Among 21 human SCLC cell lines...the combination of lurbinectedin with the ataxia telangiectasia and Rad3-related protein (ATR) inhibitors ceralasertib and berzosertib showed a greater than additive effect in SLFN11-low models....Opposite to single agent lurbinectedin (Figure 1C), cell lines with lower SLFN11 expression had better responses to the combination of lurbinectedin and ceralasertib (i.e., smaller ΔAUC values; P=0.068, Figure 3C) or berzosertib (P=0.101, Figure S3C). All three cell lines in which a greater than additive response to the combination of lurbinectedin and ceralasertib or berzosertib was observed were in the SLFN11 low group, and were relatively resistant to single agent ceralasertib or berzosertib.