The QED score is determined using the RDKit implementation , and the hERG bioactivity score is a probability value given by an oracle (described in Appendix D), to which a probability flipping transformation is applied, ensuring that molecules with lower hERG bioactivity probabilities get higher reward scores. The hERG bioactivity objective here was considered among the non-data-driven descriptors since our focus in this experiment is not to fine-tune it. We leave the fine-tuning of multi-task target property predictors for future work.