Outcomes and clinical characteristics of the compassionate use of plitidepsin in COVID-19 patients with solid tumours, haematological malignancies or anti-CD20 antibody treatment.

OBJECTIVE: To study the effect of plitidepsin antiviral treatment in immunocompromised COVID-19 patients with underlying haematological malignancies or solid tumours, particularly those who have undergone anti-CD20 therapies. DESIGN: We conducted a retrospective observational study, involving 54 adults treated with plitidepsin on compassionate use as an antiviral drug. Our analysis compared outcomes between patients with solid tumours and those with haematological malignancies, and a cohort of cases treated or not with anti-CD20 monoclonal antibodies. RESULTS: Patients with a history of anti-CD20 therapies showed a prolonged time-to-negative RT-PCR for SARS-CoV-2 infection compared to non-treated patients (33 d (28;75) vs 15 (11;25); p = .002). Similar results were observed in patients with solid tumours in comparison to those with haematological malignancies (13 (10;16) vs 26 (17;50); p < .001). No serious adverse events were documented. CONCLUSIONS: Patients with haematological malignancies appear to be at a heightened risk for delayed SARS-CoV-2 clearance and subsequent clinical complications. These findings support plitidepsin as a well-tolerated treatment in this high-risk group. A phase II clinical trial (NCT05705167) is ongoing to evaluate plitidepsin as an antiviral drug in this population.KEY POINTSHaematological patients face an increased risk for severe COVID-19.Anti-CD20 therapies could increase fatal outcomes in COVID-19 patients.Persistent viral replication is increased in immunocompromised patients.Plitidepsin does not lead to new serious adverse events in immunocompromised patients.

Outcomes and clinical characteristics of the compassionate use of plitidepsin for immunocompromised adult patients with COVID-19.

OBJECTIVES: To evaluate the compassionate use of plitidepsin as an antiviral treatment in hospitalized immunocompromised adult patients with moderate-to-severe COVID-19. DESIGN: Retrospective observational study of data -collected from January 01, 2021 to April 30, 2022- from 35 immunocompromised adult patients with COVID-19 non-eligible for other available antiviral treatments. Main outcome measures were time to respiratory recovery (SpFi ≥ 315); COVID-19-related 30-day-cumulative mortality after first plitidepsin infusion; and time to undetectable levels of viral RNA. RESULTS: Thirty-three patients receiving a full course of plitidepsin (2.5 mg [n = 29] or 1.5 mg [n = 4]) were included. Most (69.7%) had a malignant hematologic disease and 27.3% had solid tumors. A total of 111 infusions were administered with lack of relevant safety events. Median time from plitidepsin initiation to SpFi ≥315 was 8 days (95% confidence interval [CI], 7-19). Median time to first negative reverse transcription-polymerase chain reaction for SARS-CoV-2 (cycle threshold >36) was 17 days (95% CI 13-25). Mortality rate was 16.3% (95% CI 3-37.3). CONCLUSION: These data support plitidepsin as a well-tolerated treatment that might have potential clinical and antiviral efficacy in COVID-19 immunocompromised patients.

3D bioprinted functional skeletal muscle models have potential applications for studies of muscle wasting in cancer cachexia.

Acquired muscle diseases such as cancer cachexia are responsible for the poor prognosis of many patients suffering from cancer. In vitro models are needed to study the underlying mechanisms of those pathologies. Extrusion bioprinting is an emerging tool to emulate the aligned architecture of fibers while implementing additive manufacturing techniques in tissue engineering. However, designing bioinks that reconcile the rheological needs of bioprinting and the biological requirements of muscle tissue is a challenging matter. Here we formulate a biomaterial with dual crosslinking to modulate the physical properties of bioprinted models. We design 3D bioprinted muscle models that resemble the mechanical properties of native tissue and show improved proliferation and high maturation of differentiated myotubes suggesting that the GelMA-AlgMA-Fibrin biomaterial possesses myogenic properties. The electrical stimulation of the 3D model confirmed the contractile capability of the tissue and enhanced the formation of sarcomeres. Regarding the functionality of the models, they served as platforms to recapitulate skeletal muscle diseases such as muscle wasting produced by cancer cachexia. The genetic expression of 3D models demonstrated a better resemblance to the muscular biopsies of cachectic mouse models. Altogether, this biomaterial is aimed to fabricate manipulable skeletal muscle in vitro models in a non-costly, fast and feasible manner.

A phase II trial of weekly nab-paclitaxel for progressive and symptomatic desmoid tumors.

Desmoid fibromatosis (DF) are mesenchymal neoplasms, with potential aggressive course and relevant clinical impact. New systemic therapy modalities are needed in this symptomatic/progressive population. In this multicenter, phase II trial (NCT03275818), patients with symptomatic/progressing DF received three cycles of weekly nab-paclitaxel. Brief pain inventory short form (BPI-SF) was collected at baseline and in every visit. MRI was performed every 3 months. Primary composite endpoint was RECIST 1.1 overall response rate (ORR) and/or clinical response (improvement ≥ 2 points in BPI-SF). If 40% of patients achieved clinical/radiological response, further investigation would be warranted. Toxicity, progression-free survival (PFS), pattern of response and its correlation with clinical best response and BPI, variation of physical function, and analgesic consumption were secondary endpoints. The translational research reported was not a pre-specified secondary outcome. Forty eligible patients started therapy, being 35 radiologically and clinically evaluable. The study achieved its primary endpoint, as 7(20%) patients obtained RECIST partial response, whereas 31(89%) experienced pain reduction of ≥2 points in BPI-SF worst pain. Therapy was well tolerated. With a median follow-up of 30(14-44) months, median 12 and 24-months PFS rates were 91%(CI 95%, 82-100) and 84%(CI 95%, 71-97). For clinical progression, 12 and 24-months PFS rates were 85% (CI 95%, 73-97) and 74% (CI 95%, 58-90) respectively. Short course of nab-paclitaxel is active, safe and achieves quick and durable responses in progressing/symptomatic DF patients.

Intermittent BRAF inhibition in advanced BRAF mutated melanoma results of a phase II randomized trial.

Combination treatment with BRAF (BRAFi) plus MEK inhibitors (MEKi) has demonstrated survival benefit in patients with advanced melanoma harboring activating BRAF mutations. Previous preclinical studies suggested that an intermittent dosing of these drugs could delay the emergence of resistance. Contrary to expectations, the first published phase 2 randomized study comparing continuous versus intermittent schedule of dabrafenib (BRAFi) plus trametinib (MEKi) demonstrated a detrimental effect of the "on-off" schedule. Here we report confirmatory data from the Phase II randomized open-label clinical trial comparing the antitumoral activity of the standard schedule versus an intermittent combination of vemurafenib (BRAFi) plus cobimetinib (MEKi) in advanced BRAF mutant melanoma patients (NCT02583516). The trial did not meet its primary endpoint of progression free survival (PFS) improvement. Our results show that the antitumor activity of the experimental intermittent schedule of vemurafenib plus cobimetinib is not superior to the standard continuous schedule. Detection of BRAF mutation in cell free tumor DNA has prognostic value for survival and its dynamics has an excellent correlation with clinical response, but not with progression. NGS analysis demonstrated de novo mutations in resistant cases.

Health Care Resource Utilization and Costs among Adult Patients with Advanced Soft Tissue Sarcoma: A Retrospective Medical Record Review in the United Kingdom, Spain, Germany, and France.

OBJECTIVE: To describe health care resource utilization and costs for patients with advanced soft tissue sarcoma (STS) in the United Kingdom (UK), Spain, Germany, and France. METHODS: Physicians abstracted data for adult patients with a diagnosis of advanced STS (other than Kaposi's sarcoma or gastrointestinal stromal tumor) who received ≥1 lines of systemic therapy. Health care resource utilization related to advanced STS treatment was recorded; associated costs were estimated by applying unit costs. RESULTS: A total of 130 physicians provided data for 807 patients (UK: 199; Spain: 203; Germany: 204; and France: 201). The site of care during active treatment varied based on differences in the health care systems of these four countries. Total mean per-patient health care cost in the UK was £19,457; in Spain, €26,814; in Germany, €20,468; and in France, €24,368. Advanced STS-related systemic treatment costs were driven primarily by drug acquisition and administration costs. Treatment-related costs increased during later lines of therapy for all countries except France, where they decreased after first-line therapy. Pain control and antiemetics were the most common supportive care medications. CONCLUSIONS: This study provides real-world data on resource utilization and estimated costs in advanced STS and could inform policymakers about treatment burden.

Treatment Patterns and Survival among Adult Patients with Advanced Soft Tissue Sarcoma: A Retrospective Medical Record Review in the United Kingdom, Spain, Germany, and France.

OBJECTIVE: To describe real-world treatment patterns and outcomes for patients with advanced soft tissue sarcoma (STS) not amenable to surgery or radiotherapy in the United Kingdom, Spain, Germany, and France. METHODS: Physicians completed a web-based medical record abstraction for adult patients with advanced STS (other than Kaposi's sarcoma or gastrointestinal stromal tumor) who received ≥1 line of systemic therapy. Clinical characteristics, treatments, tumor responses, and mortality data were recorded. RESULTS: A total of 130 physicians provided data for 807 patients. Patients' mean age at advanced STS diagnosis was 57.1 (±12.3) years; 59% were male. The most commonly identified histologic categories were leiomyosarcoma (28%), liposarcoma (13%), and rhabdomyosarcoma (11%). Overall, 57% of patients received only 1 line of therapy, 32% received 2 lines of therapy, and 11% received ≥3 lines of therapy. The most common first-line regimens were doxorubicin alone (41%), doxorubicin plus ifosfamide (19%), docetaxel plus gemcitabine (9%), paclitaxel alone (4%), and ifosfamide (4%). Median overall survival from start of treatment was estimated to be 17.6 months (95% confidence interval, 15.6-19.0 months). CONCLUSIONS: In real-world clinical practice, advanced STS is most commonly treated with older therapies in the United Kingdom, Spain, Germany, and France. New therapies that improve overall survival in advanced STS are needed.

Multiplatform plasma fingerprinting in cancer cachexia: a pilot observational and translational study.

BACKGROUND: Cachexia is a metabolic syndrome that affects up to 50-80% of cancer patients. The pathophysiology is characterized by a variable combination of reduced food intake and abnormal metabolism, including systemic inflammation and negative protein and energy balance. Despite its high clinical significance, defined diagnostic criteria and established therapeutic strategies are lacking. The 'omics' technologies provide a global view of biological systems. We hypothesize that blood-based metabolomics might identify findings in cachectic patients that could provide clues to gain knowledge on its pathophysiology, and eventually postulate new therapeutic strategies. METHODS: This is a cross-sectional observational study in two cohorts of cancer patients, with and without cachexia. Patients were consecutively recruited from routine clinical practice of a General Oncology Department at '12 de Octubre' University Hospital. Selected clinical and biochemical features were collected. Blood metabolite fingerprinting was performed using three analytical platforms, gas chromatography coupled to mass spectrometry (GC-MS), capillary electrophoresis coupled to mass spectrometry (CE-MS), and liquid chromatography coupled to mass spectrometry (LC-MS). Besides, we performed pathway-based metabolite analyses to obtain more information on biological functions. RESULTS: A total of 15 subjects were included in this study, 8 cachectic and 7 non-cachectic patients. Metabolomic analyses were able to correctly classify their samples in 80% (GC-MS), 97% (CE-MS), 96% [LC-MS (positive mode)], and 89% [LC-MS (negative mode)] of the cases. The most prominent metabolic alteration in plasma of cachectic patients was the decrease of amino acids and derivatives [especially arginine, tryptophan, indolelactic acid, and threonine, with 0.4-fold change (FC) compared with non-cachectic patients], along with the reduction of glycerophospholipids [mainly lysophosphatidylcholines(O-16:0) and lysophosphatidylcholines(20:3) sn-1, FC = 0.1] and sphingolipids [SM(d30:0), FC = 0.5]. The metabolite with the highest increase was cortisol (FC = 1.6). Such alterations suggest a role of the following metabolic pathways in the pathophysiology of cancer cachexia: arginine and proline metabolism; alanine, aspartate, and glutamate metabolism; phenylalanine metabolism; lysine degradation; aminoacyl-tRNA biosynthesis; fatty acid elongation in mitochondria; tricarboxylic acids cycle; among others. CONCLUSIONS: These findings suggest that plasma amino acids and lipids profiling has great potential to find the mechanisms involved in the pathogenesis of cachexia. Metabolic profiling of plasma from cancer patients show differences between cachexia and non-cachexia in amino acids and lipids that might be related to mechanisms involved in its pathophysiology. A better understanding of these mechanisms might identify novel therapeutic approaches to palliate this unmet medical condition.

Phase II Study of Gemcitabine Plus Sirolimus in Previously Treated Patients with Advanced Soft-Tissue Sarcoma: a Spanish Group for Research on Sarcomas (GEIS) Study.

BACKGROUND: Gemcitabine plus sirolimus enhances apoptosis in vitro and increases anti-tumor efficacy in vivo in soft-tissue sarcoma (STS) models. OBJECTIVE: The objective of this study was to evaluate the activity and toxicity of the combination of gemcitabine plus sirolimus in patients with STS after failure of standard chemotherapy. PATIENTS AND METHODS: Advanced STS patients, previously treated with doxorubicin and/or ifosfamide, were included in this single-arm phase II study. Patients received gemcitabine 800 mg/m2 intravenously (iv) at 10 mg/m2/min on days 1 and 8 every 3 weeks plus sirolimus 5 mg daily orally (po). After enrolment of the first 12 patients, the study protocol was amended due to toxicity and the starting dose of sirolimus was reduced to 3 mg daily po. Archival tumor samples were analyzed for extracellular signal-regulated kinase 1 and 2 (ERK1/2) expression and correlated with outcome. The primary endpoint was progression-free rate (PFR) at 3 months. RESULTS: From May 2012 to May 2013, 28 patients were enrolled at eight centers. PFR at 3 and 6 months was 44% and 20%, respectively, with 12 patients being free of progression at 3 months. Median progression-free survival (PFS) was 1.85 months (95% confidence interval [CI] 0.73-2.97) and median overall survival (OS) was 9.2 months (95% CI 5.8-12.5). No responses were observed. The most common grade 3-4 hematologic toxicities were neutropenia (48%) and leukopenia (41%) and the most frequent grade 3 non-hematologic toxicities were infection (18.5%), transaminitis (15%), fatigue (11%), and pneumonitis (11%). ERK1/2 expression was significantly correlated with PFS (p = 0.026). CONCLUSIONS: The combination of gemcitabine and sirolimus is an active treatment in STS. Further investigation is warranted. ClinicalTrials.gov identifier: NCT01684449.

Dabrafenib plus trametinib for compassionate use in metastatic melanoma: A STROBE-compliant retrospective observational postauthorization study.

The main objective of the study was to evaluate the efficacy and safety of dabrafenib alone or combined with trametinib for compassionate use in patients with metastatic melanoma.This retrospective, observational study involved 135 patients with unresectable stage IIIC or stage IV melanoma from an expanded-access program at 30 Spanish centers.Forty-eight patients received dabrafenib monotherapy and 87 received combination dabrafenib and trametinib; 4.4% and 95.6% of the patients had stage IIIC and IV melanoma, respectively. All patients showed BRAF mutations in their primary or metastatic lesions; 3 were positive for V600K while the remainder had V600E or V600+. A positive response to treatment was reported in 89.3% of the patients. Overall survival rates at 12 and 24 months were 59.6% (95% confidence interval [CI], 52.5-68.9%) and 36.4% (95% CI, 27.8-45%), respectively. Progression-free survival rates at 12 and 24 months were 39.3% (95% CI, 31.1-47.5%) and 21.6% (95% CI, 14.5-28.7%), respectively. Fifty-seven patients (42.2%) reported cutaneous toxicity of any type, mainly hyperkeratosis (14.8%) and rash (11.9%). The most frequent adverse events were pyrexia (27.4%), asthenia (19.3%), arthralgia (16.9%), and diarrhoea (13.2%).Our results suggest that both dabrafenib alone or in combination with trametinib are effective for compassionate use in terms of response and/or survival rates. However, differences in patients' prognostic features ought to be considered. No new findings were revealed regarding the safety profiles of either regimen. This is the first study to evaluate the efficacy of these 2 selective BRAF and mitogen-activated extracellular signal-regulated kinase inhibitors in a real-world setting in Spain.

Ipilimumab for advanced melanoma: experience from the Spanish Expanded Access Program.

Ipilimumab, a fully human, recombinant, monoclonal antibody to cytotoxic T-lymphocyte antigen 4 improves overall survival (OS) in previously treated and untreated metastatic melanoma. This retrospective analysis reports data gathered by a questionnaire on the demographics, outcomes, and toxicity of ipilimumab administered through an Expanded Access Program (EAP). Ipilimumab 3 mg/kg was administered intravenously every 3 weeks for four cycles to adults with metastatic melanoma. Efficacy outcomes included complete response, partial response (PR), progressive disease, stabilized disease, and OS. EAP data were collected from EAP physicians. A subgroup analysis examined efficacy in elderly patients (≥70 years) and factors predictive of survival were identified. Of 355 requests for ipilimumab, resulting in 288 treatments, completed questionnaires were received for 153 ipilimumab recipients (median age 58 years, 57.2% men). Efficacy was evaluated in 144 patients: complete response in 1.3%, PR in 9.6%, PR with previous progression 8.4%, stabilized disease in 14.5%, and progressive disease in 66.2%. The median OS was 6.5 months (199 days); 1-year survival was 32.9%. Predictive survival factors included lymphocytes over 1000/ml (P=0.0008) and lactate dehydrogenase more than 1.5×upper limit of normal (P=0.003). Cutaneous, hepatic, and gastrointestinal toxicities were mild. In 30 patients aged more than 70 years, ipilimumab efficacy and tolerability was similar to that of the overall population. In the clinical practice setting, ipilimumab is effective and well tolerated in patients with advanced melanoma, including elderly patients, when administered at the recommended dosage. Ipilimumab improves treatment options for patients who, until recently, have had little hope of an improved prognosis.

Recomendaciones para la determinación de biomarcadores en el melanoma metastásico. Consenso Nacional de la Sociedad Española de Anatomía Patológica y de la Sociedad Española de Oncología Médica / Guidelines for biomarker testing in metastatic melanoma. A National Consensus of the Spanish Society of Pathology and the Spanish Society of Medical Oncology

Este documento de consenso nace como una iniciativa conjunta de la Sociedad Española de Anatomía Patológica (SEAP) y de la Sociedad Española de Oncología Médica (SEOM) y propone recomendaciones diagnósticas y terapéuticas para el manejo del paciente con melanoma avanzado o metastásico basadas en la evidencia científica que existe en la actualidad sobre el uso de biomarcadores. Por tanto, este documento supone una oportunidad para mejorar la eficiencia de la actividad asistencial y la utilización de recursos, lo que redundará en un beneficio para estos pacientes. Con los datos disponibles hasta el momento, este grupo de expertos recomienda que en los pacientes con melanoma metastásico se analice de forma rutinaria el estado mutacional de BRAF, ya que su resultado condiciona el manejo terapéutico posterior de estos pacientes. El análisis de alteraciones genéticas de KIT puede ser razonable en pacientes con tumores primarios de localización acral, en mucosas o en piel crónicamente expuesta al sol, en situación avanzada, pero no en pacientes con otro tipo de melanomas. Este panel no considera actualmente indicado como práctica clínica habitual el estudio de otras alteraciones genéticas, como pueden ser el estado mutacional de NRAS en pacientes no portadores de mutaciones de BRAF, el análisis mutacional de GNAQ/GNA11 o las alteraciones genéticas de PTEN, ya que hoy por hoy sus resultados no influyen en la planificación del tratamiento de estos pacientes. Otros aspectos importantes que se desarrollan en este documento son los requisitos organizativos y los controles de calidad necesarios para la determinación adecuada de estos biomarcadores, y las implicaciones legales que se deben tener en cuenta (AU)

This consensus statement is a joint initiative of the Spanish Society of Pathology (SEAP) and the Spanish Society of Medical Oncology (SEOM). Based on current scientific evidence of biomarker use, it makes diagnostic and therapeutic recommendations for the management of patients with advanced or metastatic melanoma. Its aim is to improve both healthcare efficiency and the use of resources in benefit of the patients. Based on the most recent available data, the group of experts recommends testing patients with metastatic melanoma routinely for BRAF mutation status, as the result affects their subsequent therapeutic management. Analysis of genetic alterations in KIT may be practical in patients with primary tumours in acral or mucosal sites or on skin subjected to chronic sun exposure, in an advanced condition; however, this does not apply to patients with other types of melanomas. This expert panel believes that testing for other genetic alterations, such as NRAS mutation status in patients not carrying BRAF mutations, GNAQ/GNA11 mutational analysis or genetic alterations in PTEN, is not currently indicated as a routine clinical practice because, at the present time, the results do not influence treatment. The organizational requirements and quality controls needed for the correct testing of biomarkers as well as the legal implications involved are also considered (AU)

Advances in cutaneous melanoma.

After several decades of slow progress in the field of melanoma, significant advances have been reported in recent years. These include a better understanding of the molecular biology of the tumour, a new staging classification system, insights into the patterns of relapse in early stage, and new drugs for the treatment of advanced disease. Ipilimumab and vemurafenib have just been approved and provide a survival benefit in stage IV. Both compounds are under evaluation in the adjuvant setting, where interferon remains the only drug with proven efficacy. Further investigation is required to treat patients with primary or secondary resistance to new drugs.

A phase I first-in-human pharmacokinetic and pharmacodynamic study of serdemetan in patients with advanced solid tumors.

PURPOSE: Originally isolated on the basis of its ability to induce p53, serdemetan showed potent activity in various preclinical models, inducing S-phase arrest and apoptosis in TP53 wild-type and mutant tumors. This study evaluated the safety and tolerability of serdemetan, determined the pharmacokinetic and pharmacodynamic profiles, and identified a recommended phase II dose. PATIENTS AND METHODS: Patients (71) with refractory solid tumors were allocated to dose-escalating cohorts (3+3 patients each) and received oral serdemetan once daily in 21-day cycles to determine the maximum tolerated dose (MTD) and dose-limiting toxicities (DLT). Plasma was collected for pharmacokinetic analyses. Paired baseline and on-treatment skin and tumor biopsies were done; blood samples were collected for pharmacodynamic analyses, including p53 and macrophage inhibitory cytokine-1 induction. RESULTS: The MTD of serdemetan was determined to be 350 mg once daily. During this study, grade 3 QTc prolongation was the most common DLT and nausea (66.2%) was the most frequent treatment-emergent adverse event. Serdemetan was rapidly absorbed after oral administration and exhibited dose-proportional pharmacokinetics. At steady state, mean maximum plasma concentration (C(max)) was 2,330 ng/mL and mean area under plasma concentration curve (AUC(0-24h)) was 43.0 µg.h/mL, with serdemetan 300 mg/d. There was a dose- and exposure-dependent p53 induction. One patient with breast cancer showed a partial response; 22 (38.6%) patients had stable disease. CONCLUSIONS: Serdemetan treatment was associated with p53 induction in both tumor and surrogate tissue pharmacodynamic studies and modest clinical activity. Although serdemetan was well tolerated with dose-proportional pharmacokinetics, exposure-related QTc liability was observed.

Phase II randomized study of Plitidepsin (Aplidin), alone or in association with L-carnitine, in patients with unresectable advanced renal cell carcinoma.

This randomized phase II study evaluated two schedules of the marine compound Plitidepsin with or without co-administration of L-carnitine in patients with renal cell carcinoma. Patients had adequate performance status and organ function. The primary endpoint was the rate of disease control (no progression) at 12 weeks (RECIST). Other endpoints included the response rate and time dependent efficacy measures. The trial also assessed the efficacy of L-carnitine to prevent Plitidepsin-related toxicity. The two regimes given as 24 hour infusion every two weeks showed hints of antitumoral activity. Disease control at 12 weeks was 15.8% in Arm A (5mg/m2, no L-carnitine) and 11,1% in Arm B (7 mg/m2 with L-carnitine). Two partial responses were observed in Arm A (19 patients), none in Arm B (20 patients). Both schedules had the same progression-free interval (2.1 months). The median overall survival was 7.0 and 7.6 months. The safety profile was similar in both arms of the trial and adverse events were mainly mild to moderate (NCI CTC version 2.0). Increasing the dose to 7 mg/m2 did not increase the treatment efficacy but the incidence of transaminase and CPK elevations and serious AEs. Coadministration of L-carnitine did not prevent muscular toxicity or CPK-elevation associated with Plitidepsin.

In vitro radiosensitisation by trabectedin in human cancer cell lines.

PURPOSE: To examine the potential radiosensitising properties of trabectedin (ET-743, Yondelis). METHODS AND MATERIALS: In vitro chemosensitivity was assessed in four tumour cell lines (DU145, HeLa, HT29, HOP62) by the crystal violet method. IC10s and IC50s were established for 1-h, 24-h and 7-day (continuous) exposure times. Radiosensitisation was evaluated by conventional colony assay. BrdUrd DNA-labelling and flow cytometry were used to analyse cell cycle kinetics. The rate of apoptotic induction was assed by annexyn-V labelling. RESULTS: Mean IC50s were 18.8 nM (10.5 - 30), 2.5 nM (1.5 - 5) and 0.25 nM (0.2-0.8) for 1 h, 24 h and continuous exposure times, respectively. HT29 and HOP62 were the most sensitive cells lines to trabectedin. Radiosensitisation was observed in DU145 and HeLa cells with a dose enhancement factor (DEF) of 1.92 and 1.77 at IC50 dose level, respectively. Trabectedin induced early S phase arrest in all cell lines studied. CONCLUSIONS: Trabectedin, at pharmacologically appropriated concentrations, harbours a significant in vitro radiosensitising effect and induces cell cycle changes and apoptosis in several human cancer cell lines. Further studies to define the clinical potential of the combination of trabectedin and radiotherapy are needed.