Growth factor proteins and/or their receptors are overexpressed in many types of cancer, and hence development of their antagonists can hinder malignant tumor growth as a form of treatment in cancer therapy. Consequently, enantiomeric segments of both the epidermal growth factor (EGF) and vascular endothelial growth factor (VEGF-A) were synthesized for MIPD. A 12-residue linear D-peptide ligand for EGF, D-PI_4, was identified with both binding affinity and half-maximal inhibitory concentration (IC50) in micromolar range. In the case of VEGF-A, the mini-protein GB1 was used as a template scaffold to create a 56 residue D-mini-protein RFX001.D that has a binding affinity as low as 85 nM. A heterochiral protein complex between a vascular endothelial growth factor (L-VEGF-A) and a D-protein antagonist was also solved using racemic protein crystallography (Figure ), providing a foundation for structure-based optimization of the D-protein antagonist. Upon optimization, the binder RFX037.D was created, increasing both binding affinity (KD = 6 nM vs 85 nM) and thermal stability (Tm >95 °C vs 33 °C). Of note, RFX037.D was non-immunogenic in mice, whereas the L-enantiomer generated a strong immune response. In an extension of the MIPD against VEGF-A, bivalent D-protein ligands were also developed using orthogonal MIPD assays with two different scaffold mini-proteins (53 and 58 residues). The two best scaffolds were connected via a covalent linkage to yield the bivalent D-protein RFX-V1a2a, with sub-nanomolar (KD = 0.8 nM) affinity for VEGF-A.