Using peptides to promote delivery and improve anti-tumour efficacy of liposomal drug

Liposomal drugs exhibit advantages for cancer therapy, but efficacy is often limited by their rapid clearance from blood by the reticuloendothelial system, and an inability to target and penetrate tumours. Interestingly, a 21-amino acid SIRP-α- (signal regulatory protein-α) interacting 'self' peptide is reported to inhibit uptake by phagocytes. Also, 'iRGD' a 9-amino acid cyclic peptide that binds αvβ3 integrins and neuropilin-1 (NRP-1), promotes targeting and penetration of drug into tumours. Here we explore the potential of nitrilotriacetic acid-ditetra-decylamine (NTA₃-DTDA)-containing liposomes (NTA-liposomes) engrafted with His-tagged forms of 'self' peptide (pCD47) to prolong circulation time in blood after iv administration, and of iRGD peptide (piRGD) to enhance treatment efficacy of doxorubicin-containing liposomes (Caelyx). Our results show that pre-incubation of murine phagocytic DC2.4 and RAW246.7 cells with pCD47 inhibits uptake of NTA-liposomes in vitro, but engraftment of pCD47 surprisingly reduces liposome lifetime in blood. Engraftment of piRGD promoted binding of NTA-liposomes to murine B16 melanoma and CT26 colorectal carcinoma cells in vitro. Importantly, iv administration of piRGD-engrafted Caelyx was found to significantly inhibit tumour growth and prolong survival in both B16 and CT26 murine tumour models. Our results show that engraftment of piRGD onto Caelyx is a convenient strategy to enhance treatment efficacy.

iRGD Peptide as a Tumor-Penetrating Enhancer for Tumor-Targeted Drug Delivery

The unique structure and physiology of a tumor microenvironment impede intra-tumoral penetration of chemotherapeutic agents. A novel iRGD peptide that exploits the tumor microenvironment can activate integrin-dependent binding to tumor vasculatures and neuropilin-1 (NRP-1)-dependent transport to tumor tissues. Recent studies have focused on its dual-targeting ability to achieve enhanced penetration of chemotherapeutics for the efficient eradication of cancer cells. Both the covalent conjugation and the co-administration of iRGD with chemotherapeutic agents and engineered delivery vehicles have been explored. Interestingly, the iRGD-mediated drug delivery also enhances penetration through the blood-brain barrier (BBB). Recent studies have shown its synergistic effect with BBB disruptive techniques. The efficacy of immunotherapy involving immune checkpoint blockades has also been amplified by using iRGD as a targeting moiety. In this review, we presented the recent advances in iRGD technology, focusing on cancer treatment modalities, including the current clinical trials using iRGD. The iRGD-mediated nano-carrier system could serve as a promising strategy in drug delivery to the deeper tumor regions, and be combined with various therapeutic interventions due to its novel targeting ability.

Specific HER2 targeting and triggered drug release by conformational transformation of a dual-functional peptide gatekeeper on mesoporous nanocontainers

For specific targeting of HER2 and triggered drug release by stimuli-responsive conformational transformation, we developed a dual-functional cyclic peptide gatekeeper containing a HER2-binding sequence on the surface of mesoporous nanocontainers.