Combretastatin A4-derived payloads for antibody-drug conjugates

Triptolide-based cleavable antibody-drug conjugates for pancreatic cancer

Antibody-drug conjugates (ADCs) have emerged as a highly promising modality for the treatment of various tumors, including pancreatic cancer. Due to the modular nature of ADCs, their efficacy is heavily influenced by the choice of antibody, payload, and linker. Given the therapeutic potential of triptolide for pancreatic cancer, this study aims to harness triptolide as the cytotoxic payload to construct ADCs targeting pancreatic cancer. Silyl ethers were utilized for the first time as cleavable linkers to connect triptolide with an antibody. This is because silyl ethers can be easily synthesized and the rate of drug release can be regulated by modifying the silyl ether groups. The release profile of the resulting linkers was investigated. And considering the balance between cleavage and stability, one silyl ether-based linker was selected to prepare an ADC, named A10. Meanwhile, a traditional dipeptide linker-based ADC, A9, was synthesized for comparison. The ADC A10 demonstrated superior inhibitory effects compared to ADC A9, both in vitro and in vivo. A10 displayed targeted cytotoxicity against cells with high PD-L1 expression and demonstrated a bystander killing effect on cells with low PD-L1 expression. In vivo imaging studies indicated that fluorescently labeled A10 accumulated in tumor regions. Additionally, significant antitumor activities of A10 were observed against Panc 08.13-derived tumor xenografts.

Synthesis and evaluation of KX-01 analogs with an exploration of linker attachment points for antibody-drug conjugates

KX-01 (tirbanibulin, Klisyri®) is a recently FDA-approved drug for treating actinic keratosis, with a distinct dual mechanism of action combining microtubule disruption and non-ATP-competitive Src inhibition. This unique mechanism and novel chemotype highlight KX-01's potential as a payload for antibody-drug conjugates. In this study, we synthesized and evaluated KX-01 derivatives to enhance anticancer potency and explore functional groups suitable for antibody conjugation. Notably, replacing the morpholine group with an N-benzoylpiperazine scaffold resulted in an analog with significantly improved in vitro antiproliferative activity, attributed to enhanced microtubule disruption and Src inhibition. Furthermore, introducing a phenol or aniline functionality as a common linker attachment point preserved substantial cytotoxicity. These results suggest the potential of KX-01 derivatives for future use as ADC payloads.

Exploiting synthetic lethality in PDAC with antibody drug conjugates and ATR inhibition

Pancreatic ductal adenocarcinoma (PDAC) remains a highly lethal malignancy with poor prognosis. Antibody-drug conjugates (ADCs) and their combinations with various anti-tumor drugs have made great progress. Camptothecin, and its derivatives (Dxd, SN-38 or exatecan) targeted TOP1 are effective payloads due to their potent anti-tumor activity. ADCs offer a promising avenue, particularly when integrated with synthetic lethality strategies. In this study, the ADC SA-7-49 is engineered by conjugating exatecan to an anti-TROP2 antibody. The synthetic lethality between camptothecin and the ataxia telangiectasia-mutated and rad3-related (ATR) inhibitors in PDAC cells has been identified through a comprehensive screening of DNA damage response pathways. Drug interactions are quantified using Zero interaction potency (ZIP) scores. RNA sequencing is employed to elucidate the mechanisms driving synergistic effects. ATR inhibitors synergize with camptothecin by inducing apoptosis via ATR-Chk1 pathway inhibition. Knockdown of ATR enhances the sensitivity of PDAC cells to camptothecin and SA-7-49. SA-7-49 selectively targets and eradicates PDAC cells and xenografts without side effects, augmenting anti-tumor activity via synthetic lethality. Our findings reveal a novel therapeutic strategy by integrating ADC technology with synthetic lethality in PDAC.

Recent advances of selenized tubulin inhibitors in cancer therapy

Cancer treatment always a huge challenge amidst the resistance and relapse caused by the various treatments. Inhibitors targeting mitosis have been considered as promising therapeutic drugs in clinic, of which tubulins play an important role. Selenium (Se) as an essential microelement in humans and animals, playing a crucial role in the formation of anti-oxidase (glutathione peroxidase) and selenoprotein, also attracted broad attention in cancer therapy. Because the introduction of Se atom could change the length and angle of chemical bond and alter their functional properties, regulating selenized chemotherapeutics has become one of the hot spots. However, little attention has been paid to studying the combination of Se and tubulin inhibitors. Herein, we review the latest research results of selenized tubulin inhibitors in cancer therapy, including its mechanisms, categories and biological activities, providing a theoretical basis for different selenized microtubules inhibitors therapies.

A novel life for antitumor combretastatins: Recent developments of hybrids, prodrugs, combination therapies, and antibody-drug conjugates

Since their discovery from natural sources, the potent cytotoxic effects of combretastatins were widely studied for the application in antitumor therapy. However, major pharmacokinetic issues as low water solubility and chemical instability of the double bond configuration prevented their use in therapy. A lot of efforts have been directed towards the search of novel strategies, allowing a safer use of combretastatins as anticancer agents. This review analyses the recent landscape in combretastatin research, characterized by the identification of hybrids, prodrugs, and novel combination treatments. Interestingly, the potent cytotoxic agent combretastatin A4 (CA4) was recently proposed as payload in the construction of novel antibody-drug conjugates (ADCs), allowing an efficient targeting of the cytotoxic agent to specific tumors.

Development of a MMAE-based antibody-drug conjugate targeting B7-H3 for glioblastoma

B7-H3 (immunoregulatory protein B7-homologue 3) is overexpressed in many cancer cells with limited expression in normal tissues, considered to be a promising target for tumor therapeutics. Clinical trials of antibody-drug conjugates (ADCs) against different targets for glioblastoma have been investigated and showed potent efficacies. In this study, we developed a homogeneous ADC 401-4 with a drug-to-antibody ratio (DAR) of 4, which was prepared by conjugation of Monomethyl auristatin E (MMAE) to a humanized anti-B7-H3 mAb 401, through a divinylsulfonamide-mediated disulfide re-bridging approach. In vitro studies, 401-4 displayed specific killing against B7-H3-expressing tumors and was more effective in cells with higher levels of B7-H3 for different glioblastoma cells. 401-4 was furthered labeled with Cy5.5 to yield a fluorescent conjugate 401-4-Cy5.5. The in vivo imaging studies showed that the conjugate accumulated in tumor regions and exhibited the ability to target-specific delivery. In addition, significant antitumor activities for 401-4 was observed against U87-derived tumor xenografts in a dose dependent manner.

Fabrication of Poly Dopamine@poly (Lactic Acid-Co-Glycolic Acid) Nanohybrids for Cancer Therapy via a Triple Collaboration Strategy

Breast cancer is a common malignant tumor among women and has a higher risk of early recurrence, distant metastasis, and poor prognosis. Systemic chemotherapy is still the most widely used treatment for patients with breast cancer. However, unavoidable side effects and acquired resistance severely limit the efficacy of treatment. The multi-drug combination strategy has been identified as an effective tumor therapy pattern. In this investigation, we demonstrated a triple collaboration strategy of incorporating the chemotherapeutic drug doxorubicin (DOX) and anti-angiogenesis agent combretastatin A4 (CA4) into poly(lactic-co-glycolic acid) (PLGA)-based co-delivery nanohybrids (PLGA/DC NPs) via an improved double emulsion technology, and then a polydopamine (PDA) was modified on the PLGA/DC NPs' surface through the self-assembly method for photothermal therapy. In the drug-loaded PDA co-delivery nanohybrids (PDA@PLGA/DC NPs), DOX and CA4 synergistically induced tumor cell apoptosis by interfering with DNA replication and inhibiting tumor angiogenesis, respectively. The controlled release of DOX and CA4-loaded PDA@PLGA NPs in the tumor region was pH dependent and triggered by the hyperthermia generated via laser irradiation. Both in vitro and in vivo studies demonstrated that PDA@PLGA/DC NPs enhanced cytotoxicity under laser irradiation, and combined therapeutic effects were obtained when DOX, CA4, and PDA were integrated into a single nanoplatform. Taken together, the present study demonstrates a nanoplatform for combined DOX, CA4, and photothermal therapy, providing a potentially promising strategy for the synergistic treatment of breast cancer.

Phenyldivinylsulfonamides for the construction of antibody-drug conjugates with controlled four payloads

Phenyldivinylsulfonamides emerged from a series of divinylsulfonamides, demonstrating their ability to effectively re-bridge disulfide bonds. This kind of linkers was attached to monomethyl auristatin E (MMAE) and further conjugated with a model antibody, trastuzumab. After optimization, the linker 20 can deliver stable and highly homogenous DAR (Drug-to-Antibody Ratio) four antibody-drug conjugates (ADCs). The method was also applicable for other IgG1 antibodies to obtain ADCs with controlled four payloads. Moreover, the MMAE-bearing ADC is potent, selective and efficacious against target cell lines.

Recent advances in combretastatin A-4 codrugs for cancer therapy

CA4 is a potent microtubule polymerization inhibitor and vascular disrupting agent. However, the in vivo efficiency of CA4 is limited owing to its poor pharmacokinetics resulting from its high lipophilicity and low water solubility. To improve the water solubility, CA4 phosphate (CA4P) has been developed and shows potent antivascular and antitumor effects. CA4P had been evaluated as a vascular disrupting agent in previousc linical trials. However, it had been discontinued due to the lack of a meaningful improvement in progression-free survival and unfavorable partial response data. Codrug is a drug design approach to chemically bind two or more drugs to improve therapeutic efficiency or decrease adverse effects. This review describes the progress made over the last twenty years in developing CA4-based codrugs to improve the therapeutic profile and achieve targeted delivery to cancer tissues. It also discusses the existing problems and the developmental prospects of CA4 codrugs.

Site-specific construction of triptolide-based antibody-drug conjugates

Antibody-drug conjugates (ADCs) have emerging as efficient agents to target deliver cytotoxic drugs and reduce their off-target side effects. Triptolide has attracted attention to be used in ADC development. Herein, three rationally designed triptolide drug-linkers have been synthesized for use in site-specific construction of ADCs. Carbamates that were supposed to be more stable than carbonates were introduced to attach triptolide to the linkers. PEG and discrete PEG chains were incorporated to improve the hydrophilicity of drug-linkers. The ADCs were finally site-specifically prepared by conjugation of the drug-linkers to trastuzumab through disulfide re-bridging approach. The preliminary anti-tumor activities of these ADCs were evaluated and they displayed high potencies against HER2-targeted cancer in vitro and in vivo.

Anticancer properties of indole derivatives as IsoCombretastatin A-4 analogues

In this study, a variety of original ligands related to Combretastatin A-4 and isoCombretastatin A-4, able to inhibit the tubulin polymerization into microtubules, was designed, synthesized, and evaluated. Our lead compound 15d having a quinazoline as A-ring and a 2-substituted indole as B-ring separated by a N-methyl linker displayed a remarkable sub-nanomolar level of cytotoxicity (IC₅₀ < 1 nM) against 9 human cancer cell lines.