James Carmichael

Randomized Comparative Study of Tegafur/Uracil and Oral Leucovorin Versus Parenteral Fluorouracil and Leucovorin in Patients With Previously Untreated Metastatic Colorectal Cancer

PURPOSE This phase III study compared the time to progression (TTP) of an oral regimen of dihydropyrimidine dehydrogenase inhibitory fluoropyrimidine composed of a fixed combination of tegafur and uracil in a 1:4 molar ratio (UFT) and leucovorin (LV) to intravenous (IV) fluorouracil (5-FU) and LV in previously untreated metastatic colorectal carcinoma (CRC) patients. Secondary end points were survival, tumor response, safety, and quality of life. PATIENTS AND METHODS Between May 1996 and July 1997, 380 patients were randomized to receive either UFT (300 mg/m(2)/d) and LV (90 mg/d), administered for 28 days every 35 days, or 5-FU (425 mg/m(2)/d) and LV (20 mg/m(2)/d), given IV for 5 days every 35 days. RESULTS No statistically significant difference in TTP was observed between treatments. With 320 events assessed, the median TTP was 3.4 months (95% Confidence interval [CI], 2.6 to 3.8) on UFT/LV and 3.3 months (95% CI, 2.5 to 3.7) on 5-FU/LV (P =.591, stratified log-rank test). There were no statistically significant differences in survival, tumor response, duration of response, and time to response. Substantial safety benefits were observed in patients treated with UFT/LV. They experienced significantly less stomatitis/mucositis (P <.001) and myelosuppression, resulting in fewer episodes of febrile neutropenia (P <.001) and less documented infection (P =.04). Concomitant medication usage was significantly greater on 5-FU/LV (P =.010). With respect to quality of life, after correcting for baseline imbalances, there were no significant differences between treatments for any scale, except diarrhea. CONCLUSION The oral UFT/LV regimen failed to achieve improved TTP; however, the study confirms significant safety improvements compared with bolus IV 5-FU/LV for the first-line treatment of metastatic CRC.

Taxanes alone or in combination with anthracyclines as first-line therapy of patients with metastatic breast cancer.

PURPOSE Taxanes (paclitaxel or docetaxel) have been sequenced or combined with anthracyclines (doxorubicin or epirubicin) for the first-line treatment of advanced breast cancer. This meta-analysis uses data from all relevant trials to detect any advantages of taxanes in terms of tumor response, progression-free survival (PFS), and survival. PATIENTS AND METHODS Individual patient data were collected on eight randomized combination trials comparing anthracyclines + taxanes (+ cyclophosphamide in one trial) with anthracyclines + cyclophosphamide (+ fluorouracil in four trials), and on three single-agent trials comparing taxanes with anthracyclines. Combination trials included 3,034 patients; single-agent trials included 919 patients. RESULTS Median follow-up of living patients was 43 months, median survival was 19.3 months, and median PFS was 7.1 months. In single-agent trials, response rates were similar in the taxanes (38%) and in the anthracyclines (33%) arms (P = .08). The hazard ratios for taxanes compared with anthracyclines were 1.19 (95% CI, 1.04 to 1.36; P = .011) for PFS and 1.01 (95% CI, 0.88 to 1.16; P = .90) for survival. In combination trials, response rates were 57% (10% complete) in taxane-based combinations and 46% (6% complete) in control arms (P < .001). The hazard ratios for taxane-based combinations compared with control arms were 0.92 (95% CI, 0.85 to 0.99; P = .031) for PFS and 0.95 (95% CI, 0.88 to 1.03; P = .24) for survival. CONCLUSION Taxanes were significantly worse than single-agent anthracyclines in terms of PFS, but not in terms of response rates or survival. Taxane-based combinations were significantly better than anthracycline-based combinations in terms of response rates and PFS, but not in terms of survival.

THE ROLES OF INTRACELLULAR GLUTATHIONE IN ANTINEOPLASTIC CHEMOTHERAPY

Glutathione is a sulfhydryl containing tripeptide that participates in detoxification of xenobiotic compounds, including the alkylating agents melphalan, cyclophosphamide, and BCNU. The role of glutathione in the detoxification of these compounds, both in terms of initial tumor response, and drug-induced resistance to these alkylating agents is examined. Since glutathione disulfide and glutathione are a pivotal redox pair, the modulation of intracellular glutathione levels is shown to change the cytotoxicity of drugs dependent on the redox cycle, such as adriamycin and bleomycin, as well as the oxygen dependent drug neocarzinostatin. Areas of further research are discussed.

Phase III Trial of Epirubicin Plus Paclitaxel Compared With Epirubicin Plus Cyclophosphamide As First-Line Chemotherapy for Metastatic Breast Cancer: United Kingdom National Cancer Research Institute Trial AB01

PURPOSE To compare the effectiveness and tolerability of epirubicin and paclitaxel (EP) with epirubicin and cyclophosphamide (EC) as first-line chemotherapy for metastatic breast cancer (MBC). PATIENTS AND METHODS Patients previously untreated with chemotherapy (except for adjuvant therapy) were randomly assigned to receive either EP (epirubicin 75 mg/m2 and paclitaxel 200 mg/m2) or EC (epirubicin 75 mg/m2 and cyclophosphamide 600 mg/m2) administered intravenously every 3 weeks for a maximum of six cycles. The primary outcome was progression-free survival; secondary outcome measures were overall survival, response rates, and toxicity. RESULTS Between 1996 and 1999, 705 patients (353 EP patients and 352 EC patients) underwent random assignment. Patient characteristics were well matched between the two groups, and 71% of patients received six cycles of treatment. Objective response rates were 65% for the EP group and 55% for the EC group (P = .015). At the time of analysis, 641 patients (91%) had died. Median progression-free survival time was 7.0 months for the EP group and 7.1 months for the EC group (hazard ratio = 1.07; 95% CI, 0.92 to 1.24; P = .41), and median overall survival time was 13 months for the EP group and 14 months for the EC group (hazard ratio = 1.02; 95% CI, 0.87 to 1.19; P = .8). EP patients, compared with EC patients, had more grade 3 and 4 mucositis (6% v 2%, respectively; P = .0006) and grade 3 and 4 neurotoxicity (5% v 1%, respectively; P < .0001). CONCLUSION In terms of progression-free survival and overall survival, there was no evidence of a difference between EP and EC. The data demonstrate no additional advantage to using EP instead of EC as first-line chemotherapy for MBC in taxane-naïve patients.

The relationship of SR-2508 sensitizer enhancement ratio to cellular glutathione levels in human tumor cell lines.

We have recently demonstrated that intracellular elevation of glutathione (GSH) by oxothiazolidine 4-carboxylate lessens SR-2508 hypoxic cell radiosensitization in Chinese hamster cells. This observation, coupled with the fact that GSH depletion potentiates SR-2508 hypoxic radiosensitization, prompted a study of human tumor cell lines whose inherent GSH levels are high compared to normal human cell lines or rodent cell lines. Sensitizer enhancement ratios (SER) for a range of SR-2508 concentrations were determined for human tumor cell lines varying in inherent GSH levels. The SER (at the 1% survival level) for 1 mM SR-2508 was found to decrease as the inherent intracellular GSH level increased, particularly for clinically relevant SR-2508 concentrations. All human tumor cell lines studied yielded lower SER values than Chinese hamster V79 cells over the SR-2508 concentrations studied. GSH depletion by buthionine sulfoximine (BSO) of a human tumor line (A549) particularly high in GSH resulted in potentiation of SR-2508 effects. Maximal sensitization occurred when extremely low GSH levels were attained; however, enhancement was observed for a drop of only 30% in GSH levels. Should these high GSH levels seen in human tumor cell lines also apply to clonogenic or potentially clonogenic cells in human tumors in vivo, these findings might explain, in part, the negative results of some human nitroimidazole clinical trials.

Clinical response benefit in patients with advanced pancreatic cancer. Role of gemcitabine.

The prognosis for patients with pancreatic cancer remains extremely poor. A minority are surgically resectable, but the remainder suffer problems from locally invasive disease and also metastatic spread. Median survival in these patients approximates 4 months, with limited systemic options. Many chemotherapy drugs have been evaluated in pancreatic cancer and the results have been disappointing. Of the newer agents, gemcitabine shows the greatest promise in this tumour type. Gemcitabine is a novel pyrimidine antagonist with activity in a number of tumour types. Gemcitabine has been evaluated in 3 phase II studies revealing anti-tumour activity, albeit to a modest degree of around 10%. Many objective tumour reductions have been seen, and more importantly improved symptom control is reported by many investigators. In view of these findings a randomized phase III study was performed in the United States comparing gemcitabine with weekly 5-fluorouracil chemotherapy. Patients receiving gemcitabine achieved a higher response rate, improved symptom control and prolonged survival. These results were statistically significant. Despite the statistically significant improvement in objective response rate and survival in these patients, the outcome of systemic treatment in these patients remains extremely poor. These studies raise the question about the appropriate end-points for systemic chemotherapy trials in pancreatic cancer. Despite low objective response rates and survival improvement of approximately 6 weeks, these patients did achieve symptom control and improvements in quality of life (clinical benefit response). Gemcitabine is the first agent to be evaluated in this way and has been shown to be a benefit for approximately a quarter of the patients treated. Single agent gemcitabine could represent the standard on which to develop and evaluate new approaches. We need to improve on these results and one way forward is to look to gemcitabine containing combination chemotherapy regimens. The relative lack of toxicity associated with this drug lends itself to this approach.

in vivo modulation of glutathione by buthionine sulfoximine: Effect on marrow response to melphalan☆

The effect of giving buthionine sulfoximine (BSO), 0.0265 g/mouse (6 mM), at 12 and 6 hr before treatment with melphalan--0.0 mg, 3 mg, 6 mg, and 9 mg/kg, was studied in C3H mice, and was compared with control groups that received normal saline 12 and 6 hr before identical melphalan treatment. BSO treatment resulted in depletion of GSH levels in bone marrow, liver, and muscle to 65, 13, and 41% of control levels, respectively. Hematological toxicity was assessed by measurement of CFU-S survival and peripheral white cell counts. CFU-S survival decreased with increasing doses of melphalan, but no difference was observed with BSO pre-treatment. Likewise, WBC counts following melphalan 9 mg/kg, were similar irrespective of BSO pre-treatment. These data suggest that the marrow toxicity seen with melphalan is not worsened by pre-treatment with BSO and that if tumors can be pre-sensitized with BSO, there may be a clinical role for melphalan/BSO drug combination.

Inhibition of the protective effect of cyclophosphamide by pre-treatment with buthionine sulfoximine

Low dose cyclophosphamide (CTX) is protective against a subsequent challenge with a lethal dose of the same drug administered 5 days later. At the time of maximal protection, elevation of glutathione (GSH) and glutathione transferase (GST) levels are detectable in the bone marrow of pre-treated animals. Elevation of GSH levels in the bone marrow was inhibited with the use of D,L-buthionine-S,R-sulfoximine (BSO), and this resulted in loss of the protective effect of CTX pre-treatment. In contrast, the overshoot in GST levels observed in these animals was not affected by BSO therapy. Bone marrow GSH levels in animals treated with BSO alone were minimally depleted (68% of control); whereas, animals pre-treated with CTX followed by BSO exhibited a greater reduction in GSH levels (47% of control). These results suggest that GSH is important in the protective effect afforded by low dose CTX pre-treatment and that the elevation of GSH levels observed is the result of a rebound synthetic process. In CTX pre-treated animals, BSO treatment resulted in greater than predicted depletion in GSH levels, and, therefore, caution is recommended with the potential use of combinations of BSO and cytotoxic drugs in the presence of a regenerating bone marrow.

A Cereblon Modulator (CC-220) with Improved Degradation of Ikaros and Aiolos

The drugs lenalidomide and pomalidomide bind to the protein cereblon, directing the CRL4-CRBN E3 ligase toward the transcription factors Ikaros and Aiolos to cause their ubiquitination and degradation. Here we describe CC-220 (compound 6), a cereblon modulator in clinical development for systemic lupus erythematosis and relapsed/refractory multiple myeloma. Compound 6 binds cereblon with a higher affinity than lenalidomide or pomalidomide. Consistent with this, the cellular degradation of Ikaros and Aiolos is more potent and the extent of substrate depletion is greater. The crystal structure of cereblon in complex with DDB1 and compound 6 reveals that the increase in potency correlates with increased contacts between compound 6 and cereblon away from the modeled binding site for Ikaros/Aiolos. These results describe a new cereblon modulator which achieves greater substrate degradation via tighter binding to the cereblon E3 ligase and provides an example of the effect of E3 ligase binding affinity with relevance to other drug discovery efforts in targeted protein degradation.

Phase I/II study of first-line irinotecan combined with 5-fluorouracil and folinic acid Mayo Clinic schedule in patients with advanced colorectal cancer.

BackgroundThis multicentre phase I/II study was designed to determine the maximum tolerated dose of irinotecan when combined with 5-fluorouracil and folinic acid according to the Mayo Clinic schedule and to evaluate the activity of this combination as first-line therapy in patients with advanced colorectal cancer.MethodsSixty-three patients received irinotecan (250 or 300 mg/m2, 30- to 90-minute intravenous infusion on day 1), immediately followed by folinic acid (20 mg/m2/day) and 5-fluorouracil (425 mg/m2, 15-minute bolus infusion) days 1 to 5, every four weeks.ResultsDiarrhoea was dose limiting at 300 mg/m2 irinotecan in combination with 5-fluorouracil and folinic acid, and this was determined to be the maximum tolerated dose. Grade 3–4 neutropenia was the most frequently reported toxicity. The recommended dose of irinotecan for the phase II part of the study was 250 mg/m2. The response rate for the evaluable patient population was 36% (13/36), and 44% (16 patients) had stable disease (including 19% of minor response). For the intention-to-treat population, the response rate was 29% (14/49) and 35% (17 patients) stable disease (including 14% of minor response). The median time to progression was 7.0 months and the median survival was 12.0 months. Grade 3–4 non-haematological drug-related toxicities included delayed diarrhoea, stomatitis, fatigue, and nausea/vomiting. There were three deaths due to septic shock that were possibly or probably treatment-related.ConclusionsThis regimen of irinotecan in combination with the Mayo Clinic schedule of bolus 5-fluorouracil/folinic acid every four weeks showed activity as first-line therapy in patients with advanced colorectal cancer. In keeping with other published results of studies using bolus 5-fluorouracil combined with irinotecan, the use of this regimen is limited by a relatively high rate of grade 3–4 neutropenia, and the combination of irinotecan and infusional 5-fluorouracil / folinic acid should remain the regimen of first choice.