The search for novel treatments and cures is an ongoing endeavour in the field of modern medicine. The potential of small molecules in the field of pharmaceuticals has drawn more and more research interest in recent years. Small molecules, as the name suggests, are compounds with a relatively low molecular weight. Unlike large chemical moieties or biological molecules such as proteins, small molecules can easily penetrate cell membranes making them ideal candidates for drug development. To put it simply, our cells are equipped with switches called receptors that are located on the cell membrane. These receptors act like the switches we encounter in our daily lives and play a vital role in controlling various molecular pathways within our bodies.
Most of the drug molecules can attach to specific receptors and, similar to how electrical activity regulates our routines, they have the ability to regulate specific molecular pathways. On the other hand, there are also small molecules that not only bind to the receptors on the cell membrane but also have the remarkable ability to enter the cell and connect with the internal circuitry. These small molecules act as multiple switches, allowing them to robustly control the molecular pathways. They possess the remarkable ability to interact with specific targets within cells, modulating the activity of proteins and enzymes crucial to disease pathways. One of the most significant advantages of small molecules lies in their versatility. Scientists can modify their chemical structure to enhance their effectiveness and fine-tune their properties. This flexibility allows for a wide range of applications across various therapeutic areas, from infectious diseases to cancer and beyond. As the history of pharmacology reveals, small molecules have revolutionised cancer treatment by targeting specific molecular aberrations driving tumour growth. Drugs like imatinib, commonly known as Gleevec, have transformed the landscape of chronic myelogenous leukemia (CML) treatment. By selectively inhibiting the activity of a mutated protein that fuels the disease, Gleevec has turned a once-fatal diagnosis into a manageable chronic condition for many patients. Antiviral drugs like oseltamivir (Tamiflu) have proven instrumental in mitigating the severity and duration of influenza infections.
From aspirin, the earliest and widely used synthetic drug, to the revolutionary discovery of Penicillin during World War II, these small pharmaceuticals have provided relief from pain, fought infections, and even contributed to societal changes. The introduction of Enovid in 1960, the first hormonal birth control pill, empowered women to take control of their fertility. In 1987, Retrovir marked a turning point in managing HIV, transforming it from a once-deadly infection to a manageable chronic condition. Xarelto, approved in 2008, revolutionised anticoagulant treatment, offering a more convenient oral option. Adempas, introduced in 2014, treated forms of pulmonary hypertension and Vitrakvi, launched in 2018, targeted specific genetic alterations in various cancers, representing a milestone in precision oncology. In the year 2021, the majority of newly approved drugs, accounting for 62% of them, consisted of small molecules. These included groundbreaking treatments for various medical conditions such as HIV, cancer, infections, heart and kidney disease, and neurological disorders. Several small molecules have gained approval in the year 2022 for various medical conditions. The emergence of new chemical modalities has further expanded the possibilities, allowing for the exploration of previously inaccessible drug targets. This exciting avenue opens up possibilities for treating genetic disorders at their root cause.
Despite their immense potential, some disadvantages should also be considered. One drawback is their potential for off-target effects. Due to their multiple binding sites and robust control, they may interact with unintended targets, leading to unwanted side effects. Additionally, their versatile nature can make it challenging to design small molecules that specifically target a particular pathway without affecting others. Delivery challenges hinder the effectiveness of small molecules, impeding precise targeting and concentration. Technological advancements like computer-aided drug design and high-throughput screening accelerate discovery. Despite hurdles, dedicated researchers offer hope to patients and families awaiting medical breakthroughs.
(The author is a research scholar at BIT, Mesra, Ranchi.)