13b-K for COVID-19

 13b-K has been reported as potentially beneficial for COVID-19 in the following study.
COVID-19 involves the interplay of 350+ viral and host proteins and factors providing many therapeutic targets. Scientists have proposed 10,000+ potential treatments. c19early.org analyzes 200+ treatments. We have not reviewed 13b-K in detail.
El Kilani et al., 13b-K and Nirmatrelvir Resistance Mutations of SARS-CoV-2 Main Protease: Structural, Biochemical, and Biophysical Characterization of Free Enzymes and Inhibitor Complexes, Crystals, doi:10.3390/cryst15090758
The SARS-CoV-2 main protease (Mpro) is a well-established target for antiviral drug development One such inhibitor, nirmatrelvir, in combination with ritonavir as a booster, has already been introduced into the market, under the name Paxlovid. However, being an RNA virus, SARS-CoV-2 is prone to the emergence of resistance mutations. A number of such mutations have been characterized, although they have not yet been shown to play a significant role in clinical settings; these include S144A, E166V, H172Y, and Q189K. We recombinantly produced these mutants and studied the corresponding proteins using X-ray crystallography, enzymology, and biophysical approaches. We discuss the potential of each mutant to lead to a widespread nirmatrelvir resistance scenario. We also demonstrate that one of our own inhibitors (13b-K), while showing some degree of cross-resistance with nirmatrelvir, exhibits much higher inhibitory activity against the Mpro carrying the E166V mutation.