Monoclonal Antibody 2C5-Modified Mixed Dendrimer Micelles for Tumor-Targeted Codelivery of Chemotherapeutics and siRNA

Targeted delivery of chemotherapeutics to tumors has the potential to reach a high dose at the tumor while minimizing systemic exposure. Incorporation of antibody within a micellar platform represents a drug delivery system for tumor-targeted delivery of antitumor agents. Such modified immunomicelles can result in an increased accumulation of antitumor agents and enhanced cytotoxicity toward cancer cells. Here, mixed dendrimer micelles (MDM) composed of PEG_2k-DOPE-conjugated generation 4 polyamidoamine dendrimer G4-PAMAM-PEG_2k-DOPE and PEG_5k-DOPE were coloaded with doxorubicin and siMDR-1. This formulation was further modified with monoclonal antibodies 2C5 with nucleosome-restricted specificity that effectively recognized cancer cells via the cell-surface-bound nucleosomes. Micelles with attached 2C5 antibodies significantly enhanced cellular association and tumor killing in both monolayer and spheroid tumor models as well as in vivo in experimental animals compared to the nontargeted formulations.

Combretastatin A4 Nanodrug-Induced MMP9 Amplification Boosts Tumor-Selective Release of Doxorubicin Prodrug

Tumor-associated enzyme-activated prodrugs can potentially improve the selectivity of chemotherapeutics. However, the paucity of tumor-associated enzymes which are essential for prodrug activation usually limits the antitumor potency. A cooperative strategy that utilizes combretastatin A4 nanodrug (CA4-NPs) and matrix metalloproteinase 9 (MMP9)-activated doxorubicin prodrug (MMP9-DOX-NPs) is developed. CA4 is a typical vascular disrupting agent that can selectively disrupt immature tumor blood vessels and exacerbate the tumor hypoxia state. After treatment with CA4-NPs, MMP9 expression can be significantly enhanced by 5.6-fold in treated tumors, which further boosts tumor-selective active drug release of MMP9-DOX-NPs by 3.7-fold in an orthotopic 4T1 mammary adenocarcinoma mouse model. The sequential delivery of CA4-NPs and MMP9-DOX-NPs exhibits enhanced antitumor efficacy with reduced systemic toxicity compared with the noncooperative controls.

Strategies of Combination Drug Delivery for Immune Checkpoint Blockades

The past few years have witnessed vast clinical accomplishments of immune checkpoint blockades (ICB), which block the regulatory receptor expressed on immune cells or tumor cells to prevent the suppression of antitumor cytotoxic T-cell responses. Despite this, limitations still exist, such as low objective response rate (ORR) and the risk of immune-related side effects. To address these issues, combination treatment strategies are vastly explored and recommended. This review summarizes recent advances in combination of ICB with therapies that participate in different stages of cancer immune cycle, including tumor antigen release, tumor antigen presentation, T-cell activation, recognition of cancer cells by T-cells, and tumor-killing activity. Challenges and potential opportunities of combination approaches in this field are also discussed.

Mixed Liposome Approach for Ratiometric and Sequential Delivery of Paclitaxel and Gemcitabine

Paclitaxel (PTX) and gemcitabine (GEM) are often used in combination due to the synergistic anticancer effects. PTX and GEM combination showed a synergistic effect to SKOV-3 cells at a molar ratio of 1 to 1 and in PTX ➔ GEM sequence. Liposomes were explored as a carrier of PTX and GEM combination. We optimized the drug loading in liposomes varying the preparation method and co-encapsulated PTX and GEM in a single liposome preparation maintaining the maximum loading efficiency of each drug. However, drug release kinetics from the co-loaded liposomes (LpPG) was suboptimal because of the detrimental effect of PTX on GEM-release control. Instead, a mixture of LpP and LpG, which were separately optimized according to the desired release kinetics, achieved a greater cytotoxic effect than LpPG, due to the attenuation of GEM release relative to PTX. This study illustrates that co-encapsulation in a single carrier is not always desirable for the delivery of drug combinations, when the activity depends on the dosing sequence. These combinations may benefit from the mixed liposome approach, which offers greater flexibility in controlling the ratio and release kinetics of component drugs.

Intracellular Delivery of Molecular Cargo Using Cell-Penetrating Peptides and the Combination Strategies

Cell-penetrating peptides (CPPs) can cross cellular membranes in a non-toxic fashion, improving the intracellular delivery of various molecular cargos such as nanoparticles, small molecules and plasmid DNA. Because CPPs provide a safe, efficient, and non-invasive mode of transport for various cargos into cells, they have been developed as vectors for the delivery of genetic and biologic products in recent years. Most common CPPs are positively charged peptides. While delivering negatively charged molecules (e.g., nucleic acids) to target cells, the internalization efficiency of CPPs is reduced and inhibited because the cationic charges on the CPPs are neutralized through the covering of CPPs by cargos on the structure. Even under these circumstances, the CPPs can still be non-covalently complexed with the negatively charged molecules. To address this issue, combination strategies of CPPs with other typical carriers provide a promising and novel delivery system. This review summarizes the latest research work in using CPPs combined with molecular cargos including liposomes, polymers, cationic peptides, nanoparticles, adeno-associated virus (AAV) and calcium for the delivery of genetic products, especially for small interfering RNA (siRNA). This combination strategy remedies the reduced internalization efficiency caused by neutralization.