Last week, we registered the 250 millionth unique substance in CAS REGISTRY® - a short strand of genetic material comprised of both DNA and RNA. Hybrid oligonucleotides like this may have important application in quality control assays required for state-of-the-art mRNA drugs and vaccines, including those recently developed for COVID-19.
Assigned CAS Registry Number® 2627558-64-7, the 250 millionth substance was disclosed in a Moderna, Inc. patent application recently published by the World Intellectual Property Organization (WO 2021/055811 A1 ).

Chemically modified to prevent degradation, this oligonucleotide binds to a specific region of mRNA and “guides” enzymatic breakdown by RNase H. The resulting signature profile, detected using HPLC-UV or LC-MS, can be used by drug manufacturers to reveal any inadvertent degradation or other problems in the tested batch of mRNA. This system represents a breakthrough in providing the stringent quality control needed as scientists work to develop an increasing number of safe new therapeutic applications for mRNA.
Watch this video to see how mRNA vaccines uses our bodies’ cells to generate immunity.
Given the long history of CAS REGISTRY as the authoritative resource for information on small molecules, it is easy to overlook the large volume of nucleic acid and amino acid sequences the collection contains. As the focus on COVID-19 treatments and vaccines has highlighted, biologics have become a critical therapeutic modality - a trend reflected in the growing biosequence content available in CAS REGISTRY.
As we celebrate this major milestone, on behalf of all of the scientists, technologists and business leaders here at CAS, I offer our congratulations and sincere thanks to each of the countless individuals who have contributed to the multitude of unique discoveries these 250 million CAS Registry Numbers represent. Each is a small piece in the never-ending puzzle of knowledge that we all collectively pursue across the years.