Definition of proprietary
2: something that is used, produced, or marketed under exclusive legal right of the inventor or maker
specifically : a drug (such as a patent medicine) that is protected by secrecy, patent, or copyright against free competition as to name, product, composition, or process of manufacture
https://www.merriam-webster.com/dictionary/proprietary
"The presence in SARS-CoV-2 of a 19-nucleotide RNA sequence encoding an FCS at amino acid 681 of its spike protein with 100% identity to the reverse complement of a proprietary MSH3 mRNA sequence is highly unusual. Potential explanations for this correlation should be further investigated."
https://www.frontiersin.org/articles/10.3389/fviro.2022.834808/full
The SARs-CoV-2 virus (COVID-19) contains a proprietary (owned by Moderna) MRNA sequence.