藥物開發公司或團體引入臨床前檢測的新的待選藥物分子。盡管通常制藥工業只在決定NCEs產生的數量時，只對小有機分子中（傳統藥物）計數，NCEs也可以包括基因或基因片段，蛋白或多肽，或者小分子。制藥工業每年產生的NCEs的數量對公司保持發展的能力致關重要。最近人們意識到NCE短缺，希望基因組學、組合化學和高效篩選這些新技術的應用能改變這一不平衡。

New candidate drug molecules that are advanced into preclinical testing by the research arm of a drug discovery company or organization. NCEs may include genes or gene fragments, proteins or peptides, or small molecules, although typically the pharmaceutical industry has counted only small organic molecules (“classical” drugs) in their determination of the number of NCEs generated. The number of NCEs created by the pharmaceutical industry each year is critical to the ability of companies to maintain growth. An NCE deficit has recently been identified, and it is hoped that the application of new technologies such as genomics, combinatorial chemistry and high-throughput screening will redress the balance.