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A dosage formula has been derived from a retrospective analysis of carboplatin pharmacokinetics in 18 patients with pretreatment glomerular filtration rates (GFR) in the range of 33 to 136 mL/min. Carboplatin plasma clearance was linearly related to GFR (r = 0.85, P less than .00001) and rearrangements of the equation describing the correlation gave the dosage formula dose (mg) = target area under the free carboplatin plasma concentration versus time curve (AUC) x (1.2 x GFR + 20). In a prospective clinical and pharmacokinetic study the formula was used to determine the dose required to treat 31 patients (GFR range, 33 to 135 mL/min) with 40 courses of carboplatin. The target AUC was escalated from 3 to 8 mg carboplatin/mL/min. Over this AUC range the formula accurately predicted the observed AUC (observed/predicted ratio 1.24 +/- 0.11, r = 0.886) and using these additional data, the formula was refined. Dose (mg) = target AUC x (GFR + 25) is now the recommended formula. AUC values of 4 to 6 and 6 to 8 mg/mL. min gave rise to manageable hematological toxicity in previously treated and untreated patients, respectively, and hence target AUC values of 5 and 7 mg/mL min are recommended for single-agent carboplatin in these patient groups. Pharmacokinetic modeling demonstrated that the formula was reasonably accurate regardless of whether a one- or two-compartment model most accurately described carboplatin pharmacokinetics, assuming that body size did not influence nonrenal clearance. The validity of this assumption was demonstrated in 13 patients where no correlation between surface area and nonrenal clearance was found (r = .31, P = .30). Therefore, the formula provides a simple and consistent method of determining carboplatin dose in adults. Since the measure of carboplatin exposure in the formula is AUC, and not toxicity, it will not be influenced by previous or concurrent myelosuppressive therapy or supportive measures. The formula is therefore applicable to combination and high-dose studies as well as conventional single-agent therapy, although the target AUC for carboplatin will need to be redefined for combination chemotherapy.

Liver metastases have long been known to indicate an unfavourable disease course in breast cancer (BC). However, a small subset of patients with liver metastases alone who were treated with pre-taxane chemotherapy regimens was reported to have longer survival compared with patients with liver and metastases at other sites. In the present study, we examined the clinical outcome of breast cancer patients with liver metastases alone in the context of two phase III European Organisation for Research and Treatment of Cancer (EORTC) trials which compared the efficacy of doxorubicin (A) versus paclitaxel (T) (trial 10923) and of AC (cyclophosphamide) versus AT (trial 10961), given as first-line chemotherapy in metastatic BC patients. The median follow-up for the patients with liver metastases was 90.5 months in trial 10923 and 56.6 months in trial 10961. Patients with liver metastases alone comprised 18% of all patients with liver metastases, in both the 10923 and 10961 trials. The median survival of patients with liver metastases alone and liver plus other sites of metastases were 22.7 and 14.2 months (log rank test, P=0.002) in trial 10923 and 27.1 and 16.8 months (log rank test, P=0.19) in trial 10961. The median TTP (time to progression) for patients with liver metastases alone was also longer compared with the liver plus other sites of metastases group in both trials: 10.2 versus 8.8 months (log rank test, P=0.02) in trial 10923 and 8.3 versus 6.7 months (log rank test, P=0.37) in trial 10961. Most patients with liver metastases alone have progression of their disease in their liver again (96 and 60% of patients in trials 10923 and 10961, respectively). Given the high prevalence of breast cancer, improved detection of liver metastases, encouraging survival achieved with currently available cytotoxic agents and the fact that a significant portion of patients with liver metastases alone have progression of their tumour in the liver again, a more aggressive multimodality treatment approach through prospective clinical trials seems worth exploring in this specific subset of women.

A phase II study was conducted to evaluate the activity of pemetrexed in patients with locally recurrent or metastatic breast cancer. 38 patients, median age 52 years (range 36-71 years), were given pemetrexed 600 mg/m(2) as a 10-min intravenous (i.v.) infusion every 3 weeks. Median time from diagnosis to study entry was 48 months (range 14.7-310 months). 33 of 38 patients had prior chemotherapy; 16 adjuvant, 12 metastatic and 5 in both settings. Sites of disease included skin and soft tissue (19/38) nodes (18/38), lung (17/38), liver (13/38) and bone (3/38). An overall response rate of 28% (95% confidence interval (CI): 14.2-45.2%) in 10/36 evaluable patients (1 complete response (CR), 9 partial responses (PR)), included reductions in hepatic and pulmonary metastases. 5 of 10 responders had received taxoid or anthracycline therapy for metastatic disease; 3 of these 5 had also received adjuvant chemotherapy. Median duration of response was 8 months (range 1.6-14+ months), and median survival was 13 months (95% CI 9.56-17.38 months). 167 courses were given (median five per patient; range 1-9), with 37 reductions and 33 delays. Reasons for reduction included neutropenia (11%) and mucositis (5%), with delays due to raised LFTs (21%), neutropenia (12%) and other non-treatment related events. The major haematological toxicities (Common Toxicity Criteria) (CTC) were grade 3/4 neutropenia (47%) and thrombocytopenia (15.7%) of patients. There was one report of a grade 3 infection. Non-haematological toxicities (all grades 2/3) included elevated transaminases (92%), vomiting (34%), nausea (34%) and mucositis (32%). One episode of grade 4 diarrhoea was reported. Other toxicities included a skin rash, grade 2 (42%), 3 (5%) and 4 (13%), which was ameliorated by the use of prophylactic dexamethasone. These results suggest that pemetrexed has significant antitumour activity in advanced breast cancer with responses in patients who had previously received anthracyclines and taxoids.

Substituted guanines and pyrimidines were tested as inhibitors of cyclin B1/CDK1 and cyclin A3/CDK2 and soaked into crystals of monomeric CDK2. O6-Cyclohexylmethylguanine (NU2058) was a competitive inhibitor of CDK1 and CDK2 with respect to ATP (Ki values: CDK1, 5 +/- 1 microM; CDK2, 12 +/- 3 microM) and formed a triplet of hydrogen bonds (i.e., NH-9 to Glu 81, N-3 to Leu 83, and 2-NH2 to Leu 83). The triplet of hydrogen bonding and CDK inhibition was reproduced by 2,6-diamino-4-cyclohexylmethyloxy-5-nitrosopyrimidine (NU6027, Ki values: CDK1, 2.5 +/- 0.4 microM; CDK2, 1.3 +/- 0.2 microM). Against human tumor cells, NU2058 and NU6027 were growth inhibitory in vitro (mean GI50 values of 13 +/- 7 microM and 10 +/- 6 microM, respectively), with a pattern of sensitivity distinct from flavopiridol and olomoucine. These CDK inhibition and chemosensitivity data indicate that the distinct mode of binding of NU2058 and NU6027 has direct consequences for enzyme and cell growth inhibition.

Potent poly(ADP-ribose) polymerase (PARP) inhibitors have been developed that potentiate the cytotoxicity of ionizing radiation and anticancer drugs. The biological effects of two novel PARP inhibitors, NU1025 (8-hydroxy-2-methylquinazolin-4-[3H]one, Ki = 48 nM) and NU1085 [2-(4-hydroxyphenyl)benzamidazole-4-carboxamide, Ki = 6 nM], in combination with temozolomide (TM) or topotecan (TP) have been studied in 12 human tumor cell lines (lung, colon, ovary, and breast cancer). Cells were treated with increasing concentrations of TM or TP +/- NU1025 (50, 200 microM) or NU1085 (10 microM) for 72 h. The potentiation of growth inhibition by NU1025 and NU1085 varied between the cell lines from 1.5- to 4-fold for TM and 1- to 5-fold for TP and was unaffected by p53 status. Clonogenic assays undertaken in two of the cell lines confirmed that the potentiation of growth inhibition reflected the potentiation of cytotoxicity. NU1025 (50 microM) was about as effective as 10 microM NU1085 at potentiating growth inhibition and cytotoxicity, consistent with the relative potencies of the two molecules as PARP inhibitors. Potentiation of cytotoxicity was obtained at concentrations of NU1025 and NU1085 that were not toxic per se; however, NU1085 alone was 3-fold more cytotoxic (LC50 values ranged from 83 to 94 microM) than NU1025 alone (LC50 > 900 microM). These data demonstrate that PARP inhibitors are effective resistance-modifying agents in human tumor cell lines and have provided a comprehensive assessment protocol for the selection of optimum combinations of anticancer drugs, PARP inhibitors, and cell lines for in vivo studies.

Introduction: Cereport (RMP-7) is a novel bradykinin agonist which is being developed as a modulator of the blood-brain barrier (BBB). In order to investigate the pharmacokinetics of carboplatin in combination with Cereport, we performed pharmacological studies in conjunction with early clinical trials., Methods: Pharmacokinetic samples were collected from eight patients in a phase I study (Cereport 100-300 ng/ kg) and ten patients in a phase II study (Cereport 300 ng/kg). Pharmacokinetic parameters for carboplatin were compared with respect to the dose of Cereport and with historical controls., Results: Cereport combined with carboplatin was well-tolerated, with mild haematological toxicities consistent with the target area under the concentration time curve (AUC) of 7 mg/ml x min. Although the clearance of carboplatin was within the range reported for this drug alone, the addition of Cereport resulted in a higher than expected carboplatin AUC. This effect was related to the dose of Cereport in the phase I study (AUC values 104-133% of target, Spearman rank correlation coefficient = 0.71, P < 0.001). The higher than expected AUC value was confirmed in the phase II study (AUC values 106-189% of target)., Conclusions: Co-administration of Cereport with carboplatin may result in a greater than predicted AUC. The mechanism of this possible interaction remains to be determined, although this did not result in any increased toxicity. Thus, the clinical potential of this combination in the treatment of brain tumours warrants further investigation.

Dipyridamole has been shown to enhance the in vitro activity of antimetabolite anticancer drugs through the inhibition of nucleoside transport. However, the clinical potential of dipyridamole has not been realized because of the avid binding of the drug to the plasma protein alpha1-acid glycoprotein (AGP). Dipyridamole analogues that retain potent nucleoside transport inhibitory activity in the presence of AGP are described and their ability to enhance the growth inhibitory and cytotoxic effects of thymidylate synthase (TS) inhibitors has been evaluated. Three dipyridamole analogues (NU3026, NU3059 and NU3060) were shown to enhance the growth inhibitory activity of the TS inhibitor CB3717 and block thymidine rescue in L1210 cells. The extent of potentiation at a fixed analogue concentration (10 microM) was related to the potency of inhibition of thymidine uptake. A further analogue, NU3076, was identified, which was more potent than dipyridamole with a Ki value for inhibition of thymidine uptake of 0.1 microM compared to 0.28 microM for dipyridamole. In marked contrast to dipyridamole, inhibition of thymidine uptake by NU3076 was not significantly affected by the presence of AGP (5 mg ml(-1)). NU3076 and dipyridamole produced equivalent potentiation of the cytotoxicity of the non-classical antifolate TS inhibitor, nolatrexed, in L1210 cells with both compounds significantly reducing the LC90, by > threefold in the absence of salvageable thymidine. Thymidine rescue of L1210 cells from nolatrexed cytotoxicity was partially blocked by both 1 microM NU3076 and 1 microM dipyridamole. NU3076 also caused a significant potentiation of FU cytotoxicity in L1210 cells. These studies demonstrate that nucleoside transport inhibition can be maintained in the absence of AGP binding with the dipyridamole pharmacophore and that such analogues can enhance the cytotoxicity of TS inhibitors.

Background: Platinum based drugs are active agents in epithelial ovarian cancer and increased platinum drug dose intensity is thought to lead to improved survival, because of the largely untested assumption that increased dose intensity results in an increased interaction of the platinum drug with its target, DNA. In a previously reported phase I trial (Lind et al., J Clin Oncol 1996; 14: 800-5), carboplatin dose intensity was increased by the use of G-CSF to support the bone marrow and using pharmacokinetically-guided carboplatin dosing. The objectives of this study were to validate the carboplatin dosing formula during high dose intensity therapy and evaluate the relationship between systemic carboplatin exposure and Pt-DNA adduct levels in peripheral blood leucocytes., Patients and Methods: A total of 17 patients were studied over four levels of dose intensification. The carboplatin dose was calculated using the 'Calvert formula'. Levels of drug-target interaction in peripheral blood leukocytes were measured using an immunoassay based on a monoclonal antibody that recognises DNA-platinum adducts. Pharmacokinetic measurements were carried out using a previously validated single sample method., Results: The area under the curve of concentration of unbound carboplatin in plasma versus time (AUC) for target AUC values of 5, 7 and 9 mg/ml x min were: 5.6 +/- 1.0, 7.3 +/- 0.7 and 9.8 +/- 0.5 mg/ml x min (mean +/- S.D.). There was a good correlation between target and achieved dose intensities (r2 = 0.899) and the slope of the linear regression line was 0.95 (+/- 0.09 SD) not significantly different to 1.0 (P > 0.6). The levels of immunoreactive DNA adducts were not detectable at a target AUC of 5 mg/ml x min but increased progressively at the higher AUC levels. Accumulation of adducts between courses was not detected., Conclusions: Pharmacokinetically-based carboplatin dosing during high intensity therapy accurately predicted the dose required to achieve a target AUC and resulted in consistent patient exposure to active drug. During the dose escalation study, peripheral blood leucocyte DNA platinum-DNA adduct levels were positively related to drug dose and drug AUC.

Clinical studies concerning the role of poly(ADP-ribose) polymerase (PARP) in the repair of drug- and radiation-induced DNA damage have been impeded by the poor solubility, lack of potency, and limited specificity of currently available inhibitors. A series of 2-alkyl- and 2-aryl-substituted 8-hydroxy-, 8-methoxy-, and 8-methylquinazolin-4(3H)-ones has been synthesized and evaluated for PARP inhibitory activity in permeabilized L1210 murine leukemia cells. 8-Methoxy- and 8-methylquinazolinones (14-34) were readily prepared by acylation of 3-substituted anthranilamides with the appropriate acid chloride, followed by base-catalyzed cyclization. The requisite 8-hydroxyquinazolinones (6, 35-39) were synthesized by demethylation of the corresponding 8-methoxyquinazolinones with BBr3. N-Methylation of 8-methoxy-2-methylquinazolinone (15) with MeI, followed by O-demethylation by BBr3, afforded the control N3-methylquinazolinones 42 and 43, respectively. In general, an 8-hydroxy or 8-methyl substituent enhanced inhibitory activity in comparison with an 8-methoxy group. 2-Phenylquinazolinones were marginally less potent than the corresponding 2-methylquinazolinones, but the introduction of an electron-withdrawing or electron-donating 4'-substituent on the 2-aryl ring invariably increased potency. This was particularly evident in the 8-methylquinazolinone series (IC50 values 0.13-0.27 microM), which are among the most potent PARP inhibitors reported to date. N3-Methylquinazolinones 42 and 43 were essentially devoid of activity (IC50 values > 100 microM). In studies with L1210 cells in vitro, a concentration of 200 microM 8-hydroxy-2-methylquinazolinone (6, NU1025) (IC50 value 0.40 microM) potentiated the cytotoxicity of the monomethylating agent 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide and gamma-radiation 3.5- and 1.4-fold, respectively, at the 10% survival level.

The cytotoxicity of the antifolate inhibitors of de novo purine biosynthesis, lometrexol (LTX) and LY309887, can be abolished by hypoxanthine (HPX) salvage. The nucleoside transport inhibitor, dipyridamole (DP) can prevent HPX rescue from LTX growth inhibition in a cell line-specific manner. The studies described here have shown that, excluding colon and hematological malignancies, DP prevents HPX rescue from LTX growth inhibition in approximately one-third of cell lines with otherwise limited tissue specificity. The clinical dose-limiting toxicities of antipurine antifolates are to the bone marrow and gastrointestinal tract. In vitro models of these normal tissues were established, and the effect of DP on HPX rescue from LY309887 treatment was studied. Growth inhibition assays are not feasible in these primary cultures; therefore, an alternative assay, cellular ATP depletion, was validated in four tumor cell lines as a marker of de novo and salvage purine synthesis. In LY309887-treated cells, DP prevented HPX-mediated maintenance of ATP levels only in cell lines in which DP inhibited HPX rescue from antifolate cytotoxicity. Hence, ATP depletion is a reliable indicator of sensitivity of HPX transport to DP when direct cell growth measurement is impractical. In primary cultures of human hematopoetic progenitor cells and mouse small intestine, coincubation with HPX prevented LY309887-mediated ATP depletion, which was not blocked by DP. These data suggest that DP would not prevent HPX rescue from antipurine antifolate growth inhibition in sensitive normal tissues, whereas activity against certain solid human tumors would be maintained.

LY231514 is a novel antifolate that principally inhibits thymidylate synthase, but with additional folate-dependent enzyme targets. A Phase I study of single-agent LY231514 administered as a daily i.v. infusion over 10 minutes for 5 days, repeated every 3 weeks, was conducted to evaluate the maximum tolerated dose, pharmacokinetic profile, and antitumor activity of the drug using this schedule. Thirty-eight patients with advanced malignancies that were refractory or not amenable to standard therapy were treated with a total of 116 courses of LY231514, escalating treatment doses through 10 dose levels, from 0.2-5.2 mg/m2/day. No objective clinical responses were observed, although minor antitumor activity not fulfilling the response criteria was seen in three patients. A maximum tolerated dose of 4.0 mg/m2/day was determined, with neutropenia as the predominant dose-limiting toxicity. Reversible disturbances of liver biochemistry, fulfilling the protocol definitions of dose-limiting toxicity, were also observed. Other toxicities included diarrhea, mucositis, skin rash, and fatigue. Pharmacokinetic studies were performed at all treatment levels. Analysis showed a linear relation between administered dose and both maximum plasma concentration (Cmax) and area under the plasma concentration/time curve. The drug was cleared with a day 1 total body clearance of 108.9 +/- 38.8 ml/min/m2, with plasma concentrations declining with a mean harmonic terminal half-life of 1.4 +/- 0.98 h. When given by this schedule, LY231514 is tolerable, and Phase II studies are in progress.

MTA (LY231514), a multi-targeted antifolate, is a classical antifolate undergoing intracellular polyglutamation. Polyglutamated MTA is a potent thymidylate synthase (TS) inhibitor and inhibits other folate-dependent enzymes, including dihydrofolate reductase and glycinamide ribonucleotide formyl transferase. Multifocal antifolates may overcome antifolate resistance, but it is not known whether the anti-tumour activity of MTA depends on its TS inhibition, its primary locus of action, or whether other loci contribute. MTA was examined in three phase I trials using different schedules: a 10-min i.v. infusion given once every 3 weeks, once weekly for 4 weeks every 6 weeks or daily for 5 days every 3 weeks. Dose-limiting toxicities were neutropenia and thrombocytopenia. Other consistently seen side-effects, which were manageable, included mucositis, skin rashes and transient elevations of transaminases. Toxicity was highly schedule dependent: the recommended dose for the 3-weekly schedule (600 mg m(-2)) was 30 times that for the daily x 5 schedule (4 mg m(-2)day(-1)). The 3-weekly dosing schedule was chosen for phase II evaluation. Phase II trials are underway to investigate the activity and toxicity of MTA in several tumour types, including colorectal, pancreas, breast, bladder and non-small-cell lung cancer (NSCLC) Further phase I trials will investigate MTA in combination with other agents, including gemcitabine, cisplatin, 5-fluorouracil and folate. Preliminary phase II trials results are encouraging; responses were seen in colorectal, pancreas, NSCLC and breast cancer.

There is evidence to suggest that glutathione (GSH) and glutathione-S-transferases (GST) are important factors in determining sensitivity to cytotoxic drugs in vitro and in preclinical in vivo model systems. To define the relationship between tumour GSH concentration, GST isoenzyme expression and response to carboplatin in epithelial ovarian cancer (EOC), tumour samples from 39 patients with assessable disease after primary surgery were analyzed for GSH content and GST expression. Response was assessed after completing six courses of single agent carboplatin therapy. GSH was measured by high performance liquid chromatography (HPLC) in fresh tumour samples taken at primary laparatomy. GST isoenzyme expression was assessed by immunohistochemistry of fixed tumour material using antibodies specific for pi, alpha and mu classes. GST isoenzyme expression was defined as positive if the staining intensity was strong and more than 10% of tumour cells were involved. The mean GSH concentrations were: 8351 +/- 4496, 7211 +/- 5026, 6559 +/- 4573 and 3758 +/- 1885 (nmol g-1 tissue dry weight mean +/- s.d.) for tumours from patients who subsequently achieved a complete response (CR, n = 18), partial response (PR, n = 10) or who had static disease (SD, n = 7) or progressive disease (PD, n = 4) respectively. There was no relationship between GSH concentration and response (ANOVA, P = 0.32). There were also no relationship between GST isoenzyme expression and response (P Fisher's exact test 0.51-0.55 and chi-squared test 0.98-0.99). In conclusion, there was no association between the concentration of GSH or expression of GST isoenzymes and response to single agent carboplatin in primary previously untreated EOC.

Purpose: The aim of this study was to increase the dose intensity of carboplatin in women with International Federation of Gynecology and Obstetrics (FIGO) Stage Ic-IV epithelial ovarian cancer with the use of granulocyte colony-stimulating factor (G-CSF; filgrastim; Amgen, Thousand Oaks, CA)., Patients and Methods: A phase I study of escalating target area under the curves (AUCs) of carboplatin with G-CSF (filgrastim) ws undertaken. The target AUCs were 5 mg/mL.min every 21 days for four cycles, 5 mg/mL.min every 14 days for four cycles, 7 mg/mL.min every 14 days for four cycles, 9 mg/mL.min every 14 days for four cycles, and 11 mg/mL.min every 14 days for four cycles. G-CSF was given at a dose of 5 microg/kg/d starting 24 hours after carboplatin administration and lasting until 24 hours before the next cycle and until day 14 after the last cycle., Results: We were able to escalate to an AUC level of 9 mg/mL.min every 14 days for four cycles. At this dose, severe thrombocytopenia, that necessitated dosage delays, and failure to give subsequent cycles of carboplatin were observed. We then reduced the AUC level to 8 mg/mL.min every 14 days for four cycles. However, severe thrombocytopenia was also observed at this level., Conclusion: An AUC of 7 mg/mL.min every 14 days for four cycles is the maximum tolerated AUC level that can be achieved with G-CSF. Further escalations may be possible using either combinations of cytokines or peripheral stem-cell collections.

The aim of this study was to develop and validate a simple and rapid method for the estimation of the area under the free carboplatin plasma concentration versus time curve (AUC). The relationship between the carboplatin AUC and the total plasma platinum (Pt) concentration 24 h after treatment was studied using data from 49 patients treated with 20-1600 mg/m2 carboplatin as a 60-100 min infusion (median 60 min). The relationship was confirmed by the in vitro incubation of carboplatin in human plasma and prospectively validated in 13 ovarian cancer patients. Free carboplatin was separated by ultrafiltration (MW cut off 30,000), and free and total Pt measured by atomic absorption spectrophotometry. There was a linear relationship in vivo between the 24 h (median 24.4; range 16.3-27.3 h) total plasma Pt concentration (microM) and free carboplatin AUC (mg/ml.min): AUC=(24 h Pt+0.3)/0.82 (r2=0.93, AUC median 5.8 (0.13-28)mg/ml.min, 24h Pt median 4.4 (0.1-23) microM). A similar relationship was observed in vitro [AUC =(24h Pt +0.1)/0.93 (r2=0.98, AUC median 7.9 (2.0-17) mg/ml.min, 24 h Pt median 7.1 (1.8-15) microM)]. The relationship derived from the in vivo data gave an unbiased and reasonably accurate estimate of the measured carboplatin AUC in 13 patients (AUC =5.1-8.7 mg/ml.min, GFR=59-129 ml/min, infusion time 30-45 min, 24 h sampling time 22.9-24.5 h), giving a percentage mean error of -4.2% and root mean squared percentage error of 11.5%. These results show that the analysis of a single blood sample taken 24 h after carboplatin administration can be used to produce an unbiased and reasonably accurate measure of the free carboplatin AUC. Unlike published limited sampling strategies, this method is not complicated by the need to accurately control the duration of the carboplatin infusion or the time at which the sample is taken.

The enzyme, thymidylate synthase (TS) is considered an important target for the development of new anticancer agents. Moreover, the folate-binding site in TS is believed to offer better opportunities for the design of highly specific inhibitors than the pyrimidine (dUMP) binding site. This belief led to the design of N10-propargyl-5,8-dideazafolic acid (CB3717), a quinazoline-based drug which had antitumour activity in clinical studies. Occasional, but serious nephrotoxicity led to the withdrawal of CB3717 from further clinical study. More water-soluble and non-nephrotoxic analogues were developed with an interesting diversity in biochemical profile, particularly with respect to interactions with the reduced-folate cell membrane carrier (RFC) and folylpolyglutamate synthetase (FPGS). An example of a compound that uses both of these processes well is the quinazoline, ZD1694 (Tomudex), a drug which is about to complete phase III evaluation for colorectal cancer. High chain length polyglutamates are formed that are up to 70-fold more potent TS inhibitors than the parent drug (Ki tetraglutamate = 1 nM). Furthermore they are retained in cells/tissues for a prolonged period. A number of other novel folate-based TS inhibitors are currently in pre-clinical or clinical study. For example, LY231514 is a pyrrolopyrimidine analogue in phase I study and, although less potent as a TS inhibitor, has biochemical properties similar to ZD1694. Another compound in phase I study is the benzoquinazoline, BW1843U89 which has somewhat different properties. It is a very potent TS inhibitor (Ki = 0.09 nM) and an excellent substrate for the RFC (human) and FPGS, but polyglutamation proceeds to diglutamate only and is not accompanied by increased TS inhibition. Another highly water-soluble compound in pre-clinical development is ZD9331 which was specifically designed to use the RFC but not be a substrate for FPGS. Potent TS inhibition (Ki = 0.4 nM) was achieved through a rational programme of computerised molecular modelling of the active site of TS and a large database of structure-activity relationships. Two lipophilic compounds were designed to be devoid of interactions with either the RFC or FPGS. High resolutions crystal complexes of E. coli TS were central to obtaining potent TS inhibitors and both AG337 (Ki human recombinant TS = 16 nM) and AG331 (Ki = 12 nM) are in clinical studies. This portfolio of novel compounds therefore comprehensively addresses the potential of TS as a target for cancer chemotherapy.

Resistance to anti-cancer drugs has proved to be a major barrier in the clinical management of neoplastic disease. We have investigated the mechanistic basis for resistance to folate-based thymidylate synthase (TS) inhibitors using two cell lines selected for resistance to ZD1694 (N-(5-[N-(3,4-dihydro-2-methyl-4-oxoquinazolin-6-ylmethyl)-N -methylamino]-2 - thenoyl)-L-glutamic acid), a drug currently in phase III clinical trial. The degree of resistance was > 20,000 for the human lymphoblastoid cell line W1L2:R and approximately 14 for the ovarian carcinoma cell line CH1:R. In both cases resistance was associated with increased TS activity. The W1L2:R cell line had an approximately 100-fold increase in TS gene copy number and mRNA levels and a 500- to 1000-fold increase in enzyme levels determined using quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Southern and Western blotting. The CH1:R cell line had an approximately 2- to 2.5-fold increase in TS gene copy number, mRNA and protein levels. In both cell lines the fold resistance determined was significantly higher than the fold increase in target enzyme DNA, mRNA or protein levels. Small changes in TS levels may therefore translate to clinically significant alterations in drug sensitivity.

Purpose: Sixty patients with metastatic melanoma were treated in a phase II study with the imidazotetrazine derivative temozolamide to assess further the efficacy demonstrated in previous phase I studies., Patients and Methods: Fifty-five of 56 eligible patients were assessable for toxicity and 49 for response. The patients received temozolomide 150 mg/m2/d over 5 successive days orally (total dose, 750 mg/m2) in the first course. Courses were repeated every 4 weeks and the dose was escalated to 200 mg/m2/d x 5 (total dose, 1 g/m2) after the first course if toxicity was acceptable. Patients were all chemotherapy-naive, except for two who had previously received interferon alfa and one who had received interleukin-2 (the latter patient had also received two phase I drugs some time previously)., Results: A complete response (CR) was documented in three patients (all with lung metastases) and a partial response (PR) in nine patients (21% CR plus PR rate). Seven of 56 patients were not assessable for response because of early death or deterioration. The overall response rate excluding these patients is 12 of 49 (24%). The median response duration was 6 months (range, 2.5 to 22+). Toxicity of the regimen, which was mainly hematopoietic, was low. The median survival duration for all patients was 5.5 months (range, 0.5 to 29.5). For responders, the median survival duration was 14.5 months (range, 3 to 28+), with four patients still alive., Conclusion: Temozolomide in the schedule used has as good activity in chemotherapy-naive metastatic melanoma as the other most active agents currently in use. Further studies of the drug on its own and in combination with other agents is recommended.

The synthesis of a series of analogues of the potent thymidylate synthase (TS) inhibitor N-[4-[N-[(3,4-dihydro-2-methyl-4-oxo-6- quinazolinyl)methyl]-N-prop-2-ynylamino]benzoyl]-L-glutamic acid (ICI 198583, 1) is described in which the glutamic acid residue has been replaced by other alpha-amino acids. Most of these analogues were prepared by coupling of tert-butyl-4-(prop-2-ynylamino)benzoate (37) with 6-(bromomethyl)-3,4-dihydro-2-methyl-4-oxoquinazoline (34) followed by deprotection of the tert-butyl ester to the acid and azide-mediated coupling to the appropriate amino acid or amino acid ester. In cases where the amino acid ester was unreactive with the acid azide, a modification was used in which the quinazolinone moiety was protected as its 3-(pivaloyloxy)methyl derivative. This permitted the generation of the more reactive acid chloride of the p-aminobenzoate unit. In general these modifications result in compounds that have equivalent potency to 1 as inhibitors of isolated TS except where the amino acid lacks a lipophilic alpha-substituent. These compounds appear to require the reduced folate carrier (RFC) for transport into cells, but since they are not converted intracellularly into polyglutamated forms, they have a lower level of cytotoxicity compared to 1. The removal of the alpha-carboxylic acid has given a second set of analogues of 1 which contain simple alkyl amide, benzyl, substituted benzyl, and heterocyclic benzyl amide derivatives. These are considerably less potent than 1 as TS inhibitors but display 1-10 microM cytotoxicities due to the fact that they do not require RFC transport and can presumably readily enter cells by passive diffusion through the cell membrane. Molecular modeling and NMR studies indicated that the incorporation of, respectively, 7-methyl and 2'-fluoro substituents would favor the optimum conformation of these molecules for interaction with the TS enzyme. Accordingly, these substituents were incorporated into selected examples to give the series of analogues 47-55. These all show enhanced (approximately 10-fold) inhibition of TS compared to their unsubstituted counterparts. In the substituted benzylamides (51, 52) and heterocyclic benzyl amides (53-55) the ability to enter cells by passive diffusion results in highly potent (< 1 microM) cytotoxic agents.

The decarbazine analogue CB10-277 has been investigated for anti-tumour activity in a phase II study on malignant melanoma. Treatment was administered as a slow infusion of 12,000 mg m-2 over 24 h and repeated every 3 weeks. A total of 28 patients were entered into the study, of whom 23 were eligible for review. A total of 64 courses was given. There was one objective partial response in 22 patients assessable for response. The major toxicities were leucopenia and thrombocytopenia. CB10-277 in this schedule therefore does not appear to have major activity in melanoma.

Decarbazine is an imidazole dimethyltriazene with reproducible activity in patients with metastatic melanoma. CB10-277 is a phenyl dimethyltriazene which, like dacarbazine, requires metabolic activation to its corresponding monomethyl species for antitumour activity. In preclinical models (human melanoma xenografts and transplantable rodent tumours) CB10-277 showed a similar spectrum and level of activity when compared to dacarbazine. Pharmacokinetic studies were performed with CB10-277 in mice treated i.v. at the LD10 (750 mg m-2) and plasma analysed by HPLC. The parent drug area under the plasma concentration vs time curve (AUC) was 142 mM x minutes. Drug metabolism occurred as evidenced by the HPLC identification of the monomethyl species (AUC = 8 mM x minutes) as well as other metabolites. A Phase I trial using a short infusion with doses repeated every 21 days has been performed. Thirty-six patients received 80 courses over a dose range of 80-6,000 mg m-2. The dose limiting toxicity was nausea and vomiting which occurred in 80% of the evaluable courses > or = 900 mg m-2. The only other common side effect was a flushing or warm sensation, which occurred in over 75% of courses at > or = 1,350 mg m-2. There were no hemodynamic consequences. Responses occurred in patients with melanoma (one complete, two partial, one mixed/11), sarcoma (one mixed/6) and carcinoid (one partial/l). Pharmacokinetics were performed in 46 courses. The CB10-277 AUC increased linearly with dose (r = 0.9203, P < 0.001) up to 700 mM x minutes at 6,000 mg m-2). Evidence of CB10-277 metabolism was observed, as in mice, by detection of the monomethyl species and other metabolites. However, the plasma levels of the monomethyl species in patients (1.8 and 3.7 mM x minutes at 6,000 mg m-2) were less than those predicted from studies in mice. Despite this, antitumour activity in dacarbazine sensitive histologies was observed and additional studies with CB10-277 are recommended.

The dose limiting toxicities of the short infusion trial of the dacarbazine analog, CB10-277, were nausea and vomiting which appeared to be related to the peak plasma level of the parent drug. In addition, based on mouse studies, these dose limiting toxicities occurred at a less than optimal level of the monomethyl metabolite, the presumed species required for antitumour activity. An alternative schedule that would avoid the parent drug peak plasma levels of short infusion, while possibly allowing an increase in the amount of monomethyl metabolite produced was considered. Thus, a 24 h continuous infusion schedule, repeated every 21 days was explored. Twenty-two patients received 42 courses with a dose range of 4,700-15,000 mg m-2. The dose limiting toxicity was myelosuppression (leucopenia and thrombocytopenia). Although nausea and vomiting also occurred, it was manageable with routine antiemetic therapy. Other toxicities included diarrhoea, hallucinations, malaise, muscle ache, headache and flushing and all were < or = WHO grade 2. Pharmacokinetic studies were performed with 13 courses which included all dose levels. The mean t1/2 of the parent drug was 178 min. Area under the concentration x time curve (AUC) at the highest dose for the parent drug and the monomethyl metabolite were 2,350 and 9 mM x minutes, respectively. This monomethyl metabolite AUC and the associated myelosuppression showed a more favourable comparison to the preclinical data determined in mice than the results from the short infusion trial of CB10-277. Therefore, the recommended Phase II dose and schedule of this drug was 12,000 mg m-2 given by 24 h continuous infusion.

The synthesis of a series of new C2-methyl-N10-alkylquinazoline-based thymidylate synthase (TS) inhibitors containing difluroinated p-aminobenzoate rings is described. Derivatives of the N10-propargyl and N10-methylquinazoline antifolates were prepared with 2',3'-, 2',5'-, and 2',6'-difluoro substitution. The synthesis of the 2',5'-difluoro analogues involved oxidation of the difluoronitrotoluene to 2,5-difluoro-4-nitrobenzoic acid followed by glutamation, reduction, and alkylation (propargyl bromide or MeI) to the diethyl N-(4-(alkylamino)-2,5-difluorobenzoyl)-L-glutamates. For the synthesis of the 2',3'- and 2',6'-difluoro compounds a new route was devised starting from methyl 4-((tert-butoxycarbonyl)amino)-2,6-difluorobenzoate and its 2,3-substituted counterpart. Treatment with NaH and then an alkyl halide introduced the N10-substituent. The methyl ester was hydrolyzed and the resulting acid was condensed with diethyl L-glutamate. The secondary amine was liberated using CF3CO2H and coupled with 6-(bromo-methyl)-3,4-dihydro-2-methyl-4-oxoquinazoline to yield the antifolate diesters. Final deprotection with mild alkali completed the synthesis in each case. The target compounds were tested as inhibitors of partially purified L1210 TS and also examined for their inhibition of the growth of L1210 cells in culture. Compared to their nonfluorinated parent compounds all the difluoro analogues were poorer inhibitors of TS. The greatest loss of enzyme activity was seen in the N10-propargyl analogues which contained one of the fluorine atoms ortho to the amine substituent. This loss was less apparent in the N10-methyl derivatives. Despite this lower inhibition of TS the majority of new compounds have equivalent cytotoxicity to their nonfluorinated predecessors.

We describe the characterization of human lymphoblastoid cell lines with acquired resistance (greater than 20,000-fold) to a novel folate-based thymidylate synthase (TS) (EC 2.1.1.45) inhibitor, C2-desamino-C2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI198583). This acquired resistance was associated with a 64-fold amplification of the TS gene, a similar elevation in the corresponding mRNA, and an approximately 200-fold increase in both TS activity and TS protein. This amplification was maintained when the cells were grown in the absence of the selective agent, ICI198583, for 340 generations. TS isolated from one of the resistant cell lines, W1-L2:C1, displayed inhibition kinetic parameters similar to those of TS isolated from the parent W1-L2 cell line. It thus appears unlikely that resistance is due to an altered TS enzyme having a lower affinity for ICI198583. The resistant cell line, W1-L2:C1, was cross-resistant to other folate-based TS inhibitors but was as sensitive as the parent cell line, W1-L2, to 5-fluorodeoxyuridine. The W1-L2:C1 cell line was collaterally sensitive to the classical dihydrofolate reductase (EC 1.5.1.3) inhibitor methotrexate as well as to the lipophilic dihydrofolate reductase inhibitors metoprine and 2,4-diamino-5-methyl-6-[(3,4,5-trimethoxyanilino)methyl]quinazolin e glucuronic acid salt (also called trimetrexate). When the W1-L2 and W1-L2:C1 cell lines were exposed to 1 microM ICI198583 for 24 h they accumulated the same concentration of total cellular ICI198583 polyglutamates despite the fact that the latter cell line accumulated a 300-fold greater concentration of ICI198583 monoglutamate. As polyglutamates, the tetra- and pentaglutamate forms predominated in the W1-L2 cell line, whereas the diglutamate form predominated in the W1-L2:C1 cell line, with few higher polyglutamates being detected. The lack of tri- and higher polyglutamates of ICI198583 (i.e., the more active species) in the W1-L2:C1 cell line may also contribute to the observed resistance. These findings may have important implications in light of the rapid onset of resistance to antifolates in the clinic.

The pharmacokinetics of the anthrapyrazole CI-941 has been investigated in conjunction with the Phase I evaluation of the drug with the intent of applying a pharmacokinetically guided dose escalation strategy. A starting dose of 5 mg/m2 was chosen, based on one-tenth the 10% lethal dose in mice. Due to the steep dose lethality relationship and nonlinear pharmacokinetics in mice, a target area under the CI-941 plasma concentration x time curve (AUC) of 110 microM x min (i.e., 40% of the mouse 10% lethal dose AUC) was chosen. This AUC was achieved in mice at 40 mg/m2. A total of 37 patients received 74 courses of CI-941 (5 to 55 mg/m2), with 26 patients consenting to pharmacokinetic monitoring. CI-941 was rapidly cleared from plasma, and a triexponential open model could be fitted to the data (t1/2 alpha = 7.6 +/- 2 min, t1/2 beta = 65 +/- 27 min, t1/2 zeta = 21 +/- 9 h). CI-941 was subjected to only limited urinary elimination, accounting for 5.2 +/- 2.8% of the administered dose. Wide interpatient variability in plasma CI-941 clearance at the starting dose and subsequent doses precluded the implementation of a pharmacokinetically guided dose escalation scheme, and the dose was escalated in 5-mg/m2 increments until the maximally tolerated dose was achieved. A number of investigations were performed to study potential reasons for variability in CI-941 clearance. However, CI-941 plasma protein binding (95 +/- 1%) and measures of pretreatment renal (51Cr-EDTA clearance), hepatic (plasma alanine transaminase and alkaline phosphatase levels), or cardiac function (left ventricular ejection fractions) did not relate strongly to CI-941 clearance. In patients treated at 40 mg/m2, the AUC values (156 to 415 microM x min) approximated or exceeded the target AUC. Fifty mg/m2 was the Phase II recommended dose. Further prospective studies are warranted to assess the utility of pharmacokinetically guided dose escalation strategies and to determine whether or not the variability encountered in clearance is unique to CI-941.

Thirty-one patients with advanced breast cancer were treated with CI941, an anthrapyrazole structurally related to mitoxantrone. Patients had not previously been treated with anthracyclines or mitoxantrone, and 15 patients had not received any previous cytotoxic chemotherapy. CI941 was given at a dose of 50 mg/m2 by intravenous bolus injection every 21 days. Thirty patients were assessable for response, and all were assessable for toxicity. Two patients (7%) had complete responses (CRs), and 17 (56%) achieved partial responses (PRs; overall response rate, 63%; 95% confidence interval, 46% to 81%). The response rates in patients with and without prior chemotherapy were 63% and 64%, respectively. The median response duration was 37 weeks from start of treatment, with a maximum response duration of greater than 70 weeks. Median survival has not yet been reached. Leukopenia was the most frequently encountered toxicity, with a World Health Organization (WHO) grade greater than 3 occurring in 74% of courses. Thrombocytopenia and anemia were negligible. Only 10 patients (32%) had alopecia severe enough to wear a wig. There were no cardiac symptoms or events in any patient, but a slight median fall in left ventricular ejection fraction (LVEF) of 6% (from +7 to -12) during stress and 6% (from +14 to -14) at rest occurred. Other toxicities were mild, and the drug was generally well tolerated. CI941 is a very active and well-tolerated new agent in the treatment of advanced breast cancer, with neutropenia being the main toxicity.

2-Desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) is a more water-soluble analogue of the quinazoline-based thymidylate synthase (TS) inhibitor, N10-propargyl-5,8-dideazafolic acid (CB3717). A 3-fold loss in TS inhibitory activity (murine and human TS, Ki = 10 nM) was accompanied by a 40-fold increase in growth inhibitory potency against L1210 and W1L2 cells in vitro (IC50 = 0.085 and 0.05 microM, respectively) when compared with CB3717. In L1210 cells a concentrative uptake mechanism was demonstrated for [3H]ICI 198583 (Kt = 2.9 microM). The L1210:1565 cell line, with an impaired ability to transport reduced folates or methotrexate (MTX), was resistant (100-fold relative to the wild-type L1210 line) to ICI 198583 (but not CB3717) and did not take up [3H]ICI 198583 significantly. The measurement of folylpolyglutamate synthetase (FPGS) substrate activity demonstrated a Km of 40 microM for ICI 198583 and a Vmax/Km (relative to folic acid) of 3.5. The formation of intracellular polyglutamate derivatives was demonstrated in both L1210 (mouse) and WIL2 (human) cells grown in vitro after exposure to 1 microM [3H]ICI 198583. In L1210 cells, by 4 hr, approximately 50% of the intracellular 3H(approximately 1 microM) was found as polyglutamate forms of ICI 198583, principally as tri- and tetraglutamates. After 24 hr the ICI 198583 polyglutamate pool had expanded, the tetraglutamate metabolite predominated and there was significant formation of the pentaglutamate. Upon resuspension of L1210 cells in drug free medium, ICI 198583 was largely lost from the cells but the polyglutamates were preferentially retained, after 24 hr approximately 70% remained. Synthetic ICI 198583 polyglutamates were shown to be up to 100-fold more potent as inhibitors of isolated TS than the parent compound. Following in vivo administration (500 mg/kg i.v.) ICI 198583 was cleared rapidly from the plasma of mice (T1/2 beta = 16 min, clearance = 42 mL/min/kg). Despite this clearance there was prolonged, dose-dependent inhibition of TS in L1210:NCI cells in vivo. Thus, following 500 mg/kg i.v. the flux through TS was inhibited by greater than 80% for at least 24 hr. Administration of five doses at 5 mg/kg daily of ICI 198583 to L1210:ICR tumour-bearing mice resulted in greater than 60% of the mice being cured, a 10-fold improvement in potency over CB3717. The maximum tolerated dose (MTD) for ICI 198583 using this schedule was greater than 500 mg/kg/day compared with 200 mg/kg/day of CB3717.(ABSTRACT TRUNCATED AT 250 WORDS)

The synthesis is described of a series of C2-methyl-N10-alkylquinazoline-based antifolates in which the p-aminobenzoate ring is replaced by the heterocycles thiophene, thiazole, thiadiazole, pyridine, and pyrimidine. These were generally elaborated by the reaction of (bromomethyl)quinazoline 18 or its N3-[(pivaloyloxy)methyl]-protected derivative 36 with suitable heterocyclic amines although each heterocyclic system required its own particular synthetic approach. The compounds were tested as inhibitors of partially purified L1210 thymidylate synthase (TS). They were also examined for their inhibition of the growth of L1210 cells in culture. The thiophene system 7 and its related thiazole 8 gave analogues that were considerably more potent than the parent benzene series 2 as inhibitors of L1210 cell growth although in general these heterocycles were somewhat poorer inhibitors of the isolated TS enzyme. The enhanced cytotoxicities of the thiophene and thiazole analogues result, at least in part, from their efficient transport into the cells via the reduced folate carrier mechanism and very good substrate activity for folylpolyglutamate synthetase. The replacement of the C2-methyl group by C2-(fluoromethyl) and C2-(hydroxymethyl) substituents in the thiophene and thiazole series gave derivatives that were only slightly less potent inhibitors of the TS enzyme but which were considerably less cytotoxic.

Trimelamol is an analogue of hexamethymelamine which exhibited activity against refractory ovarian cancer in phase I clinical trial. The dose limiting toxicity was leukopenia. In a phase II study, 42 patients with recurrent, or platinum-complex resistant, advanced ovarian cancer were treated using the dose schedule 800 mg m-2 i.v. daily for 3 days. There were one complete, three partial and five minor responses, objective response rate: 9.5%. The main toxicity observed was nausea and vomiting, myelosuppression was minor. The role of Trimelamol in the treatment of ovarian cancer remains to be defined, but its activity is limited in refractory disease.

N-(5-[N-(3,4-Dihydro-2-methyl-4-oxoquinazolin-6-ylmethyl)-N- methylamino]-2-thenoyl)-L-glutamic acid (ICI D1694) is an analogue of the thymidylate synthase inhibitor N10-propargyl-5,8-dideazafolic acid (CB3717). CB3717 was found to be an active anticancer agent in early clinical studies, but its use was limited by its relative insolubility at physiological pH. ICI D1694 has been shown to be a more active anticancer agent than CB3717 in model systems, and it is devoid of the acute renal toxicity associated with the administration of the latter drug to mice. In the present study, the pharmacokinetics of ICI D1694 were studied in both mice and rats using reverse-phase HPLC. In rats, ICI D1694 clearance (CL) conformed to a two-compartment open model and was rapid (CL = 10.7 ml min-1 kg-1, t1/2 beta = 30 min). Excretion was mainly biliary (65% of the delivered dose in 4 h vs 12% in urine) in the rat following a 100-mg/kg i.v. bolus. A high degree of protein binding was seen in rat plasma (greater than or equal to 90% over the range of 20-100 microM). In mice, ICI D1694 CL = 27 ml min-1 kg-1 and t1/2 beta = 30 min following 100 mg/kg i.v., which was significantly faster than CB3717 clearance (CL = 6 ml min-1 kg-1, t1/2 beta = 93 min). ICI D1694 was fully bioavailable following i.p. administration (AUC = 3.73 mg ml-1 min i.v. 4.03 mg ml-1 min i.p.), but its bioavailability following oral administration appeared to be low (approximately 10%-20%). Tissue distribution and excretion studies in mice suggested that biliary excretion predominated, confirming the results obtained in rats. Following an i.v. dose of 500 mg/kg ICI D1694 in mice, drug was detectable at 24 h, suggesting the presence of a third phase of plasma clearance. The initial HPLC assay could not detect this third phase following a dose of 100 mg/kg; hence, a more sensitive assay was developed that includes a solid-phase extraction step. The latter assay was used to define the third phase of ICI D1694 clearance in mice, and preliminary studies demonstrated a terminal half-life of 6.5 +/- 2.7 h.

The synthesis of 2'-fluoro-10-propargyl-5,8-dideazafolic acid and its 2-desamino, 2-desamino-2-hydroxymethyl, and 2-desamino-2-methoxy analogues is described. In general the synthetic route involved the coupling of diethyl N-[2-fluoro-4-(prop-2-ynylamino)benzoyl]-L-glutamate with the appropriate 6-(bromomethyl)quinazoline followed by deprotection with mild alkali. These four compounds together with the 2-desamino-2-methyl analogue were tested for their activity against L1210 thymidylate synthase (TS). They were also examined for their inhibition of the growth of the L1210 cell line and of two mutant L1210 cell lines, the L1210:R7A that overproduces dihydrofolate reductase (DHFR) and the L1210:1565 that has impaired uptake of reduced folates. Compared with their non-fluorinated parent compounds, the 2'-fluoro analogues were all approximately 2-fold more potent as TS inhibitors. Similarly, they also showed improved inhibition of L1210 cell growth (1.5-5-fold), and this activity was prevented by co-incubation with thymidine. All had retained or improved activity against both the L1210:R7A and L1210:1565 cell lines.

The synthesis of nine new 2-methyl-10-propargylquinazoline antifolates with substituents in the p-aminobenzoyl ring is described. In general the synthetic route involved the coupling of the appropriate ring-substituted diethyl N-[4-(prop-2-ynylamino)benzoyl]-L-glutamate with 6-(bromomethyl)-3,4-dihydro-2-methyl-4-oxoquinazoline followed by deprotection using mild alkali. The compounds were tested as inhibitors of partially purified L1210 thymidylate synthase (TS). They were also examined for their inhibition of the growth L1210 cells in culture. Compared to the parent compound 1a the 2'-fluoro analogue 2a exhibited enhanced potency in both systems whereas the 3'-fluoro analogue 3a showed enhanced growth inhibitory properties against L1210 cells despite being a poorer inhibitor of the isolated enzyme. Chloro, hydroxy, methoxy, and nitro substituents in the 2'-position were also well tolerated by the enzyme but failed to give enhanced growth inhibition. The series was extended to cover analogues of the 2'-fluoro, 3'-fluoro, 2'-chloro, 2'-methyl, 2'-amino, 2'-methoxy, and 2'-nitro derivatives with modified alkyl substituents at N10.

Modification of the potent thymidylate synthase (TS) inhibitor N-[4-[N-[(2-amino-3,4-dihydro-4-oxo-6-quinazolinyl)methyl]-N-prop-2- ynylamino]benzoyl]-L-glutamic acid (1a) has led to the synthesis of quinazoline antifolates bearing alkyl, substituted alkyl, and aryl substituents at C2. In general the synthetic route involved the coupling of the appropriate diethyl N-[4-(alkylamino)benzoyl]-L-glutamate with a C2-substituted 6-(bromo-methyl)-3,4-dihydro-4-oxoquinazoline followed by deprotection using mild alkali. Good enzyme inhibition and cytotoxicity were found with compounds containing small nonpolar groups in the C2 position with the 2-desamino-2-methyl analogue 3a being the most potent. Larger C2 substituents were tolerated by the enzyme, but cytotoxicity was reduced. Highly potent series were followed up by the synthesis of a number of analogues in which the N10 substituent was varied. In this manner a number of interesting TS inhibitors have been prepared. Although none of these was more potent than 1a against the isolated enzyme, over half of the compounds prepared were more potent as cytotoxic agents against L1210 cells in culture. The potential of such compounds as useful antitumor agents was further enhanced by the finding that the improved aqueous solubilities of compounds such as 3a over 1a were reflected in vivo in that 3a was at least 5 times less toxic to mice than 1a.

We examined the in vitro activity of 2-desamino-5,8-dideazafolate and 2-desamino-N10-propargyl-5,8-dideazafolate (desamino-CB3717), the more water-soluble 2-desamino analogues of 5,8-dideazafolate and N10-propargyl-5,8-dideazafolic acid (CB3717). We report Ki values for the inhibition of L1210 thymidylate synthase (TS) of 2 and 0.027 microM for 2-desamino-5,8-dideazafolate and desamino-CB3717, respectively, indicating a 30- and 10-fold loss in TS-inhibitory activity compared with the corresponding 2-NH2 compounds. The synthetic tri- and tetrapolyglutamate derivatives of desamino-CB3717 were 66- and 101-fold more potent than the monoglutamate form as inhibitors of TS. Both desamino compounds were more potent as inhibitors of L1210 and W1L2 cell growth than were their 2-amino counterparts. 2-Desamino-5,8-dideazafolate retains quite good activity against both the TS-overproducing W1L2:C1 line and the L1210 cell line grown in the presence of thymidine, suggesting that a secondary locus of action may be involved. This other target is a folate-dependent enzyme as evidenced by the protection of the inhibition of cell growth by the addition of hypoxanthine or folinic acid together with thymidine. The methotrexate-resistant, dihydrofolate reductase-overproducing L1210:R7A cell line is cross-resistant to 2-desamino-5,8-dideazafolate, which suggests that dihydrofolate reductase is the other target. An L1210 subline (1565) unable to transport reduced folates is 10-fold resistant to desamino-CB3717 and 2-desamino-5,8-dideazafolate but is not cross-resistant to CB3717 or 5,8-dideazafolate. The removal of the 2-amino function of CB3717 did not affect folylpolyglutamate synthetase substrate activity (CB3717 Km = 48 microM, desamino-CB3717 Km = 40 microM). However, both 5,8-dideazafolate and its desamino analogue were about 10-fold better substrates for folylpolyglutamate synthase than were the N10-propargyl compounds, and this may contribute to their good growth-inhibitory properties. In vivo, desamino-CB3717 cured approximately 75% of mice bearing the L1210:ICR tumor at doses of 50 mg/kg daily for 5 days and above (maximum tolerated dose greater than 1000 mg/kg daily for 5 days).(ABSTRACT TRUNCATED AT 400 WORDS)

Forty-six patients who were treated with cisplatin or carboplatin for ovarian cancer developed resistant disease (no change in measurable disease or progressive disease) and 'crossed over' to the other platinum compound. Three patients (6.5%) responded to this second treatment but these patients had no survival advantage compared to the non-responders. One responder had progressive disease on cisplatin before crossing over to carboplatin.

cis-Diammine-1,1-cyclobutane dicarboxylate platinum(II) (CBDCA, JM8) is a nonnephrotoxic analogue of cisplatin currently undergoing clinical evaluation. Pharmacokinetic studies have been performed in patients receiving CBDCA (20 to 520 mg/sq m) as a 1-hr infusion without hydration or diuresis. Following the end of the infusion, plasma levels of total platinum and ultrafilterable (Mr less than 50,000) platinum (free platinum) decayed biphasically with first-order kinetics (total platinum t alpha 1/2 = 98 min; t beta 1/2 range, 399 to greater than 1440 min; free platinum t alpha 1/2 = 87 min; t beta 1/2 = 354 min). During the first four hr, binding of platinum to plasma protein was limited (24%), with most of the free platinum in the form of unchanged CBDCA (94%). However, by 24 hr, the majority of platinum was protein bound (87%). The major route of elimination was renal, 65% of the platinum administered being excreted in the urine within 24 hr, with 32% of the dose excreted as unchanged CBDCA. No evidence was found from studies on the renal clearance of free platinum to indicate renal tubular secretion (mean free platinum renal clearance, 69 ml/min). However, the plasma clearance of free platinum did correlate positively with glomerular filtration rates (p = 0.005). None of the pharmacokinetic parameters determined were dose dependent. In vitro studies with plasma and urine demonstrated that, in contrast to cisplatin, CBDCA is a stable complex [t 1/2 - 37 degrees; plasma, 30 hr, and urine (range), 20 to 460 hr]. The differences in the pharmacokinetics of cisplatin and CBDCA may explain why the latter complex is not nephrotoxic.

One hundred and seventeen patients with advanced squamous cell carcinoma of the head and neck were randomised between two combination schedules, one with and the other without adramycin. Responses (more than 50% tumor regression) were 67% overall with 63% responding to the combination without adriamycin and 82% responding to the schedule containing it. The increase in response rate seen with the addition of adriamycin is not statistically significant. Prior radiotherapy reduced the likelihood of response to chemotherapy.

A dosage formula has been derived from a retrospective analysis of carboplatin pharmacokinetics in 18 patients with pretreatment glomerular filtration rates (GFR) in the range of 33 to 136 mL/min. Carboplatin plasma clearance was linearly related to GFR (r = 0.85, P less than .00001) and rearrangements of the equation describing the correlation gave the dosage formula dose (mg) = target area under the free carboplatin plasma concentration versus time curve (AUC) x (1.2 x GFR + 20). In a prospective clinical and pharmacokinetic study the formula was used to determine the dose required to treat 31 patients (GFR range, 33 to 135 mL/min) with 40 courses of carboplatin. The target AUC was escalated from 3 to 8 mg carboplatin/mL/min. Over this AUC range the formula accurately predicted the observed AUC (observed/predicted ratio 1.24 +/- 0.11, r = 0.886) and using these additional data, the formula was refined. Dose (mg) = target AUC x (GFR + 25) is now the recommended formula. AUC values of 4 to 6 and 6 to 8 mg/mL. min gave rise to manageable hematological toxicity in previously treated and untreated patients, respectively, and hence target AUC values of 5 and 7 mg/mL min are recommended for single-agent carboplatin in these patient groups. Pharmacokinetic modeling demonstrated that the formula was reasonably accurate regardless of whether a one- or two-compartment model most accurately described carboplatin pharmacokinetics, assuming that body size did not influence nonrenal clearance. The validity of this assumption was demonstrated in 13 patients where no correlation between surface area and nonrenal clearance was found (r = .31, P = .30). Therefore, the formula provides a simple and consistent method of determining carboplatin dose in adults. Since the measure of carboplatin exposure in the formula is AUC, and not toxicity, it will not be influenced by previous or concurrent myelosuppressive therapy or supportive measures. The formula is therefore applicable to combination and high-dose studies as well as conventional single-agent therapy, although the target AUC for carboplatin will need to be redefined for combination chemotherapy.

The biochemical effects of the antitumor agent N-(4-(N-(( 2-amino-4-hydroxy-6-quinazolinyl)methyl)prop-2-ynylamino) benzoyl)-L -glutamic acid (CB3717) were studied in WI-L2 cultured human lymphoblastoid cells. CB3717 was a potent inhibitor of human thymidylate synthetase; the inhibition was competitive with 5,10-methylenetetrahydrofolate (Ki = 4.9 X 10(-9) M). CB3717 also inhibited human dihydrofolate reductase, competitively with dihydrofolate (Ki = 2.3 X 10(-8) M). The growth-inhibitory effect of CB3717 could be prevented completely by 10 microM thymidine. Administration of thymidine could be delayed for up to 8 hr after CB3717 treatment without cytotoxicity but, if thymidine was delayed for 24 hr, severe toxicity resulted. Incubation for 16 hr in the presence of a growth-inhibitory concentration of CB3717 did not result in the appearance of dihydrofolate in WI-L2 cells. These results indicate that, in the presence of CB3717, thymidylate synthetase, rather than dihydrofolate reductase, became rate-limiting for the cycle of dihydrofolate oxidation and reduction. Treatment of cells for 16 hr at an IC50 concentration of CB3717 caused a decrease of 88% in cellular dTTP and a 2,300% increase in dUMP. The level of dUDP also increased, and traces of dUTP appeared in treated cells. No large changes were seen in ribonucleotide pools. A kinetic analysis was made, by computer simulation, of predicted consequences of metabolic effects of compounds that inhibit both dihydrofolate reductase and thymidylate synthetase. It was concluded that, even if the Ki of the inhibitor for thymidylate synthetase were 3 orders of magnitude higher (weaker) than the Ki for dihydrofolate reductase, thymidylate synthetase could still become rate-limiting.

Trimelamol is an analogue of hexamethylmelamine and pentamethylmelamine which does not require metabolic activation and is sufficiently soluble to allow parenteral administration. A Phase I trial has been performed at the Royal Marsden Hospital in which two schedules of administration have been evaluated, a single i.v. infusion repeated every 3 weeks and 3 daily doses repeated every 3 weeks. Pharmacokinetic analysis was performed at all dose levels on both schedules and a linear correlation was demonstrated between dose and area under the curve. Myelosuppression was dose limiting for single dose administration with a maximum tolerated dose of 2400 mg/m2. Median leukocyte nadirs at 1800, 2100, and 2400 mg/m2 were 3.2, 2.6, and 1.5 x 10(9)/liter. Thrombocytopenia and anemia also occurred but were not dose limiting. Doses greater than 1500 mg/m2 caused WHO grade 3 nausea and vomiting but no acute sedation. Three day administration appeared to be less myelosuppressive, giving a maximum tolerated dose of 1000 mg/m2. Median leukocyte nadirs at 800, 900, and 1000 mg/m2 daily for 3 days were 3.0, 2.3, and 1.5 x 10(9)/liter. Nonhematological toxicities were also less marked on the fractionated schedule. Antitumor effects were observed including 1 complete and 9 partial responses. Demonstration of activity in ovarian cancer has led to further evaluation in this disease using the 3-day schedule at a dose of 800 mg/m2 daily for 3 days.

Plasma free platinum (less than 50,000 mol. wt) pharmacokinetics have been studied in eight patients treated with high-dose (800-1600 mg/m2) carboplatin as a 1 h infusion with moderate hydration. Following the infusion, levels decayed biphasically with half-lives (means +/- S.D.) of 83 +/- 15 min and 6.1 +/- 2.8 h. The plasma free platinum area under the concentration vs. time curve (AUC) at 1600 mg/m2 in five patients was 23 +/- 2 mg carboplatin/ml.min. Comparison with data at conventional doses (less than or equal to 500 mg/m2) gave no indication of non-linear kinetics. Total body clearance of free platinum was found to correlate with glomerular filtration rate (r = 0.769, P = 0.03), and haematological toxicity, white cell nadir and duration of thrombocytopenia, correlated with plasma free platinum AUC (r = 0.784, P = 0.02 and r = 0.885, P = 0.01, respectively). Persistence of platinum was demonstrated in tissues removed at autopsy from a patient who had received carboplatin 14 days earlier. Highest platinum levels were found in the liver, kidney, skin and small cell lung tumour.

CB3717 is a quinazoline antifolate whose cytotoxic activity is mediated by inhibition of thymidylate synthase (TS). A phase I clinical trial commenced in September 1981 and 99 patients have received 296 treatments. Doses were dissolved in 0.15 mol/L NaHCO3 (pH 9.0) at a concentration of 4 mg/mL infused over one hour or in a total volume of 1 L infused over 12 hours. Doses were repeated every 3 weeks. The starting dose of 140 mg/m2 was escalated to 600 mg/m2. Renal toxicity, detected by a decrease in the 51Cr EDTA clearance, was dose-related and occurred in seven of ten patients receiving greater than 450 mg/m2. Reversible hepatic toxicity often associated with malaise occurred in 223 of 288 assessable courses (77%). Fifty-nine courses (20%) were associated with increases in alanine transaminase (ALT) levels to greater than 2.5 times the upper limit of the normal laboratory range. Increases in alkaline phosphatase levels also occurred, but were less marked. The severity and prevalence of these elevations were unaffected by the duration of the infusion. A self-limiting rash appeared in 12 patients and a radiation recall reaction was seen in two. Leukopenia developed in 17 patients (WBC less than 3 X 10(9)/L), and thrombocytopenia occurred in six patients (platelets less than 100 X 10(9)/L). The mean leucocyte nadir occurred on day 10 and was followed by recovery at 11 to 19 days. Neither the incidence nor the severity of any of these latter toxicities was dose related. The maximum tolerated dose was in the region of 600 mg/m2 with renal toxicity being dose limiting, although the inter-patient variation did not allow a precise definition. Seventy-six patients were evaluable for response. Responses occurred at doses greater than or equal to 200 mg/m2 and were ovary, one complete response (CR), one partial response (PR), seven minor responses (MR) in 30 cases; breast, two PRs and one MR in eight cases; adenocarcinoma of the lung, one MR in 5 cases; mesothelioma, one PR in five cases; and colon, two MRs in four cases. CB3717 has activity in heavily pretreated patients. The recommended phase II dose for good-risk patients is 400 mg/m2 using the one-hour infusion schedule of administration.

Carboplatin was evaluated in a Phase I and pharmacokinetic study at the Royal Marsden Hospital between April 1981 and November 1981. Sixty patients were entered of whom 16 had impaired renal function. No evidence of ototoxicity or nephrotoxicity was found. Nausea and vomiting were much reduced compared to cisplatin. The dose limiting toxicity was delayed myelosuppression with thrombocytopenia being more severe than leucopenia. A number of clinical responses were seen, particularly in patients with ovarian carcinoma. Pharmacokinetic studies suggested that the dose of JM8 should be adjusted according to the glomerular filtration rate.

The pharmacokinetics of the new antifolate CB 3717 were studied in 20 patients during its phase-I clinical evaluation. The drug was administered at doses of 100-550 mg/m2 in 1-h and 12-h infusions, resulting in peak plasma concentrations of CB 3717 of 40-200 microM. There was a linear relationship between the dose and both CB 3717 AUC and peak plasma levels. Following a 1-h infusion, drug levels in the plasma decayed biphasically (t1/2 alpha = 49 +/- 9 min, t1/2 beta = 739 +/- 209 min). 27% +/- 2% of the dose was excreted in urine in the 24-h period after treatment, suggesting that the major route of elimination was via the bile. Furthermore, the parent compound CB 3717 and its desglutamyl metabolite, CB 3751, were found in a faecal collection although the metabolite was not detected in plasma or urine samples. Plasma protein binding of CB 3717 was extensive (97.6% +/- 0.1%). Significant quantities of CB 3717 penetrated into ascitic fluid but not into cerebrospinal fluid. Residual drug was detected in postmortem kidney tissue from a patient who died of progressive disease 8 days after treatment with 330 mg/m2 CB 3717. Thus, dose-limiting renal toxicity (maximum tolerated dose 600 mg/m2) may be due to drug precipitation in the renal tubules. Elevation of liver enzymes, in particular transaminases, occurred frequently as a toxic manifestation of CB 3717 therapy. In 11 patients studied after their first treatment there was a positive correlation between the rise in serum alanine transaminase and peak drug levels (r = 0.69, P = 0.02). These pharmacokinetic studies have shown that, by analogy with experimental systems, cytotoxic plasma levels of CB 3717 are archieved in man. In addition, they have been valuable in interpreting toxicities observed during phase-I clinical studies.

Fifty-two patients with progressive advanced breast cancer were treated with the novel antifolate CB 3717 (N10-propargyl-5,8-dideazofolic acid) which inhibits thymidylate synthetase. Forty-six patients were pretreated with hormones, 43 with cytotoxic chemotherapy and 39 patients with both treatments. Eight of 48 patients (16.6%) evaluable for response had partial responses (confidence limits 7.4-30.2%, 95% confidence level) following CB 3717 administration. Liver function abnormalities, reversible in most cases, were the most commonest toxicities and were frequently accompanied by malaise. Severe renal failure occurred in eight patients, five of whom had had partial responses to CB 3717. This study shows the importance of thymidylate synthetase as a target for therapy but the clinical value of CB 3717 is limited by its hepatic and renal toxicities.

Seventeen patients with malignant mesothelioma were treated in a phase II study with carboplatin, a cisplatin analogue without significant nephrotoxicity or neurotoxicity. The drug was given in a dose of 300-400 mg/m2 by i.v. infusion, repeating at 28-day intervals. One patient achieved a complete clinical and radiological remission of 15 months' duration, and a second patient achieved a partial response of 11 months' duration (overall response rate 12%; overall response rate in previously untreated patients 20%). Four other previously untreated patients achieved symptomatic relief. Treatment was well tolerated without severe side-effects. Carboplatin, like most other cytotoxic drugs, is active only in a small minority of patients with mesothelioma, but its ability to achieve occasional good responses and frequent symptomatic relief, combined with low toxicity, may justify a short therapeutic trial in patients whose tumour is symptomatic.