Phase I study of TCNU, a novel nitrosourea

Phase I study of fotemustine in pediatric patients with refractory brain tumors

BACKGROUND

Fotemustine is a nitrosourea with theoretic and preclinical advantages over the original analogs, carmustine and lomustine, in the treatment of brain tumors. This is the first pediatric Phase I study of fotemustine.

METHODS

Patients younger than 21 with recurrent/resistant brain tumors were enrolled in a conventional Phase I study. Fotemustine was administered intravenously every 3 weeks at increasing dose levels starting at 100 mg/m(2). Toxicity and response data were monitored closely.

RESULTS

Fifteen evaluable patients entered the study and received a total of 45 courses of fotemustine (dose range, 100-175 mg/m(2)). Myelosuppression was observed, with the dose-limiting toxicity being Grade 4 neutropenia and thrombocytopenia. Toxicity was delayed and cumulative. The maximum tolerated dose was 150 mg/m(2) every 3 weeks. There were three documented radiologic responses (20% of patients) comprising one partial response and two minor responses in patients with a sarcoma, medulloblastoma, and ependymoma, respectively.

CONCLUSIONS

Fotemustine administered at a dose of 150 mg/m(2) every 3 weeks is well tolerated in children and has antitumor activity in several brain tumors. This is the first dedicated Phase I study of a single agent nitrosourea in a pediatric population. More comparative studies should be undertaken to define the optimum nitrosourea analog for use in children with brain tumors.

Tauromustine is more effective than conventional chemotherapy in the treatment of colonic tumors

Despite recent advances in chemotherapy, the prognosis of advanced colorectal cancer remains poor. Although the taurine-based nitrosourea tauromustine (TCNU) has demonstrated schedule-dependent synergism with 5-fluorouracil (5-FU) and leucovorin (LV) against a variety of tumors in vitro, its efficacy relative to and in combination with these drugs in vivo remains unknown. To study this, BALB/C mice had C26 tumor implanted subcutaneously five days prior to the following treatment (doses and route of administration being the same in all groups): Group 1--no treatment; Group 2--TCNU (30 mg/kg by gavage); Group 3--LV (100 mg/kg intraperitoneally [IP]) and, one hour later, LV plus 5-FU (100 mg/kg IP); Group 4--LV and, one hour later, LV plus 5-FU and TCNU; and Group 5--TCNU and, on the following day, LV and, one hour later, LV plus 5-FU. All treatments were repeated seven days later. Body weight and tumor weight were measured twice weekly, and survival was noted. Postmortems were performed in all animals, and evidence of primary or secondary tumor was recorded. All surviving animals were sacrificed at 60 days. We found that 1) 87 percent of animals receiving TCNU and 60 percent of animals receiving LV, 5-FU, and TCNU survived to day 60; none of these animals had evidence of tumor when sacrificed; 2) animals in all other groups died by day 34; 3) evidence of metastases was found in five animals in Group 1 and one each in Groups 2 and 5; and 4) administering TCNU 24 hours prior to 5-FU plus LV resulted in death from toxicity in all animals. Thus, while synergism between TCNU and 5-FU plus LV was not seen, the antitumor properties of TCNU are significantly greater than those of conventional chemotherapy.

Phase I study of tauromustine administered in a weekly schedule

Tauromustine was administered orally in weekly doses with interindividual dose escalation to patients with disseminated malignant melanoma. The dose in the first cohort of 6 patients was 20 mg/m2/week. The dose escalation was 5 mg/m2/week. The limit of tolerance was 55 mg/m2/week. 99 patients completed at least 8 weeks of treatment and eight dose levels were evaluated for toxicity. Reversible thrombocytopenia, and to a lesser degree leukopenia, were dose limiting. From a starting dose of 40 mg/m2/week, the long-term tolerated dose was 35 mg/m2/week, thus achieving a considerable increase of dose intensity without a significant increase of toxicity by employing this weekly schedule of tauromustine.

The influence of hydralazine on the vasculature, blood perfusion and chemosensitivity of MAC tumours

We have studied the influence of the peripheral vasodilator hydralazine (HDZ) on the vasculature and blood perfusion of two members of a series of subcutaneous murine adenocarcinomata of the colon (MAC tumours), and the influence of HDZ on the efficacy and/or toxicity of TCNU and melphalan. The fluorescent DNA stain Hoechst 33342, showed that HDZ caused a shutdown of tumour vasculature, related in magnitude to both dose and tumour differentiation state; 10 mg kg-1 caused an 80% vascular shutdown of well differentiated MAC 26 tumours, but only a 50% shutdown of the poorly differentiated MAC 15A tumours. 2.5 mg kg-1 was ineffective. The blood perfusion marker 99mTc-HMPAO showed that the normal perfusion of MAC tumours was consistently markedly less than that of lung, liver or kidneys (4-5% of lung perfusion). HDZ (10 mg kg-1) decreased MAC 26 perfusion by 63%, and that of MAC 15A by 20%. Again, 2.5 mg kg-1) was ineffective. Use of in vivo to in vitro clonogenic assays showed that HDZ (10 mg kg-1) potentiated the efficacy of melphalan (1-10 mg kg-1 i.p.) by a factor of 2.1, and increased the efficacy of TCNU (1-10 mg kg-1 i.v., factor = 1.7) when given 10 or 15 min respectively after dosing. However, the addition of HDZ increased the acute bone marrow toxicity of melphalan, but not that of TCNU. The clinical relevance of these results is discussed.

Phase II study of tauromustine in malignant glioma

46 eligible patients with either anaplastic astrocytoma (AA) or glioblastoma (GBM) and clinical and computed-tomography-confirmed relapse following primary surgery and radiotherapy received oral tauromustine 130 mg/m2 every 5 weeks. A prospective design allowed for concurrent assessment of both clinical and radiological responses and drug toxicity. 41% of patients improved clinically whilst 46% improved radiologically with 3 complete, 7 partial and 7 minimal responses (WHO criteria). Toxicity included grade III or IV gastrointestinal side-effects (15%), grade III or IV leukopenia (24%) and grade III and IV thrombocytopenia (44%). In 9 clinically responding patients, haematological toxicity led to discontinuation of treatment. All patients were followed-up until death and second-line chemotherapy was not used. Median post-treatment survival was 26 weeks for patients with GBM and 57 weeks for patients with AA. Overall 2-year survival rate was 69% for AA and 23% for GBM. Tauromustine given at the time of relapse has demonstrable antitumour activity in patients not previously treated with chemotherapy.

TCNU in adenocarcinoma of the lung: a phase II study with divided doses

TCNU, a new water soluble nitrosourea, has in preclinical studies shown higher activity when given as divided doses compared with one day single treatment. Accordingly, 38 consecutive patients with non-resectable adenocarcinoma of the lung received TCNU 40 mg/m2 p.o. daily for three days every 4 weeks. The response rate among 37 evaluable patients was 14%, median response duration was 17 weeks (range 5-57+ weeks) and median survival 22 weeks (range 3-96+ weeks). Hematologic toxicity was pronounced, especially thrombocytopenia, and 57% of the patients had WHO grade 3 or 4 WBC or platelet count. Overall, dose reduction or delay of treatment due to hematologic toxicity was necessary in 66% of the patients. This, together with the limited activity, renders TCNU in the present dose and schedule unsuitable for further investigations in this disease entity.

The disposition of TCNU (tauromustine) in human malignant glioma: pharmacokinetic studies and clinical implications

Tauromustine (TCNU), 130 mg/sq m, was administered intraoperatively by nasogastric tube to 10 patients with malignant glioma (seven glioblastomas and three anaplastic astrocytomas). High-performance liquid chromatography analysis of 32 tumor specimens for TCNU revealed that tissue concentrations ranged from 0 to 554 ng/gm: TCNU was not detected in necrotic regions of the tumor. Levels of TCNU in brain adjacent to tumor were similar to those recorded within the gliomas (range 0 to 635 ng/gm). The variability in the tissue level of TCNU was partly attributable to variable absorption of the drug, since peak plasma TCNU levels ranged from 164 to 3333 ng/ml. There were close quantitative and temporal relationships between the times of peak plasma levels (median 456 ng/ml at 45 minutes after administration), peak tumor levels (median 250 ng/gm tissue at 55 minutes), and brain adjacent to tumor levels (median 256 ng/gm tissue at 50 minutes). Linear regression analysis of the ratio between tissue and plasma TCNU levels at particular times after drug administration suggest that plasma concentrations can be used to estimate tissue concentrations. This study demonstrates that TCNU enters malignant glioma. In view of the activity of TCNU against a range of tumors, a full clinical evaluation of this new nitrosourea in malignant glioma seems justified.

Determination of tauromustine and its demethylated metabolites in plasma and urine

A sensitive, selective and precise high-performance liquid chromatographic method for simultaneous determination of tauromustine and its demethylated metabolites in plasma and urine has been developed. It is based on solid-phase extraction on C18 sorbent and separation on a semipolar column. The analytical procedure is described in detail. The method has been validated with respect to linearity, recovery, selectivity, precision and detection limit. The stability of the determined substances in various media has also been studied.

TCNU (LS 2667), a new active drug in the treatment of advanced colorectal cancer. EORTC Early Clinical Trials Group

Fifty-seven patients with advanced measurable or evaluable colorectal cancer not previously treated with chemotherapy and tumor manifestations from colorectal cancer were treated with tauromustine (TCNU), a new nitrosourea with a therapeutic index against murine tumors better to or equal to that of the established nitrosoureas. The dose was 130 mg/m2 orally q 5 weeks. There were one CR and seven PR, for an overall response rate of 14%. Responding sites included the liver (one CR and two PR), lung (four PR) and lymph nodes (two PR). The median duration of response was 33+ weeks (21+ to 34 weeks). The main dose limiting toxicity was myelosuppression which seemed to be cumulative. Subjectively, the drug was well tolerated although most patients experienced nausea and vomiting for some hours. It is concluded that TCNU is a well tolerated compound with limited, but definite antitumor activity against colorectal cancer and that further studies in this disease could be of interest.

Phase II study of tauromustine in disseminated malignant melanoma

Forty-seven patients with metastatic malignant melanoma took part in a phase II trial of tauromustine (TCNU), a new chlorethylnitrosourea based on the endogenous amino acid taurine. TCNU was given orally at a dosage of 130 mg/m2 every fifth week. No patient had previously received cytotoxic therapy. Among 37 evaluable patients, 26 patients experienced progressive disease including seven patients with early death, five showed no change, and six partial responses, yielding an objective response rate of 16%. Responses were limited to subcutaneous, lymph node, bone and lung metastases. Median time to progression was 26 weeks for responders. The treatment schedule was well tolerated with a median dose of 88% of the predicted dose given during all cycles. Dose-limiting toxicity was thrombocytopenia. It appears that TCNU is active in disseminated malignant melanoma with a response rate similar to other nitrosoureas.

Activity of a new nitrosourea (TCNU) in human lung cancer xenografts

The activity of a new nitrosourea (TCNU) based on the endogenous amino acid taurine was assessed in three human lung cancer xenografts growing in immunodeficient mice. Moderate activity (specific growth delays of 0.63 and 1.13 compared with controls) was seen in two non-small cell tumours after a single oral administration of 20 mg-1kg. This dose was curative in a small cell xenograft. By using high performance liquid chromatography it was possible to detect parent drug in the tumours as well as the plasma and tissues after oral administration of TCNU. Drug sensitivity was correlated inversely with the amount of the DNA repair enzyme 0(6)-methylguanine-DNA methyltransferase assayed from extracts of the tumour cells but not with the levels of parent drug within the tumour. This compound appears to have unique pharmacokinetic properties compared with other chloroethylnitrosoureas.