Therapeutic compositions can include modified peptides which are derived from the chain of the Bbeta(15-42)-fibrin fragment and wherein one or several of the amino acids of the sequence have been substituted by genetically encoded or not genetically encoded amino acids or peptidomimetics. They may exist as free peptides or as C-terminal derivative and/or being linked to a polyethylene glycol (PEG)-polymer, and have anti-inflammatory and/or endothelium stabilizing effects. Esters or amides may for instance be taken into consideration as C-terminal derivatives. Processes for production of the peptides and derivatives thereof are also described.