Synthesis and biological evaluation of dual actioncyclo-RGD/SMAC mimetic conjugates targeting α_vβ₃/α_vβ₅integrins and IAP proteins

Abstract

The rational design, synthesis and in vitro biological evaluation of dual action conjugates 11-13, containing a tumour targeting, integrin αvβ3/αvβ5 ligand portion and a pro-apoptotic SMAC mimetic portion (cyclo-RGD/SMAC mimetic conjugates) are reported. The binding strength of the two separate units is generally maintained by these dual action conjugates. In particular, the connection between the separate units (anchor points on each unit; nature, length and stability of the linker) influences the activity of each portion against its molecular targets (integrins αvβ3/αvβ5 for cyclo-RGD, IAP proteins for SMAC mimetics). Each conjugate portion tolerates different substitutions while preserving the binding affinity for each target.

Synthesis and Biological Evaluation of RGD Peptidomimetic–Paclitaxel Conjugates Bearing Lysosomally Cleavable Linkers

“…[ [17][18][19] Notably, the RGD-PTX conjugate 7, besides showing the worst inhibition of biotinylated vitronectin binding to integrin a v b 3 in the series, did not allow us to obtain reproducible binding curves to a v b 5 integrin. This unusual behavior is possibly due to the low solubility of conjugate 7 in the medium, which might interfere with the binding process, especially at the highest concentration (10 À5 m).…”

“…These compounds were activated as Nhydroxysuccinimidyl esters and coupled with the integrin ligand cyclo[DKP-RGD]-CH 2 NH 2 (2), as previously reported by our group. [17,19] Conjugation was performed at a controlled pH value, because the reaction does not proceed at pH < 7.0, whereas the hydrolysis of the NHS ester significantly competes with the desired amidation process at pH > 7.6. In all of the conjugation reactions of our RGD peptidomimetic with the NHS esters, the pH value was maintained in the 7.3-7.6 range by adding aliquots of 0.2 m aqueous NaOH to the reaction mixture.…”

“…[6] Several peptides and peptidomimetics bearing the RGD sequence have been reported to show high affinity for the receptor, [7] and the structural basis for this recognition was provided by a v b 3 -integrin cocrystallization with the cyclopentapeptide Cilengitide. [8] Due to their ability to selectively bind integrin receptors, RGD ligands have been conjugated to a number of cytotoxic agents (for example, doxorubicin, [9,10] doxsaliform, [11] monomethylauristatin E, [12] camptothecin, [13] cisplatin, [14] paclitaxel [15] ) and to proapoptotic compounds, [16,17] with the aim to target these drugs at integrin-rich tumor tissues.…”

Synthesis, Characterization, and Biological Evaluation of a Dual‐Action Ligand Targeting αvβ3 Integrin and VEGF Receptors

“…We thus designed a new dual‐action ligand (compound 5 in Figure ) targeting integrin α V β 3 and VEGFR. As integrin binding moiety, we exploited cyclo [DKP‐RGD]‐CH 2 NH 2 ( 2 ) (Figure ), a functionalized analog of ligand 1 that we had previously used for conjugation to paclitaxel and SMAC mimetic molecules . As VEGFR ligand moiety we selected the α‐helical decapentapeptide 3 (Figure ), recently reported by D′Andrea and co‐workers, because of its simple preparation and efficacy in inhibiting angiogenesis in vivo.…”

Redefining the role(s) of endothelial αvβ3-integrin in angiogenesis

“…Several have also been conjugated to RGD peptides. Another promising example is the chemical synthesis of a proapoptotic SMAC mimetic conjugated to an RGD-mimetic [45]. Another promising example is the chemical synthesis of a proapoptotic SMAC mimetic conjugated to an RGD-mimetic [45].…”