7Antimicrobial peptides (AMPs) are naturally occurring or synthetic peptides that show promise for treating 8 antibiotic-resistant pathogens. Machine learning techniques are increasingly used to identify naturally occurring 9AMPs, but there is a dearth of purely computational methods to design novel effective AMPs, which would speed 10 AMP development. We collected a large database, Giant Repository of AMP Activities (GRAMPA), containing 11 AMP sequences and associated MICs. We designed a convolutional neural network to perform combined 12 classification and regression on peptide sequences to quantitatively predict AMP activity against Escherichia coli. 13Our predictions outperformed the state of the art at AMP classification and were also effective at regression, for 14 which there were no publicly available comparisons. We then used our model to design novel AMPs and 15 experimentally demonstrated activity of these AMPs against the pathogens E. coli, Pseudomonas aeruginosa, and 16Staphylococcus aureus. Data, code, and neural network architecture and parameters are available at