Compounds comprising R-G-Cysteic Acid (i.e., R-G-NH—CH(CH2—SO3H)COOH or Arg-Gly-NH—CH(CH2—SO3H)COOH) and derivatives thereof, including pharmaceutically acceptable salts, hydrates, stereoisomers, multimers, cyclic forms, linear forms, drug-conjugates, pro-drugs and their derivatives. Also disclosed are methods for making and using such compounds including methods for inhibiting integrins including but not necessarily limited to α5β1-Integrin, αvβ3-Integrin and αvβ5-Integrin, inhibiting cellular adhesion to RGD binding sites, preventing or treating viral or other microbial infections, inhibiting angiogenesis in tumors, retinal tissue or other tissues or delivering other diagnostic or therapeutic agents to RGD binding sites in human or animal subjects.