{"entity":{"id":"small-molecule","kind":"term","name":"Small molecule drug","aka":["small molecule","small molecules","small-molecule inhibitor","small-molecule drug","oral targeted drug","chemical drug"],"tldr":"A small molecule drug is a chemically made medicine small enough to slip inside cells, so it can usually be taken as a tablet.","summary":"A small molecule is a drug built by chemical synthesis rather than grown in living cells. Its molecules are hundreds of times lighter than an antibody, which lets them cross cell membranes and reach targets inside the cell, such as kinases, DNA repair enzymes and survival proteins. Most kinase inhibitors, PARP inhibitors, BCL2 inhibitors and hormone blockers are small molecules, and so is almost every classic chemotherapy drug.\n\nBecause they are stable and absorbed from the gut, small molecules are usually tablets or capsules taken at home, which is why so much of modern targeted therapy is oral. The trade-offs are the flip side of the same chemistry: they are cleared by liver enzymes, so food and other medicines can change their levels; they can bind related proteins and cause off-target side effects; and a single mutation in the target can stop them binding, which is a common route to resistance.\n\nThe other big class is biologics: antibodies, antibody-drug conjugates, bispecifics and cell therapies. These are made in cells, given by infusion or injection, and act mainly on targets at the cell surface or in the blood. Many treatment plans combine both, for example a small-molecule inhibitor with an antibody, or chemotherapy with a checkpoint inhibitor. The rule-of-thumb properties that predict whether a small molecule will be absorbed by mouth were set out by Lipinski and by Veber, and still guide drug design.","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Small_molecule","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Small_molecule"}],"tags":[],"related":[],"cancers":[],"sections":[],"technologies":["kinase-inhibitors","protac-degrader","peptide-drug-conjugate","cytotoxic-chemotherapy"],"targets":[],"drugs":["imatinib","osimertinib","olaparib","venetoclax"],"companies":[],"institutions":[],"pathways":[],"terms":["antibody","monoclonal","targeted-therapy-term"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":["paper-veber-oral-bioavailability-jmedchem-2002"],"journals":[],"dependsOn":[],"notes":[],"category":"Treatment jargon"},"route":"/terms/small-molecule/","neighbours":{"technology":[{"id":"cytotoxic-chemotherapy","kind":"technology","name":"Cytotoxic chemotherapy","route":"/technologies/cytotoxic-chemotherapy/"},{"id":"peptide-drug-conjugate","kind":"technology","name":"Peptide-drug & small-molecule-drug conjugates","route":"/technologies/peptide-drug-conjugate/"},{"id":"protac-degrader","kind":"technology","name":"PROTACs & molecular glues (targeted protein degradation)","route":"/technologies/protac-degrader/"},{"id":"kinase-inhibitors","kind":"technology","name":"Small-molecule kinase inhibitors","route":"/technologies/kinase-inhibitors/"}],"drug":[{"id":"imatinib","kind":"drug","name":"Imatinib","route":"/drugs/imatinib/"},{"id":"olaparib","kind":"drug","name":"Olaparib","route":"/drugs/olaparib/"},{"id":"osimertinib","kind":"drug","name":"Osimertinib","route":"/drugs/osimertinib/"},{"id":"venetoclax","kind":"drug","name":"Venetoclax","route":"/drugs/venetoclax/"}],"term":[{"id":"antibody","kind":"term","name":"Antibody","route":"/terms/antibody/"},{"id":"monoclonal","kind":"term","name":"Monoclonal","route":"/terms/monoclonal/"},{"id":"targeted-therapy-term","kind":"term","name":"Targeted therapy","route":"/terms/targeted-therapy-term/"}],"paper":[{"id":"paper-veber-oral-bioavailability-jmedchem-2002","kind":"paper","name":"Veber 2002: molecular properties that influence the oral bioavailability of drug candidates","route":"/key-papers/paper-veber-oral-bioavailability-jmedchem-2002/"}]}}