Impact of the biomarker enrichment strategy in drug development

The application of Aptamer in biomarker discovery

Biomarkers are detectable molecules that can reflect specific physiological states of cells, organs, and organisms and therefore be regarded as indicators for specific diseases. And the discovery of biomarkers plays an essential role in cancer management from the initial diagnosis to the final treatment regime. Practically, reliable clinical biomarkers are still limited, restricted by the suboptimal methods in biomarker discovery. Nucleic acid aptamers nowadays could be used as a powerful tool in the discovery of protein biomarkers. Nucleic acid aptamers are single-strand oligonucleotides that can specifically bind to various targets with high affinity. As artificial ssDNA or RNA, aptamers possess unique advantages compared to conventional antibodies. They can be flexible in design, low immunogenicity, relative chemical/thermos stability, as well as modifying convenience. Several SELEX (Systematic Evolution of Ligands by Exponential Enrichment) based methods have been generated recently to construct aptamers for discovering new biomarkers in different cell locations. Secretome SELEX-based aptamers selection can facilitate the identification of secreted protein biomarkers. The aptamers developed by cell-SELEX can be used to unveil those biomarkers presented on the cell surface. The aptamers from tissue-SELEX could target intracellular biomarkers. And as a multiplexed protein biomarker detection technology, aptamer-based SOMAScan can analyze thousands of proteins in a single run. In this review, we will introduce the principle and workflow of variations of SELEX-based methods, including secretome SELEX, ADAPT, Cell-SELEX and tissue SELEX. Another powerful proteome analyzing tool, SOMAScan, will also be covered. In the second half of this review, how these methods accelerate biomarker discovery in various diseases, including cardiovascular diseases, cancer and neurodegenerative diseases, will be discussed.

Missing Companion Diagnostic for US Food and Drug Administration-Approved Hematological and Oncological Drugs

Within hematology and oncology, companion diagnostics (CDxs) play an increasing role in securing an optimal therapy for individual patients, and the US Food and Drug Administration (FDA) consider this type of assay essential for the safe and effective use of a corresponding therapeutic product. Most CDxs are developed prospectively using the drug-diagnostic codevelopment model, which normally secures the simultaneous approval of both drugs and diagnostics. A CDx assay is an important treatment decision tool that needs to be available simultaneously with the drug. However, within the past few years, several targeted drugs and new indications have been approved by the FDA without a CDx, despite the use of a predictive biomarker assay for patient selection during clinical development. A missing analytical and clinically validated CDx assay could affect the correct use of these drugs and ultimately patient safety. An alternative to FDA-approved or FDA-cleared CDxs could be to use a laboratory-developed test, which will normally miss documentation on the clinical validity. On the basis of the information available from different publicly available FDA databases, this article briefly discusses the issue of missing CDx assays in relation to the approval of hematological and oncological drugs and new indications.