Current Role of Topoisomerase I Inhibitors for the Treatment of Mesenchymal Malignancies and Their Potential Future Use as Payload of Sarcoma-Specific Antibody-Drug Conjugates.

BACKGROUND: Topoisomerase I is an enzyme that plays a crucial part in DNA replication and transcription by the relaxation of supercoiled double-stranded DNA. Topoisomerase I inhibitors bind to the topoisomerase I cleavage complex, thereby stabilizing it and preventing the religation of the DNA strands, leading to DNA damage, cell cycle arrest, and apoptosis. Various topoisomerase I inhibitors have been evaluated in solid tumors, and irinotecan and topotecan have been approved for the treatment of epithelial malignancies. None of them have been approved for sarcoma, a diverse group of rare solid tumors with an unmet need for effective treatments. SUMMARY: Topoisomerase I inhibitors have been evaluated in preclinical studies as single agents or in combination in solid tumors, some of which have included sarcomas where activity was observed. Clinical trials evaluating topoisomerase I inhibitors for the treatment of sarcoma have shown limited efficacy as monotherapy. In combination with other cytotoxic agents, topoisomerase I inhibitors have become part of clinical routine in selected sarcoma subtypes. Regimens such as irinotecan/vincristine/temozolomide are used in relapsed rhabdomyosarcoma, irinotecan/temozolomide and vincristine/topotecan/cyclophosphamide are commonly given in refractory Ewing sarcoma, and topotecan/carboplatin showed some activity in advanced soft tissue sarcoma. This review provides an overview of key studies with topoisomerase I inhibitors for the treatment of sarcoma. Topoisomerase I inhibitors are currently also being assessed as "payloads" for antibody-drug conjugates (ADCs), allowing for the targeting of specific antigen-expressing tumor cells and the delivery of the inhibitor directly to the tumor cells with the potential of enhancing therapeutic efficacy while minimizing systemic toxicity. Here, we also provide a brief overview on topoisomerase I-ADCs. KEY MESSAGE: Topoisomerase I inhibitors are an important component of some systemic therapies for selected sarcomas and have potent cytotoxic properties and pharmacological characteristics that make them relevant candidates as payloads for the development of sarcoma-specific ADCs. ADCs are antibody-based targeted agents allowing for efficient and specific delivery of a given drug to the tumor cell. Topoisomerase I-ADCs are a novel targeted delivery approach which may have the potential to improve the therapeutic index of topoisomerase I inhibitors in the treatment of sarcoma and warrants investigation in a broad variety of mesenchymal malignancies.

Immunogenicity of small-cell lung cancer associates with STING pathway activation and is enhanced by ATR and TOP1 inhibition.

INTRODUCTION: The activation of STING (stimulator of interferon genes) pathway enhances antitumor immunity in small-cell lung cancer (SCLC), while the DNA damage induced by non-cGAMP-based agonists is a potent inducer of STING activity. Here, we investigate the intrinsic expression of STING in cancer cells and evaluate the value of the combination of ATR and TOP1 inhibitors in enhancing antitumor immunity. METHODS: STING expression was assessed at mRNA and protein levels in SCLC and normal lung tissues. Transcriptomic subsets of SCLC were identified based on STING-related genes. Distinct mutation and immunogenomic profiles of these subsets were determined. The direct antitumor efficacy and the potential of enhancing antitumor immunity of the strategy using the ATR-TOP1-inhibitor combination were tested in SCLC cell lines. RESULTS: The intrinsic expression of STING was significantly reduced in SCLC compared to normal lung tissues (p < 0.0001). Three STING-related SCLC subtypes were identified in which the STING-high subtype was associated with (1) high immune infiltration, (2) high expression of genes related to MHC and immune checkpoints, and (3) high EMT and ferroptosis score. On the contrary, the STING-low subtype was enriched with pathways related to DNA damage response (DDR) and cell cycle progression. The association between the DDR pathway activity and the STING-IFN innate immune response was verified by in vitro experiments in which the inhibition of ATR and TOP1 triggered the expression of genes encoding type I IFN signaling and pro-inflammatory cytokines/chemokines in a STING-low SCLC cell line. CONCLUSION: Our study verifies that activation of the STING-IFN response by ATR and TOP1 inhibitors might be a therapeutic strategy to improve the response to immune checkpoint therapy in STING-low SCLC. Furthermore, the combinations of ATR and TOP1 inhibitors can augment tumor inflammation in STING-low SCLC.

TOP1 inhibition induces bifurcated JNK/MYC signaling that dictates cancer cell sensitivity.

Rationale: Triple-negative breast cancer (TNBC) does not respond to anti-estrogen and anti-HER2 therapies and is commonly treated by chemotherapy. TNBC has a high recurrence rate, particularly within the first 3 years. Thus, there is an urgent clinical need to develop more effective therapies for TNBC. Topoisomerase I (TOP1) inhibitors cause DNA damage, making these drugs desirable for TNBC treatment since DNA repair machinery is defective in this subtype of breast cancer. Among the main molecular subtypes of breast cancer, the TNBC cell lines exhibited the highest TOP1 inhibition sensitivity. However, clinically used TOP1 inhibitors, such as topotecan and irinotecan, have shown limited clinical applications and the reasons remain unclear. Understanding the mechanism of differential responses to TOP1 blockade and identifying the predictive markers for cancer cell sensitivity will help further TOP1-targeted therapy for TNBC treatment and improve the clinical use of TOP1 inhibitors. Methods: Viability assays were used to evaluate breast cancer cell sensitivity to topotecan and other TOP1 inhibitors as well as TOP2 inhibitors. An in vitro-derived topotecan-resistant TNBC cell model and TNBC xenograft models were employed to confirm cancer cell response to TOP1 blockade. RNA-seq was used to identify potential predictive markers for TNBC cell response to TOP1 blockade. Western blotting and qRT-PCR were performed to measure the protein levels and RNA expression. ATAC-seq and luciferase reporter assays were used to examine MYC transcriptional regulations. The effects of MYC and JNK in cancer cell response to TOP1 inhibition were validated via loss-of-function and gain-of-function experiments. Results: We observed two distinct and diverging cancer cell responses - sensitive versus resistant to TOP1 inhibition, which was confirmed by TNBC xenograft mouse models treated by topotecan. TNBC cells exhibited bifurcated temporal patterns of ATR pathway activation upon TOP1 inhibitor treatment. The sensitive TNBC cells showed an "up then down" dynamic pattern of ATR/Chk1 signaling, while the resistant TNBC cells exhibited a "persistently up" profile. On the contrary, opposite temporal patterns of induced expression of MYC, a key regulator and effector of DNA damage, were found in TNBC cells treated by TOP1 inhibitors. Mechanistically, we showed that TOP1-induced JNK signaling upregulated MYC expression. Furthermore, pharmacological inhibition of ATR reversed TNBC cell resistance to topotecan, whereas MYC knockdown and JNK inhibition reduced cancer cell sensitivity. Conclusions: Dynamic temporal profiles of induced ATR/Chk1 and JNK activation as well as MYC expression, may predict cancer cell response to TOP1 inhibitors. JNK activation-mediated constitutive elevation of MYC expression may represent a novel mechanism governing cancer cell sensitivity to TOP1-targeting therapy. Our results may provide implications for identifying TNBC patients who might benefit from the treatment with TOP1 inhibitors.

The design and discovery of topoisomerase I inhibitors as anticancer therapies.

INTRODUCTION: Cancer has been identified as one of the leading causes of death worldwide. The biological target of some anticancer agents is topoisomerase I, an enzyme involved in the relaxation of supercoiled DNA. The synthesis of new compounds with antiproliferative effect and behaving as topoisomerase I inhibitors has become an active field of research. Depending on their mechanism of inhibition, they can be classified as catalytic inhibitors or poisons. AREAS COVERED: This review article summarizes the state of the art for the development of selective topoisomerase I inhibitors. Collected compounds showed inhibition of the enzyme, highlighting those approved for clinical use, the combination therapies developed, as well as related drawbacks and future focus. EXPERT OPINION: Research related to topoisomerase I inhibitors in cancer therapy started with camptothecin (CPT). This compound was first selected as a good anticancer agent and then topoisomerase I was identified as its therapeutic target. Derivatives of CPT irinotecan, topotecan, and belotecan are the only clinically approved inhibitors. Currently, their limitations are being addressed by different stretegies. Future studies should focus not only on developing other active molecules but also on improving the bioavailability and pharmacokinetics of potent synthetic derivatives.

Seguridad y eficacia del uso de regorafenib para el tratamiento de cáncer colorrectal metastásico con progresión de enfermedad al menos a dos líneas de quimioterapia previa / Safety and efficacy of the use of regorafenib for the treatment of metastatic colorectal cancer with progression of disease to at least two lines of prior chemotherapy

INTRODUCCIÓN: El presente dictamen expone la evaluación de la eficacia y seguridad del uso de regorafenib para el tratamiento de cáncer colorrectal metastásico con progresión de enfermedad al menos a dos líneas de quimioterapia previa. A nivel mundial, el cáncer colorrectal es el tercer tipo de cáncer más frecuente y la cuarta causa de muerte por cáncer. Alrededor del 20% a 55% de los pacientes con cáncer colorrectal presentan enfermedad metastásica al momento del diagnóstico, y aproximadamente un 50% a 60% de los pacientes diagnosticados en estadíos tempranos desarrollarán metástasis en algún momento del trascurso de la enfermedad. En la actualidad, el petitorio farmacológico de EsSalud cuenta con los esquemas de quimioterapia a base de fluoropirimidas, oxaliplatino e irinotecán, los cuales son el tratamiento estándar para el manejo de cáncer colorrectal metastásico, suponiendo alternativas de tratamiento eficaces y seguras para pacientes con cáncer colorrectal metastásico. Sin embargo, existen pacientes que ya han progresado a todas éstas alternativas surgiendo la necesidad de evaluar otras posibles opciones. TECNOLOGIA SANITARIA DE INTERÉS: Regorafenib es un inhibidor multiquinasa de los receptores de tirosina quinasa intracelulares y de membrana, con actividad antitumoral y anti angiogénica. El cual ha sido aprobado por la Food and Drug Administration (FDA) para su uso en pacientes que han progresado a quimioterapia previa basada en fluoropirimidas, oxaliplatino, e irinotecán; así como terapias biológicas anti-VEGF, y anti-EGFR de ser KRAS salvaje (i.e., wild type o KRAS no mutado). De igual manera, la European Medicines Agency (EMA) menciona su uso en pacientes que han progresado a quimioterapia a base de fluoropirimidas y tratamientos anti-VEGF y anti-EGFR. METODOLOGÍA: Se realizó una búsqueda de la literatura con respecto a la eficacia y seguridad del uso de regorafenib para el tratamiento de cáncer colorrectal metastásico con progresión a enfermedad luego de al menos dos líneas de quimioterapia previa. Esta búsqueda se realizó utilizando los meta-buscadores: Translating Research into Practice (TRIPDATABASE) y National Library of Medicine (Pubmed-Medline). Adicionalmente, se realizó una búsqueda manual del listado de referencias bibliográficas de los estudios seleccionados a fin de identificar otros estudios que pudieran ser útiles para la presente evaluación. Por otro lado, se amplió la búsqueda revisando la evidencia generada por grupos internacionales que realizan revisiones sistemáticas (RS), evaluación de tecnologías sanitarias (ETS) y guías de práctica clínica (GPC), tales como la Cochrane Group, The National Institute for Health and Care Excellence (NICE), the Agency for Health care Research and Quality (AHRQ), The Scottish Medicines Consortium (SMC), y The Canadian Agency for Drugs and Technologies in Health (CADTH). Esta búsqueda se completó revisando publicaciones de grupos dedicados a la educación, investigación y mejora de la práctica clínica oncológica dentro de América y Europa, como The National Comprehensive Cancer Network (NCCN), The American Society of Clinical Oncology (ASCO) y The European Society of Medical Oncology (ESMO). Por último, se completó la búsqueda ingresando a la página web www.clinicaltrials.gov, para así poder identificar ensayos clínicos en elaboración o que no hayan sido publicados aún, y así disminuir el riesgo de sesgo de publicación. RESULTADOS: Se realizó la búsqueda bibliográfica y de evidencia científica hasta la actualidad para el sustento del uso de regorafenib para el tratamiento de cáncer de colon metastásico con progresión a enfermedad al menos a dos líneas de quimioterapia previa. Se presenta la evidencia disponible según el tipo de publicación priorizada en los critérios de inclusión (i.e., GP, ETS, RS y ECA fase III). A la fecha la evidencia detrás del uso de regorafenib para el tratamiento de cáncer colorrectal metastásico en pacientes que han progresado a terapias estándar previa se basan principalmente en los ensayos de fase III CORRECT publicado por Grothey et al., 2013; y CONCUR publicado por Li et al., 2015. Ambos ensayos mostraron un beneficio modesto en el uso de regorafenib en términos de sobrevida global (diferencia en la mediana de 1.4 meses y 2.5 meses, respectivamente). Adicionalmente, es de notar que los resultados obtenidos del ensayo CORRECT provienen del segundo análisis interino, último análisis realizado. Así, este análisis solo incluyó el 74% de las muertes estimadas para el cálculo de la sobrevida global final. Si bien se tomó en consideración el desgaste del alfa debido a los análisis interinos realizados, según Basseler et al., 2010 el estimado puntual obtenido de los ensayos truncados sobreestimaría el riesgo relativo en un 30% (RR a los tres meses 0.75, IC 95%: 0.57- 0.98, valor p=0.0352; a los seis meses 0.84, IC 95% 0.73-0.99, valor p=0.0167; y a los 12 meses 1.00, IC 95% 0.92-1.09, valor p=0.9905. aplicando el ajuste por sobre estimación del RR de 1.1, 1.2, y 1.6, espectivamente), con lo cual se perdería la modesta diferencia en la sobrevida global reportada. Por otro lado, en ambos ensayos se observó una disminución de la calidad de vida en relación a la línea de base para los pacientes que usaron regorafenib, con puntajes menores que los del grupo placebo. Asimismo, se observó una gran proporción de eventos adversos grado 3-4 para el grupo de regorafenib (~54% para ambos ensayos). En el ensayo CONCUR además se menciona una proporción de 32% de eventos sérios De manera consistente con lo observado en ambos ensayos, la evaluación de tecnología sanitaria realizada por la Canadian Agency for Drugs and Technologies in Health (CADTH), decide que regorafenib, al presentar una eficacia modesta y no presentar mejoras en la calidad de vida, no es costo-efectiva en comparación con mejor terapia de soporte, además de presentar mayor proporción de eventos adverso; y por lo tanto no la recomienda dentro de su sistema de salud. CONCLUSIÓN: El Instituto de Evaluación de Tecnologías Sanitarias-IETSI, no aprueba el uso de regorafenib para el tratamiento de cáncer de colon metastásico con progresión a enfermedad al menos a dos líneas de quimioterapia previa.

Combined topoisomerase I inhibition for the treatment of metastatic colon cancer.

The objective of this study was to define the maximally tolerated dose (MTD) and response rate of a combination of two topoisomerase I inhibitors, topotecan and irinotecan, in patients with metastatic colon cancer. Eleven patients, the majority with previously progressive disease on 5-fluorouracil-based regimens, were enrolled onto a phase I/II dose escalation trial utilizing continuous infusion topotecan for 2 weeks and weekly irinotecan x 3 with cycles repeated every 28 days. Dosages of topotecan utilized included 0.2 and 0.25mg/m2/day. Irinotecan was administered at a dose of 62 mg/m2 by i.v. bolus. Patients were followed for toxicity and response. The MTD of the combination of agents was found to be 0.25mg/m2/day for topotecan and 62 mg/m2 for irinotecan. The most common serious toxicities were diarrhea and nausea/vomiting. Only one patient experienced grade III neutropenia. There were no complete or partial responses. However, four patients had prolonged disease stabilization (SD) of up to 324 days and this group remained on protocol therapy for an average of 227 days (p=0.0005 versus patients not achieving SD). We concluded that the MTD for this combination of topoisomerase I inhibitors, given on this particular schedule, has been defined. This combination cannot be recommended as a first- or second-line therapy for patients with metastatic colon cancer based on the responses observed. However, approximately one-third of patients achieved prolonged disease stabilization. Topotecan with irinotecan may be useful as a palliative regimen for a subgroup of colon cancer patients.

Complete remission of unresectable hepatocellular carcinoma on healthy liver by the combination of aggressive surgery and high-dose-intensity chemotherapy by CPT-11.

Hepatocellular carcinoma (HCC) is one of the most frequent cancers. The only curative treatment is liver transplantation or complete surgical resection; however, most patients have inoperable disease at diagnosis. To date, no cytotoxic agent has demonstrated a clinical impact on time-related parameters, especially survival. The development of new treatments of inoperable HCC patients is highly desirable. Among the new cytotoxic agents, DNA topoisomerase I poisons are those with the widest spectrum of antitumor activity. However, few data are available in HCC patients. One of the main obstacles to the use of irinotecan in HCC is the frequent alterations of liver function at diagnosis. A 48-year-old patient with a HCC that had developed within a normal liver but of very poor prognosis because of a multifocal primary tumor with a large nodule measuring 10 cm of diameter, associated with a portal thrombosis, could tolerate very intensive treatment with irinotecan using doses up to 700 mg/m2 every 2 weeks and was responsive to treatment as measured by alpha-fetoprotein levels. Despite initial criteria of inoperability, the absence of disease progression under therapy with a follow-up of 1 year invited us to propose a liver transplant. The patient is still in post-surgical complete remission and has consolidation chemotherapy with irinotecan. This result invites us to consider the evaluation of the efficacy of topoisomerase I poisons in HCC patients and to escalate the dose of irinotecan in patients with less than grade 4 neutropenia.

[Topoisomerases: therapeutic value]. / Les topoisomérases: intérêt thérapeutique.

Anticancer pharmacology offers rich prospects for future therapeutic design. Knowledge of antitumoral agents pharmacology have widely advanced: understanding of the molecular cytotoxic mechanism of available agents, discovery of new compounds with a different and no-interfering mechanism of action. Since ten years, the identification of a couple of nuclear enzyme, DNA-topoisomerases, has answered to this goal. These enzymes catalyse the topological changes of the double strand DNA, participating to vital processes of cell metabolism. These enzymes are now know to be the intracellular target of widely used cytotoxic agents (such as anthracycline, Etoposide, Teniposide for DNA topoisomerase II) and for two new compounds in clinical trials (irinotecan and topotecan, both analogues of camptothecin, for DNA-topoisomerase I). This two last molecules, currently in phase II development, are promising. They seem to be synergistic in combination with available anticancer agents, but this remains to be demonstrated. Other drugs, inhibiting both DNA-topoisomerases I and II, are yet investigating. Would they provide new answers for the future?

New anticancer agents in clinical development.

A better understanding of the biology and biochemistry of the cancer cell has led to the development of various promising new antineoplastic compounds that are now undergoing phase I, II, and III clinical testing. These drugs include topoisomerase I inhibitors, such as camptothecin and its analogs 9-aminocamptothecin, irinotecan, and topotecan; the paclitaxel analog docetaxel; gemcitabine, an antimetabolite structurally related to cytarabine; and fluorouracil prodrugs and other thymidylate synthase (TS) inhibitors. Another exciting approach to cancer treatment is the use of agents that induce a less malignant state by altering cellular phenotype. Such agents include angiogenesis inhibitors, differentiating agents, signal transduction inhibitors, and gene therapy.

Effects of CPT-11 (a unique DNA topoisomerase I inhibitor) on a highly malignant xeno-transplanted neuroblastoma.

Although many advances have been made in the management of neuroblastoma, the prognosis of patients with advanced neuroblastoma remains poor, and constant efforts are being made to search for newer effective drugs. CPT-11 is a newly developed derivative of camptothecin and shows a unique anti-tumor activity by inhibiting DNA topoisomerase I. In this study the effects of CPT-11 on a human neuroblastoma xenograft, TNB9, were investigated according to the standard Battelle Columbus Laboratories protocol. TNB9 is one of the most malignant strains of neuroblastoma, showing a homogeneously staining resion (HSR) on chromosome 20 and 80-fold amplification of the N-myc gene. This study disclosed that CPT-11 was highly effective against TNB9. Maximum inhibition rate (IR) was 72.5% at a standard dose and 52.8% even at half the dose. No nude mouse used in this study lost weight after an administration of CPT-11. Plasma pharmacokinetics of CPT-11 administered in this experimental model were compared to that in clinical patients. Our data suggested that CPT-11 might be a promising new drug in the treatment of high-risk neuroblastoma patients and encouraged us to employ CPT-11 in the protocol of the Study Group of Japan.