Delivery of tumor-homing TRAIL sensitizer with long-acting TRAIL as a therapy for TRAIL-resistant tumors.

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) has attracted great interest as a cancer therapy because it selectively induces death receptor (DR)-mediated apoptosis in cancer cells while sparing normal tissue. However, recombinant human TRAIL demonstrates limited therapeutic efficacy in clinical trials, possibly due to TRAIL-resistance of primary cancers and its inherent short half-life. Here we introduce drug delivery approaches to maximize in vivo potency of TRAIL in TRAIL-resistant tumor xenografts by (1) extending the half-life of the ligand with PEGylated TRAIL (TRAILPEG) and (2) concentrating a TRAIL sensitizer, selected from in vitro screening, in tumors via tumor-homing nanoparticles. Antitumor efficacy of TRAILPEG with tumor-homing sensitizer was evaluated in HCT116 and HT-29 colon xenografts. Western blot, real-time PCR, immunohistochemistry and cell viability assays were employed to investigate mechanisms of action and antitumor efficacy of the combination. We discovered that doxorubicin (DOX) sensitizes TRAIL-resistant HT-29 colon cancer cells to TRAIL by upregulating mRNA expression of DR5 by 60% in vitro. Intravenously administered free DOX does not effectively upregulate DR5 in tumor tissues nor demonstrate synergy with TRAILPEG in HT-29 xenografts, but rather introduces significant systemic toxicity. Alternatively, when DOX was encapsulated in hyaluronic acid-based nanoparticles (HAC/DOX) and intravenously administered with TRAILPEG, DR-mediated apoptosis was potentiated in HT-29 tumors by upregulating DR5 protein expression by 70% and initiating both extrinsic and intrinsic apoptotic pathways with reduced systemic toxicity compared to HAC/DOX or free DOX combined with TRAILPEG (80% vs. 40% survival rate; 75% vs. 34% tumor growth inhibition). This study demonstrates a unique approach to overcome TRAIL-based therapy drawbacks using sequential administration of a tumor-homing TRAIL sensitizer and long-acting TRAILPEG.

Evaluation of PEGylated exendin-4 released from poly (lactic-co-glycolic acid) microspheres for antidiabetic therapy.

Peptide-based therapies have the potential to induce antibody formation if the molecules differ from a native human peptide. Several reports have disclosed the occurrence of antibody generation in a patient treated with exenatide. The immune response can be problematic from a clinical stand point, particularly if the antibodies neutralize the efficacy of the biotherapeutic agent or cause a general immune reaction. To overcome this limit, PEGylated exendin-4 analogs were designed and examined for metabolic stability and biological activity. To develop an extended release delivery system for exendin-4 for the safe and effective delivery of bioactive exendin-4 without peptide acylation and immunogenicity, PEGylated exendin-4 was encapsulated into poly (lactic-co-glycolic acid) (PLGA) microspheres by w/o/w double emulsion solvent evaporation method. Peptide-loaded microspheres were characterized in terms of morphology, particle diameter, and peptide encapsulation efficiency. Then, the release profile of the peptide from PLGA microspheres and the acylated products from PLGA polymer degradation was determined. The results obtained showed that the stability of exendin-4 was greatly improved by PEGylation. Moreover, eliminated acylation during PLGA polymer degradation in vitro and reduced immunogenicity in vivo were observed. The findings demonstrate that PEGylated exendin-4-loaded microspheres may be a safe and biocompatible system for clinical development.