Compounds comprising peptides capable of binding C3 protein and inhibiting complement activation are disclosed. The compounds comprise compstatin analogs in which the N-terminus and/or C-terminus contains an added component that improves (1) the peptide's solubility at physiological pH; (2) the peptide's plasma half-life; (3) the peptide's intraocular retention; and/or (4) the peptide's binding affinity to C3 or its fragments as compared to an unmodified compstatin peptide under equivalent conditions. Pharmaceutical compositions and methods of using the compounds are also disclosed.