## 4 Examples of Commercial Targeted Libraries
### SARS-CoV-2- or COVID-19-Targeted Libraries
#### 4.1.5 TargetMol  
The library contains compounds shown to be active against coronavirus or possessing a broad-spectrum antiviral activity. The molecules were obtained by molecular docking screening against seven SARS-CoV-2 target proteins and one human (ACE2) target protein. The library was extended by virtual screening of the natural products obtained from traditional Chinese medicinal plants (Figure 7).  
Figure 6: Process algorithm for generating the LifeChemicals SARS-CoV-2-targeted molecular library.  
For each library described, we performed an analysis of the most common molecular descriptors that were found to be relevant [80]: Molecular Weight (MW), Total Polar Surface Area (TPSA), SlogP, number of hydrogen bond acceptors (HBA), number of hydrogen bond donors (HBD), number of rings present and the number of rotatable bonds (Table 2). Compound retention when passing through each individual filter was assessed, as well (Table 3), with the results for joined filter provided in Figure 8.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Database** & **No. of** & **MW** & **TPSA** & **SlogP** & **HBA** & **HBD** & **No. of** & **No. of** & **Rotatable** \\  **Name** & **Compounds** & **MW** & **TPSA** & **SlogP** & **HBA** & **HBD** & **Rings** & **Bonds** \\ \hline Chembridge & 16,777 & 391.5 \(\pm\) 62 & 80 \(\pm\) 26 & 3.2 \(\pm\) 1.5 & 4.9 \(\pm\) 1.7 & 1.4 \(\pm\) 1.0 & 4.3 \(\pm\) 0.8 & 3.9 \(\pm\) 1.4 \\ Enamine & 16,800 & 362 \(\pm\) 61 & 79.3 \(\pm\) 21 & 2.7 \(\pm\) 1.2 & 4.5 \(\pm\) 1.4 & 1.58 \(\pm\) 0.8 & 3.1 \(\pm\) 0.8 & 5.1 \(\pm\) 1.8 \\ LifeChemical & 7311 & 404 \(\pm\) 75 & 84.8 \(\pm\) 23 & 3.1 \(\pm\) 1.4 & 5.8 \(\pm\) 1.8 & 1.4 \(\pm\) 0.9 & 3.6 \(\pm\) 0.9 & 5.6 \(\pm\) 1.9 \\ Otava & 9018 & 383 \(\pm\) 56 & 77.3 \(\pm\) 20 & 3.7 \(\pm\) 1.0 & 5.2 \(\pm\) 1.5 & 1 \(\pm\) 0.8 & 3.9 \(\pm\) 0.8 & 4.0 \(\pm\) 1.5 \\ TargetMol & 2448 & 460 \(\pm\) 211 & 110 \(\pm\) 151 & 2.6 \(\pm\) 4.6 & 6.6 \(\pm\) 4.0 & 2.2 \(\pm\) 3.2 & 3.6 \(\pm\) 1.5 & 7.5 \(\pm\) 4.8 \\ Joined SARS-CoV-2-Targeted Library & 52,354 & 385 \(\pm\) 79 & 81 \(\pm\) 40 & 3.1 \(\pm\) 1.7 & 5.0 \(\pm\) 1.9 & 1.4 \(\pm\) 1.1 & 3.7 \(\pm\) 1.0 & 4.7 \(\pm\) 2.1 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Analysis of the most important descriptors for the SARS-CoV-2-targeted library.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Chembridge** & **Enamine** & **LifeChemicals** & **Otava** & **TargetMol** \\ \hline Unfiltered & 16,777 & 16,800 & 7311 & 9018 & 2448 \\ \hline Isolated filter: & \multicolumn{4}{c}{Number of filtered out compounds (\%)} \\ \hline REOS & 1160 (7\%) & 4565 (27\%) & 1414 (19\%) & 1486 (17\%) & 858 (35\%) \\ PAINS & 454 (3\%) & 267 (2\%) & 11 (-0\%) & 430 (5\%) & 248 (10\%) \\ Aggregators & 9053 (54\%) & 6702 (40\%) & 4002 (55\%) & 6784 (75\%) & 1445 (60\%) \\ Lipinski Ro5 & 258 (2\%) & 193 (1\%) & 380 (5\%) & 5 (-0\%) & 522 (21\%) \\ All filters & 10,000 (60\%) & 9412 (56\%) & 4937 (68\%) & 7202 (80\%) & 1887 (77\%) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Analysis of the attrition rate of various filters for the SARS-CoV-2-targeted library.  
Figure 7: Process algorithm for generating the TargetMol SARS-CoV-2-targeted molecular library.