We used RFD2-MI (Figure 1A, B) to design binders to phosphopeptide targets central to cellular signaling: 1) CD3ε, a component of the T-cell receptor, 2) two sites on epidermal growth factor receptor (EGFR), a potent oncogene, and 3) insulin receptor (INSR), a regulator of glucose metabolism dysregulated in diabetes. Here, INSR is linked to diabetes mellitus.