Paul Ehrlich (Germany; 1854–1915), the founder of chemotherapy, postulated more than 100 years ago that chemicals, just as histologic dyes, have selectivity for certain components in cells and tissues, and, therefore, could be used to fight against specific human diseases if the culprit was identified and targeted.

This concept has inspired generations of cancer researchers to pursue drugs and biological products that selectively target cancer cells or molecular events that are believed to drive the malignant phenotype, while doing little damage to normal cells. The following chart summarizes almost 120 years of progress in targeted cancer therapy.