to determine their reaction to drugs or any other form of treatment. With this information, healthcare professionals will be able to tailor treatment plans to the individual patient, increasing the chances of success of that treatment exponentially.


The Need for Personalized Medicine:

Personalized medicine is the need of the future. In 2003, a Glaxo chief (multinational British pharmaceutical company) admitted that the drugs they made for Alzheimer’s worked on less than 1 in 3 patients and drugs for migraines worked in just about half of the patients. The main reason for this is that recipients of these drugs may have specific genes that interfere with the intended functioning of the drug. An example of this is a form of cytochrome P450 (CYP2D6) which controls the metabolism of around 25% of drugs in the market, currently. CYP2D6 controls the metabolism of codeine to its active form, morphine. Codeine is therefore ineffective in individuals who are poor metabolizers. On the other hand, some people are very good metabolizers and metabolize codeine extremely fast which is fatal. If we had information about our individual genetic makeup and used that to consume drugs complementary to our genome, such instances would be reduced.


Personalized Medicine in the Modern Day:

Although personalized medicine seems like a technological advancement in the distant future, we already use personalized medicine in our current healthcare setting - although it has great capability to be improved. Herceptin is a pioneering drug, making use of this approach. Around 30% of breast cancers are caused due to the overexpression of HER2 (Human Epidermal Growth Factor Receptor 2) and are known as HER+ tumours. Herceptin blocks the activity of HER2 and is therefore effective in HER+ tumours. This approach means that patients don’t need to immediately undergo chemotherapy, radiotherapy or surgery. This is why breast cancer patients are first tested for HER2 overexpression before discussing treatment options. This approach is cheaper, faster, more effective and has a high success rate. By identifying HER+ tumours and prescribing Herceptin, resources can be allocated to patients who need it more therefore improving the quality of care for all patients.

Currently, companies are developing personalized immunotherapy to treat cancers - specific to the person and tumour. Neoantigens are peptides or fragments of protein found on the cancer cell surface due to genetic mutations. These are optimal therapeutic targets as they are selectively present on the cancer cell surface and not on normal cells. Neoantigens are unique to every single patient and next-generation sequencing has now made it possible to identify the mutations present in every cancer cell of every patient. Biopharmaceutical companies are working on new approaches within cancer immunotherapy such as neoantigen-targeting vaccines, which are both patient and tumour specific. The ability to sequence cancer genomes, identify targets specific to each cancer patient and reengineer their own immune system to attack the tumour is a revolutionary step towards personalised medicine.


Drawbacks of Personalized Medicine:

A major concern with personalized medicine is the loss of patient privacy. A patient’s genetic information would be available in the public domain. Knowing which diseases a patient is susceptible to, insurance companies can refuse to insure those patients or increase their premiums - defeating the purpose of medical insurance companies.

The costs of analyzing every patient’s genome and then creating personalized drugs, currently, is too high. This means that only the rich and privileged will be able to afford these treatments leading to inequitable healthcare provision which healthcare systems around the world have been trying to reduce for years.

Lastly, for personalized medicine to come into existence, we still need to do a lot of research on the human genome and the genetic differences between humans. The Human Genome Project was an important first step in this direction. However, like many other research studies, this project also focused on the European male population, not representing women and minorities proportionately. Ethnicity is an important factor leading to differences in genomes and unless we account for that, personalized medicine will not be available to everyone.


Summary:

  • Personalized medicine is the tailoring of treatments to a patient’s individual genetic make-up (genome).

  • Herceptin is a pioneering drug, making use of this approach - inhibiting HER2, which is overexpressed in almost 30% of breast cancers.

  • Despite being very beneficial in the prevention of disease, there are drawbacks of personalized medicine such as the loss of patient privacy, lack of representation of minorities and women and high costs that cannot be ignored.



Further Reading:


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