Faculty Bibliography

The potential cytoprotective effect of amifostine (WR2721) was studied by analysing toxicities and platinum-DNA adducts in patients with solid tumours entered into two consecutive clinical trials of carboplatin 300 mg/m-2 day 1 and cisplatin 100 mg/m-2 day 3 given without amifostine (seven patients) and with amifostine (nine patients). Haematological toxicity was reduced by amifostine: grades 2-4 granulocytopenia was observed in only 3/21 courses and thrombocytopenia was observed in only 2/21 courses compared to grades 2-4 granulocytopenia in 22128 and thrombocytopenia in 13/28 when amifostine was not added. No delay in chemotherapy administration due to haematological recovery was seen in the group treated with amifostine as opposed to the need for delay in 50% of the chemotherapy cycles (14/28) given without chemoprotectant: mean delay was 16.2 days (range 8-21 days). Within this small sample size, no differences in other toxicities or in response rates could be observed between the two treatment groups. The addition of amifostine did not decrease the extent of platinum-DNA adducts formation in buccal cells collected before and after carboplatin and cisplatin, respectively during the first cycle of therapy. Amifostine appears to diminish the myelosuppression induced by platinum compounds, although no obvious modification of platinum-DNA adduct formation in other normal tissue (buccal cells) was noted

Stability and preclinical pharmacokinetics of isophosphoramide mustard (IPM), an active metabolite of ifosphamide, were investigated using analytical methods developed in this laboratory. For stability evaluation of IPM we used a rapid, high-pressure liquid chromatographic (HPLC) method by which IPM is analyzed directly from aqueous solutions without derivatization on a 10-microns C-18 reversed-phase column with theophylline as the internal standard. IPM in sodium phosphate buffers was found to undergo pH-dependent first-order degradations. At pH 7.4 and 38 degrees C, the IPM solution showed a half-life of 45 min. A gas chromatographic-mass spectrometry (GC/MS) method for the analysis of IPM in plasma was also developed. This method utilized solid-phase extraction with deuterium-labeled IPM as the internal standard. The routine detection limit for the assay was 50 ng/ml with within-run and between-run coefficients of variation of 6% and 11%, respectively. By this method, stability of IPM in plasma and in RPMI 1640 tissue culture medium was evaluated, and its pharmacokinetics in the Sprague-Dawley rat following i.v. administration at 40 mg/kg were investigated. IPM was found to be more stable in these media, with half-lives in the range of 100 min. IPM plasma pharmacokinetics were found to decline monoexponentially with terminal half-lives ranging from 6.8 to 18.7 min and total clearance between 6.0 and 18.3 ml/min. Plasma protein binding of IPM was found to be 55%, and the partition ratio between plasma and red blood cells of 4.9 to 1, respectively. Cytotoxicity of IPM to L1210 cells was evaluated, and the results indicated that the IC50 with 1-h and 4-h exposure was 33 and 15 microM, respectively. Based on these data, IPM plasma levels in the rat declined below the IC50 in about 1 h at this dose. More frequent dosing or infusion may be necessary to maintain adequate drug levels for antitumor activity when IPM is administered directly.

We have completed a phase I and pharmacology study of liposomally-encapsulated daunorubicin (DaunoXome). Of 32 patients entered, 30 were evaluable. No toxicity was encountered at the initial dose-escalation steps from 10 to 60 mg/m2. At 80 mg/m2, two patients manifested grade 2 neutropenia. At least grade 3 neutropenia occurred in all patients receiving 120 mg/m2. Alopecia and subjective intolerance were mild. Cardiotoxicity was not observed except for an episode of arrhythmia in a patient with lung cancer and prior radiation. Only one minor objective response was observed in this population of refractory solid tumors. Pharmacokinetics differed from those of the free drug with no detection of daunorubicinol. We recommend future phase II studies with a dose of 100 mg/m2 in previously treated and 120 mg/m2 of DaunoXome in previously untreated patients with solid tumors.

Teniposide was introduced into clinical trials prior to etoposide, but its role was not defined because interest shifted early on to etoposide. However, long-term encouraging results obtained in acute leukemia treated with teniposide have rekindled interest in this compound. In addition to pharmacokinetic differences, teniposide has greater CNS penetrance and is more lipophilic. Its greater potency is related to enhanced intracellular uptake. Although its antitumor spectrum of activity appears to be very similar to that of etoposide, a search for some differences might prove instructive.

In a preceding study, we established the tolerance and pharmacokinetic behavior of 5-fluoro-2'-deoxyuridine (FdUrd) given by the intraperitoneal (IP) route. A dose of 3 g daily x 3 days was found satisfactory for Phase II study and exploration of biochemical modulation. Therefore, the current study was conducted to study the tolerance and pharmacokinetics of such a dose-schedule and route of FdUrd combined with escalating doses of leucovorin (LV). Fourteen patients were entered and 13 were evaluable for tolerance determination. Pharmacologic determinations of IP FdUrd and 5-Fluorouracil (FUra) derived from it and LV were obtained by HPLC methods on 11 occasions. Findings were compared with the preceding study of FdUrd alone. LV did not appear to alter the tolerance of IP FdUrd even in the four patients receiving the highest dose of LV (640 mg). Toxicities included nausea, vomiting, and rarely neutropenia and diarrhea. Pharmacokinetic parameters indicate a parallel rate of egress of FdUrd and LV from the peritoneal cavity. The pharmacologic advantage for FdUrd is at least 3 logs as previously reported and one log for LV. Evidence of antitumor effect was noted particularly among untreated patients with gastrointestinal primaries. We conclude that IP FdUrd 3 g and LV in doses of up to 640 mg x 3 days are well tolerated. Since FdUrd is more potent, has an even greater hepatic clearance and shows greater potential for modulation with LV than FUra, it may be the preferred fluoropyrimidine for subsequent studies via the IP route in the treatment of carcinomas with prominent peritoneal spread. The pharmacologic advantage for leucovorin is limited but it is a good marker for peritoneal clearance since it parallels FdUrd clearance.

Twenty-six patients with a variety of tumor types were treated according to a phase 1 experimental treatment protocol consisting of repetitive cycles of cis-diammine(1,1-cyclobutanedicarboxylato)platinum(II) (carboplatin, 200-480 mg/m2) at day 1 and cis-diamminedichloroplatinum(II) (cisplatin, 50-100 mg/m2) at day 3. Buccal cells were collected in one or two treatment cycles prior to carboplatin, 24 h after carboplatin, just prior to cisplatin, and approximately 24 h after cisplatin administration. Drug-induced DNA modification was visualized at the single cell level by anti-serum NKI-A59 and quantitated by microdensitometry. All (39 of 39) treatments with carboplatin, and almost all (33 of 35) treatments with cisplatin resulted in an increase in nuclear stain. Interindividual variation in drug-induced, adduct-specific nuclear stain amounted to a factor of 5-8 for carboplatin and 5-12 for cisplatin. This drug-induced increase was, however, not related to the dose of either carboplatin or cisplatin, suggesting that large interindividual differences in DNA adduct formation and/or repair obscured the effects of dose variation within the relatively small range used for the drugs (2.4 for carboplatin and 2.0 for cisplatin). This explanation was strengthened by the good reproducibility of the immunocytochemical assay and by the reasonable correlation between carboplatin-induced nuclear stain in cycles 1 and 2 (correlation coefficient, 0.69; P = 0.009). Mean carboplatin-induced nuclear stain was significantly higher in the first cycle than in the second cycle (P = 0.0001) but this difference was no longer significant when drug-induced nuclear stain was corrected for carboplatin dose. Differences in cisplatin-induced nuclear stain between cycle 1 and cycle 2 were small and not significant. Carboplatin-induced nuclear stain was significantly higher in the partial responders than in the nonresponders (P < 0.0001, two cycles combined); the level of statistical significance remained the same after dose correction. Cisplatin-induced nuclear stain did not differ significantly between partial responders and nonresponders; this result might, however, be confounded to some extent by remaining carboplatin-induced nuclear stain at the moment of cisplatin administration. It is concluded that determination of the extent of platinum-induced DNA modification might be helpful in predicting the tumor response in cancer patients.

The feasibility to deliver chemotherapeutic agents by protracted i.v. infusion has greatly increased in the recent past. Indwelling ports, longer lasting central venous catheters requiring less than daily maintenance 'flushing', surgical expertise in placement, use in analgesia and nutrition, and 'smart' pump technology have all contributed to their increasing popularity. Justification for use of infusions in cancer chemotherapy has been slow in appearing with few studies proceeding to the comparative stage. This review will focus on three drugs in common use in cancer treatment, with the purpose of appraising the role of such infusions in cancer therapeutics and of deriving some lessons that might be applicable to other drugs or to drug development in general. For fluorouracil and doxorubicin the rationale and clinical findings favoring further development of infusion regimens is particularly strong. In the case of platinum compounds, some toxicologic advantages have emerged, but other measures designed to protect against the toxicities of cisplatin compete with infusion regimens in this regard. The therapeutic potential for this form of drug delivery, therefore, appears still confined to a subset of patients. Stronger rationales for the use of protracted infusions may be forthcoming from pharmacodynamic findings as in the case of etoposide, combined modality therapy with radiation for FU and cisplatin, biochemical modulation for FU, and reversal of multidrug resistance and its modulation for doxorubicin. While awaiting research into these areas of clinical and pre-clinical investigations, the role of infusion appears most evident in the cardiotoxicity protection of anthracyclines, and in further efficacy exploration (through dose or modulation) of FU. Both mechanistic and pharmacologic considerations could also provide additional stimulus for development of new formulations such as long circulating liposomes, and drugs more suitable for oral administration.

Using atomic absorbance spectrometry with Zeeman background correction, we measured platinum-DNA adduct levels in leukocyte DNA of 49 patients receiving therapy consisting of only carboplatin and cisplatin. Twenty-four histological types of malignancy were included in the cohort. Peripheral blood leukocytes were collected at defined times during the first two cycles of treatment. The relationship between adduct level and disease response was highly statistically significant during cycle 1 of therapy (two-sided P = 0.007 at day 2), but statistical significance was lost during cycle 2. On all days studied, median and mean adduct levels were consistently higher in responders as compared to nonresponders (summary two-sided P = 0.0004). These data suggest that the processes which protect cellular DNA may be common to malignant and nonmalignant rapidly dividing tissues of the same individual, regardless of the type of tumor that individual may harbor.

Eighteen women with epithelial ovarian cancer and small-volume disease within the peritoneal cavity at reassessment laparotomy after initial treatment with platinum-based regimens received treatment with a combination of intraperitoneal (ip) carboplatin and etoposide administration. The dose of carboplatin was fixed at 200 mg/m2 whereas the dose of etoposide was escalated in cohorts of 4 patients from 50 to 75 and eventually to 100 mg/m2. Hematologic toxicities appeared to be related to decreased renal function, and, in the last cohort of 10 patients, with prior treatment with systemic carboplatin. Because of this shift in patient population, escalations ceased and ip cisplatin was partly substituted for ip carboplatin in 5 patients. The study opened July 1988 and closed on July 1991: 8 patients are alive, with 4 enjoying progression-free survival and no clinical evidence of disease 1 to 4 years after onset of treatment. One patient is alive with no clinical evidence of disease 3+ years after a late relapse was treated with systemic carboplatin. Three other patients are alive with evidence of disease, having experienced improvements with taxol and ip floxuridine. Analysis of this small experience by pretreatment characteristics suggests that patients who are platinum sensitive and not allowed to relapse, have normal baseline CA-125s, and undergo successful secondary cytoreductive surgery may benefit from platinum-based ip therapy.