What Is a Digital Twin in <scp>QSP</scp> , and Are We Doing It Right?

The field of Quantitative Systems Pharmacology continues to innovate new methods to derive insights from clinical data. In the past few years, Digital Twins have emerged as a "new" way of deriving patient-specific model parameterizations to inform possible outcomes for novel scenarios using limited clinical data. Here, we explore the meaning of Digital Twins for QSP, its relationship with definitions in other contexts, and principles guiding their efficient and correct generation using patient data.