Distinct drug activity patterns can be detected for individual samples and patient groups of interest. (A) RR PDX (n = 12) samples exhibit general resistance to conventional clinical compounds but remain sensitive to some experimental drugs. (B) Primary RR patients (n = 5) tested before last salvage therapy demonstrate persistent resistance to standard chemotherapy and individual sensitivity to experimental molecules. All responses are represented as IC₅₀ (log[nM]) and are compared with other diagnostic and relapse ALL patients depicted in the background. **P < .005 (2-sided Student t test); *P < .05.