Medicinal Chemistry: What is It?
As an interdisciplinary science that connects various disciplines such as organic chemistry, pharmacology, biochemistry, biology and medicine, medicinal chemistry aims to discover, design and develop new bioactive compounds suitable for therapeutic use. Specifically, these compounds are known as pharmaceutical drugs and have a variety of positive and negative effects on the functioning of the human body. For example, they may be used to prevent or treat diseases, alleviate the symptoms of health conditions, or even assist in medical diagnostics.
Image Courtesy of The University of Sydney.
These pharmaceutical drugs can be classified according to their physical and chemical properties, nature of administration, and therapeutic effects. Because most drugs are organic compounds, their properties depend on the functional groups present in their molecules, which alter the polarity of the molecule. Drugs with many polar groups are generally water-soluble and can be administered orally (i.e. ingested by mouth). However, some chemical compounds are unstable in the highly acidic gastric juice of the stomach and must be administered rectally (i.e. in the form of suppositories or enemas), parenterally (i.e. injected under the skin through a subcutaneous injection), injected into muscle tissue (i.e. an intramuscular injection), or injected directly into the bloodstream (i.e. an intravenous injection). The latter is the fastest way the drug will be distributed throughout the body, producing the most rapid therapeutic results. Lastly, some volatile or highly dispersed drugs can be taken through inhalation (i.e. breathed in through the nose or the mouth), while nonpolar compounds are often administered transdermally (i.e. applied to the skin in the form of patches, ointments, or therapeutic baths) because they are insoluble in water.
The therapeutic effects of pharmaceutical drugs depend on the chemical structure and the nature of the drug administration. They can affect the physiological state, impacting metabolism, consciousness, activity level, and coordination of the body. Additionally, they can alter mood and emotions or change the perception of sensory information. However, particular drugs may have little to no effect on the patient but instead target specific pathogenic organisms within the patient’s body or perform purely diagnostic functions.
It is important to note that certain pharmaceutical drugs may be notorious for producing side effects despite their numerous positive therapeutic effects; they interfere with biological processes, so no drug is entirely safe or free from non-beneficial effects on the human body. For instance, aspirin increases the risk of gastrointestinal bleeding while opiates are addictive and often become substances of abuse. Any drug can be toxic if used in excess, leading to an overdose. Nevertheless, insufficient doses or irregular use of antibiotics can lead to drug tolerance and or antibiotic resistance. Therefore, every pharmaceutical drug must be administered with caution and only in the recommended amounts.
At the molecular level, pharmaceutical drugs interact with the binding sites of enzymes, or cellular receptors, which are proteins composed of two amino acids. By binding to enzymes, most drugs act as inhibitors, reducing the enzymes' activity through competitive and non-competitive mechanisms. If a drug binds to a cellular receptor, the cell responds to this chemical message by altering its state or allowing specific molecules to pass through the cell membrane. Although the structures of actual drugs and their target receptors or enzymes do not match exactly, efficient binding can be achieved by slight conformational changes of both the binding site and the drug molecule. The nature and strength of binding can be affected by the chemical modification of specific functional groups of the drug.
Oncology Pharmaceutics
Unfortunately, cancer is a fast-growing phenomenon that currently touches a substantial portion of our society. In high-income countries, most of the population is affected by it, whether it be directly or indirectly, in some way, shape or form. However, through the practice of oncology pharmacy, evidence-based and patient-centred care is provided to those living with it to raise the success and comfort levels of treatment options.
In particular, numerous drug therapies operate in various ways to destroy cancerous cells, which divide at a constant pace, producing solid tumours or contaminating blood with abnormal and cytotoxic cells, which impair the functioning of internal organs. Most are systemic – travelling through the bloodstream and positively altering cancer cells at any location in the body. These therapies often have the potential to decrease the speed of their growth and spread. Primarily, chemotherapy is used to destroy or slow down the development of these harmful cells; this reduces their distribution to other parts of the body.
Hormonal drug therapy reduces the growth of cancers using natural sex hormones, such as uterine, breast and prostate cancer (e.g. estrogen, progesterone, and testosterone). This type is proven to stop cancer cells from using these hormones to grow or prevent hormone production that is causing cancer growth. Immunotherapy can reinforce the immune system’s ability to fight cancer. Targeted therapy utilizes pharmaceutical drugs to target specific molecules (e.g. proteins or genes) in cancerous cells to stop them from spreading; this reduces the damage to normal, healthy cells. Ultimately, supportive drugs prevent, manage or relieve side effects from either cancer or the treatments.
Pharmaceutical drug therapies are used alone or in conjunction with other treatments – in adjuvant, neoadjuvant or concurrent treatment. Adjuvant therapy occurs when drugs are administered to destroy any cancerous cells remaining in the body after surgery or radiation therapy, reducing cancer recurrence risk. Neoadjuvant therapy is utilized to reduce the size of a cancerous tumour before surgery or radiation treatment. This alleviates the difficulty in removing the tumour during these other treatments. Concurrent therapy occurs in concurrence with other therapies (e.g. certain chemotherapy drugs may be given when the patient undergoes radiation therapy to increase the cells’ sensitivity to the radiation). These treatments are given in cycles, allowing for a rest period in which normal cells can recover.
A medical oncologist typically decides which pharmaceutical drugs to use based on:
The type of cancer
The stage of cancer
The patient’s age
The overall health of the patient (ie. if there are any other health issues)
The previous types of cancer treatments or any treatment plans
The patient’s preference
Image is Courtesy of Cancer Today.
Case Study: Chemotherapy for Leukemia
Leukemia is a type of cancer of the bone marrow, blood and lymphatic system. Although many forms exist, the uncontrolled growth of abnormal cells produced by the bone marrow which reduces one’s red blood cells and increases white blood cells (e.g. lymphocytes and monocytes), can be reduced by chemotherapy.
This use of anti-cancer drugs are injected into a vein, under the skin or into cerebrospinal fluid, or drugs may be ingested orally. Thus, these drugs may enter the bloodstream and reach all areas of the body, which is useful for cancers like leukemia which affect all areas of the body.
Image is Courtesy of Cleveland Clinic.
References
Acute myeloid leukemia (aml). (n.d.). Retrieved February 05, 2021, from https://my.clevelandclinic.org/health/articles/6212-adult-acute-myeloid-leukemia
Chemotherapy and other drug therapies - Canadian Cancer Society. (n.d.). Retrieved February 05, 2021, from https://www.cancer.ca/en/cancer-information/diagnosis-and-treatment/chemotherapy-and-other-drug-therapies/?region=on
Types of prescription drugs. (n.d.) Retrieved February 05, 2021, from https://www.usarx.com/types-of-prescription-drugs
Leukemia-patient version. (n.d.). Retrieved February 05, 2021, from https://www.cancer.gov/types/leukemia
Lombardino, J., & Lowe, J. (n.d.). The role of the medicinal chemist in drug discovery - then and now. Retrieved February 05, 2021, from https://www.nature.com/articles/nrd1523
Nhs choices. (n.d.). Retrieved February 05, 2021, from https://www.nhs.uk/conditions/chemotherapy/
Article Author: Aneri Buch
Article Editors: Edie Whittington, Stephanie Sahadeo