Creating an uptake forecast for a first-in-class product is fraught with uncertainty. So far in this series of papers on uptake, we have covered how the Bass uptake model distils prescriber behavior into two coefficients: innovation (p) and imitation (q). For a me-too brand, it is simple to determine the values of these two coefficients because you can use analogues. But for a first-in-class product, there is rarely an obvious analogue. This short paper reveals three evidence-based and consistent drivers for predicting the coefficients of innovation and imitation when forecasting first-in-class products.