Eradication of CD19+ leukemia by targeted calicheamicin θ

Antibody-drug conjugates for targeted cancer therapy: Recent advances in potential payloads

Antibody-drug conjugates (ADCs) represent a promising cancer therapy modality which specifically delivers highly toxic payloads to cancer cells through antigen-specific monoclonal antibodies (mAbs). To date, 15 ADCs have been approved and more than 100 ADC candidates have advanced to clinical trials for the treatment of various cancers. Among these ADCs, microtubule-targeting and DNA-damaging agents are at the forefront of payload development. However, several challenges including toxicity and drug resistance limit the potential of this modality. To tackle these issues, multiple innovative payloads such as immunomodulators and proteolysis targeting chimeras (PROTACs) are incorporated into ADCs to enable multimodal cancer therapy. In this review, we describe the mechanism of ADCs, highlight the importance of ADC payloads and summarize recent progresses of conventional and unconventional ADC payloads, trying to provide an insight into payload diversification as a key step in future ADC development.

Application of a Biocatalytic Strategy for the Preparation of Tiancimycin-Based Antibody-Drug Conjugates Revealing Key Insights into Structure-Activity Relationships

Antibody-drug conjugates (ADCs) are cancer chemotherapeutics that utilize a monoclonal antibody (mAb)-based delivery system, a cytotoxic payload, and a chemical linker. ADC payloads must be strategically functionalized to allow linker attachment without perturbing the potency required for ADC efficacy. We previously developed a biocatalytic system for the precise functionalization of tiancimycin (TNM)-based payloads. The TNMs are anthraquinone-fused enediynes (AFEs) and have yet to be translated into the clinic. Herein, we report the translation of biocatalytically functionalized TNMs into ADCs in combination with the dual-variable domain (DVD)-mAb platform. The DVD enables both site-specific conjugation and a plug-and-play modularity for antigen-targeting specificity. We evaluated three linker chemistries in terms of TNM-based ADC potency and antigen selectivity, demonstrating a trade-off between potency and selectivity. This represents the first application of AFE-based payloads to DVDs for ADC development, a workflow that is generalizable to further advance AFE-based ADCs for multiple cancer types.

A brief overview of classical natural product drug synthesis and bioactivity

This manuscript briefly overviewed the total synthesis and structure–activity relationship studies of eight classical natural products, which emphasizes the important role of total synthesis in natural product-based drug development.

Antibody-drug conjugates for the treatment of lymphoma: clinical advances and latest progress

Antibody-drug conjugates (ADCs) are a promising class of immunotherapies with the potential to specifically target tumor cells and ameliorate the therapeutic index of cytotoxic drugs. ADCs comprise monoclonal antibodies, cytotoxic payloads with inherent antitumor activity, and specialized linkers connecting the two. In recent years, three ADCs, brentuximab vedotin, polatuzumab vedotin, and loncastuximab tesirine, have been approved and are already establishing their place in lymphoma treatment. As the efficacy and safety of ADCs have moved in synchrony with advances in their design, a plethora of novel ADCs have garnered growing interest as treatments. In this review, we provide an overview of the essential elements of ADC strategies in lymphoma and elucidate the up-to-date progress, current challenges, and novel targets of ADCs in this rapidly evolving field.

Challenges and Opportunities to Develop Enediyne Natural Products as Payloads for Antibody-Drug Conjugates

Calicheamicin, the payload of the antibody-drug-conjugates (ADCs) gemtuzumab ozogamicin (Mylotarg^®) and inotuzumab ozogamicin (Besponsa^®), belongs to the class of enediyne natural products. Since the isolation and structural determination of the neocarzinostatin chromophore in 1985, the enediynes have attracted considerable attention for their value as DNA damaging agents in cancer chemotherapy. Due to their non-discriminatory cytotoxicity towards both cancer and healthy cells, the clinical utilization of enediyne natural products relies on conjugation to an appropriate delivery system, such as an antibody. Here we review the current landscape of enediynes as payloads of first-generation and next-generation ADCs.

Streamlined Total Synthesis of Shishijimicin A and Its Application to the Design, Synthesis, and Biological Evaluation of Analogues thereof and Practical Syntheses of PhthNSSMe and Related Sulfenylating Reagents

Shishijimicin A is a scarce marine natural product with highly potent cytotoxicities, making it a potential payload or a lead compound for designed antibody-drug conjugates. Herein, we describe an improved total synthesis of shishijimicin A and the design, synthesis, and biological evaluation of a series of analogues. Equipped with appropriate functionalities for linker attachment, a number of these analogues exhibited extremely potent cytotoxicities for the intended purposes. The synthetic strategies and tactics developed and employed in these studies included improved preparation of previously known and new sulfenylating reagents such as PhthNSSMe and related compounds.

Novel insights on the DNA interaction of calicheamicin γ₁(I)

Calicheamicin γ1(I) (Cal) is a unique molecule in which a DNA binding motif (aryl-tetrasaccharide) is linked to a DNA cleaving moiety (calicheamicinone). The hallmark of this natural product rests in the impressive optimization of these two mechanisms leading to a drug that is extremely efficient in cleaving DNA at well-defined sites. However, the relative contributions of these two structurally distinct domains to the overall process have not been fully elucidated yet. Here, we used different experimental approaches to better dissect the role of the aryl-tetrasaccharide and the enediyne moieties in the DNA sequence selective binding step as well as the in the cleavage reaction. Our results highlight the remarkable cooperation of the two components in producing an amazing molecular machine. The herein presented molecular details of this concerted mechanism of action can be further applied to rationally design more druggable compounds.

The anti-CD19 antibody-drug conjugate SAR3419 prevents hematolymphoid relapse postinduction therapy in preclinical models of pediatric acute lymphoblastic leukemia

PURPOSE

Relapsed or refractory pediatric acute lymphoblastic leukemia (ALL) remains a major cause of death from cancer in children. In this study, we evaluated the efficacy of SAR3419, an antibody-drug conjugate of the maytansinoid DM4 and a humanized anti-CD19 antibody, against B-cell precursor (BCP)-ALL and infant mixed lineage leukemia (MLL) xenografts.

EXPERIMENTAL DESIGN

ALL xenografts were established as systemic disease in immunodeficient (NOD/SCID) mice from direct patient explants. SAR3419 was administered as a single agent and in combination with an induction-type regimen of vincristine/dexamethasone/l-asparaginase (VXL). Leukemia progression and response to treatment were assessed in real-time, and responses were evaluated using strict criteria modeled after the clinical setting.

RESULTS

SAR3419 significantly delayed the progression of 4 of 4 CD19(+) BCP-ALL and 3 of 3 MLL-ALL xenografts, induced objective responses in all but one xenograft but was ineffective against T-lineage ALL xenografts. Relative surface CD19 expression across the xenograft panel significantly correlated with leukemia progression delay and objective response measure scores. SAR3419 also exerted significant efficacy against chemoresistant BCP-ALL xenografts over a large (10-fold) dose range and significantly enhanced VXL-induced leukemia progression delay in two highly chemoresistant xenografts by up to 82 days. When administered as protracted therapy following remission induction with VXL, SAR3419 prevented disease recurrence into hematolymphoid and other major organs with the notable exception of central nervous system involvement.

CONCLUSION

These results suggest that incorporation of SAR3419 into remission induction protocols may improve the outcome for high-risk pediatric and adult CD19(+) ALL.

Targeting paediatric acute lymphoblastic leukaemia: novel therapies currently in development

Modifications to the treatment of acute lymphoblastic leukaemia (ALL) in children have led to a dramatic increase in survival in the past 40 years. Despite this success, a significant subset of paediatric leukaemia patients either relapse or fail to ever achieve a complete remission. Additionally, some patients necessitate treatment with intensified chemotherapy regimens due to clinical or laboratory findings which identify them as high risk. These patients are unlikely to respond to further minor adjustments to the dosing or timing of administration of the same chemotherapy medications. Many novel targeted therapies for the treatment of childhood ALL provide potential mechanisms to further improve cure rates, and provide the possibility of minimizing toxicity to non-malignant cells, given their specificity to malignant cell phenotypes. This article explores many of the potential targeted therapies in varying stages of development, from those currently in clinical trials to those still being refined in the research laboratory.