The invention relates to cyclic peptide derivatives, to their use in medicine, to compositions containing them, to processes for their preparation and to intermediates used in such processes. More particularly the invention relates to cyclic peptide C5a receptor antagonists of formula (Ia)or formula (Ib), or pharmaceutically acceptable salts thereof, wherein R1a, R1b, R2, R3 and R4 areas defined in the description. C5a receptor antagonists are potentially useful in the treatment of a wide range of 1 disorders, including inflammatory disorders and immune disorders.