A clinical phase I and pharmacokinetic study of BBR 2778, a novel anthracenedione analogue, administered intravenously, 3 weekly

Oncogenic functions and therapeutic potentials of targeted inhibition of SMARCAL1 in small cell lung cancer

Small cell lung cancer (SCLC) is a recalcitrant cancer characterized by high frequency loss-of-function mutations in tumor suppressors with a lack of targeted therapy due to absence of high frequency gain-of-function abnormalities in oncogenes. SMARCAL1 is a member of the ATP-dependent chromatin remodeling protein SNF2 family that plays critical roles in DNA damage repair and genome stability maintenance. Here, we showed that SMARCAL1 was overexpressed in SCLC patient samples and was inversely associated with overall survival of the patients. SMARCAL1 was required for SCLC cell proliferation and genome integrity. Mass spectrometry revealed that PAR6B was a downstream SMARCAL1 signal molecule which rescued inhibitory effects caused by silencing of SMARCAL1. By screening of 36 FDA-approved clinically available agents related to DNA damage repair, we found that an aza-anthracenedione, pixantrone, was a potent SMARCAL1 inhibitor which suppressed the expression of SMARCAL1 and PAR6B at protein level. Pixantrone caused DNA damage and exhibited inhibitory effects on SCLC cells in vitro and in a patient-derived xenograft mouse model. These results indicated that SMARCAL1 functions as an oncogene in SCLC, and pixantrone as a SMARCAL1 inhibitor bears therapeutic potentials in this deadly disease.

Current Opinion on Pixantrone in the Treatment of Non-Hodgkin B-Cell Lymphoma

Not many treatment options exist for patients with relapsed or refractory (R/R) B-cell non-Hodgkin lymphoma (NHL) in whom first- and second-line therapies were unsuccessful. This is especially true for patients with aggressive lymphomas. The innovative agent pixantrone has shown some promising results in terms of disease-free and overall survival, both in monotherapy as well as in combinations. However, recent trials (Phase III and real-world studies) reported unsatisfactory results, thereby raising the question about the role of pixantrone in the current treatment of R/R aggressive lymphomas. Nonetheless, there might still be a potential position for this drug in combinations, for use as first-line treatment of patients with cardiac dysfunction. This article summarizes the definition, structure, mechanism of action and reduced cardiotoxicity of pixantrone as well as efficacy and toxicity both in monotherapy and in combinations, as treatment for aggressive and indolent non-Hodgkin lymphomas.

An evaluation of pixantrone for the treatment of non-Hodgkin's lymphoma

INTRODUCTION

The overall prognosis for patients with relapsed or refractory aggressive non-Hodgkin's lymphomas is poor. Only a minority of patients are able to receive autologous stem cell transplantation. Patients not transplant-eligible or patients relapsing after transplantation have an urgent need for effective treatment options. Pixantrone is the only compound approved in Europe for this situation. Areas covered: This review describes the clinical development of pixantrone, starting with phase I trials up to phase III trials in order to define the role of pixantrone in treatment algorithms. The effectiveness of pixantrone is considered in relation to alternative therapeutic options. Furthermore, the similarities and differences between pixantrone and anthracyclines is highlighted, with a special focus on the mode of action and on cardiotoxicity. Expert opinion: Pixantrone is a valuable treatment option in relapsed and refractory aggressive lymphomas, with documented disease responses, manageable toxicities and clear distinctions to anthracyclines. Additional studies are needed to evaluate the role of pixantrone in combination with other compounds, especially with upcoming targeted therapies, and to confirm the effectiveness of pixantrone in other lymphoma subtypes, e.g. follicular lymphomas.

Pixantrone, a new anticancer drug with the same old cardiac problems? An in vitro study with differentiated and non-differentiated H9c2 cells

Pixantrone (PIX) is an anticancer drug approved for the treatment of multiple relapsed or refractory aggressive B-cell non-Hodgkin's lymphoma. It is an aza-anthracenedione synthesized to have the same anticancer activity as its predecessors, anthracyclines (e.g. doxorubicin) and anthracenediones (e.g. mitoxantrone), with lower cardiotoxicity. However, published data regarding its possible cardiotoxicity are scarce. Therefore, this work aimed to assess the potential cytotoxicity of PIX, at clinically relevant concentrations (0.1; 1; and 10 μM) in both non-differentiated and 7-day differentiated H9c2 cells. Cells were exposed to PIX for 48 h and cytotoxicity was evaluated through phase contrast microscopy, Hoescht staining and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction and neutral red (NR) uptake assays. Cytotoxicity was observed in differentiated and non-differentiated H9c2 cells, with detached cells and round cells evidenced by phase contrast microscopy, mainly at the highest concentration tested (10 μM). In the Hoechst staining, PIX 10 μM showed a marked decrease in the number of cells when compared to control but with no signs of nuclear condensation. Furthermore, significant concentration-dependent mitochondrial dysfunction was observed through the MTT reduction assay. The NR assay showed similar results to those obtained in the MTT reduction assay in both differentiated and non-differentiated H9c2 cells. The differentiation state of the cells was not crucial to PIX effects, although PIX toxicity was slightly higher in differentiated H9c2 cells. To the best of our knowledge, this was the first in vitro study performed with PIX in H9c2 cells and it discloses worrying cytotoxicity at clinically relevant concentrations.

Pixantrone: A Review in Relapsed or Refractory Aggressive Non-Hodgkin's Lymphoma

Pixantrone (Pixuvri^®) is an aza-anthracenedione with a novel mode of action that is conditionally approved in the EU for use as monotherapy in adult patients with multiply relapsed or refractory aggressive B-cell non-Hodgkin's lymphoma (NHL). In the randomized, open-label, multinational, phase 3 PIX301 trial in patients with multiply relapsed or refractory aggressive NHL, the complete response (CR) plus unconfirmed CR (uCR) rate at the end of treatment (primary endpoint) was significantly higher with intravenous pixantrone monotherapy than with a single-agent comparator (vinorelbine, oxaliplatin, ifosfamide, etoposide, mitoxantrone or gemcitabine). Post hoc analysis also demonstrated a significantly higher CR/uCR rate in the subgroup of patients with centrally confirmed aggressive B-cell NHL who were receiving pixantrone versus a comparator agent as third- or fourth-line therapy. Pixantrone was generally well tolerated in PIX301, with a manageable adverse event profile. In conclusion, pixantrone is a useful option in patients with multiply relapsed or refractory aggressive B-cell NHL. Further results examining the use of pixantrone in combination with rituximab in patients previously treated with rituximab-containing regimens are awaited with interest.

Critical concepts, practice recommendations, and research perspectives of pixantrone therapy in non-Hodgkin lymphoma: a SIE, SIES, and GITMO consensus paper

OBJECTIVES

In this paper, we present a review of critical concepts and research perspectives and produce recommendations on the optimal use of pixantrone in non-Hodgkin lymphoma (NHL) by group discussion from an expert panel appointed by the Italian Society of Hematology and the affiliate societies, Società Italiana di Ematologia Sperimentale and Gruppo Italiano Trapianto di Midollo Osseo.

METHODS

Recommendations were produced using the Delphi process. Scientific evidence on pixantrone efficacy was analyzed using Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) methodology in the areas where at least one randomized trial was published. The following key issues were addressed for practical recommendations: pixantrone monotherapy in aggressive relapsed or refractory non-Hodgkin B-cell lymphomas and toxicity risk management in patients candidates to pixantrone.

RESULTS AND CONCLUSIONS

After a balanced and value-oriented discussion, the panel agreed that the benefit/risk profile was in favor of pixantrone in the treatment of adult patients with multiply relapsed or refractory aggressive NHL B-cell lymphomas. Pixantrone was deemed to be contraindicated in patients with uncontrolled cardiovascular disease. Despite a low rate of cardiotoxicity of pixantrone reported in clinical trials, the panel recommended that all patients receiving pixantrone should undergo periodical cardiac monitoring.

Something Old, New, Borrowed, Blue: Anthracenedione Agents for Treatment of Multiple Sclerosis

OBJECTIVE

This study aimed to present anthracenedione agents that have been used to treat multiple sclerosis (MS), problems related to their use, and knowledge gained from our experiences using these agents to develop more efficacious drugs with fewer adverse effects.

METHODS

We review preclinical and clinical data during the development mitoxantrone, an anthracycline, for the treatment of MS; benefits and potential risks; and strategies to reduce complications of anthracyclines.

RESULTS

Mitoxantrone had unacceptable and greater-than-anticipated toxicity for use in a chronic disease such as MS. Adverse effects included cardiotoxicity, treatment-associated leukemia, and amenorrhea. Toxicity was identified primarily in retrospect. Structurally related compounds include pixantrone (BBR2278) and BBR3378. Pixantrone is in clinical development in oncology. BBR3378 prevents the development of autoimmunity and experimental autoimmune encephalomyelitis and blocks experimental autoimmune encephalomyelitis even when given after the onset of autoimmunity.

CONCLUSIONS

There remains a need for effective MS treatment, particularly for nonrelapsing forms of MS. Mitoxantrone was the first nonbiologic drug approved by the Food and Drug Administration for use in MS. Chromophore modification of anthracenedione agents yielded a novel class of DNA binding agents (aza-anthracenediones such as pixantrone and aza-anthrapyrazoles such as BBR3378) with the potential for less cardiotoxicity compared with mitoxantrone. There is a need for long-term observation for delayed toxicity among humans enrolled in pixantrone trials. Preclinical toxicity studies for delayed toxicities in rodents and other models are warranted before consideration of derivatives of anthracenediones, aza-anthrazenediones, or aza-anthrapyrazoles for use in human MS clinical trials.

Binding of pixantrone to DNA at CpA dinucleotide sequences and bulge structures

The binding of the anti-cancer drug pixantrone to three oligonucleotide sequences, d(TCATATGA)2, d(CCGAGAATTCCGG)2 {double bulge = DB} and the non-self complementary d(TACGATGAGTA) : d(TACCATCGTA) {single bulge = SB}, has been studied by NMR spectroscopy and molecular modelling. The upfield shifts observed for the aromatic resonances of pixantrone upon addition of the drug to each oligonucleotide confirmed the drug bound by intercalation. For the duplex sequence d(TCATATGA)2, NOEs were observed from the pixantrone aromatic H7/8 and aliphatic Ha/Hb protons to the H6/H8 and H1' protons of the C2, A3, T6 and G7 nucleotides, demonstrating that pixantrone preferentially binds at the symmetric CpA sites. However, weaker NOEs observed to various protons from the T4 and A5 residues indicated alternative minor binding sites. NOEs from the H7/H8 and Ha/Hb protons to both major (H6/H8) and minor groove (H1') protons indicated approximately equal proportions of intercalation was from the major and minor groove at the CpA sites. Intermolecular NOEs were observed between the H7/H8 and H4 protons of pixantrone and the A4H1' and G3H1' protons of the oligonucleotide that contains two symmetrically related bulge sites (DB), indicative of binding at the adenine bulge sites. For the oligonucleotide that only contains a single bulge site (SB), NOEs were observed from pixantrone protons to the SB G7H1', A8H1' and G9H1' protons, confirming that the drug bound selectively at the adenine bulge site. A molecular model of pixantrone-bound SB could be constructed with the drug bound from the minor groove at the A8pG9 site that was consistent with the observed NMR data. The results demonstrate that pixantrone preferentially intercalates at adenine bulge sites, compared to duplex DNA, and predominantly from the minor groove.

Reversible and formaldehyde-mediated covalent binding of a bis-amino mitoxantrone analogue to DNA

The ability of the anthracenedione anticancer drug WEHI-150 to form covalent adducts with DNA, after activation by formaldehyde, has been studied by mass spectrometry, HPLC and NMR spectroscopy.

Pixantrone for the treatment of adult patients with relapsed or refractory aggressive non-Hodgkin B-cell lymphomas

Treatment of patients with relapsed or refractory aggressive non-Hodgkin B-cell lymphoma remains an unmet clinical need, and the progressive myocardial toxicity related to cumulative, dose-dependent damage induced by anthracyclines represents a tricky issue in the planning of therapy. Pixantrone is a promising aza-anthracenedione with reduced cardiotoxicity and significant antineoplastic activity, and has been investigated in solid and hematologic tumors in several Phase I, II, and III trials. The aim of this review is to summarize the data reported so far on pixantrone as a salvage therapy in relapsed/refractory non-Hodgkin B-cell lymphoma.

Initial testing (stage 1) of the topoisomerase II inhibitor pixantrone, by the pediatric preclinical testing program

Pixantrone, a novel aza-anthracenedione with cytotoxic activity, was tested against the PPTP in vitro panel (3.0 nM to 30.0 μM) and against a limited panel of PPTP Wilms tumors and sarcomas (7.5 mg/kg) administered intravenously using an every 4 day × 3 schedule. In vitro pixantrone showed a median relative IC50 value of 54 nM (range <3 nM to 1.03 μM). In vivo pixantrone induced significant differences in EFS distribution compared to controls in two of eight solid tumor xenografts at dose levels relevant to human drug exposure. A complete response was observed for one Wilms tumor xenograft.

Pixantrone for the treatment of adult patients with multiply relapsed or refractory aggressive non-Hodgkin B-cell lymphoma

SUMMARY There is a clear need for efficacious, well-tolerated therapies in patients with multiply relapsed or refractory aggressive B-cell non-Hodgkin lymphoma. Pixantrone is a novel aza-anthracenedione manufactured by Cell Therapeutics Incorporated. Structurally related to anthracyclines and anthracenediones but engineered to minimize cardiotoxicity whilst maintaining efficacy, pixantrone has shown promise in Phase II and III clinical trials as a single agent and in combination. While further prospective studies are required to establish pixantrone as a standard salvage therapy, it has already received approval in the EU as monotherapy for adult patients with multiply relapsed or refractory aggressive B-cell non-Hodgkin lymphoma. Here we review the pharmacology, preclinical and clinical development of this novel agent and consider potential future utility.

Pixantrone: merging safety with efficacy

Pixantrone is a novel anthracycline derivative, manufactured by Cell Therapeutics Incorporated, WA, USA. It was developed with the aim to retain the efficacy of anthracyclines and be less cardiotoxic. Initial safety trials and single-arm, Phase II trials have shown preliminary evidence of anticancer activity and manageable toxicity. These results were validated in multicenter, randomized clinical trials where pixantrone was used as single agent or in combination with other cytotoxics. Following the results of PIX301, it is now approved by the EMA for use as monotherapy in pretreated patients with refractory non-Hodgkin lymphomas. Ongoing trials are assessing the use of pixantrone in combination with other drugs.

The European Medicines Agency review of pixantrone for the treatment of adult patients with multiply relapsed or refractory aggressive non-Hodgkin's B-cell lymphomas: summary of the scientific assessment of the committee for medicinal products for human use

On May 10, 2012, the European Commission issued a conditional marketing authorization valid throughout the European Union for pixantrone for the treatment of adult patients with multiply relapsed or refractory aggressive non-Hodgkin's B-cell lymphoma (NHL). Pixantrone is a cytotoxic aza-anthracenedione that directly alkylates DNA-forming stable DNA adducts and cross-strand breaks. The recommended dose of pixantrone is 50 mg/m(2) administered on days 1, 8, and 15 of each 28-day cycle for up to 6 cycles. In the main study submitted for this application, a significant difference in response rate (proportion of complete responses and unconfirmed complete responses) was observed in favor of pixantrone (20.0% vs. 5.7% for pixantrone and physician's best choice, respectively), supported by the results of secondary endpoints of median progression-free and overall survival times (increase of 2.7 and 2.6 months, respectively). The most common side effects with pixantrone were bone marrow suppression (particularly of the neutrophil lineage) nausea, vomiting, and asthenia. This article summarizes the scientific review of the application leading to approval in the European Union. The detailed scientific assessment report and product information, including the summary of product characteristics, are available on the European Medicines Agency website (http://www.ema.europa.eu).

DNA binding by pixantrone

The binding of the anticancer drug pixantrone (6,9-bis[(2-aminoethyl)amino]benzo[g]isoquinoline-5,10-dione dimaleate) to the octanucleotide duplexes d(ACGATCGT)(2) and the corresponding C-5 methylated cytosine ((5Me)C) analogue d(A(5Me)CGAT(5Me)CGT)(2) has been studied by NMR spectroscopy and molecular modelling. The large upfield shifts observed for the resonances from the aromatic protons of pixantrone upon addition to either d(ACGATCGT)(2) or the corresponding (5Me)C analogue is consistent with the drug binding the octanucleotides by intercalation. The selective reduction in the sequential NOEs between the C(2)-G(3) and C(6)-G(7) nucleotides in NOESY spectra of either octanucleotide with added pixantrone confirms the intercalative binding mechanism. Strong NOEs from the side-chain ethylene protons of pixantrone to the H5 protons and the 5-CH(3) protons of the C(2) and C(6) residues of d(ACGATCGT)(2) and d(A(5Me)CGAT(5Me)CGT)(2), respectively, indicate that pixantrone predominantly intercalates from the DNA major groove at the 5'-CG and 5'-(5Me)CG sites. Simple molecular models based on the conclusions from the NMR experiments indicated that the (5Me)C groups do not represent a steric barrier to intercalation from the major groove. However, the observation of weak NOEs from the ethylene protons of pixantrone to a variety of minor groove protons from either octanucleotide suggests that the drug can also associate in the minor groove.

A phase I/II trial of pixantrone (BBR2778), methylprednisolone, cisplatin, and cytosine arabinoside (PSHAP) in relapsed/refractory aggressive non-Hodgkin's lymphoma

The purpose of the study was to evaluate the safety, efficacy, and pharmacokinetics of pixantrone (BBR2778) when substituted for etoposide in the ESHAP regimen in patients with aggressive relapsed or refractory non-Hodgkin's lymphoma. Nineteen patients received protocol therapy, consisting of pixantrone 80 mg/m2 over 1 h on day 1, methylprednisolone 500 mg on days 1 - 5, cisplatin 25 mg/m2 on days 1 - 4, and cytarabine 2000 mg/m2 on day 5. Cycles were repeated every 21 days, in the outpatient setting. Dose limiting toxicity, consisting of bone marrow suppression, occurred at the first dose level (80 mg/m2), which was defined as the recommended dose. Grade 3 and 4 toxicities were mainly hematologic. Only one patient had grade 4 febrile neutropenia. No significant decreases in ejection fraction greater than 20% occurred. Overall response rate was 58%, with 37% complete and 21% partial responses. Six of the 11 responders (55%) underwent stem cell transplant. Median time to progression and overall median survival were 5.7 months and 14.5 months, respectively. There is no significant interaction between pixantrone and the combined drugs. The recommended dose of pixantrone in combination with methylprednisolone, cytarabine, and cisplatin (PSHAP) is 80 mg/m2. PSHAP is an active salvage regimen and should be further evaluated as a pretransplant cytoreductive regimen.

Pixantrone: a promising drug in the treatment of non-Hodgkin lymphomas

Pixantrone (BBR2778) is a novel anthracycline derivative, manufactured by Cell Therapeutics Incorporated, WA, USA. In both preclinical and clinical studies pixantrone exhibited a significantly lower cardiac toxicity and better activity than that observed with alternative anthracyclines, as it is devoid of the putative cardiac toxicity generating 5,8-dihydroxy groups. With single-agent pixantrone, neutropenia was the dose-limiting toxicity. In relapsed aggressive non-Hodgkin lymphomas, weekly single-agent pixantrone 85 mg/m2 for 3 weeks every 4 weeks was associated with a 27% overall response rate and a 15% complete response rate. When used in combination with chemotherapy regimens overall response rates of 58–74% and complete response rates of 37–57% were achieved.

Design and synthesis of new pyranoxanthenones bearing a nitro group or an aminosubstituted side chain on the pyran ring. Evaluation of their growth inhibitory activity in breast cancer cells

Some new 2,6-disubstituted pyrano- and 1,2-dihydropyrano[2,3-c]xanthen-7-ones have been synthesized and their antiproliferative activity has been evaluated against MDA-MB-231 breast cancer cells. The antiproliferative activity evaluation of the compounds provided evidence that a dimethylamino substituted side chain and the presence of 1,2 double bond play a key role in cell growth inhibition. Among the tested derivatives the 6-dimethylaminoethylamino-2-nitropyranoxanthenone analogue possessed a significant inhibitory effect in a wide range of concentrations.

Pixantrone (BBR2778): a new immunosuppressant in multiple sclerosis with a low cardiotoxicity

Mitoxantrone (MX) has been approved by the Food and Drug Administration for the treatment of rapidly progressive multiple sclerosis (MS). Unfortunately, its long-term administration is prevented by the cardiotoxicity. Pixantrone (PIX) is an analogue of MX devoid of toxic effects on cardiac tissue and was developed as a replacement for other anthracenediones in cancer patients. With a view to an application in MS patients, experimental data demonstrated that PIX is as potent as MX in preventing acute experimental allergic encephalomyelitis development as well as the occurrence of relapses in the chronic model. Safety data from animal studies and from phase II trials in cancer patients confirm a very weak cardiotoxicity, if any. A phase I trial with PIX in patients with a rapidly progressive MS seems thus warranted.

Pixantrone (BBR2778) reduces the severity of experimental allergic encephalomyelitis

Pixantrone is less cardiotoxic and is similarly effective to mitoxantrone (MTX) as an antineoplastic drug. In our study, pixantrone reduced the severity of acute and decreased the relapse rate of chronic relapsing experimental allergic encephalomyelitis (EAE) in rats. A marked and long-lasting decrease in CD3+, CD4+, CD8+ and CD45RA+ blood cells and reduced anti-MBP titers were observed with both pixantrone and MTX. In vitro mitogen- and antigen-induced T-cell proliferation tests of human and rodents cells evidenced that pixantrone was effective at concentrations which can be effectively obtained after i.v. administration in humans. Cardiotoxicity was present only in MTX-treated rats. The effectiveness and the favorable safety profile makes pixantrone a most promising immunosuppressant agent for clinical use in multiple sclerosis (MS).

Antitumor AZA-anthrapyrazoles: biophysical and biochemical studies on 8- and 9-aza regioisomers

Aza-bioisosteres of anthrapyrazoles (Aza-APs) bearing the C-N substitution at position 9 are powerful anticancer agents now in clinical trials. In contrast, their 8-substituted regioisomers are practically devoid of chemotherapeutic effects. To understand the molecular basis for a dramatically different response by otherwise very similar compounds, we performed a detailed investigation on the physico-chemical properties of several aza-APs belonging to the two families, on their DNA-binding affinity and specificity as well as on their capacity to impair the activity of the two isoforms of human Topoisomerase II (top2alpha and top2beta). Our results indicate that molecular size and shape, electronic distribution, redox properties, lipophilicity and protonation equilibria are essentially the same when comparing 9- with 8-substituted congeners. Although no major difference could be picked up when comparing the DNA binding properties of corresponding members of the 8- and 9-aza families, interestingly the affinity and specificity for the nucleic acid is modulated by the nature of the side-arms linked to the aza-AP scaffold, suggesting structural motifs that may determine DNA sequence recognition by the studied drug. Topoisomerase II poisoning activity was much higher for 9-aza derivatives than 8-aza analogues as shown by a cleavage assay with purified recombinant top2 isoforms. The difference appears to account for the divergent anticancer potential exhibited by different aza-AP regioisomers and suggests a specific molecular recognition of the cleavage complex by the studied drugs.

Phase I clinical and pharmacokinetic study of BBR 3576, a novel aza-anthrapyrazole, administered i.v. every 4 weeks in patients with advanced solid tumors: a phase I study group trial of the Central European Society of Anticancer-Drug Research (CESAR)

BBR 3576 is a novel aza-anthrapyrazole with limited potential for cardiotoxicity in preclinical models. This phase I clinical and pharmacokinetic study was performed to determine the maximum tolerated dose, the dose-limiting toxicity (DLT) and the pharmacokinetic profile of BBR 3576 administered i.v. as a 1-h infusion repeated every 4 weeks. In total, 27 patients were treated at doses starting from 1 to 150 mg/m2. The dose levels 1, 2, 4, 8, 16, 32, 64, 90, 125 and 150 mg/m2 were investigated in one, three, one, three, two, one, three, four, three and six patients, respectively. The DLT was a grade 3 stomatitis at 150 mg/m2. At this dose level as well as at 125 mg/m2, neutropenia grade 3 and 4 were frequently seen, but not reaching the criteria for DLT. Time to neutrophil nadir was about 2 weeks and recovery took place within 1 week. Other bone marrow toxicities were mild; lymphopenia was also observed. No significant drug-induced cardiotoxicity was observed. The plasma concentration versus time curves of BBR 3576 showed a biexponential profile with a linear kinetic behavior. A very large volume of distribution, a high plasma clearance and long elimination half-lives were calculated. Renal unchanged drug excretion was less than 10% and therefore a minor excretion route. No objective antitumor responses were found. On the basis of this study, the recommended dose for phase II studies is 150 mg/m2, although the maximum tolerated dose as per protocol definition was not reached. This trial showed that BBR 3576 has a manageable toxicity profile on a 4-week schedule. Phase II studies have started in patients with solid tumors, as suggested by preclinical data in different in vivo model systems.