In vivo drug sensitivity assay of clonogenic human melanoma cells and correlation with treatment outcome.

In vitro tests of tumor cell drug sensitivity have been suggested as a means of selecting more appropriate clinical strategies against human cancer and improving preclinical drug development. The lack of biotransformation in these in vitro assays precludes the meaningful assessment of several major chemotherapeutic agents, including dacarbazine and cyclophosphamide. In vivo drug exposure of tumor cells in agar diffusion chambers placed in mice offers a possible solution to problems of drug biotransformation and pharmacokinetics. We have prospectively used this system as an assay for sensitivity of clonogenic human melanoma cells. Tumor cells were tested fresh, cryopreserved, and/or cultured in vitro before or after clinical use of dacarbazine, semustine, and mitolactol in 41 patient-drug combinations in which a clinical correlation could be made. Tumor cell drug sensitivity in the assay using fresh or cryopreserved tumor cells was highly correlated with clinical response and resistance with clinical nonresponse. Cultured melanoma cells exhibited enhanced plating efficiency in comparison to both fresh and cryopreserved cells of the same tumor. Cultured cells also showed increased drug sensitivity which did not correlate with drug sensitivity of the same fresh or cryopreserved tumor or with clinical response. Tumor cell drug sensitivity assays carried out in vivo provide a possible basis for preclinical evaluation of drugs which are unsuitable for in vitro testing.

Pharmacokinetics of dibromodulcitol in humans: a phase I study.

A combined clinical and pharmacokinetic phase I study of the substituted hexitol dibromodulcitol (DBD), administered as a single oral monthly dose, has been performed. Twenty-three patients with advanced neoplasms received DBD doses ranging from 600 to 1,800 mg/m2 body surface area (BSA). The dose-limiting toxicity was myelosuppression, with both significant granulocytopenia and thrombocytopenia occurring at dose levels of 1,500 to 1,800 mg/m2. The average pharmacokinetic parameters for DBD, calculated on the basis of a one-compartment model with first-order absorption and elimination, include the elimination constant, .005 +/- .002/min; absorption constant, .012 +/- .009/min; and an apparent volume of distribution, 1.03 +/- .4 L/kg. The area under the drug concentration curve (AUC) and the peak drug level (Cmax) were linearly related to the dose administered (P less than .001). The mean AUC was 18.7 +/- 6.1 mmol/L min, and the mean Cmax was 47.1 +/- 16.8 mumol/L when normalized to a DBD dose of 1 gm/m2. The elimination constant was significantly reduced in patients with abnormal hepatic function (P less than .01). The elimination constant was not correlated with renal function. The half-life of DBD in plasma (158 minutes) was considerably shorter than the four-to eight-hour half-life of total radioactivity in plasma measured by previous investigators following the administration of radiolabeled DBD.

The distribution of bromine content of dibromodulcitol in the central nervous system of patients with malignant gliomas.

The bromine content of human gliomas and white matter was determined by neutron activation analysis (NAA) following p.o. administration of a single dose of 400-500 mg/m2 dibromodulcitol (DBD). In another group of patients with brain gliomas, the bromine content was measured subsequent to application of a single dose of 334 mg/m2 of sodium bromide (equivalent dose regarding the bromine content of DBD). The bromine content of these two groups was compared to the values found in a third control group of untreated patients. The amount of bromine after DBD application was three to four times higher than in the untreated samples and the average accumulation ratio of 1.8 +/- 0.4 proved to be nearly identical both in tumour and white matter. The bromine values after NaBr treatment showed a different pattern of distribution. The accumulation was higher in the tumour tissue than in the normal white matter. These findings demonstrate that the pharmacokinetic properties of DBD- and NaBr-derived bromine are different, suggesting that the increase of bromine after DBD administration could be due to covalently bound bromine in DBD.

Chemotherapeutic approaches to brain tumors. Experimental observations with dianhydrogalactitol and dibromodulcitol.

Dianhydrogalactitol (DAG) or its active cell-killing moiety has a relatively long biological half-life in 9L cells cultured in vitro. The shape of the DAG dose-response curves was similar to that of those observed for most oncolytic agents. The prominent shoulder on the 24-h dose-response curve indicates that 9L cells can accumulate a reasonable amount of DAG-induced sublethal damage before they are killed. The appearance of 9L colonies in petri dishes was delayed 3-5 days after a DAG treatment that killed more than 99% of the cells, an observation not previously made with radiation, hyperthermia, the nitrosoureas, or other chemotherapeutic agents. Comparison of the in vitro exposure integral and the in vivo tumor tissue integral indicated that DAG would have to be administered at a dose in excess of its LD10 to achieve an in vivo 2 log cell kill. The lack of a significant increase in lifespan after a LD10 dose confirmed this prediction. While DAG alone is active against IC ependymoblastoma, it had very limited activity against IC glioma 26; however, the combination of DAG with BCNU was curative in 85%-100% of animals at 120 days. BCNU alone achieved no more than 4%-16% survival at 120 days. The combination of DBD and BCNU was not consistently better than BCNU alone against IC glioma 26. It appears that DAG may have a limited place in CNS chemotherapy for specific kinds of tumors. BCNU-DAG combination studies suggest that we may, under the right conditions, enhance the antitumor activity of the hexitol epoxides by drug combination therapies, although the mechanism for this enhanced antitumor activity is presently unknown.

Incorporation of 3H-dibromodulcitol and 3H-dianhydrodulcitol into ascites tumor cells. Autoradiographic study.

The incorporation of 3H-Dibromodulcitol and 3H-Dianhydrodulcitol into S37 ascites tumor cells has been studied with autoradiography. Both drugs war incorporated very rapidly into the cells. The labeling of nucleus was higher than that of cytoplasm. A slight accumulation of grains was found above the condensed chromatin and along the membranes. The uptake of DAD has been more intensive than that of DBD.

Association between serotonin transporter availability and overall rating scores of quality of life in healthy volunteers.

Depression and impaired quality of life (QOL) are frequently observed in patients suffering from a variety of diseases. In addition, it has been reported that an enhanced degradation of the serotonin precursor tryptophan may contribute to QOL deterioration in some diseases. However, it is unclear whether the correlation between the QOL scores and the central serotonergic tone is only mediated by the severity of either the depression symptoms or the physical illness itself. The present study examined the relationship between serotonin transporter (SERT) availability and life quality as measured by the World Health Organization Quality of Life brief version questionnaire (WHO-QOL) in healthy participants in order to exclude the influence of depressive mood and disease. The SERT availability in the midbrain was approximated using SPECT with [(123)I] ADAM ligand in fifty-eight healthy volunteers. The overall rating sub scores of the WHO-QOL correlated positively with serotonin transporter availability in the males. Central serotoninergic activity may play a role in the overall rating scores of the WHO-QOL.

Metabolism and pharmacokinetics of dibromodulcitol (DBD, NSC-104800) in man--II. pharmacokinetics of DBD.

Dibromodulcitol (DBD), labelled with [3H] at position C-1, was administered orally to 6 patients in a single dose of 15 mg/kg. Kinetic parameters were calculated for the effective drug (DBD + BrEpG + DAG), protein-bound hexitol moieties and free metabolites. Approximate values were estimated for the oral bioavailability of DBD. Disposal of the drug by metabolism and excretion was described by a simplified catenary model. The results indicated that 8-20% of the drug became firmly bound to macromolecules, probably by alkylation. The slow rate of alkylation in vivo (half-life 14 hr) may imply conversion of DBD into epoxides and their alkylating interaction with the target nucleophiles. The long retention of the firmly bound hexitol moieties in the body may be an indicator of the cumulative potency of DBD and must be taken into consideration by developing dosage schedules.

Rat liver-mediated degradation of dibromodulcitol.

The rate and extent of dibromodulcitol (DBD) conversion by 9000 g rat liver supernatant with an NADPH-generating system (S-9 mix) were studied using 3H-labelled drug. Results indicated that S-9 mix seemed to exert an initial protective effect delaying the solvolysis of DBD for about 30 min at 37 degrees C followed by rapid degradation into exclusively pharmacologically inactive products. Thus S-9 mix contained merely DBD as an effective agent; it amounted to less than 40% of the total radioactive compounds by 120 min. In the control mixtures the sovolytically produced effective drug content, i.e. the sum of DBD, 1,2-anhydro-6-bromo-6-deoxygalactitol (BrEpG), 1,2-5,6-dianhydrogalactitol (DAG) was 63%. Our results suggest the involvement of liver enzymes in the detoxification of DBD into inactive products. Therefore the antitumour effect of DBD cannot be attributed to its active BrEpG and DAG alone. The drug in its unchanged form may contribute to a somewhat greater extent to its cytostatic action than was believed before.

The distribution of [3H]-dibromodulcitol in the central nervous system of patients with brain tumour.

The uptake of [3H]-dibromodulcitol ( [3H]-DBD) into glioblastomas, white matter and cerebrospinal fluid was studied in 10 patients. Single-tissue samples were taken from different subjects at 4, 15 and 24 hr after [3H]-DBD administration. The level of 3H-compounds in the central nervous system was similar after a single (400 mg/m2), or 3 smaller daily oral doses of 150-180 mg/m2 of [3H]-DBD. The distribution of radioactivity was uniform in the tumour, white matter and muscle. Between 3 and 15 hr after administration of DBD the concentration of radioactivity did not change significantly and was between 5 and 13 micrograms of DBD/g tissue wet wt. At the same time the level in the cerebrospinal fluid (CSF) remained between 1 and 4 micrograms/ml. Meanwhile, the average concentration of radioactivity in the plasma fell from 11 to 3 micrograms/ml. The elimination half-life of the labelled compounds from the tissues was about 1 day as judged from the limited number of non-serial data obtained 4 and 24 hr after the last dose of repeated drug administration.

Clinical trials with the hexitol derivatives in the U.S.

Three hexitol derivatives, dibromomannitol (DBM), dibromodulcitol (DBD), and dianhydrogalactitol (DAG), originally investigated in Hungary, have been evaluated as anticancer agents in the United States. Their principal mechanism of action is attributed to alkylation via actual or derived epoxide groups. Their preclinical spectrum includes activity against murine leukemias and against the murine ependymoblastoma, which is particularly noteworthy for DAG. Dibromomannitol trials were targeted to chronic myelogenous leukemia but no advantage over busulfan therapy was demonstrable. Dibromodulcitol and DAG were sequentially evaluated for their usefulness against a wide variety of tumors. The activity of DBD against breast cancer has stimulated several continuing trials in this disease. On the other hand, DAG was disappointing in breast cancer and in several other malignancies, but some activity has been noted against lung cancer. Both DBD and DAG are being investigated for possible usefulness in the management of patients with intracranial neoplasms. The present clinical experience does not allow firm judgment on the advantage of one analogue over another. Such comparative analysis does point out the desirable direction of future studies as well as the limitations of current preclinical systems for the selection of analogues.

Pharmacokinetics and metabolism of dianhydrogalactitol DAG in patients: a comparison with the human disposition of dibromodulcitol DBD.

Dianhydrogalactitol (DAG), labelled with 3H, was administered in single intravenous or oral doses to six patients (three in each group) with cancer. Kinetic parameters were calculated for the unchanged DAG and its biotransformation products. Elimination of the drug by metabolism and excretion was described by a catenary model. In order to elucidate the role of DAG as a mediator of the alkylating action of the cytostatic drug dibromodulcitol (DBD), the pharmacokinetic parameters of DAG and DBD were compared. The mean residence time for pharmacologically active molecules in the body was six times shorter for DAG (1.9 hr) than for DBD (11.4 hr). Alkylating action and metabolic degradation proceeded about 8-9 times faster for DAG than for DBD. The process of DBD alkylation implies a slow solvolytic conversion of the parent drug into the more reactive bromoepoxide and DAG. The preformed DAG would be rapidly consumed by intracellular alkylation and degradation, while unchanged DBD could form a depot in the cells and exert its cytostatic activity through the epoxides released in situ by solvolytic activation. Thus DBD entering the cells in unchanged form may have a more important role in its therapeutic effects than had been assumed earlier.