Anti-inflammatory activity of c(ILDV-NH(CH2)(5)CO), a novel, selective, cyclic peptide inhibitor of VLA-4-mediated cell adhesion

1 Small, N- to C-terminal cyclized peptides containing the leucyl-aspartyl- valine (LDV) motif from fibronectin connecting segment-1 (CS-1) have been i nvestigated for their effects on the adhesion of human T-lymphoblastic leuk aemia cells (MOLT-4) to human plasma fibronectin in vitro mediated by the i ntegrin Very Late Antigen (VLA)-4 (alpha(4)beta(1), CD49d/CD29). 2 Cyclo(-isoleucyl-leucyl-aspartyl-valyl-aminohexanoyl-) (c(ILDV-NH(CH2)(5) CO)) was approximately 5 fold more potent (IC50 3.6+/-0.44 mu M) than the 2 5-amino acid linear CS-1 peptide. Cyclic peptides containing two more or on e less methylene groups had similar potency to c(ILDV-NH(CH2)(5)CO) while a compound containing three less methylene groups, c(ILDV-NH(CH2)(2)CO), was inactive at 100 mu M. 3 c(ILDV-NH(CH2)(5)CO) had little effect on cell adhesion mediated by two o ther integrins, VLA-5 (alpha(5), beta(1), CD49e/CD29) (K562 cell adhesion t o fibronectin) or Leukocyte Function Associated molecule-1 (LFA-1, alpha(L) beta(2), CD11a/CD18) (U937 cell adhesion to Chinese hamster ovary cells tra nsfected with intercellular adhesion molecule-1) at concentrations up to 30 0 mu M. 4 c(ILDV-NH(CH2)(5)CO) inhibited ovalbumin delayed-type hypersensitivity or oxazolone contact hypersensitivity in Balb/c mice when dosed continuously from subcutaneous osmotic mini-pumps (0.1-10 mg kg(-1) day(-1)). Maximum in hibition (approximately 40%) was similar to that caused by the monoclonal a ntibody PS/2 (7.5 mg kg(-1) i.v.) directed against the alpha(4) integrin su bunit. 5 c(ILDV-NH(CK)5CO) also inhibited oxazolone contact hypersensitivity when dosed intravenously 20 h after oxazolone challenge (1-10 mg kg(-1)). Ear sw elling was reduced at 3 h and 4 h but not at 1 h and 2 h post-dose (10 mg k g(-1)). 6 Small molecule VLA-4 inhibitors derived from c(ILDV-NH(CH2)(5)CO) may be useful as antiinflammatory agents.