Entrapping Instantly‐Cleaved CPT Prodrugs in Polymeric Micelles for CPT Delivery

The Effect of Lipid Composition on the Liposomal Delivery of Camptothecin Developed by Active Click Loading

In the present study, we investigated the role of lipid composition of camptothecin (CPT)-loaded liposomes (CPT-Lips) to adjust their residence time, drug distribution, and therefore the toxicities and antitumor activity. The CPT was loaded into liposomes using a click drug loading method, which utilized liposomes preloaded with GSH and then exposed to CPT-maleimide. The method produced CPT-Lips with a high encapsulation efficiency (>95%) and sustained drug release. It is shown that the residence times of CPT-Lips in the body were highly dependent on lipid compositions with an order of non-PEGylated liposomes of unsaturated lipids < non-PEGylated liposomes of saturated lipids < PEGylated liposomes of saturated lipids. Interestingly, the fast clearance of CPT-Lips resulted in significantly decreased toxicities but did not cause a significant decrease in their in vivo antitumor activity. These results suggested that the lipid composition could effectively adjust the residence time of CPT-Lips in the body and further optimize their therapeutic index, which would guide the development of a liposomal formulation of CPT.

Advances in self-assembled nanotechnology in tumor therapy

The emergence of nanotechnology has opened up a new way for tumor therapy. Among them, self-assembled nanotechnology has received extensive attention in medicine due to its simple preparation process, high drug-loading capacity, low toxicity, and low cost. This review mainly summarizes the preparation methods of self-assembled nano-delivery systems, as well as the self-assembled mechanism of carrier-free nanomedicine, polymer-carried nanomedicine, polypeptide, and metal drugs, and their applications in tumor therapy. In addition, we discuss the advantages and disadvantages, future challenges, and opportunities of these self-assembled nanomedicines, which provide important references for the development and application of self-assembled nanotechnology in the field of medical therapy.

Development of a novel sialic acid-conjugated camptothecin prodrug for enhanced cancer chemotherapy

Camptothecin (CPT) is an attractive natural drug for cancer chemotherapy. However, the poor water solubility, non-targeting feature, and adverse side effects of CPT are significant obstacles to developing an effective anticancer drug. Here, for the first time, 9-thiol-sialic acid (9-SH-Sia) is coupled to CPT by forming a disulfide releasable carbonate linkage, resulting in a novel CPT prodrug (CPT-ss-Sia) that self-assembles into nanostructures in an aqueous solution. Strikingly, CPT-ss-Sia exhibited excellent in vitro properties, including enhanced water solubility, glutathione (GSH)-triggered CPT release, and increased E-lactone ring stability. Furthermore, CPT-ss-Sia had good cancer cell-killing ability comparable to CPT. Intravenous administration of CPT-ss-Sia significantly inhibited the growth of multiple types of tumors. Histological analysis showed that CPT-ss-Sia treatment significantly reduced lesions in tumor-bearing mice compared to CPT treatment. Notably, CPT-ss-Sia treatment did not adversely affect the body weight of the mice. This is the first report of the 9-SH-Sia conjugate-based prodrug. Overall, CPT-ss-Sia has broad clinical application prospects.

Acyl and oligo(lactic acid) prodrugs for PEG-b-PLA and PEG-b-PCL nano-assemblies for injection

Poly(ethylene glycol)-block-poly(D,L-lactic acid) (PEG-b-PLA) and poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) form nano-assemblies, including micelles and nanoparticles, that increase the water solubility of anticancer drugs for injection. PEG-b-PLA and PEG-b-PCL are less toxic than commonly used organic solvents or solubilizers for injection, such as Cremophor EL® in Taxol®. Formulating paclitaxel in PEG-b-PLA micelles, as Genexol-PM®, permits dose escalation over Taxol®, enhancing antitumor efficacy in breast, lung and ovarian cancers. To expand the repertoire of anticancer drugs for injection, acyl and oligo(lactic acid) ester prodrugs have been synthesized for PEG-b-PLA and PEG-b-PCL nano-assemblies, compatibility, and novel nanomedicines for injection. Notably, acyl and oligo(lactic acid) taxane prodrugs delivered by PEG-b-PLA and PEG-b-PCL nano-assemblies display heightened plasma exposure, reduction in biodistribution into major organs and enhanced tumor exposure in murine tumor models, versus parent anticancer drugs in conventional formulations. As a result, acyl and oligo(lactic acid) ester prodrugs are less toxic and induce durable antitumor responses. In summary, acyl and oligo(lactic acid) ester prodrugs widen the range of anticancer drugs that can be tested safely and effectively by using PEG-b-PLA and PEG-b-PCL nano-assemblies, and they display superior anticancer efficacy over parent anticancer drugs, which are often approved products. Oligo(lactic acid) ester taxane prodrugs are in pre-clinical development as novel drug combinations and immunotherapy combinations for cancer therapy.