Per Olov Gunnarsson

Growth and cell survival following treatment with estramustine nor-nitrogen mustard, estradiol and testosterone of a human prostatic cancer cell line (DU 145).

Estramustine at concentrations ranging from 3-40 x 10(-6) M inhibited the cell growth and clonogenic survival of a human prostatic carcinoma cell line (DU 145). This cell line was found to be unresponsive to estradiol and testosterone at concentrations ranging from 10(-9) M to 5 x 10(-5) M. Metabolism studies with estramustine showed that only a few per cent of the ester linkage was cleaved during the exposure period. This small amount of metabolism could possibly lead to the release of nor-nitrogen mustard, which was however found not to be as inhibitory as estramustine in this cell line. The results indicate that estramustine per se causes the cell death of hormone unresponsive human prostatic carcinoma cells in cell culture.

Uptake of estramustine phosphate (estracyt) metabolites in prostatic cancer.

Plasma and tumour concentrations of estramustine, estromustine, estradiol and estrone, the major metabolites of estramustine phosphate (estracyt), were determined in patients with prostatic carcinoma treated between one and nine years with repeated oral doses of estracyt (560 to 840 mg./day). The last dose was given 12 to 16 hours before sampling. The binding of radioactive estramustine and estromustine was determined in the tumour tissue to examine the possible role of estramustine-binding protein for the accumulation of these metabolites into the tumour. Comparison was made with benign prostate hyperplastic tissue from untreated patients. Estromustine was the main metabolite in plasma as well as in the tumour (range 235 to 450 and 205 to 485 ng./gm., respectively), whereas estramustine (20 to 45; 95 to 370), estrone (62 to 140; 63 to 160) and estradiol (8 to 15; 7 to 36) were found in lower concentrations. Interestingly the concentration of estramustine was as an average six times higher in the tumour than in plasma contrasting with the other metabolites which were present in equal amounts of the two localities. Binding of 3H-estramustine and 3H-estromustine was two to three times higher in the tumour than in benign hyperplastic tissue and negligible in plasma samples. The present study is the first where substantial amounts of cytotoxically active estramustine and estromustine are demonstrated in tumour tissue from estracyt treated patients. Our findings suggest a mechanism for selective uptake of these metabolites in prostatic cancer (estramustine-binding protein). The uptake and binding of estramustine and estromustine in the tumour may account for the clinical effects of estracyt in prostatic carcinoma.

Possible bone-preserving capacity of high-dose intramuscular depot estrogen as compared to orchidectomy in the treatment of patients with prostatic carcinoma.

Treatment of prostatic disease with GnRH agonists or by orchidectomy affects bone mass negatively. Estrogen treatment has beneficial effects on bone mass in women and might hypothetically have a bone preserving capacity also in patients with prostatic cancer.

Time for revival of estrogens in the treatment of advanced prostatic carcinoma? Pharmacokinetics, and endocrine and clinical effects, of a parenteral estrogen regimen.

The present pilot study tested the clinical performance of a new pharmacokinetically guided dosing regimen of parenteral estrogen in patients with advanced prostatic carcinoma. The aim was to accelerate endocrine effects and to avoid cardiovascular side effects.

Phase I Clinical and Pharmacologic Trial of Intravenous Estramustine Phosphate

PURPOSE To determine the dose-limiting toxicities, maximum-tolerated dose, and pharmacokinetics of intravenous estramustine phosphate (IV EMP). PATIENTS AND METHODS A total of 31 patients with hormone-refractory prostate cancer received IV EMP as a 30- to 90-minute infusion weekly (n = 28) or for 3 consecutive days followed by a single weekly dose (n = 3). IV EMP dose was escalated from 500 to 3,000 mg/m(2). Pharmacokinetics of EMP and the metabolites estramustine (EaM), estromustine (EoM), estradiol, and estrone were assessed after weeks 1 and 4 of treatment. RESULTS The initial IV EMP infusion caused perineal discomfort that was ameliorated by lengthening the infusion time. Other common toxicities were grade 1 to 2 hepatotoxicity, nausea or vomiting, and fatigue or malaise. Lower-extremity thrombosis occurred in one patient, and two others developed upper-extremity thrombosis associated with venous infusion catheters. Dose-limiting fatigue and hypotension occurred at 3,000 mg/m(2), and cumulative fatigue developed after multiple cycles at 2,500 mg/m(2). Mean EMP clearance, estimated steady-state volume of distribution, and elimination half-life were 3.7 L/h, 10.6 L, and 3.7 hours, respectively. Variability of EMP clearance was 21%, and variation in area under the curve per dose for the metabolites was 28% to 36%. Elimination half-lives of EoM and EaM were 110 hours and 64 hours, and peak plasma concentrations of these active metabolites exceeded 10 micromol/L after IV EMP doses greater-than-or-equal 2,000 mg/m(2). CONCLUSION High-dose IV EMP can be administered safely as a weekly short infusion to patients with HRPC. High peak concentrations of active metabolites after IV EMP may provide an advantage over oral EMP in antimicrotubule drug combinations.

Anti-tumour, toxicological and pharmacokinetic properties of a novel taurine-based nitrosourea (TCNU)

SummaryA 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.

Absorption and disposition including enterohepatic circulation of (14C) roquinimex after oral administration to healthy volunteers

The absorption and disposition of roquinimex (Linomide®) were studied in four male and two female healthy volunteers. The subjects received a single oral aqueous solution of 14C‐labelled roquinimex, about 0.1 mg/kg, after an overnight fast. Blood samples were taken and urine and faeces were collected for 10 days after dosing. The plasma, urine and faeces concentrations of roquinimex and metabolites were determined by high‐performance liquid chromatography (HPLC) with radiochemical detection. The metabolites were identified by HPLC–mass spectroscopy (MS). The plasma concentration–time profiles of roquinimex exhibited a rapid absorption followed by a bi‐exponential disposition. A secondary peak was observed between 6 and 8 h, indicating enterohepatic circulation (EHC) of roquinimex. The terminal disposition half‐life was estimated as 27 h. The primary metabolic pathways of roquinimex were hydroxylation, demethylation and conjugation. The major compound in plasma was roquinimex; metabolites were only occasionally detected. In urine and faeces, roquinimex accounted for 2% of the dose and conjugated and hydroxylated metabolites each accounted for about 30% of the dose. A model was derived for the plasma concentrations of roquinimex and the amount of urinary excreted roquinimex to take into account EHC. This model improved the goodness‐of‐fit according to common goodness‐of‐fit criteria. The values of the pharmacokinetic parameters were similar using compartmental and non‐compartmental methods, indicating that the contribution of EHC of roquinimex is of minor importance in the evaluation of the pharmacokinetics of roquinimex. Copyright

Cytotoxicity and metabolism of prednimustine, chlorambucil and prednisolone in a Chinese hamster cell line

SummaryPrednimustine and chlorambucil induce dose-and time-dependent cell death in V79 Chinese hamster cells in vitro. Prednimustine was found to be 3–4 times more potent than either chlorambucil or an equimolar mixture of its components chlorambucil and prednisolone after 24 h treatment.Prednimustine was hydrolyzed to prednisolone and chlorambucil in the system, and the concentration of prednimustine was reduced by one half within 15 h. Prednisolone was not further metabolized, but chlorambucil was rapidly inactivated by dechlorination, the half-life being 2.5 h. No dechlorinated prednimustine was formed during the experiments. The higher stability of prednimustine than chlorambucil is probably due to protective binding to different serum proteins from those that bind chlorambucil.Substitution of fetal calf serum by human serum albumin revealed that hydrolysis of prednimustine is catalyzed by esterases present in the serum. In similar substitution experiments cell survival studies indicated that prednimustine itself was not cytotoxic. Rather, cytotoxicity was found to correlate with hydrolysis to chlorambucil. Thus, it appears that the prolonged availability of chlorambucil is responsible for the increased potency of prednimustine in this system.

Accumulation of estramustine and estromustine in adipose tissue of rats and humans.

SummaryThe tissue distribution of estramustine and estromustine, two cytotoxic lipophilic metabolites of estramustine phosphate (Estracyt, EMP) was studied in rats and humans. A single dose of [3H]-estramustine was given i. v. to groups of rats. At 24 h after administration, the concentration of radioactivity in fat was about 20, 12, and 2 times that in muscle, plasma, and liver, respectively. Liquid chromatography verified that the radioactivity represented estramustine and estromustine. The clinical relevance of these results was investigated in pancreas cancer treated with a single oral dose of Estracyt at 12–16 h before surgery. As judged by gas chromatography, the concentration of estromustine, which is the main metabolite in man, was about 13 times higher in fat than in plasma and was also higher in adipose tissue than in muscle and liver. After 5 days of Estracyt treatment, the adipose uptake of estromustine was even higher, namely, about 40 times that in plasma and 8 times that in muscle and liver. Thus, our results demonstrate that estramustine and estromustine are stored in adipose tissue after the administration of EMP; this is important for the pharmacokinetics and, consequently for the therapeutic effects of Estracyt.

A pharmacokinetic study of prednimustine as compared with prednisolone plus chlorambucil in cancer patients

SummaryThe pharmacokinetic characteristics of prednisolone and of chlorambucil and its β-oxidized metabolite, phenylacetic mustard (PAM) were studied in plasma after the oral administration of 200 mg prednimustine (Sterecyt) and a regimen consisting of 20 mg prednisolone plus 20 mg chlorambucil, respectively. A total of 12 cancer patients completed this trial. The drugs were given in a cross-over study as single doses, and serial plasma samples were collected for 32 h. Chlorambucil and PAM were assayed by a gas chromatographic/mass spectrometry method and prednisolone, by radioimmunoassay. The median relative availability of the prednisolone and chlorambucil moiety in prednimustine was 19% and 16%, respectively. Prednisolone, as well as chlorambucil and PAM, appeared later and at a significantly lower concentration in plasma after treatment with prednimustine as compared with the mixture of chlorambucil and prednisolone. We also found that the elimination phase of chlorambucil and PAM in plasma is prolonged after the administration of prednimustine as compared with chlorambucil per se. In contrast, the elimination of the prednisolone moiety of prednimustine and that following the administration of a plain prednisolone tablet did not seem to differ. The modified plasma profile of the alkylating components following prednimustine administration may be important for the clinical efficacy of prednimustine.