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Taurine was discovered more than two hundred years ago from animal sources. It is distributed in both mammals and non-mammals and its content is high in several tissues. For more than a century-and-a-half, taurine was regarded just as an end product of sulfur metabolism. Recently, taurine has been rediscovered and its beneficial effects in processes like epilepsy, hypertension, congestive heart failure and diabetes have been well-documented. It was patented and found some clinical utility, but being an amino acid, therapeutic use confronts limitations like restricted permeability and more. This necessitates the development of pro-drugs (analogues) mainly derivatives of taurine. A large number of taurine derivatives have been reported in the literature with partial to marked activity. Taurine derivatives like taltrimide, acamprosate and tauromustine, are already in the market as anti-convulsant, anti-alcoholic and anti-cancer agents. Many other analogues are effective in experimental models. The in depth analysis of these analogues and their biological actions can provide certain clues for further consideration. In the present review, attempts have been made to provide synopsis, synthesis and symbiosis of chemical and biological actions, which may provide future guidance and facilitate further research in this area. The successful journey of these analogues to clinical utility is a healthy and happy sign and an index of bright future, and we hope that this review will provide enough input to ignite the minds.

The stability of two nitrosoureas, tauromustine and lomustine, has been investigated in different media and buffers. All media tested, except Leibovitz's L-15 medium, significantly increased the degradation rate of the investigated nitrosoureas at pH 7.4. Sodium bicarbonate seems to be the cause of the observed increase of the degradation rate, since it provides the main buffering capacity of all the media except for Leibovitz's L-15 medium, which is based on phosphate buffer. Other ingredients in the media, such as amino acids, vitamins, and inorganic salts, or the ionic strength of a buffer, did not have any major effect on the degradation rate of the nitrosoureas. These results suggest that media containing carbonated buffer should be avoided when the anti-tumor effect of nitrosoureas is to be investigated in different cell cultures.

1. The cytochrome P450 (CYP)-mediated metabolism of tauromustine has been evaluated in liver and lung microsomes from various species. Liver microsomes from rat pretreated with typical CYP inducers, human liver microsomes and cDNA-expressed human CYP enzymes were used to study the enzymatic basis of the metabolism. The further metabolism of the monodemethylated product of tauromustine and that of the denitrosated product were also investigated. 2. The major routes of tauromustine metabolism were demethylation to the alkylating active compound, R2, and denitrosation to the inactive metabolite, M3. The extent of metabolism and the activity of demethylation versus denitrosation varied among the species. The highest metabolism was found in mouse (BDF strain) followed by dog, rat and the human liver. Tauromustine was also metabolized to a low extent in lung microsomes from these species. 3. The further metabolism of R2 and M3 was approximately 100 times lower in activity than that of tauromustine. Both the demethylation and the denitrosation of tauromustine were increased 3-fold in liver microsomes from rat pretreated with phenobarbital, whereas treatment with cyanopregnenolone enhanced the denitrosation 11-fold, indicating the involvement of CYP3A. 4. Metabolism across a panel of 10 human liver microsomal samples demonstrated a correlation with testosterone 6beta-hydroxylation of demethylation (r2 = 0.86) and denitrosation of tauromustine (r2 = 0.79). Among the human cDNA expressed CYP enzymes, not only was tauromustine determined to be catalysed predominantly by CYP3A4, but also to some extent by CYP2C19 and CYP2D6. 5. In conclusion, the present results indicate a major role of CYP3A enzymes in the metabolism of tauromustine.

A reversed phase high performance liquid chromatography (HPLC) method was developed for the determination of tauromustine (TM) in presence of its metabolited in biological fluids and its degradation products in tablets. The proposed HPLC method was conducted using a lichrosorb C18 column [250 × 4 mm], with acetonitrile - water - acetate buffer pH5 (40: 55: 5) eluent, the detection was affected at 235 nm. The detector response was linear in the range 0.2–4 μg/ml for TM with minimum detectability (S/N=2) of 2 ng/ml. The proposed HPLC method was applied to the determination of TM in presence of its metabolites in biological fluids. The percentage recoveries of TM and its metabolites from spiked urine range from 93.1 to 92.9 and for plasma 90.3 to 89.6. The proposed HPLC method was used to study the kinetics of degradation of TM in standard solution as a function of temperature and alkalinity. TM degraded followed first-order kineties in agreement with the Arrhenius theory. The proposed HPLC method w...

The pharmacokinetic profiles of 5-fluorouracil (5-FU) and tauromustine (TCNU) were investigated in NMRI mice following their administration either alone or as part of simultaneous or sequential combinations. The profile of 5-FU remained unaltered irrespective of the sequence of administration. However, following simultaneous administration of 5-FU and TCNU or pretreatment with 5-FU, plasma levels of TCNU were decreased by a factor of 2.5-3 as compared with those seen when TCNU was given alone. These decreased plasma levels were explained by an increase in the TCNU volume of distribution, although this was not due to alterations in TCNU plasma protein binding. These sequence-dependent alterations in the pharmacokinetic profile of TCNU correlate with and may explain previously reported differences in the anti-tumour activity and toxicity profile of this combination.

The effect of administering divided dose schedules of TCNU was examined against the murine adenocarcinomas of the colon, MAC 13 and MAC 26, and the Lewis lung tumour and drug metabolism was examined in the different tumour bearing mouse strains. Bone marrow toxicity of the dose schedules was assessed using a spleen colony forming unit assay. In addition, the effect of drug scheduling was investigated in a Phase I clinical setting. Differing levels of efficacy of the divided dose schedules were observed in the different murine tumour models. A therapeutic advantage was found in the Lewis lung tumour whereas none was found in either MAC 13 or MAC 26 tumours. The extent and nature of TCNU metabolism varied between the mouse strains which might contribute to the differing activity-toxicity patterns obtained. The results suggest that divided dose scheduling of TCNU might only be useful in selected patients.

Tauromustine was found to be reducible at the dropping mercury electrode (DME) over the whole pH range in Britton-Robinson (BR) buffers. A well-defined cathodic wave was produced in the acid range, followed by an ill-defined, more negative additional wave starting from pH 4.0. The main reduction wave was characterized as being diffusion-controlled, although adsorption phenomena played a limited role in the electrode process. Using either direct current or differential pulse polarographic modes, the limiting current-concentration plot is linear over a convenient range with a minimum detectability of 5 × 10−8 M using the latter technique. Tablets containing tauromustine (20 and 50 mg) were successfully analyzed adopting the United States Pharmacopoeia (USP) content uniformity test.

The denitrosation of a novel nitrosourea, 1-(2-chloroethyl)-3-[(2-dimethylaminosulfonyl)-ethyl]-1-nitrosoure a, tauromustine (TCNU), has been investigated in liver cytosol from various species and with a pool of cytosolic rat liver glutathione transferases (GSTs). In addition, the denitrosation of related nitrosoureas, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) have been investigated. By using radioactive nitrosoureas as substrates and HPLC to detect the denitrosated products, a sensitive assay has been developed. The activities towards additional substrates, 1-chloro-2,4-dinitrobenzene (CDNB) and trans-stilbene oxide (tSBO) were also measured in the various cytosol fractions. The apparent Vmax and Km values for the denitrosation of TCNU in rat liver cytosol were calculated to be 830 pmol/min/mg protein and 8.4 mM respectively. The rate of denitrosation of TCNU was found to be highest in the mouse, followed by the rat and the dog. The induction of GSTs by phenobarbital in rats increased the denitrosation of TCNU similar to the activities found towards CDNB and tSBO as substrates. The highest denitrosation activity by GST was determined towards BCNU, followed by CCNU and TCNU. Our results suggest that the denitrosation of various nitrosoureas via GST may play an important role in the deactivating process occurring in vivo and for the efficacy of nitrosoureas used in chemotherapy.

Several investigators including ourselves have shown that hydralazine can potentiate the anti-tumour activity of certain agents against murine tumours probably by manipulating tumour blood flow. In order to investigate the effects of administration of hydralazine on systemic and tumour drug concentrations, we have examined the plasma and tissue pharmacokinetics of the recently developed nitrosourea, Tauromustine (TCNU). The effect of hydralazine on glomerular filtration rate (GFR) in mice was also examined using inulin single injection plasma clearance. An active dose of TCNU (30 mg kg-1) was administered intravenously into non-tumour bearing NMRI mice or mice bearing MAC 15A or MAC 26 subcutaneous tumours. Plasma and tissue levels of TCNU were measured by HPLC. Hydralazine significantly increased (P less than .005 in all cases) the AUCs and decreased the plasma clearance of the drug. Inulin plasma clearance was decreased from 0.258 +/- 0.046 ml min-1 to 0.096 +/- 0.017 ml min-1 (a factor of 2.69) after administration of hydralazine. This decrease in GFR would explain the increased plasma half-lives of a renally cleared drug. It is likely that the increased AUC values are partly responsible for the improved anti-tumour activity of TCNU when administered with hydralazine, but the impact of these findings on toxicity needs to be established.

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.

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.

Tauromustine (TCNU) is a newly developed nitrosourea compound. As a result of molecular modification, TCNU is more hydrophilic than BCNU and CCNU. In experimental data there was a high therapeutic index, especially in Walker 256 carcinosarcoma in rats, and in phase I trials antitumor activity was observed in NSCLC (10/33 remissions). There was also activity in melanoma, breast cancer, pleurameso-theliomas and ovarian cancer. To determine the effectiveness, duration of response and toxicity of TCNU the following phase II trial was performed. Patients received 130 mg/m2 TCNU every 35 days orally. Twenty-five patients were treated; 22 were evaluable. The female/male ratio was 18/4, 1 patient was stage III, 21 patients stage IV, the mean age was 62.3 years (range 32–70). Between 1 and 4 courses (mean 1.9) were administered. Histology was as follows: 6 squamous cell, 11 adeno-carcinoma, 2 large cell and 3 polymorph cell carcinomas. No objective response (CR + PR) was observed; 6/18 patients had stable disease, 7/18 progression and 5/18 early progression. The median survival time is 4.9 months. The most severe side effect was thrombocytopenia (WHO grade 3 + 4, 4/22 patients). TCNU administered at this dose and schedule does not show substantial antitumor activity in patients with NSCLC. The fact that no objective tumor remission was observed suggests that the true response rate is

Tauromustine (TCNU) is an exploratory drug that has demonstrated activity in various solid tumors. We examined chromosome aberrations and plasma levels of the drug in two groups of patients receiving either a single dose of 130 mg/m2 or 40 mg/m2 on 3 consecutive days. Peak plasma concentrations (mean +/- SD) were obtained at a similar time after both treatments, i.e., at 38 +/- 25, 32 +/- 24, 28 +/- 14, and 40 +/- 26 min after administration of 130 mg/m2 on day 1 and after that of 40 mg/m2 on days 1, 2, and 3, respectively. In addition, the cumulative area under the curve (AUC value) determined after administration of 40 mg/m2 x 3 was similar to that noted after treatment with a single dose of 130 mg/m2, i.e., 180 and 179 micrograms min ml-1, respectively. Both treatments induced chromosome aberrations (CAs) in peripheral blood lymphocytes. A dose-dependent increase in the number of CAs was found, with 40 mg/m2 producing 5.5% CAs and 130 mg/m2 yielding 20.9% CAs at 24 h after treatment. In addition, although the drug concentration declined to a level under the detection limit between the daily treatments, drug-induced chromosome damage was cumulative, with the 90-min values increasing from 4.8% on day 1 to 14.3% CAs on day 3. In individual patients, no correlation was found between CAs and kinetic parameters; however, the total mean CA yield was in agreement with the total drug exposure (CAs, 14.3% and 14.6%, AUC 180 +/- 62.8 and 179 +/- 115 micrograms min ml-1, respectively.

Tumour uptake of a radiolabelled anticancer drug, tauromustine ([14C]TCNU), was investigated, using two different routes of administration in rats with colon adenocarcinomas implanted in the liver. Intra-arterial administration produced higher concentrations of the drug and/or its metabolites in tumour tissue and lower concentrations in normal tissue compared to intravenous administration. The investigation of co-injection of [14C]TCNU intra-arterially with degradable starch microspheres (DSM) indicated that a high dose of DSM (30 mg/kg) resulted in a high concentration of radioactivity in normal liver tissue, and in adjacent organs. This unfavourable pattern was not observed with the low dose of DSM (12.5 mg/kg), which produced a significant increase in tumour uptake. The results demonstrate the efficacy of partial vascular blockade, as elicited by the low dose of DSM. This regime caused [14C]TCNU to be preferentially retained in the active peripheral regions of the tumour.

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.

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.

Tauromustine (TCNU) a new taurine-based nitrosourea in phase III clinical trials against colon cancer, has been tested and compared with 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (CCNU) for mutagenic potential in Salmonella typhimurium TA98 and TA100 and, for its ability to cause chromosome aberrations and sister chromatid exchanges (SCE) in human lymphocytes. A dose dependent increase in the number of mutations in S. typhimurium TA100 but not in TA98 was found from 1.6 to 1000 micrograms/plate for both TCNU and CCNU. In addition, in the presence of Aroclor activated liver microsomes, CCNU caused a further increase in the mutation frequency which was not found for TCNU. A dose dependent increase in the chromosome aberration rate in human lymphocytes was induced by both TCNU and CCNU at concentrations ranging from 3.75 to 30 micrograms/ml after 24 h treatment during the last cell cycle. When lymphocytes were treated in G0 both TCNU and CCNU induced a higher frequency of aberrations at 15 and 30 micrograms/ml than during the last cell cycle and, unexpectedly, chromosome-type, i.e. dicentrics appeared. The difference in the frequency of aberrations in these two phases may be related to the different levels of O6-methyl guanine transferase present in resting contra cycling lymphocytes. TCNU at 0.8-8 micrograms/ml also induced a dose dependent increase in the number of SCE in human lymphocytes. Neither the number of chromosomal aberrations nor the number of SCE were affected by the addition of 1000 micrograms/ml taurine to the culture medium.

A novel nitrosourea, 1-(2-chloroethyl)-3-[2-(dimethylaminosulphonyl)ethyl]1-nitrosourea , tauromustine (TCNU), has been investigated for in vitro metabolism by different rat organs. Two kinds of reactions were seen, demethylation and denitrosation, both reactions required NADPH. These reactions were achieved by the liver microsomes and to a much lesser extent by lung microsomes. Induction of cytochrome P450 system with phenobarbital resulted in increased demethylation (10 times) and denitrosation (6 times) of tauromustine while induction with 3-methylcholanthrene did not have any significant effect on these reactions. Known inhibitors of different cytochrome P450 activities inhibited the demethylation and denitrosation of tauromustine to different levels. After oral administration of [14C]tauromustine a metabolic pattern similar to that observed in vitro experiments, was seen in the urine. The demethylated compound, which has alkylating cytotoxic activity, could be detected in the urine up to 8 hr after oral administration.

✓ 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.

To further clarify the mode of action of estramustine, the influence on macromolecular synthesis in the human prostatic tumour cell line 1013L was investigated. Cell treatment with estramustine, nor-nitrogen mustard and tauromustine, followed by radioactive nucleotide and leucine incorporations, as a measure of RNA, DNA and protein labelling, were carried out. The initial effect of estramustine clearly differed from that obtained after treatment with nor-nitrogen mustard and tauromustine. No inhibition of DNA synthesis was found whereas an inhibition of overall RNA synthesis was predominant. Adaption of an established RNA separation method was used in an indepth study of RNA labelling after estramustine treatment. An inhibition of 29S, 18S and 4-7S RNA was found after estramustine treatment, indicating disturbances in either RNA processing or RNA transport. The lack of 45S RNA labelling additionally indicates pre-ribosomal inhibition.

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.

Tauromustine (TCNU, LS2667, 1-(2-chloroethyl)-3-[2-(dimethyl-aminosulfonyl)ethyl]-1-nitrosourea) stability in solution has been investigated by reversed-phase high-performance liquid chromatography. Dissolved in dimethylsulfoxide and diluted with an appropriate buffer, the drug was found to be most stable in either citrate buffer (pH 4.0) or normal saline (pH 6.25). TCNU degraded under a variety of conditions: alkahne pH, elevated temperatures, light, and in phosphate-buffered saline (pH 7.4). Long-term studies showed that the drug could be stored in 150 mM citrate buffer at −20° C or −70° C for 3 months with no loss of drug. No adverse affects were found when using different types of container material. Filtration with polyvinylidene difluoride filter units gave rise to a high degree of drug adsorption whilst with other filter units minimal loss was observed.

The novel nitrosourea, 1-(2-chloroethyl)-3-[2-(dimethylaminosulphonyl)ethyl]-1-nitrosoure a (TCNU) is active against a panel of three transplantable murine adenocarcinomas of the colon of varying growth characteristics and morphology (MAC system). It shows greater activity than previously tested nitrosoureas in this system and the routes of administration of TCNU do not significantly alter its anti-tumour activity. These data suggest that TCNU may be useful in the management of large bowel cancer as the MAC system has been previously shown to be a good model of human disease.

A novel nitrosourea, 1-(2-chloroethyl)-3-[2-(dimethylaminosulfonyl) ethyl]-1-nitrosourea (TCNU) tauromustine, has been investigated in a broad anti-tumour screen and, in depth toxicology and initial pharmacokinetics carried out. TCNU and its two metabolites were found to exhibit equal or better oral efficacy than that of BCNU, CCNU, MeCCNU or chorozotocin against L1210 leukemia, Walker mammary carcinoma, Lewis Lung, Harding Passey melanoma and colon carcinoma C26. The toxicological profile of TCNU after acute and 3 months treatment was similar in mice and rats to that of CCNU, with the exception that, TCNU did not cause the chronic liver disturbances found for CCNU. In dogs treated for 6 weeks with TCNU leucopenia and thrombocytopenia were the major side effects. Parent TCNU was found in all dogs. The absorption was fast, the maximum level being reach after 25 mins and the mean absorption time was 22 mins. The mean half life was 16.1 mins after intravenous and 17.4 after oral administration. The combination of these factors make TCNU an interesting clinical candidate.

This study assessed the antitumor activity of 1-(2-chloroethyl)-3-/2-(dimethylaminosulfonyl)ethyl-1-nitrosourea (TCNU), a newly soluble nitrosourea, on NMU-1 lung tumor, a transplantable murine model poorly sensitive to BCNU. TCNU delivered orally was more effective after weekly than after biweekly treatments. When TCNU was given weekly intravenously, its therapeutic index was higher than after oral treatment. Compared with BCNU, TCNU showed superior antitumor effects on NMU-1 murine lung tumor. In this experimental model, TCNU activity was comparable to that of drugs active on human lung cancer.

The cytotoxic activity of a new nitrosourea, TCNU, was compared with that of BCNU in five human small cell lung cancer cell lines in vitro. TCNU was found to be equivalent or inferior to BCNU when compared on a microgram to microgram basis. If the potential of in vitro phase II trials for selection of new drugs can be validated, it can be concluded that TCNU is not superior to other nitrosoureas for the treatment of SCCL.

The pharmacokinetic properties of tauromustine (TCNU) were studied in 31 cancer patients who participated in phase I trials. The patients received single oral doses of tauromustine in the range of 20-170 mg/m2. Plasma samples were taken over 24 h after administration and analysed for tauromustine by reversed-phase liquid chromatography. Parent TCNU could be demonstrated in the plasma of all patients. Its absorption was rapid (tmax = 38 +/- 22 min), the half-life was 57 +/- 22 min (mean +/- SD), and maximal concentration (Cmax) and AUC values were linearly related to the dose level. Thus, our study does not indicate dose-dependent pharmacokinetics for the drug in the range of 20-170 mg/m2. Thrombocytopenia was the dose-limiting toxicity of TCNU; the reduction of platelet counts appeared to be linearly related to the log dose and Cmax and AUC values. TCNU appears to exhibit pharmacokinetic properties that are different from those of other nitrosoureas, which might be important for the clinical effect of the drug.

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.