On Feb. 8, 2021, Tonix Pharmaceuticals announced it had received the written response from the U.S. Food and Drug Administration (FDA) to a Type B pre-investigational new drug (IND) meeting package describing its technology and plans to develop a diagnostic skin test, TNX-2100 (SARS-CoV-2 epitope peptide mixtures for intradermal administration), to measure the delayed-type hypersensitivity (DTH) reaction to SARS-CoV-2 (CoV-2), the virus that causes COVID-19.

TNX-2100 is designed to measure T cell immunity to CoV-2. There currently is no standardized laboratory test available to measure T cell immune responses to CoV-2. T cell immunity to CoV-2 persists longer than antibody immunity, is sometimes present in the absence of a measurable antibody response and is believed to provide an important element of protection against serious COVID-19 illness after infection with CoV-2.

TNX-2100 is a test comprising three different mixtures of synthetic peptides (TNX-2110, -2120 and -2130), which are designed to represent different protein components of the CoV-2 virus.