Revival of a potent therapeutic maytansinoid agent using a strategy that combines covalent drug conjugation with sequential nanoparticle assembly

An esterase-activatable prodrug formulated liposome strategy: potentiating the anticancer therapeutic efficacy and drug safety

Liposomal nanomedicine represents a common and versatile carrier for the delivery of both lipophilic and hydrophilic drugs. However, the direct formulation of many chemotherapeutics into a liposomal system remains an enormous challenge. Using the topoisomerase I inhibitor 7-ethyl-10-hydroxycamptothecin (SN38) as a model drug, we combined lipophilic prodrug construction with subsequent integration into an exogenous liposomal scaffold to assemble a prodrug-formulated liposome for systemic administration. Reconstructing SN38 with lipid cholesterol via the esterase-activatable bond endows the resulting prodrug with elevated miscibility with liposomal compositions and esterase-responsive drug release in cancerous cells. The systemic administration of the prodrug-based nanoassemblies (Chol-SN38@LP) exhibited preferential accumulation of therapeutic payloads in tumor lesions. Compared to the SN38 clinical counterpart irinotecan, our prodrug-based nanoassemblies with adaptive features showed elevated therapeutic efficacy (∼1.5 times increase of tumor inhibition) in a preclinical A549 lung carcinoma cell-derived mouse model and improved drug tolerability (i.e., alleviated bloody diarrhea and liver damage) in multiple mice models. These results may be ascribed to extended systemic circulation and preferential tumor accumulation of our nanodrugs. Hence, our findings demonstrate that rational engineering of therapeutic nanomedicine is a promising approach for effective and safe delivery of antitumor chemotherapeutics, especially to rescue drug candidates that have failed in clinical trials owing to poor PK properties or severe toxicity in patients.

Microfluidic assembly of small-molecule prodrug cocktail nanoparticles with high reproducibility for synergistic combination of cancer therapy

Therapeutic nanoparticles (NPs) self-assembled from small molecular (pro)drug entities, opens up novel avenues for the generation of a wide range of drug delivery systems. Particularly, cocktail NPs created by co-assembly of multiple therapeutics often show profound efficacy beyond their individual agents. However, fabrication of synergistic NPs with high reproducibility and capability to deliver multiple therapeutics in a predefined ratio remains a challenge, which deters NP therapeutics from further clinical translation. In this work, a simple but versatile strategy has been developed to combine drug reconstitution and supramolecular nanoassembly to prodrug cocktail nanoparticle fabrication with microfluidics. Prodrugs reconstructed by PUFAylation were self-assembled into hybrid nanoparticles via microfluidic chip to synergistically deliver two chemotherapeutic drugs, 7-ethyl-10-hydroxy camptothecin (SN38) and paclitaxel (PTX), in a single nanoparticle container. In vitro cell-based assays demonstrate that the combinatorial chemotherapy is superior to each prodrug used alone while reduces the dosage of both drugs at the same time. Furthermore, the double-drug combination suppresses colon tumors by 86% at a total dosage of 16.7 mg/kg through synergy, and histological analysis indicates the safety of the hybrid nanoparticles. In general, this work shows that the nanomedicine synthesized by microfluidics provides considerable advantages including better size control and reproducibility, and great potential in effective combination therapy. It is expected to be applied to the fabrication of more chemical agent combination for other cancer types.

Repurposing of camptothecin: An esterase-activatable prodrug delivered by a self-emulsifying formulation that improves efficacy in colorectal cancer

The global burden of colorectal cancer (CRC), the third most commonly diagnosed malignancy, continues to rise. Therefore, more effective and less toxic therapies are needed for CRC. CPT-11 (also called irinotecan), the standard-of-care treatment for CRC, has only had limited effects on survival outcomes. In vivo, CPT-11 must be converted to an active metabolite, SN38, to exert antitumor activity in the presence of carboxylesterases, but the conversion rate is extremely low (usually less than 8%). To fully harness the active SN38 compound, we showed here that esterification of SN38 using α-linolenic acid (LNA) generated a prodrug (termed LSN38), which can be formulated in pharmaceutically acceptable surfactants, such as polysorbate 80. Upon blending with an aqueous ethanolic solution, the mixture of LSN38/polysorbate 80 formed self-emulsifying nanomicelles (termed LSN38 NMs), enabling systemic injection. Unlike the insufficient release of active SN38 from CPT-11, drug activation from the LSN38 prodrug was quantitative and relied on esterase, which is abundant in cancerous cells. Pharmacokinetics studies revealed that polysorbate 80-based nanomicelles stably constrained the prodrug in the reservoir and prolonged blood circulation compared to CPT-11. Furthermore, LSN38 NMs showed superior therapeutic efficacy against a colorectal xenograft-bearing mouse model that failed to be treated with clinically approved CPT-11. Overall, these studies highlight the feasibility of converting a chemotherapeutic agent that is not miscible or compatible with pharmaceutical surfactants into an injectable self-emulsifying formulation. This approach could be applied to rescue other drugs or drug candidates that are abandoned in the preclinical stages due to pharmaceutical challenges.

Tuning the efficacy of esterase-activatable prodrug nanoparticles for the treatment of colorectal malignancies

Colorectal cancer (CRC) is one of the most common and lethal human cancers, and the clinical outcomes remain unsatisfactory because of the lack of effective and safe therapeutic regimens. Here, we describe a practical and potent delivery approach for the human topoisomerase I inhibitor 7-ethyl-10-hydroxycamptothecin (SN38) against CRC. Injectable SN38-loaded nanoparticles are obtained through covalent ligation of the SN38 agent with oligo-ε-caprolactone (oligoCL) to form oligoCL-SN38 conjugates via an esterase-activatable linkage followed by encapsulation of these prodrugs in exogenous polymer matrices. Prodrug nanoparticles with adaptive features are sufficiently stable during blood circulation, while active drugs can be released in response to intracellular esterase. The administration of nanoparticle drugs results in durable tumor recession, and the efficacy is superior to that of the current standard-of-care therapy, CPT-11, in multiple mouse models of CRC, one of which is a chemically induced orthotopic CRC. Elucidation of the mechanism underlying these differing efficacies shows that nanoparticle delivery produces a substantial increase in the intratumoral concentration of the therapeutic agent relative to CPT-11, which contributes to improved antitumor efficacy. Finally, these nanoparticle drugs are potentially less toxic in animals than CPT-11, as evidenced by the low incidence of bloody diarrhea and attenuated colonic damage. Overall, these results demonstrate that precisely engineered therapeutic nanoparticles are capable of enhancing efficacy, addressing the risk of tumor recurrence, and increasing drug tolerance, thus deserving further investigation.

New Organometallic Ruthenium(II) Compounds Synergistically Show Cytotoxic, Antimetastatic and Antiangiogenic Activities for the Treatment of Metastatic Cancer

In this study, we newly designed and synthesized a small library of ten structurally related C,N-cyclometalated ruthenium(II) complexes containing various pyridine-functionalized NHC ligand and chelating bipyridyl ligands (e.g., 2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, and 1,10-phenanthroline (phen)). The complexes were well characterized by NMR, electrospray ionization-mass spectrometry, and single-crystal X-ray structure analyses. Among the new ruthenium(II) derivatives, we identified that the complex Ru8 bearing bulky moieties (i.e., phen and pentamethyl benzene) had the most potent cytotoxicity against all tested cancer cell lines, generating dose- and cell line-dependent IC₅₀ values at the range of 3.3-15.0 μm. More significantly, Ru8 not only efficiently inhibited the metastasis process against invasion and migration of tumor cells but also exhibited potent antivascular effects by suppressing HUVEC cells migration and tube formation in vitro and blocking vessel generation in vivo (chicken chorioallantoic membrane model). In a metastatic A2780 tumor xenograft-bearing mouse model, administration of Ru8 outperformed antimetastatic agent NAMI-A and clinically approved cisplatin in terms of antitumor efficacy and inhibition of metastases to other organs. Overall, these data provided compelling evidence that the new cyclometalated ruthenium complex Ru8 is an attractive agent because of synergistically suppressing bulky tumors and metastasized tumor nudes. Therefore, the complex Ru8 deserves further investigations.

Nanoparticles in Colorectal Cancer Therapy: Latest In Vivo Assays, Clinical Trials, and Patents

Colorectal cancer (CRC) is the third most common cancer worldwide. Its poor response to current treatment options in advanced stages and the need for efficient diagnosis in early stages call for the development of new therapeutic and diagnostic strategies. Some of them are based on the use of nanometric materials as carriers and releasers of therapeutic agents and fluorescent molecules, or even on the utilization of magnetic materials that provide very interesting properties. These nanoformulations present several advantages compared with the free molecular cargo, including increased drug solubility, bioavailability, stability, and tumor specificity. Moreover, tumor multidrug resistance has been decreased in some cases, leading to improved treatment effectiveness by reducing drug dose and potential side effects. Here, we present an updated overview of the latest advances in clinical research, in vivo studies, and patents regarding the application of nanoformulations in the treatment of CRC. Based on the information gathered, a wide variety of nanomaterials are being investigated in clinical research, even in advanced phases, i.e., close to reaching the market. In sum, these novel materials can offer remarkable advantages with respect to current therapies, which could be complemented or even replaced by these nanosystems in the near future.

Self-assembling poly(ethylene glycol)-block-polylactide-cabazitaxel conjugate nanoparticles for anticancer therapy with high efficacy and low in vivo toxicity

Traditional approaches used for transforming hydrophobic anticancer drugs into therapeutically available nanoparticles heavily rely on the noncovalent formulation of drugs within amphiphilic copolymers. However, these nanotherapies have not yet shown the expected favorable clinical outcomes in cancer patients, presumably due to their insufficient stability. To solve this dilemma, we conceive a new class of nanotherapies assembled with polymeric prodrugs that maintain pharmacological activity while substantially alleviate the drug toxicity in animals. By exploiting methoxypoly(ethylene glycol)-block-poly(D, L-lactic acid) (mPEG-PLA) as a promoiety, cabazitaxel is tethered to the terminus of the PLA fragment via a hydrolysable ester linkage. These conjugates recapitulate the self-assembly to produce colloidal stable nanotherapies. In a xenograft model of prostate cancer, this nanotherapy shows a durable inhibition of tumor progression upon the administration of a tolerable dose. Our results suggest that a hydrophobic and highly toxic drug can be rationally converted into a pharmacologically efficient and self-deliverable nanotherapy.