Abstract P2-05-08: Combined neoadjuvant iniparib and carboplatin in locally advanced or metastatic canine mammary tumors (MT) to support human clinical studies

INTRODUCTION

Among breast cancers, the triple negative subtype (negative for hormone receptors and not overexpressing HER2) has the worst prognosis and its response to Iniparib has been investigated in clinical trials. Further investigations are needed to optimize drug schedule and patient selection criteria. Iniparib antitumor mechanism is not completely understood, as well as iniparib diffusion kinetic into tumoral tissues. We address these questions in spontaneous canine invasive mammary carcinomas, which are a good model for this cancer subtype (Ibisch et al., World Veterinary Cancer Congress 2012), in a neoadjuvant setting. To our knowledge, this is the first study of iniparib administration in cancer-bearing dogs.

MATERIAL AND METHODS

Twenty female dogs with spontaneous MT with malignant criteria (tumor size, speed of growth, ulceration, relapse, or metastasis) were included. All tumors were described as rapidly growing. Dogs received a first infusion of iniparib at day 0 and a combination of carboplatin and iniparib at day 7. Biological materials (tumor biopsies and blood) were collected before and 5 minutes after iniparib infusion for pharmacokinetic and metabolism studies. Tumor response was evaluated by caliper measurements and histopathological analysis of mammary tumors and draining lymph nodes. A chain mastectomy was performed 3 or 4 weeks later. Histological records included the subtype of carcinoma (WHO 1999), Elston & Ellis grade, presence of emboli, lymph node metastasis and IHC stainings using ER, PR, Her2 (scored according to Wolff et al.2007), CK5/6, EGF-R and Ki67. Intensity of necrosis and apoptosis was evaluated using PAS coloration and immunohistochemistry for caspase 3, at DO on tumor biopsies and at surgery. Toxicity of the protocol was evaluated and its efficiency on invasive carcinomas was compared to surgery alone (control group of 27 female dogs with invasive mammary carcinomas treated by chain mastectomy alone).

RESULTS

Treated and control groups shared similar features concerning animal breeds, age, neutering status and tumor location. 75% of the treated MT were malignant. Necrosis and apoptosis were significantly increased in respectively 63 and 56% of iniparib treated tumors. Clinical evidence of toxicity was minimal (15% of dogs with nausea, 60% with transient polyuria-polydipsia). Tumor stabilization was observed before surgery in all dogs but one. Median survival has not been reached.

CONCLUSION

Iniparib at 35mg/kg combined with carboplatin at 300 mg/m2 seemed well tolerated in this study and deserves further investigations. The degree of necrosis and apoptosis in the treated tumors can be evaluated with these techniques. Iniparib pharmacokinetic and metabolism studies in cancer-bearing dogs are ongoing.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-05-08.

Can taxanes provide benefit in patients with CNS tumors and in pediatric patients with tumors? An update on the preclinical development of cabazitaxel

PURPOSE

While first-generation taxanes are valuable treatment options for many solid tumors, they are limited by an inability to cross the blood-brain barrier (BBB) and by limited efficacy in pediatric patients. Following promising preclinical data for the next-generation taxane cabazitaxel, including activity in tumor models fully sensitive, poorly sensitive or insensitive to docetaxel, and its ability to cross the BBB, further preclinical studies of cabazitaxel relevant to these two clinical indications were performed.

METHODS

Cabazitaxel brain distribution was assessed in mice, rats and dogs. Cabazitaxel antitumor activity was assessed in mice bearing intracranial human glioblastoma (SF295; U251) xenografts, and subcutaneous cell line-derived human pediatric sarcoma (rhabdomyosarcoma RH-30; Ewing's sarcoma TC-71 and SK-ES-1) or patient-derived pediatric sarcoma (osteosarcoma DM77 and DM113; Ewing's sarcoma DM101) xenografts. The activity of cabazitaxel-cisplatin combination was evaluated in BALB/C mice bearing the syngeneic murine colon adenocarcinoma, C51.

RESULTS

Cabazitaxel penetrated rapidly in the brain, with a similar brain-blood radioactivity exposure relationship across different animal species. In intracranial human glioblastoma models, cabazitaxel demonstrated superior activity to docetaxel both at early (before BBB disruption) and at advanced stages, consistent with enhanced brain penetration. Compared with similar dose levels of docetaxel, cabazitaxel induced significantly greater tumor growth inhibition across six pediatric tumor models and more tumor regressions in five of the six models. Therapeutic synergism was observed between cisplatin and cabazitaxel, regardless of administration sequence.

CONCLUSIONS

These preclinical data suggest that cabazitaxel could be an effective therapy in CNS and pediatric tumors, supporting ongoing clinical evaluation in these indications.

Predictors of depression in multiple sclerosis patients

Depression is one of the major problems associated with multiple sclerosis (MS). Several physical and psychological factors tend to interact and make it difficult to pinpoint the predictors of the depression. It seemed particularly important to examine how anxiety and illness evolution (characterized by the functional status) influence the appearance of depression symptoms. Thus, the aim of this article was to clarify the relationship between depression and the factors associated with it. One hundred and fifteen participants living at home recruited through various associations and MS clinics answered socio demographic, medical and psychological questions and questionnaires (depression, anxiety, coping, social support, locus of control, alexithymia, self-esteem). Results show that functional status (EDSS), trait anxiety, alexithymia and satisfaction with social support system are the predicting factors of depression. Trait anxiety and functional status are two predictors that independently and simultaneously lead to the appearance of depression symptoms, with trait anxiety playing a predominant role. Alexithymia and social support indirectly influence the appearance of these symptoms.

Differences in effective connectivity between dyslexic children and normal readers during a pseudoword reading task: an fMRI study

PURPOSE

This fMRI study investigated phonological and lexicosemantic processing in dyslexic and in chronological age- and reading level-matched children in a pseudoword reading task.

MATERIALS AND METHODS

The effective connectivity network was compared between the three groups using a structural model including the supramarginal cortex (BA 40; BA: Brodmann area), fusiform cortex (BA 37) and inferior frontal cortex (BA 44/45) areas of the left hemisphere.

RESULTS

The results revealed differences in connectivity patterns. In dyslexic patients, in contrast with chronological age- and reading level-matched groups, no causal relationship was demonstrated between BA 40 and BA 44/45. However, a significant causal relationship was demonstrated between BA 37 and BA 44/45 both in dyslexic children and in the reading level-matched group.

CONCLUSIONS

These findings were interpreted as evidence for a phonological deficit in developmental dyslexia.

[Translational research and Cancer Plan]

The French Cancer Plan 2003-2007 has made translational research central to its research programme, to ensure the care-research continuum and the quickest application possible for the most recent discoveries, for the patients' benefit. This is a new field of research, still little-known or ill-understood. A working group, composed of physicians and researchers from academic research and industrial research, sought to define translational research in cancerology and define the issues at stake in it. Translational research needs to develop in close connection with the patients in order to enable a bi-directional flow of knowledge from cognitive research toward medical applications and from observations made on patients toward cognitive research. Placed under the aegis of the French National Cancer Institute and Leem Research, the group has put forth a strategy for implementing translational research in cancerology in France to make it attractive, competitive and efficient and to foster the development of public-private partnerships.

In vivo synergy combining oxaliplatin with AVE8062, a vascular-disrupting agent

13074

Background: AVE8062 is a synthetic, water-soluble compound, analog of Combretastatin A4, currently in Phase I clinical trials. It inhibits tubulin polymerization through binding to the colchicine site of tubulin. In vivo, it induces rapid tumor blood flow shutdown and necrosis, leading to tumor regressions (Proc AACR, 2002). Previously (Proc AACR, 2003), we reported a high synergy resulting from the combination of AVE8062 with either cisplatin or carboplatin in a preclinical in vivo model. We report here the combination data of AVE8062 with oxaliplatin. Methods: A 3-arm dose-response study was performed comparing the single agents and their combination. Synergy was defined as a log cell kill (lck) of at least 1 log superior to the lck of the best single agent. The AVE8062 / oxaliplatin simultaneous combination was evaluated in female BALB/c mice bearing advanced stage (250mg) SC murine colon C51 adenocarcinoma. Drugs were administered IV with 2 intermittent injections, 4 days apart. The combination arm was evaluated over 7 dose levels. Results: At the Highest nontoxic dose (HNTD - 58 mg/kg/inj), AVE8062 was found active: 0.9 lck, 1/5 partial regression (PR) and no complete regression (CR). At the HNTD (7 mg/kg/inj), oxaliplatin was found highly active [5.8 lck, 5/5 CR, no tumor free survivors (TFS)]. The HNTD for the combination (58 mg/kg/inj of AVE8062 with 7 mg/kg/inj of oxaliplatin) was well tolerated with 11.7% body weight loss at nadir. The combination was highly active over the 2 highest dose levels with TFS on day 148 post tumor implantation (4/6 TFS at combination HNTD and 6/6 TFS at 80% HNTD). A high antitumor activity was maintained at 60% HNTD (5.9 lck, 6/6 CR and no TFS). The lowest dose tested, corresponding to 1/10 of the HNTD fractions, was found active with a lck of 1.0 and no regression. Conclusions: The combination of AVE8062 with oxaliplatin was found highly synergistic (superior activity than either of the single agents alone). The combination was well tolerated with a combination toxicity index of 2, indicating that there was no overlap in host toxicity. These data provide a good rationale to perform Phase I combination trials combining AVE8062 with oxaliplatin.

[Table: see text]

Changes in effective connectivity during incidental and intentional perception of fearful faces

The present fMRI study examined effective connectivity within an emotional network composed of three brain areas: Amygdala (AMY), Anterior Cingulate Cortex (AAC) and Orbito-Frontal (OFC) in processing fearful faces. Two tasks: an incidental perception (gender identification) and an intentional detection (effortful discrimination) task were performed by 14 and 10 young healthy volunteers, respectively. Participants were scanned while viewing fearful, neutral and ambiguous facial expressions. Effective connectivity was assessed using Structural Equation Modeling (SEM). Results show that the hypothetical network fits the experimental data for both tasks and in both hemispheres. The comparison between Tasks 1 and 2 reveals significant differences in strength and direction of the connectivity patterns for the left and to a less stringent threshold for the right hemisphere. The path coefficients analysis suggests that the fearful information generated in AMY, reaches the OFC through the ACC in incidental perception, while in intentional perception, the route followed is in a reverse direction from OFC to ACC. Our findings confirm a differential brain connectivity between incidental and intentional processing of fearful faces.

[Rhythm of expression of BCL-2 protein of MA13/C mammaryadenocarcinoma bearing-mice]

We previously demonstrated a circadian rhythm in response to docetaxel chemotherapy in C3H/HeN mice bearing MA13/C mammary adenocarcinoma. We investigated the relation between this rhythm and the expression of BCL-2 in bone marrow and in tumor tissues. A circadian rhythm characterized BCL-2 expression in the bone marrow, which was hardly modified in tumor-bearing animals. BCL-2 acrophase coincided with the time of highest docetaxel tolerability and efficacy in this model. This suggests that BCL-2 protects the bone marrow from the drug toxicity, especially during the light phase.

Circadian optimisation of irinotecan and oxaliplatin efficacy in mice with Glasgow osteosarcoma

The relevance of circadian rhythms in irinotecan and oxaliplatin tolerability was investigated with regard to antitumour activity. Mice bearing Glasgow osteosarcoma (GOS) received single agent irinotecan (50 or 60 mg kg(-1) per day) or oxaliplatin (4 or 5.25 mg kg(-1) per day) at one of six dosing times expressed in hours after light onset (3, 7, 11, 15, 19 or 23 hours after light onset). Irinotecan (50 mg kg(-1) per day) and oxaliplatin (4 or 5.25 mg kg(-1) per day) were given 1 min apart at 7 or 15 hours after light onset, or at their respective times of best tolerability (7 hours after light onset for irinotecan and 15 hours after light onset for oxaliplatin) or worst tolerability (15 hours after light onset for irinotecan and 7 hours after light onset for oxaliplatin). Tumour growth rate was nearly halved and per cent increase in estimated life span (% ILS) was - doubled in the mice receiving irinotecan at 7 hours after light onset as compared to 15 hours after light onset (P<0.05). Results of similar magnitude were obtained with oxaliplatin for both endpoints, yet with 7 hours after light onset corresponding to least efficacy and 15 hours after light onset to best efficacy (P<0.05). Irinotecan addition to oxaliplatin proved therapeutic benefit only if the schedule consisted of irinotecan administration at 7 hours after light onset and oxaliplatin delivery at 15 hours after light onset, i.e. when both drugs were given near their respective "best" circadian times. These would correspond to the middle of the night for irinotecan and the middle of the day for oxaliplatin in humans.

Experimental chronotherapy of mouse mammary adenocarcinoma MA13/C with docetaxel and doxorubicin as single agents and in combination

The therapeutic index of docetaxel, doxorubicin and their combination may be improved by an adequate selection of the circadian time of administration. The present study constitutes a prerequisite to testing the clinical relevance of chronotherapy in human breast cancer. Three experiments were performed in C3H/HeN mice. Each treatment modality was administered i.v. once a week for 3 weeks at one of six circadian stages, during the light span, when the mice were resting: 3, 7, and 11 h after light onset (HALO), or during darkness, when the mice were active: 15, 19, and 23 HALO. The circadian time dependency of single agent tolerability was investigated in healthy mice using four dose levels for docetaxel (38.8, 23.3, 14, and 8.4 mg/kg/injection) and for doxorubicin (13.8, 8.3, 5 and 3 mg/kg/injection; experiment 1). The circadian time dependency of each single agent efficacy was studied in MA13/C-bearing mice, using two dose levels of docetaxel (38.8 or 23.3 mg/kg/injection) or doxorubicin (8.3 or 5 mg/kg/injection; experiment 2). The toxicity and the efficacy of the simultaneous docetaxel-doxorubicin combination were assessed as a function of dosing time in experiment 3. Two combinations were tested (A, 16.3 mg/kg/injection of docetaxel and 2.5 mg/kg/injection of doxorubicin; and B, 11.6 and 3.5 mg/kg/injection, respectively) at each of the above six circadian times. Mortality, body weight change, and tumor size were recorded for 60-70 days in each experiment. Single agent docetaxel or doxorubicin was significantly best tolerated near the middle of the rest span (7 HALO) and most toxic in the middle of the activity phase (19 HALO). Docetaxel or doxorubicin as a single drug were also most effective at 7 HALO, irrespective of dose. Treatment at 7 HALO produced highest rates of complete tumor inhibition (81% versus 11% at 3 HALO for docetaxel, p from chi2 <0.001, and 69% versus 44% at 11 HALO for doxorubicin, not significant) and highest day 60 survival rate (100% versus 28% at 3 HALO for docetaxel, p from chi2 <0.001 and 89% versus 69% at 15 HALO for doxorubicin, not significant). Docetaxel-doxorubicin combinations were most effective following dosing in the beginning of the rest span or short after the onset of the activity span, with regard to the rates of both complete tumor inhibitions (45% at 3 HALO versus 15% at 19 HALO) and day 70 survival rates (85% and 80% at 3 and 7 HALO respectively, versus 20% at 19 HALO). The efficacy of single agent docetaxel or doxorubicin and that of their combination varied largely as a function of circadian dosing time. Single agent docetaxel at 7 HALO was the best treatment option in this model with regard to both tolerability and efficacy. This timing may correspond to the middle of the night in cancer patients.

Docetaxel chronopharmacology in mice

Docetaxel tolerance and antitumor efficacy could be enhanced if drug administration was adapted to circadian rhythms. This hypothesis was investigated in seven experiments involving a total of 626 male B6D2F1 mice, synchronized with an alternation of 12 h of light and 12 h of darkness (12:12), after i.v. administration of docetaxel. In experiment (Exp) 1, the drug was given once a week (wk) for 6 wks (20 mg/kg/wk) or for 5 wks (30 mg/kg/wk) at one of six circadian times, during light when mice were resting [3, 7, or 11 hours after light onset (HALO)], or during darkness, when mice were active (15, 19, or 23 HALO). Endpoints were survival and body weight change. In Exp 2 and 3, docetaxel (30 mg/kg/wk) was administered twice, 1 wk apart, at one of four circadian stages (7, 11, 19, or 23 HALO). Endpoints were hematological and intestinal toxicities. In Exp 4, circadian changes in cell cycle phase distribution and BCL-2 immunofluorescence were investigated in bone marrow as possible mechanisms of docetaxel tolerability rhythm. In Exp 5 to 7, docetaxel was administered to mice bearing measurable P03 pancreatic adenocarcinoma (270-370 mg), with tumor weight and survival as endpoints. Mice from Exp 5 and 6 received a weekly schedule of docetaxel at one of six circadian stages (20 or 30 mg/kg/wk at 3, 7, 11, 15, 19, or 23 HALO). In Exp 7, docetaxel (30 mg/kg) was given every 2 days (day 1, 3, 5 schedule) at 7, 11, 19, or 23 HALO. Docetaxel dosing in the second half of darkness (19 or 23 HALO) resulted in significantly worse toxicity than its administration during the light span (3, 7, or 11 HALO). The survival rate ranged from 56.3% in the mice treated at 23 HALO to 93.8 or 87.5% in those injected at 3 or 11 HALO, respectively (Exp 1, P < 0.01). Granulocytopenia at nadir was -49 +/- 14% at 7 HALO compared with -84 +/- 3% at 19 HALO (Exp 2 and 3, P < 0.029), and severe jejunal mucosa necrosis occurred in 5 of 8 mice treated at 23 HALO as opposed to 2 of 18 receiving docetaxel at 7, 11, or 19 HALO (Exp 2 and 3, P < 0.02). The time of least docetaxel toxicity corresponded to the circadian nadir in S or G2-M phase and to the circadian maximum in BCL-2 immunofluorescence in bone marrow. Docetaxel increased the median survival of tumor-bearing mice in a dose-dependent manner (controls: 24 days; 20 mg/kg weekly, 33 days; 30 mg/kg weekly or day 1, 3, 5 schedule, 44 or 46 days, respectively; Exp 5-7). Survival curves of treated mice differed significantly according to dosing time for each dose and schedule (P from log rank <0.003 to P < 0.03). In Exp 5 and 6, the percentage of increase in life span was largest if docetaxel was administered weekly at 7 HALO (20 mg/kg, 220%; 30 mg/kg, 372%) and lowest after docetaxel dosing at 19 HALO (80% with 20 mg/kg) or at 15 HALO (78% with 30 mg/kg). In Exp 7, (day 1, 3, 5 schedule), docetaxel was most active at 11 HALO (percentage increase in life span, 390%) and least active at 23 HALO (210%). Docetaxel tolerability and antitumor efficacy were simultaneously enhanced by drug dosing in the light span, when mice were resting. Mechanisms underlying the tolerability rhythm likely involved the circadian organization of cell cycle regulation. Docetaxel therapeutic index may be improved with an administration at night in cancer patients, when fewest bone marrow cells are in S or G2-M phase.

Syntheses and structure-activity relationships of the second-generation antitumor taxoids: exceptional activity against drug-resistant cancer cells

A series of new 3'-(2-methyl-1-propenyl) and 3'-(2-methylpropyl) taxoids with modifications at C-10 was synthesized by means of the beta-lactam synthon method using 10-modified 7-(triethylsilyl)-10-deacetylbaccatin III derivatives. The new taxoids thus synthesized show excellent cytotoxicity against human ovarian (A121), non-small-cell lung (A549), colon (HT-29), and breast (MCF-7) cancer cell lines. All but one of these new taxoids possess better activity than paclitaxel and docetaxel in the same assay, i.e., the IC50 values of almost all the taxoids are in the subnanomolar level. It is found that a variety of modifications at C-10 is tolerated for the activity against normal cancer cell lines, but the activity against a drug-resistant human breast cancer cell line expressing MDR phenotype (MCF7-R) is highly dependent on the structure of the C-10 modifier. A number of the new taxoids exhibit remarkable activity (IC50 = 2.1-9.1 nM) against MCF7-R. Among these, three new taxoids, SB-T-1213 (4a), SB-T-1214 (4b), and SB-T-1102 (5a), are found to be exceptionally potent, possessing 2 orders of magnitude better activity than paclitaxel and docetaxel. The observed exceptional activity of these taxoids may well be ascribed to an effective inhibition of P-glycoprotein binding by the modified C-10 moieties. The new taxoid SB-T-1213 (4a) shows an excellent activity (T/C = 0% at 12.4 and 7.7 mg/kg/dose, log10 cell kill = 2.3 and 2.0, respectively) against B16 melanoma in B6D2F1 mice via intravenous administration.

Experimental antitumor activity and pharmacokinetics of the camptothecin analog irinotecan (CPT-11) in mice

Irinotecan (CPT-11) is a semi-synthetic derivative of camptothecin currently in clinical trials. In vitro, CPT-11 presented preferential cytotoxicity toward some solid tumor cells (mouse colon 38 and pancreas 03; human pancreas MIA PaCa-2) as compared to leukemia cells (L1210), whereas SN-38, a metabolite of CPT-11, was not solid tumor selective. In vivo, schedule of administration studies in P388 leukemia and mammary adenocarcinoma 16/C (MA16/C) showed that CPT-11 was not markedly schedule dependent. In order to determine its spectrum of anticancer activity, CPT-11 was evaluated against a variety of mouse and human tumors. The end points used were total log cell kill (Lck) for solid tumors and increase in life span (% ILS) for leukemia. Intravenous CPT-11 was found highly active against both early and advanced stage pancreatic ductal adenocarcinoma 03 (P03), with 60% long-term survivors and 100% complete regressions, respectively. Other responsive tumors included: colon adenocarcinomas 38 and 51 (both 1.0 Lck); MA16/C (3.4 Lck); MA13/C (1.0 Lck); human Calc18 breast adenocarcinoma (2.8 Lck); Glasgow osteogenic sarcoma (1.8 Lck); Lewis lung carcinoma (1.4 Lck); B16 melanoma (1.4 Lck); P388 leukemia (170% ILS) and L1210 leukemia (64% ILS). Of interest, CPT-11 was active against tumors with acquired resistance to vincristine (P388/Vcr), to doxorubicin (P388/Dox) and to docetaxel (Calc18/TXT). CPT-11 was also found highly active after oral administration in mice bearing P03 and MA16/C tumors. Pharmacokinetic evaluations performed i.v. at the highest non-toxic dosage in mice bearing P03 tumors revealed CPT-11 peak plasma concentrations (Cmax) of 8.9 micrograms/ml and a terminal half-life of 0.6 h. The metabolite SN-38 plasma concentrations presented a Cmax of 1.6 micrograms/ml and a terminal half-life of 7.4 h. Although the CPT-11 tumor levels were similar to the plasma concentrations for early time points, drug levels decreased more slowly in the tumor compared to plasma (half-life, 5.0 h). SN-38 tumor levels reached concentrations in the range of 0.32-0.34 micrograms/g and decayed with a half-life of 6.9 h. No significant difference in plasma or tumor pharmacokinetics of either CPT-11 or SN-38 were noted after one or five daily i.v. injections. Overall, these data show that CPT-11 has good activity in experimental models, when administered both by the i.v. and the oral routes. Compared to humans, a similar schedule of administration independence was observed and similar CPT-11 levels could be reached at efficacious dosages although metabolite SN-38 levels were found higher in mice.

Preclinical profile of docetaxel (taxotere): efficacy as a single agent and in combination

Docetaxel (Taxotere; Rhône-Poulenc Rorer, Antony, France) is a new taxoid currently being studied in phase II and III clinical trials worldwide, with promising activity in breast cancer. Docetaxel was evaluated as a single agent against against seven mammary tumors, five from mice and two of human origin. Six of the seven models were found to be sensitive to docetaxel, exhibiting regressions of advanced-stage disease in murine models (MA16/C, MA13/C), and long tumor growth delays (Calc18) and cures (MX-1) in human tumor xenografts. In combination studies in tumor-bearing mice, synergism with docetaxel was observed with cyclophosphamide, 5-fluorouracil, etoposide, vinorelbine (Navelbine; Pierre Fabre Oncologie, Boulogne, France), and methotrexate. A similar level of efficacy was obtained in the cases of docetaxel/vincristine and docetaxel/mitomycin C, compared with the activity of the best single agent. Good activity was obtained with the docetaxel/doxorubicin, docetaxel/vinblastine, and docetaxel/cisplatin combinations; however, the activity of these combinations was lower than that of the best agent in the combination when tested in monotherapy. In terms of tolerance, 60% to 70% of the highest nontoxic dose of each agent could be administered in combination, except for vinca alkaloids, in which 80% to 100% of the maximum tolerated dose did not cause additional toxicity. Although docetaxel is a very potent agent when used in monotherapy, the above results suggest that it also will have a key role in clinical combination chemotherapy.

Synthesis and biological evaluation of amino-substituted benzo[f]pyrido[4,3-b] and pyrido[3,4-b]quinoxalines: a new class of antineoplastic agents

In order to study the structure-activity relationships in the series of new intercalating polycyclic agents, 1-amino-substituted pyrido[3,4-b]quinoxalines, benzo[f]pyrido[4,3-b]quinoxaline derivatives bearing a dibasic side chain and their benzo[f]pyrido[3,4-b] isomers have been synthesized. Biological evaluation was carried out for topoisomerase I and II inhibition, and for in vitro and in vivo antitumor properties in several models. Results demonstrate that appropriately substituted benzo[f]pyrido[4,3-b]quinoxaline derivatives are inhibitors of topoisomerase I and II, and have significant antitumor properties in various experimental models. In addition, the most active compounds appear to be minimally recognized by tumor cells expressing the multidrug resistance phenotype.

Preclinical evaluation of docetaxel (Taxotere)

Progress in cancer chemotherapy has been made owing to the discovery and development of drugs that have new structures, new mechanisms of action, and high levels of experimental antitumor activity. Docetaxel (Taxotere; Rhône-Poulenc Rorer, Antony, France) is prepared by semisynthesis from 10-deacetyl baccatin III, an inactive taxoid precursor extracted from the needles of the European yew Taxus baccata. Docetaxel has been found to promote tubulin assembly in microtubules and to inhibit their depolymerization. As predicted by its unique biochemical mechanism of action, docetaxel acts as a mitotic spindle poison and induces a mitotic block in proliferating cells. In vitro, the docetaxel concentrations required to reduce murine and human cell survival by 50% range from 4 to 35 ng/mL, and the cytotoxic effects are greater on proliferating cells than on nonproliferating cells. Docetaxel also is cytotoxic at clinically relevant concentrations against fresh human tumor biopsy specimens (breast, lung, ovarian, colorectal cancer, melanoma) in a soft agar cloning system. Docetaxel has significant in vivo antitumor activity in the different models generally used for the preclinical evaluation of drugs. Eleven of 12 murine transplantable tumors in syngeneic mice have been found to be sensitive to intravenous docetaxel with complete regressions of advanced-stage tumors. Activity also has been observed with human tumor xenografts in nude mice at an advanced stage. In combination studies, synergism has been observed in vivo with 5-fluorouracil, cyclophosphamide, etoposide, vinorelbine, and methotrexate. Preclinical toxicity in mice and dogs has been evaluated by using one and five daily intravenous doses, respectively. The dog was found to be the more sensitive species. The dose-limiting toxicities are hematologic and gastrointestinal in both species. Neurotoxicity also has been observed at high dosages in mice.

Synthesis and structure-activity relationships of new antitumor taxoids. Effects of cyclohexyl substitution at the C-3' and/or C-2 of taxotere (docetaxel)

Synthesis and cytotoxicity of the new analogs (11-13) of docetaxel possessing cyclohexyl groups instead of phenyl groups at the C-3' and/or C-2 benzoate positions are described. The C-2 cyclohexanecarboxylate analog of paclitaxel (15) is also synthesized for comparison. The potency of these new taxoids were examined for their inhibitory activity for microtubule disassembly and also for their cytotoxicity against murine P388 leukemia cell line as well as doxorubicin-resistant P388 leukemia cell line (P388/Dox). It is found that 3'-dephenyl-3'-cyclohexyldocetaxel (11) (0.72T) and 2-(hexahydro)docetaxel (12) (0.85T) possess strong inhibitory activity for microtubule disassembly equivalent to docetaxel (0.7T), which is more potent than paclitaxel (1.0T). The results clearly indicate that phenyl or an aromatic group at C-3' or C-2 is not a requisite for strong binding to the microtubules. This finding has opened an avenue for development of new nonaromatic analogs of docetaxel and paclitaxel. 3'-Dephenyl-3'-cyclohexyl-2-(hexahydro)docetaxel (13) (2T) turns out to be a substantially weaker inhibitor. The cytotoxicities of 11-13 against P388 are, however, in the same range that is 8-12 times weaker than docetaxel and 4-6 times weaker than paclitaxel, i.e., 13 shows equivalent cytotoxicity to that of 11 or 12 in spite of much lower microtubule disassembly inhibitory activity. The cytotoxicities of these new taxoids against the P388/Dox cell line are only 2-2.5 times lower than that of docetaxel. The potency of 2-(hexahydro)paclitaxel (15) for these assays is much lower than the docetaxel counterpart 12. The significant loss of activity in vivo against B16 melanoma is observed for 11-13, i.e., 11 is only marginal (T/C = 38% at 20 mg/kg/day), and 12 and 13 are inactive (T/C = 76% and 79%, respectively). This could be ascribed to faster metabolism, faster excretion or other bioavailability problems.

Antitumor activity of intoplicine (RP 60475, NSC 645008), a new benzo-pyrido-indole: evaluation against solid tumors and leukemias in mice

Intoplicine (RP 60475, NSC 645008) is a new 7H-benzo[e]pyrido [4,3-b] indole derivative which interacts with DNA and inhibits both topoisomerases I and II. In vitro it was found cytotoxic against various cell types with greater cytotoxicity towards solid tumor cells. We report here the anticancer activity of RP 60475 against a variety of transplantable tumors of mice, and also its cross-resistance profile in leukemias. The end points used were % T/C (median tumor weight of the Treated over the Control x 100) and logCK (log10 cell kill total). RP 60475 administered i.v. was found schedule-independent with a peak plasma level problem. It had a good therapeutic index and host recovery usually occurred 7.5 days post last treatment. RP 60475 was found to be highly active against early stage colon 38 (T/C = 0%, 2.9 logCK) and could induce 5/5 complete regressions of advanced stage tumor. It was found active against colon adenocarcinoma 51 (T/C = 3.6%, 1.9 logCK) and colon carcinoma 26 (T/C = 11.7%, 1.2 logCK). Most of the mammary adenocarcinomas were found very responsive, MA16/C (T/C = 0%, 2.8 logCK), MA14/A (T/C = 0%, 1.4 logCK), MA13/C (T/C = 0%, 3.1 log CK) and MA44 (T/C = 34%). Excellent activity was also observed against early stage pancreatic ductal adenocarcinoma 03 (T/C = 0%) and RP 60475 could achieve 5/5 complete regressions of upstaged tumor. Activity was also obtained on Glasgow osteogenic sarcoma (T/C = 0%, 3.3 logCK), on B16 melanoma (T/C = 14%, 1.3 logCK) and to a lesser extent on Lewis lung carcinoma (T/C = 33.2%). Evaluation of RP 60475 against leukemia sublines with acquired resistance, revealed that L1210/cisplatin and L1210/BCNU were not cross-resistant to RP 60475 whereas P388/vincristine was partially cross-resistant to RP 60475 and P388/doxorubicin was cross-resistant to RP 60475. Based on RP 60475 broad activity against transplantable tumors of mice, its effectiveness against some resistant sublines, its original mechanism of action and its acceptable toxicological profile, this compound was selected for clinical trials.

Cellular pharmacology of 4'-iodo-4'-deoxydoxorubicin

We have studied the growth inhibition, DNA synthesis inhibition and cell incorporation of the new anthracycline 4'-iodo-4'-deoxydoxorubicin (4'-iododoxorubicin) and of its 13-dihydroderivative in a model of doxorubicin-sensitive and -resistant rat C6 glioblastoma cells; results were compared to those obtained with doxorubicin and doxorubicinol in the same model. 4'-Iododoxorubicin was 7.5 times more potent than doxorubicin on the wild cell line and 45 times on the doxorubicin-resistant line, indicating that cross-resistance was only partial between the two drugs. Whereas doxorubicinol presented only a very faint cytotoxic activity, 4'-iododoxorubicinol retained the same activity as the parent drug against sensitive cells and a lower activity against resistant cells. DNA synthesis inhibition occurred for much higher doses than growth inhibition in the sensitive cells, but for similar doses in resistant cells. In both cell lines, 4'-iododoxorubicin and its metabolite were incorporated to a higher extent than doxorubicin and doxorubicinol respectively. Incorporation of metabolites was always lower than that of their parent compound. We have studied the metabolism of doxorubicin and 4'-iododoxorubicin by sensitive and resistant cells; only traces (less than 5%) of metabolites were identified in the cells as well as in the culture medium. A new cell line was selected for resistance in the presence of low amounts of 4'-iododoxorubicin. It presented a 6-fold resistance to 4'-iododoxorubicin and an 85-fold resistance to doxorubicin. Doxorubicin incorporation was markedly reduced in this cell line while 4'-iododoxorubicin was incorporated to the same extent as in the sensitive line. Measurements of drug efflux were performed in the three cell lines. No significant difference was exhibited between the efflux of doxorubicin and that of 4'-iododoxorubicin in each cell line; these effluxes were very rapid in the doxorubicin-selected resistant line, slow in the wild line and intermediate in the 4'-iododoxorubicin-selected line.

Assessment of the experimental model of transplanted C6 glioblastoma in Wistar rats

Establishing in vivo glioblastoma models from cell lines requires a very strict methodology, in order to obtain reproducible tumors presenting all the characteristics of human spontaneous glioblastomas. In this respect, we have developed a model of glioblastoma in Wistar rats by stereotaxic intracerebral transplantation of a 10 microliters suspension of 6 x 10(6) C6 cells grown in vitro. The tumor take was very high in these conditions, only 1 rat over 30 had no tumor. The median survival time varied from 14 to 20 days. The growth curve of the tumor has revealed an exponential growth up to the 10th day after transplantation with a doubling time of 36 h. Histological examination of the tumors has shown several characteristic features of spontaneous glioblastomas, such as neovasculature, parenchymal invasion, nuclear pleiomorphism, and presence of hemorrhagic and necrotic areas. This C6 model is closer to the usual histological characteristics of spontaneous glioblastomas when using the Wistar rather than other strain, and it should be used in that way for preclinical therapeutic evaluation of new drugs or drug combinations in glioblastoma.

Alteration of ganglioside composition and metabolism in doxorubicin-resistant rat tumoral cells

We have investigated the ganglioside levels, composition and metabolism in two lines of doxorubicin-resistant cells and in the corresponding wild strains, the C6 rat glioblastoma and the HTC rat hepatoma. The only ganglioside present was GM3, and its level was increased 2-fold in C6 resistant cells and decreased nearly 2-fold in HTC resistant cells. A decrease of cytidine 5'-monophospho-N-acetylneuraminic acid:galactosylglucosylceramide sialyltransferase activity was observed in both resistant lines as compared to sensitive ones, and could not, therefore, explain the increase in the GM3 level observed in the C6 resistant line. Alterations of acid neuraminidase activity were also observed; a 5-fold decrease was noticed in the C6 resistant line and could account for the increase in the GM3 level observed in these cells; in contrast, a 2-fold increase of acid neuraminidase activity was noticed in the HTC resistant cells: together, with reduced synthesis, it could explain the decrease in the GM3 level observed in these cells. No alterations of exogenous ganglioside transport was exhibited by the C6 resistant cells.

Free fatty acid uptake is increased in doxorubicin-resistant rat glioblastoma cells

We have investigated the mechanism by which the rat glioblastoma C6 cell line resistant to doxorubicin presented an increase of free fatty acid utilization from the nutrient source as compared to the wild sensitive strain. We have shown that this was not due to an accelerated turnover of the phospholipid hydrophobic or hydrophilic moieties, but to an important increase of the uptake of the free fatty acids. This was demonstrated by studies performed with linoleic and linolenic acids during very short incubations, at low temperatures, and in the absence of albumin in the medium. This enhancement of free fatty acid uptake may explain the differences which exist in the acyl group composition of membrane lipids between doxorubicin-sensitive and -resistant C6 cells, because of the suppression of the essential fatty acid-deficient status of the cells.

Hepatic extraction, metabolism and biliary excretion of doxorubicin in the isolated perfused rat liver

The hepatic extraction, metabolism, and biliary excretion of doxorubicin (DX) were studied in the isolated perfused rat liver. Three doses of DX equivalent to 2, 20, and 100 mg/kg in rats were studied over a period of 3 h after bolus injection into the reservoir. DX and metabolites concentration in perfusate, bile, and liver were determined by high-pressure liquid chromatography. The hepatic extraction ratio was low (less than 0.24) and decreased progressively over the 3 h. The hepatic extraction and clearance were significantly lower at the highest dose. Doxorubicinol (DX-OL) was the only metabolite detected in the perfusate, accounting for less than 4% of the total AUC. Thirty-one to thirty-three percent of the dose was excreted into bile over 3 h as unchanged DX. This was reduced to 22% at the highest dose. Only 0.35%-1.33% of the dose was excreted as DX-OL. DX aglycones were found only in the liver, where they represented 20%-30% of the total fluorescence at 3 h. In conclusion, in this model DX has a low extraction ratio, is poorly metabolized and extensively excreted into bile.

Pharmacokinetics of doxorubicin in sarcoma patients

The pharmacokinetics of doxorubicin has been studied in 26 sarcoma patients receiving polychemotherapy. Mean elimination half-life was 34.7 +/- 16.6 h and the total plasma clearance was 29.5 +/- 9.31 X h-1 X m-2. No relationship was found between the pharmacokinetic parameters and the response to treatment, or its toxicity. Special attention was paid to the early-phase kinetics of the drug (3-20 min after injection). A correlation between the early clearance and the ages of the patients was observed. The early clearance was clearly correlated with the total plasma clearance measured over 48 h after injection, indicating the importance of the distribution phase in the overall kinetics of the drug.

Fluorescence anisotropy of cell membranes of doxorubicin-sensitive and -resistant rodent tumoral cells

We have studied the plasma membrane fluidity of rat C6 glioblastoma cells and simian virus 40-transformed mouse liver cells in culture that had been rendered resistant to doxorubicin. This was done by the evaluation of fluorescence anisotropy of two probes; diphenylhexatriene was used on membrane microsomal fractions, and trimethylammonium-diphenylhexatriene was used on whole cell suspensions as a plasma membrane-specific probe since it does not enter the cells. A higher degree of membrane fluidity was exhibited with both techniques by doxorubicin-resistant glioblastoma cells as compared to the doxorubicin-sensitive strain, but in the transformed liver cells no such alteration was seen in the physical properties of their plasma membranes. A higher degree of acyl group unsaturation was noticed in the glioblastoma cells but not in the transformed liver cells upon acquisition of doxorubicin resistance. A similar simultaneous increase in acyl group unsaturation and membrane fluidity can be obtained easily by growing the sensitive cells with a medium supplemented with exogenous polyunsaturated fatty acids. This alteration does not modify the sensitivity of the cells to doxorubicin. We conclude from our work that the increase in membrane fluidity, which is frequently associated with drug resistance, is neither necessary nor sufficient for the expression of the resistance. The reason for a link between cell resistance to doxorubicin and plasma membrane fluidity remains to be found.

Fatty acid composition transport and metabolism in doxorubicin-sensitive and-resistant rat glioblastoma cells

We have studied the lipid composition and the acyl group composition, transport, and metabolism of doxorubicin-sensitive and -resistant rat glioblastoma cells in monolayer cultures (C6 clone). No difference in lipid composition was evidenced; the acyl group composition was, in contrast, highly modified in resistant cells, and these modifications appeared progressively during the acquisition of the resistance. Resistant cells were characterized by a decrease of n-9 eicosatrienoic acid and by a 2-3-fold increase of the proportions of the polyunsaturated fatty acids of the n-6 and n-3 families, especially arachidonic acid and n-3 docosahexaenoic acid. These differences were probably due to a 2-fold increase of the uptake of fatty acids by resistant cells as compared to sensitive cells, this increase allowing the suppression of an essential fatty acid deficiency. Only small changes in the transformations of 16 and 18-carbon atoms' fatty acids to higher analogues were evidenced. A small reduction of the desaturation of stearic acid to oleic acid and of linoleic acid to arachidonic acid was the main characteristic of resistant cells; these differences can be explained as a consequence of the suppression of the essential fatty acid deficiency.

Metabolism of doxorubicin and epirubicin in adult human hepatocytes in culture

Epirubicin is the only anthracycline to be metabolized in humans through a glucuronidation pathway which is not observed in laboratory animals. In search of a model for the experimental study of this metabolism, we have observed that human hepatocytes in culture exhibited this pathway and could be of interest for the understanding of the metabolism of this new drug.

Hepatic metabolism of doxorubicin in mice and rats

We have studied the metabolism of doxorubicin in rat and mouse liver, heart and hepatocytes. Doxorubicinol was present in all cases at very low levels and 7-deoxyaglycones were present only in extraphysiological conditions: no aglycones were found either in fresh livers or in hearts of animals treated with the drug, but they were produced in large amounts when the organs were left at room temperature after the death of the animal. Hepatocytes grown in primary cultures or hepatoma cells grown in continuous lines produced no 7-deoxyaglycones. Freshly isolated hepatocytes synthesized small amounts of 7-deoxyaglycones; however, when these hepatocytes were homogenized prior to incubation, high levels of 7-deoxyaglycones were produced. We conclude that 7-deoxyaglycone formation is possible only in injured tissue and is not, therefore, a normal pathway for doxorubicin.

Cellular pharmacology of doxorubicin in sensitive and resistant rat glioblastoma cells in culture

We have studied the incorporation and cytotoxicity of doxorubicin in cultured rat C6 glioma cells grown as monolayers. Net incorporation was linear up to high extracellular concentrations of drug (10 micrograms/ml). Cytotoxicity was evaluated both by tritiated thymidine incorporation inhibition and cloning efficiency inhibition. For similar total drug exposures, cytotoxicity was very different according to the exposure time and the exposure dose; incubation with a low dose for a long time was much less cytotoxic than that performed with a high dose for a short period of time. We have obtained several clones of doxorubicin-resistant cells. As compared to the wild strain, these cells were characterized by a larger size, a slower growth, a reduced cloning efficiency and a differential sensitivity of 100-1,000 to doxorubicin. Net incorporation of doxorubicin was 5-fold reduced in these cells, due to an increased efflux of the drug. These cells provide an interesting model of doxorubicin-resistant solid tumor in culture.

Tentative dose-monitoring of doxorubicin in lymphoma patients

We have investigated the feasibility of individual dose-monitoring of doxorubicin in lymphoma patients. The purpose was to overcome the large variability of the early-phase kinetic parameters of the drug. We have used a test-dose and calculated for 32 patients a therapeutic dose which could allow us to obtain a predetermined early drug exposure. Such a predetermined drug exposure was obtained in 24 patients of the study. Important variations of the early clearance occurred in 8 patients.

Pharmacokinetics and metabolism of epirubicin during repetitive courses of administration in Hodgkin's patients

We studied the pharmacokinetics and metabolism of epirubicin (4'-epidoxorubicin) in ten patients suffering from Hodgkin's disease and receiving three successive injections of epirubicin at 15-day intervals in a combined chemotherapy regimen. Doses were either constant (35 mg/m2) or escalated from 25 to 35 and 50 mg/m2. Epirubicin metabolism was characterized by the presence of high levels of epirubicin glucuronide in plasma and urine. The area under the time-concentration plasma curve of epirubicin glucuronide reached almost that of unchanged epirubicin (mean ratio = 0.7-0.85), whereas the cumulative urinary excretion of epirubicin glucuronide was one-half of that of epirubicin (mean ratio = 0.45-0.51). Repeating or escalating the doses did not change the levels of the glucuronide significantly. Only a trend towards higher relative levels of glucuronide could be noticed at the lowest dose. The pharmacokinetic parameters of epirubicin were characterized by a high total plasma clearance (mean value: 70-85 1/hr) and a mean elimination half-life of 25-35 hr. Repeating or escalating the doses was followed by a slight increase of the total plasma clearance in most patients, without changes of the elimination half-life. The cumulative urinary excretion was 11-12% of the dose administered and did not vary significantly as a function of time or dose.

Comparative pharmacokinetics and metabolism of doxorubicin and epirubicin in patients with metastatic breast cancer

We have studied the metabolism and pharmacokinetics of epirubicin (4'-epidoxorubicin), as compared to those of doxorubicin, in a total of 16 patients with metastatic breast cancer. Epirubicin metabolism markedly differs from that of doxorubicin, in that large amounts of glucuronides of epirubicinol and epirubicin were observed in plasma as well as in urine samples. The total plasma clearance of epirubicin was significantly higher than that of doxorubicin; this was interpreted as due to an increase of the distribution volume of epirubicin, since the terminal plasma half-lives of both drugs were similar. No significant modifications were observed in patients with hepatic metastases. The differences in the pharmacokinetic and metabolic properties of the two drugs may be responsible for the differences in toxicity that have been noticed between them in previous phase I and II studies.

Cellular pharmacokinetics of doxorubicin in cultured mouse sarcoma cells originating from autochthonous tumors

We have studied the cellular pharmacology of doxorubicin in a line of mouse sarcoma cells isolated from a dimethylbenzanthracene-induced autochthonous tumor. We have studied the cytotoxicity of the drugs as a function of the exposure dose and of the exposure time to the drug. Cytotoxicity was evaluated as the inhibition of the incorporation of [3H-methyl]-thymidine in the cellular nucleic acids. Intracellular drug concentrations were measured by spectrofluorometry. We have shown that the intracellular drug concentration was a linear function of the extracellular drug concentration up to 5 micrograms/ml; the cytotoxicity was an exponential function of the exposure dose up to 1 micrograms/ml, but it was not an exponential function of the exposure time: the cytotoxicity may therefore be very different for similar total drug exposures. Incubation with a low dose for a long time did not provide a cytotoxicity as high as that obtained with a high dose for a short period of time. These results emphasize the role of the peak concentration of doxorubicin for its maximal action in the target cell.

Early-phase pharmacokinetics of doxorubicin in non-Hodgkin lymphoma patients. Dose-dependent and time-dependent pharmacokinetic parameters

The early-phase (20 min) pharmacokinetics of doxorubicin was studied in 18 patients suffering from non-Hodgkin lymphoma and receiving various schedules and/or dosages of the drug. This pharmacokinetics was time-dependent in most patients over a 2-week interval: repeating similar doses in patients leads to a decrease of the drug exposure due to a decrease of the half-life and/or to a decrease of the extrapolation to 0 time (intercept parameter). The pharmacokinetics was generally time-independent within a 6-h interval in most patients. During this time interval, the kinetics was not linear: increasing the dose by large proportions does not lead to a proportional increase of drug exposure. This time- and dose-dependence of doxorubicin pharmacokinetics makes it very difficult to monitor the treatments according to the individual pharmacokinetic patterns of patients.