Preparation and evaluation of norcantharidin-encapsulated liposomes modified with a novel CD19 monoclonal antibody 2E8

Review targeted drug delivery systems for norcantharidin in cancer therapy

Norcantharidin (NCTD) is a demethylated derivative of cantharidin (CTD), the main anticancer active ingredient isolated from traditional Chinese medicine Mylabris. NCTD has been approved by the State Food and Drug Administration for the treatment of various solid tumors, especially liver cancer. Although NCTD greatly reduces the toxicity of CTD, there is still a certain degree of urinary toxicity and organ toxicity, and the poor solubility, short half-life, fast metabolism, as well as high venous irritation and weak tumor targeting ability limit its widespread application in the clinic. To reduce its toxicity and improve its efficacy, design of targeted drug delivery systems based on biomaterials and nanomaterials is one of the most feasible strategies. Therefore, this review focused on the studies of targeted drug delivery systems combined with NCTD in recent years, including passive and active targeted drug delivery systems, and physicochemical targeted drug delivery systems for improving drug bioavailability and enhancing its efficacy, as well as increasing drug targeting ability and reducing its adverse effects.

Graphical Abstract

Strategies for Solubility and Bioavailability Enhancement and Toxicity Reduction of Norcantharidin

Cantharidin (CTD) is the main active ingredient isolated from Mylabris, and norcantharidin (NCTD) is a demethylated derivative of CTD, which has similar antitumor activity to CTD and lower toxicity than CTD. However, the clinical use of NCTD is limited due to its poor solubility, low bioavailability, and toxic effects on normal cells. To overcome these shortcomings, researchers have explored a number of strategies, such as chemical structural modifications, microsphere dispersion systems, and nanodrug delivery systems. This review summarizes the structure-activity relationship of NCTD and novel strategies to improve the solubility and bioavailability of NCTD as well as reduce the toxicity. This review can provide evidence for further research of NCTD.

Successful construction and massive expression of a novel Anti-CD19 human-mouse chimeric antibody Hm2E8b

CD19 antigen is a major target for human B cell malignancies. Many studies have shown that the antibodies recognizing this antigen hold clinical therapeutic potential, while CD19 antibody of mouse origin requires genetic engineering to reduce the potential side effects of the antibody for their clinical use. There are many clones of CD19 antibodies available with different subclasses of immunoglobulin. IgM type antibody holds a high affinity and high complement activating capacities facilitating the targeting efficacy when it is used in targeting therapy. However, engineering the murine IgM antibody into a functional humanized antibody remains a challenge. The aim of this study was to construct a chimeric antibody composed of a CD19 specific murine IgM antibody 2E8 single-chain antibody fragment (scFv) and human IgG1 Fc region, which was named 2E8scFv-Fc or Hm2E8b. The function and the biological activities of this engineered antibody were characterized using a variety of approaches including cellular, immunological, flow cytometric, and molecular biological approaches. After switching from IgM- to IgG-like type antibody, Hm2E8b retained full antigen-binding activity to membrane CD19 antigen as its parental antibody 2E8, and the immune effector function analysis revealed that it could mediate complement-dependent cytotoxicity (CDC) to kill the target cells via IgG1 Fc domain. The yield of the engineered antibody Hm2E8b in the supernatant was 13.3 μg/mL expressed and secreted in the CHO cell system, which reached the secretory quantity of a regular mouse hybridoma cells. Our conclusion is that the IgM type of CD19 mouse antibody can be successfully engineered into an IgG1 type human-mouse chimeric antibody with similar affinity and biological activity. The yield of the Hm2E8b expression and secretion in CHO cell system was adequate to facilitate further development for therapeutic purpose.

Targeted liposomal drug delivery systems for the treatment of B cell malignancies

Nanoparticulate systems have demonstrated significant potential for overcoming the limitations of non-specific adverse effects related to chemotherapy. The treatment of blood malignancies employing targeted particulate drug delivery systems presents unique challenges and considerable research has been focused towards the development of targeted liposomal formulations for B cell malignancies. These formulations are aimed at achieving selectivity towards the malignant cells by targeting several cell surface markers which are over-expressed in that specific malignancy. CD19, CD20, CD22 and CD74 are few of such markers of which CD19, CD22 and CD74 are internalizing and CD20 is non-internalizing. Systems which have been developed to target both types of these cell surface markers are discussed. Specifically, the efficacy and development of targeted liposomes is considered. A number of studies have demonstrated the advantages of targeted liposomal systems encapsulating doxorubicin or vincristine. However, liposomal encapsulation of newer anti-neoplastic agents such as AD 198 which are superior to doxorubicin should be considered.