Improved Cancer Immunochemotherapy via Optimal Co-delivery of Chemotherapeutic and Immunomodulatory Agents.

It is highly demanded and still a big challenge to develop an effective formulation for immunochemotherapy against advanced tumors. We have previously reported a PEG-NLG-based immunostimulatory nanocarrier (PEG2k-Fmoc-NLG919) for co-delivery of an IDO1 inhibitor (NLG919) and a chemotherapeutic agent (paclitaxel, PTX). Although antitumor immune responses were enhanced with a PTX-loaded nanocarrier, the accumulation of myeloid-derived suppressor cells (MDSCs) was also significantly increased, which may limit the overall efficacy of therapy. In the present work, we developed an improved dual-functional nanocarrier (PEG5k-Fmoc-NLG2) to co-load PTX and sunitinib (SUN, a multitarget receptor tyrosine kinase inhibitor) for improved cancer immunochemotherapy. We found that the recruited MDSCs negatively impacted the overall antitumor activity of the PTX-loaded PEG-NLG nanocarrier. Mechanistic study suggests that this is likely attributed to the PTX-mediated induction of a number of chemokines that are involved in the recruitment of MDSCs. We have further shown that the induction of these chemokines was drastically blocked by SUN. Co-delivery of PTX and SUN via the PEG5k-Fmoc-NLG9192 nanocarrier led to a further improvement in the therapeutic efficacy with a concomitant reduction in MDSCs.

Improved Micellar Formulation for Enhanced Delivery for Paclitaxel.

We have previously improved the bioactivity of PEG5k-FTS2 system by incorporating disulfide bond (PEG5k-S-S-FTS2) to facilitate the release of farnesyl thiosalicylic acid (FTS).1 Later, fluorenylmethyloxycarbonyl (Fmoc) moiety has been introduced to PEG5k-FTS2 system (PEG5k-Fmoc-FTS2) in order to enhance drug loading capacity (DLC) and formulation stability.2 In this study, we have brought in both disulfide linkage and Fmoc group to PEG5k-FTS2 to form a simple PEG5k-Fmoc-S-S-FTS2 micellar system. PEG5k-Fmoc-S-S-FTS2 conjugate formed filamentous micelles with a ∼10-fold decrease in critical micellar concentration (CMC). Compared with PEG5k-Fmoc-FTS2, our novel system exhibited further strengthened DLC and colloidal stability. More FTS was freed from PEG5k-Fmoc-S-S-FTS2 in treated tumor cells compared to PEG5k-Fmoc-FTS2, which was correlated to an increased cytotoxicity of our new carrier in these cancer cells. After loading Paclitaxel (PTX) into PEG5k-Fmoc-S-S-FTS2 micelles, it showed more potent efficiency in inhibition of tumor cell proliferation than Taxol and PTX-loaded PEG5k-Fmoc-FTS2. PTX release kinetics of PTX/PEG5k-Fmoc-S-S-FTS2 was much slower than that of Taxol and PTX/PEG5k-Fmoc-FTS2 in normal release medium. In contrast, in glutathione (GSH)-containing medium, PTX in PEG5k-Fmoc-S-S-FTS2 micelles revealed faster and more complete release. Pharmacokinetics and tissue distribution study showed that our PEG5k-Fmoc-S-S-FTS2 system maintained PTX in circulation for a longer time and delivered more PTX to tumor sites with less accumulation in major organs. Finally, PTX-loaded PEG5k-Fmoc-S-S-FTS2 micelles resulted in a superior therapeutic effect in vivo compared to Taxol and PTX formulated in PEG5k-Fmoc-FTS2 micelles.

Lymphoma Immunochemotherapy: Targeted Delivery of Doxorubicin via a Dual Functional Nanocarrier.

Chemotherapy drug (paclitaxel, PTX) incorporated in a dual functional polymeric nanocarrier, PEG-Fmoc-NLG, has shown promise as an immunochemotherapy in a murine breast cancer model, 4T1.2. The formulation is composed of an amphiphilic polymer with a built-in immunotherapy drug NLG919 that exhibits the immunostimulatory ability through the inhibition of indoleamine 2,3-dioxygenase 1 (IDO-1) in cancer cells. This work evaluates whether the PEG-derivatized NLG polymer can also be used for delivery of doxorubicin (Dox) in treatment of leukemia. The Dox-loaded micelles were self-assembled from PEG-Fmoc-NLG conjugate, which have a spherical shape with a uniform size of ∼120 nm. In cultured murine lymphocytic leukemia cells (A20), Dox-loaded PEG-Fmoc-NLG micelles showed a cytotoxicity that was comparable to that of free Dox. For in vivo studies, significantly improved antitumor activity was observed for the Dox/PEG-Fmoc-NLG group compared to Doxil or the free Dox group in an A20 lymphoma mouse model. Flow cytometric analysis showed that treatment with Dox/PEG-Fmoc-NLG micelles led to significant increases in the numbers of both total CD4+/CD8+ T cells and the functional CD4+/CD8+ T cells with concomitant decreases in the numbers of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Treg). Dox/PEG-Fmoc-NLG may represent a promising immunochemotherapy for lymphoma, which warrants more studies in the future.

Programmable co-delivery of the immune checkpoint inhibitor NLG919 and chemotherapeutic doxorubicin via a redox-responsive immunostimulatory polymeric prodrug carrier.

To achieve synergistic therapeutic efficacy and prevent cancer relapse, chemotherapy and immunotherapy have been combined as a new modality for tumor treatment. In this work, we designed a redox-responsive immunostimulatory polymeric prodrug carrier, PSSN10, for programmable co-delivery of an immune checkpoint inhibitor NLG919 (NLG) and a chemotherapeutic doxorubicin (DOX). NLG-containing PSSN10 prodrug polymers were self-assembled into nano-sized micelles that served as a carrier to load DOX (DOX/PSSN10 micelles). DOX/PSSN10 micelles displayed spherical morphology with a size of ∼170 nm. DOX was effectively loaded into PSSN10 micelles with a loading efficiency of 84.0%. In vitro DOX release studies showed that rapid drug release could be achieved in the highly redox environment after intracellular uptake by tumor cells. In 4T1.2 tumor-bearing mice, DOX/PSSN10 micelles exhibited greater accumulation of DOX and NLG in the tumor tissues compared with other organs. The PSSN10 carrier dose-dependently enhanced T-cell immune responses in the lymphocyte-Panc02 co-culture experiments, and significantly inhibited tumor growth in vivo. DOX/PSSN10 micelles showed potent cytotoxicity in vitro against 4T1.2 mouse breast cancer cells and PC-3 human prostate cancer cells comparable to that of DOX. In 4T1.2 tumor-bearing mice, DOX/PSSN10 mixed micelles (5 mg DOX/kg, iv) was more effective than DOXIL (a clinical formulation of liposomal DOX) or free DOX in inhibiting the tumor growth and prolonging the survival of the treated mice. In addition, a more immunoactive tumor microenvironment was observed in the mice treated with PSSN10 or DOX/PSSN10 micelles compared with the other treatment groups. In conclusion, systemic delivery of DOX via PSSN10 nanocarrier results in synergistic anti-tumor activity.

PEG-Fmoc-Ibuprofen Conjugate as a Dual Functional Nanomicellar Carrier for Paclitaxel.

Ibuprofen is a kind of nonsteroidal anti-inflammatory drug (NSAIDs), and it is considered to possess some antitumor effect. In this study, a novel nanomicellar carrier based on PEG-derivatized ibuprofen, PEG2K-Fmoc-Ibuprofen (PEG2K-FIbu), was developed for delivery of anticancer agents such as paclitaxel (PTX). This conjugate readily forms stable mixed micelles with PTX with a relatively high PTX loading capacity of 67%. The release of PTX from PTX-loaded PEG2K-FIbu micelles was significantly slower than that from Taxol formulation. PTX-loaded PEG2K-FIbu micelles and Taxol showed a comparable in vitro cytotoxicity. Importantly, PTX-loaded PEG2K-FIbu micelles demonstrated a much more pronounced in vivo therapeutic efficacy compared with Taxol with respect to both inhibition of tumor growth and animal survival. Our system may represent an attractive dual-functional delivery system to achieve synergistic activity with PTX while minimizing the carrier-associated toxicity.

PEGylated Fmoc-Amino Acid Conjugates as Effective Nanocarriers for Improved Drug Delivery.

A structure-activity relationship (SAR) study was conducted using a series of PEGylated Fmoc-amino acid conjugates (PFA) as a simple model to gain more insight into carrier-drug interaction. Among the eight PEG2000-Fmoc conjugates with different neighboring structures of Fmoc motif, PEG2000-Fmoc-Lys (Cbz) (PFA2)-based nanomicelles exhibited the smallest particle size distribution, lowest critical micelle concentration (CMC) value, and highest loading capacity with paclitaxel (PTX). These biophysical properties were largely attributed to the strengthened carrier-carrier and carrier-drug interaction, including π-π stacking, hydrophobic, and hydrogen bonding interaction, as confirmed by fluorescence quenching and (13)C NMR study. In vitro and in vivo evaluation further demonstrated the effectiveness of PFA2 as a nanocarrier for efficient delivery of PTX to achieve improved antitumor activity. Importantly, PFA2 was also effective in formulating eight other model drugs of diverse structures, indicating a broad application potential. This work may shed insights into the molecular basis for the structural optimization of nanocarriers for improved delivery efficacy.

Reduction-sensitive dual functional nanomicelles for improved delivery of paclitaxel.

We have developed a dual-functional nanocarrier composed of a hydrophilic polyethylene glycol (PEG) and a hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist), which is effective in delivery of hydrophobic anticancer drug, paclitaxel (PTX). To facilitate the retention of the therapeutic activity of the carrier, FTS was coupled to PEG via a reduction-sensitive disulfide linkage (PEG5k-S-S-FTS2). PEG5k-S-S-FTS2 conjugate formed uniform micelles with very small size (∼30 nm) and the hydrophobic drug PTX could be readily incorporated into the micelles. Interestingly, inclusion of a disulfide linkage into the PEG5k-FTS2 micellar system resulted in a 4-fold decrease in the critical micelle concentration (CMC). In addition, the PTX loading capacity and colloidal stability of PTX-loaded micelles were improved. HPLC-MS showed that parent FTS could be more effectively released from PEG5k-S-S-FTS2 conjugate in tumor cells/tissues compared to PEG5k-FTS2 conjugate in vitro and in vivo. PEG5k-S-S-FTS2 exhibited a higher level of cytotoxicity toward tumor cells than PEG5k-FTS2 without a disulfide linkage. Furthermore, PTX-loaded PEG5k-S-S-FTS2 micelles were more effective in inhibiting the proliferation of cultured tumor cells compared to Taxol and PTX loaded in PEG5k-FTS2 micelles. More importantly, PTX-loaded PEG5k-S-S-FTS2 micelles demonstrated superior antitumor activity compared to Taxol and PTX formulated in PEG5k-FTS2 micelles in an aggressive murine breast cancer model (4T1.2).

PEG-farnesyl thiosalicylic acid telodendrimer micelles as an improved formulation for targeted delivery of paclitaxel.

We have recently designed and developed a dual-functional drug carrier that is based on poly(ethylene glycol) (PEG)-derivatized farnesylthiosalicylate (FTS, a nontoxic Ras antagonist). PEG5K-FTS2 readily form micelles (20-30 nm) and hydrophobic drugs such as paclitaxel (PTX) could be effectively loaded into these micelles. PTX formulated in PEG5K-FTS2 micelles showed an antitumor activity that was more efficacious than Taxol in a syngeneic mouse model of breast cancer (4T1.2). In order to further improve our PEG-FTS micellar system, four PEG-FTS conjugates were developed that vary in the molecular weight of PEG (PEG2K vs PEG5K) and the molar ratio of PEG/FTS (1/2 vs 1/4) in the conjugates. These conjugates were characterized including CMC, drug loading capacity, stability, and their efficacy in delivery of anticancer drug PTX to tumor cells in vitro and in vivo. Our data showed that the conjugates with four FTS molecules were more effective than the conjugates with two molecules of FTS and that FTS conjugates with PEG5K were more effective than the counterparts with PEG2K in forming stable mixed micelles. PTX formulated in PEG5K-FTS4 micelles was the most effective formulation in inhibiting the tumor growth in vivo.

Targeted delivery of Doxorubicin by folic acid-decorated dual functional nanocarrier.

Doxorubicin (DOX) is one of the most commonly used antineoplastic agents, but its clinical application is oftentimes coupled with severe side effects. Selective delivery of DOX to tumors via nanosized drug carrier represents an attractive approach to this problem. Previously, we developed a dual functional nanomicellar carrier, PEG5K-embelin2 (PEG5K-EB2), which was able to deliver paclitaxel (PTX) selectively to tumors and to achieve an enhanced therapeutic effect. In the present study, we examined the utility of PEG5K-EB2 to deliver DOX to tumors. In addition, folic acid (FA) was coupled to the surface of the PEG5K-EB2 micelles (FA-PEG5K-EB2) to further improve the selective targetability of the system. DOX-loaded PEG5K-EB2 micelles were uniformly spherical particles with a diameter of approximately 20 nm. Incorporation of FA had minimal effect on the size of the particles. The DOX loading efficiency was as high as 91.7% and 93.5% for PEG5K-EB2 and FA-PEG5K-EB2, respectively. DOX formulated in PEG5K-EB2 micelles (with or without FA decoration) demonstrated sustained kinetics of DOX release compared to free DOX. FA-PEG5K-EB2 significantly facilitated the intracellular uptake of DOX over free DOX and PEGylated liposomal DOX (Doxil) in breast cancer cells, 4T1.2, and drug resistant cells, NCI/ADR-RES. P-gp ATPase assay showed that PEG5K-EB2 significantly inhibited the function of the P-gp efflux pump. The maximum tolerated dose of DOX-loaded PEG5K-EB2 micelles was 15 mg/kg in mice, which was 1.5-fold greater than that for free DOX. Pharmacokinetics (PK) and biodistribution studies showed that both types of DOX-loaded micelles, especially FA-PEG5K-EB2, were able to significantly prolong the blood circulation time of DOX and facilitate its preferential accumulation at the tumor tissue. Finally, DOX/PEG5K-EB2 mixed micelles demonstrated significantly enhanced tumor growth inhibitory effect with minimal toxicity in comparison to free DOX and Doxil and the antitumor activity was further enhanced after the decoration by folic acid. Our data suggest that FA-PEG5K-EB2 micelles represent a promising DOX delivery system that warrants more study in the future.

Targeted delivery of anticancer agents via a dual function nanocarrier with an interfacial drug-interactive motif.

We have developed a dual-function drug carrier, polyethylene glycol (PEG)-derivatized farnesylthiosalicylate (FTS). Here we report that incorporation of a drug-interactive motif (Fmoc) into PEG5k-FTS2 led to further improvement in both drug loading capacity and formulation stability. Doxorubicin (DOX) formulated in PEG5k-Fmoc-FTS2 showed sustained release kinetics slower than those of DOX loaded in PEG5k-FTS2. The maximum tolerated dose of DOX- or paclitaxel (PTX)-loaded PEG5k-Fmoc-FTS2 was significantly higher than that of the free drug. Pharmacokinetics and biodistribution studies showed that DOX/PEG5k-Fmoc-FTS2 mixed micelles were able to retain DOX in the bloodstream for a significant amount of time and efficiently deliver the drug to tumor sites. More importantly, drug (DOX or PTX)-loaded PEG5k-Fmoc-FTS2 led to superior antitumor activity over other treatments including drugs formulated in PEG5k-FTS2 in breast cancer and prostate cancer models. Our improved dual function carrier with a built-in drug-interactive motif represents a simple and effective system for targeted delivery of anticancer agents.