A novel taxane with improved tolerability and therapeutic activity in a panel of human tumor xenografts

Clinically available taxanes represent one of the most promising class of antitumor agents, despite several problems with their solubility and toxicity. In an attempt to improve the pharmacological profile of taxanes, a new series of analogues was synthesized from 14beta-hydroxy-10-deacetylbaccatin III and tested in a panel of human tumor cell lines. On the basis of the pattern of cytotoxicity and lack of cross-resistance in tumor cell lines expressing the typical multidrug-resistant phenotype, a compound (IDN5109) was selected for preclinical development. A comparative efficacy study of IDN5109 and paclitaxel was performed using a large panel of human tumor xenografts, characterized by intrinsic (seven tumors) or acquired (four tumors) resistance to cisplatin or doxorubicin, including four ovarian, one breast, one cervical, three lung, one colon, and one prostatic carcinoma. Drugs were delivered i.v. according to the same schedule (four times every 4th day). IDN5109 achieved a very high level of activity (percentage tumor weight inhibition >70%; log10 cell kill >1) in all but one of the tested tumors. Compared to paclitaxel, IDN5109 exhibited a significantly superior activity in six tumors (including the four tumors that were resistant to paclitaxel) and a comparable activity against the other five paclitaxel-responsive tumors. Additional advantages of IDN5109 over paclitaxel were also suggested by its toxicity profile. IDN5109 was not only less toxic (maximal tolerated doses were 90 and 54 mg/kg for IDN5109 and paclitaxel, respectively), but it also appeared to be endowed with a reduced neurotoxic potential and an improved profile of tolerability compared to the parent drug. Furthermore, the best antitumor efficacy was often already reached with doses lower than the maximal tolerated dose, suggesting an improved therapeutic index for the new drug. In conclusion, the results support the preclinical interest of IDN5109 in terms of the toxicity profile and of the efficacy with particular reference to the ability to overcome multiple mechanisms of drug resistance.     

ZD1839 (IRESSA), an EGFR-selective tyrosine kinase inhibitor, enhances taxane activity in bcl-2 overexpressing, multidrug-resistant MCF-7 ADR human breast cancer cells

Constitutive bcl-2 overexpression increases the tumorigenic and metastatic potential of doxorubicin-resistant, estrogen-independent, MCF-7 ADR human breast cancer cells. We evaluated the sensitivity to taxanes (paclitaxel, docetaxel and IDN 5109) of 2 bcl-2-overexpressing MCF-7 ADR clones and control neomycin-transfected MCF-7 ADR neo cells. The 2 bcl-2-overexpressing MCF-7 ADR clones were relatively resistant to all 3 taxanes, whereas the MCF-7 ADR neo cells were relatively resistant to paclitaxel and docetaxel, but sensitive to IDN 5109. We found that both MCF-7 ADR neo and bcl-2-overexpressing MCF-7 ADR clones express high levels of the epidermal growth factor receptor (EGFR) and its ligand, transforming growth factor-alpha (TGF-alpha). Therefore, we tested the growth inhibitory effect of ZD1839 (Iressa, AstraZeneca, Macclesfield, UK), an orally active, selective EGFR tyrosine kinase inhibitor (EGFR-TKI) that is in clinical development. ZD1839 inhibited the growth in soft agar of all 3 clones in a dose-dependent manner (IC(50) of approximately 0.1 microm). This effect was accompanied by a dose-dependent inhibition of EGFR tyrosine autophosphorylation and of the production of TGF-alpha, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). To determine whether the blockade of EGFR signaling might affect the sensitivity of bcl-2-overexpressing MCF-7 ADR cells to taxanes, cells were treated with ZD1839 in combination with paclitaxel, docetaxel or IDN 5109, and dose-dependent cooperative growth inhibition as well as apoptosis potentiation were observed. Combined treatment with IDN 5109 and ZD1839 also resulted in a significant inhibition of bcl-2 expression in bcl-2-overexpressing MCF-7 ADR cells. These results demonstrate the ability of ZD1839 to overcome taxane resistance in a model of hormone-independent, multidrug-resistant, human breast cancer.     

IDN5109, a taxane with oral bioavailability and potent antitumor activity

IDN5109 is a new taxane, derived from 14beta-hydroxy-10-deacetylbaccatin III, selected for its lack of cross-resistance in tumor cell lines expressing the multidrug resistant phenotype. Because, unlike paclitaxel, IDN5109 is a poor substrate for P-glycoprotein, we hypothesized that IDN5109 given p.o. could improve bioavailability compared with paclitaxel. Here, we studied the p.o. and i.v. pharmacokinetics of IDN5109 together with its antitumor activity. Using a high-performance liquid chromatography method, the bioavailability of IDN5109 was determined to be 48% after oral delivery. IDN5109 given p.o. was highly active against the two human ovarian carcinoma xenografts 1A9 and HOC18 (90-100% tumor regressions) and showed significant activity on the paclitaxel-resistant MNB-PTX1 xenograft (10% tumor regressions). The p.o. administration was as active as the i.v. route at doses reflecting the pharmacokinetic data. IDN5109 is the first taxane with good oral bioavailability and potent antitumor activity and represents a potential candidate for clinical investigation.     

Antitumor effects of IDN5109 on head and neck squamous cell carcinoma

Taxanes, a new class of antitumor drugs, are effective against a large number of human tumors, although there are problems with drug resistance. The novel taxane, IDN5109, is characterized by its high tolerability, antitumor efficacy, ability to overcome multidrug resistance, and oral bioavailabilty. We investigated the cellular response of IDN5109 to head and neck squamous cell carcinoma (HNSCC), and compared the antitumor activity of IDN5109 with that of paclitaxel. This is the first demonstration of antitumor effects of IDN5109 on HNSCC. In in vitro experiments, IDN5109 showed antiproliferative effects against HNSCC cell lines. After treatment with IDN5109, Bcl-2 and Bcl-XL were down-regulated, Bax was up-regulated, and caspase-3 was activated. After treatment with IDN5109, concentrations of both VEGF and IL-8 in the culture supernatant of HNSCC cells decreased. In in vivo experiments, the oral administration of IDN5109 showed antitumor effects against HNSCC tumor xenografts. Immunohistochemistry showed that IDN5109 inhibited tumor angiogenesis and induced apoptosis in HNSCC cells, producing a decreased blood vessel density and increased apoptosis index. On the basis of these results, IDN5109 is useful as a chemotherapeutic agent against HNSCC.     

Anti-tumour activity of a panel of taxanes toward a cellular model of human cervical cancer

Using a model of human cervical cancer (ME-180 cells), the anti-tumour activity of paclitaxel was compared to that of docetaxel and IDN5109, a newly developed taxane. The growth inhibition effect of taxanes was assessed after 3 days of exposure. DNA analysis, the taxane-dependent modulation of the expression of the α and β subunits of tubulin and DNA fragmentation were assessed by flow cytometry. The presence of apoptosis was confirmed by morphological analysis using a laser scan cytometer. For the evaluation of “in vivo” anti-tumour activity, taxanes were administered to nude mice intravenously once daily, according to a q3/4d × 4 schedule. Docetaxel, IDN5109 and paclitaxel obtained “in vitro” IC₅₀ values of 0.86, 1.4 and 2.4 nM, respectively. DNA analysis demonstrated a transient block at the G₂/M phase of the cell cycle only after 12 h of culture in the presence of taxanes and an increase of nuclear fragmentation suggestive for apoptosis after additional 12 and 60 h of exposure. Morphological analysis confirmed the presence of apoptosis. Taxanes induced a down-modulation of the α subunit of tubulin in the G_0/1 phase of the cell cycle, and an overexpression of the β subunit in the G₂/M phase. A strong anti-tumour activity was obtained “in vivo” for nude mice xenografted using ME-180 cells (T/C=0% for all drugs). These data indicate that the three taxanes are strongly active both “in vitro” and “in vivo” toward ME-180 cells. Clinical studies are now needed to ascertain if the higher anti-tumour activity observed “in vitro” using docetaxel and IDN5109 yields a better clinical response in advanced cervical carcinoma with respect to paclitaxel. Received: 4 May 1999 / Accepted: 9 July 1999     

IDN 5390: an oral taxane candidate for protracted treatment schedules

The recognition of the antiangiogenic properties of taxanes provides a basis for novel therapeutic approaches. A prolonged exposure to low drug concentrations has been proposed to be the most suitable approach to exploit the antiangiogenic potential of cytotoxic agents. Such schedule is required to target preferentially slowly dividing endothelial cells. The protracted use of taxanes could benefit from the availability of a taxane endowed with a favourable tolerability profile. Among compounds of a novel series of C-seco taxanes, IDN 5390 was originally selected on the basis of its potent antimotility activity and poor cytotoxicity on endothelial cells. The aim of the study was to investigate the preclinical pharmacologic profile of IDN 5390 in a variety of human tumour xenografts, including ovarian and colon carcinoma and a glioblastoma. IDN 5390, delivered by s.c. injection, daily for 5 days per week, exhibited a high activity against all tumours investigated (tumour growth inhibition was always >85%) in the range of well-tolerated doses. The maximum tolerated dose/injection (MTD), with no signs of systemic or local vesicant toxicity, was 120 mg kg(-1). In contrast, paclitaxel, delivered according to the same schedule, exhibited a variable antitumour efficacy associated with a substantial local toxicity (MTD=10 mg kg(-1)). Considering the remarkable efficacy of IDN 5390 delivered s.c. by protracted treatment schedule, the oral route of administration was further investigated, as the most suitable for daily treatment. Indeed, a good bioavailability of oral IDN 5390 was found. Oral IDN 5390 maintained a substantial efficacy against human tumour xenografts, including paclitaxel-resistant tumours, without loss of potency with respect to s.c. administration. In conclusion, the therapeutic advantages of IDN 5390, over paclitaxel, in protracted daily treatment schedules are represented by the oral efficacy and the high tolerability, which are favourable features to exploit the antiangiogenic potential and to design combinations with other effective agents.     

Anti-proliferative activity of a new class of taxanes (14β-hydroxy-10-deacetylbaccatin III derivatives) on multidrug-resistance-positive human cancer cells

Paclitaxel, docetaxel and a series of new analogs synthesized from 14β-hydroxy-10-deacetylbaccatin III (14-OH-DAB), a natural diterpene closely related to the core synthon of the 2 above prototypes, were tested in vitro for their growth-inhibitory activity on different human cancer cell lines, including some expressing the classic multidrug-resistant (MDR) phenotype (MCF-7 ADRr and CEM VBLr). The 14-OH-DAB derivatives showed enhanced anti-proliferative activity as compared to the parent compounds on the MDR-positive cancer cell lines. Particularly, IDN 5109 showed a 25- to 30-fold higher activity than paclitaxel. The fold change in activity between paclitaxel and analogs (IC₅₀ paclitaxel/IC₅₀ analogs) on the MDR-positive cell lines was calculated and a significant correlation observed. As far as the MDR-negative MDA-MB 231 cells are concerned, docetaxel and IDN 5109 exhibited a more potent activity than paclitaxel. On the basis of the data obtained on cell growth inhibition, we selected the most active compounds to study their effect on the cell cycle. Cell cycle analysis showed that all of the compounds tested were able to induce cell cycle block at G₂/M in a concentration-dependent manner. The amount of cell block, measured as a G₁/G₂ ratio, was correlated significantly (p < 0.001) with apoptosis, as evaluated in the sub-G₁ region (% of DNA fragmentation), thereby suggesting that the G₂/M-blocked cells underwent apoptosis. To confirm the occurrence of apoptosis in this system, DNA gel agarose electrophoresis was performed and showed the typical ladder pattern. Int. J. Cancer 72:844–850, 1997. © 1997 Wiley-Liss, Inc.     

A role for loss of p53 function in sensitivity of ovarian carcinoma cells to taxanes

Loss of p53 function has been linked to increased responsiveness to taxane treatment of ovarian carcinoma in clinical studies. We recently reported that the acquisition of cisplatin resistance in an ovarian carcinoma cell line (IGROV-1) was associated with mutation of p53 and collateral sensitivity to paclitaxel. The increased sensitivity to paclitaxel of the cisplatin-resistant subline appeared to be pharmacologically relevant since it was reflected in an in vivo sensitization to taxanes. To investigate the cellular and molecular basis of this phenomenon, we performed a comparative study of cellular response to taxanes (paclitaxel and the novel analog IDN 5109) in the parental cell line, containing wild-type p53 and its cisplatin-resistant p53 mutant subline (IGROV-1/Pt1). IDN 5109 was included in this study because of its higher potency and efficacy compared with paclitaxel on both tumor systems. The pattern of cellular response of the two ovarian cell lines was different. In IGROV-1 cells, apoptosis was an early event consequent to a transient mitotic arrest. The cell death of IGROV-1/Pt1 cells was a somewhat slow and delayed event, following mitotic arrest and appearance of hyperploid cells. The increased cytotoxic effect of IDN 5109, compared with paclitaxel, was associated with more marked p34(cdc2) dephosphorylation in IGROV-1 cells and higher Bcl-2 phosphorylation in IGROV-1/Pt1 cells after 24 hr of treatment. In each cell line, these biochemical events were not correlated with parallel levels of mitotic cells. Attempts to reintroduce wild-type p53 in IGROV-1/Pt1 were unsuccessful. However, in other p53-deficient cells (osteosarcoma SAOS), taxane treatment was associated with hyperploid progression and the introduction of wild-type p53 resulted in a reduced sensivity. Although our approach does not allow definitive conclusions, these results suggest that loss of p53-dependent post-mitotic checkpoint results in a different time-course of taxane-induced cell death following DNA reduplication. These events, more evident after exposure to the potent analog IDN 5109, support the notion that the enhanced sensitivity of p53 mutant cells is closely related to the different mode of cell death.     

The seco-taxane IDN5390 is able to target class III beta-tubulin and to overcome paclitaxel resistance

A prominent mechanism of drug resistance to taxanes is the overexpression of class III beta-tubulin. The seco-taxane IDN5390 was chosen for its selective activity in paclitaxel-resistant cells with an overexpression of class III beta-tubulin. Moreover, the combined treatment paclitaxel/IDN5390 yielded a strong synergism, which was also evident in cell-free tubulin polymerization assays. In the presence of an anti-class III beta-tubulin as a blocking antibody, tubulin polymerization induced by paclitaxel and IDN5390 was enhanced and not affected, respectively, whereas synergism was abolished, thereby indicating that IDN5390 activity is not modulated by class III beta-tubulin levels. Such properties can be explained by taking into consideration the composition of class III beta-tubulin paclitaxel binding site; in fact, Ser277 interacting with paclitaxel C group in class I is replaced by an Arginine in class III. IDN5390 that has an open and flexible C ring and an acidic alpha-unsaturated enol-keton moiety better fits with class III beta-tubulin than paclitaxel at the binding site. Taking altogether, these findings indicate that the concomitant treatment IDN5390/paclitaxel is able to successfully target class I and III beta-tubulin and the combined use of two taxanes with diverse spectrum activity against tubulin isotypes could represent a novel approach to overcome paclitaxel resistance.     

自体外周血造血干细胞移植过程中淋巴细胞亚群和CD34+细胞变化的动态研究

目的动态观察动员、采集过程中外周血及造血干细胞中的淋巴细胞亚群和造血干细胞含量变化,及时指导临床选择最佳采集时机。方法 采用流式细胞术(FCM)测定大剂量化疗(HDC)联合重组人粒细胞集落刺激因子(rhG-CSF)对47例恶性实体瘤患者自体外周血造血干细胞移植(APBSCT)过程中,外周血和外周血造血干细胞(PBPC)中的淋巴细胞亚群CD3、CD4、CD8、NK、CD19和造血干细胞CD34+及其亚群CD34+CD38-、CD34+ Thy1+、AC133+细胞含量的变化,同时用体外集落培养的方法评价干细胞克隆形成能力。结果 动员后外周血淋巴细胞亚群CD3、CD4、CD8、NK和CD19细胞含量均低于动员前,其中CD3、CD8含量明显低于基础状态(P=0.007,P=0.016),而动员后外周血中的CD34及其亚群含量均明显高于动员前(P<0.05)。动员后中位时间第16天(15～17 d)外周血中的CD34含量达到最高峰,且第1次采集物中的造血干细胞含量最高。PBPC中除CD4、CD4/CD8明显低于外周血外(P<0.000 5),其他淋巴细胞亚群含量与外周血比较无明显改变。外周血单个核细胞中CD34+细胞含量与PBPC中CD34+细胞、CD34+CD38-及粒/单系集落形成单位(CFU-GM)、红系爆式集落形成单位(BFU—E)均存在显著相关性(P<0.05),而与采集的单个核细胞(MNC)总数、CD34+Thy1+、AC133+细胞含量间无相关关     

Antiangiogenic and antitumor activity of IDN 5390, a new taxane derivative.

PURPOSE: We previously reported that paclitaxel, a microtubule-stabilizing drug, inhibited angiogenesis, mainly by inhibiting endothelial cell motility (D. Belotti et al., Clin. Cancer Res., 2: 1843-1849, 1996). The aim of this study was to select a taxane with little cytotoxicity but with antimotility and hence antiangiogenic activity. EXPERIMENTAL DESIGN: Different taxanes, seco derivatives, and 14-beta-hydroxy-10-deacetyl baccatin III derivatives were tested for their effects on the proliferation and motility of human umbilical vein endothelial cells. The antiangiogenic and antineoplastic activities of the compound selected from this screening were further investigated in experimental models in vitro and in vivo. RESULTS: From the screening of different taxanes, we selected IDN 5390, a seco derivative that showed potent antimotility activity and less cytotoxicity than paclitaxel. In comparable experimental conditions, IDN 5390 inhibited endothelial cell migration without affecting proliferation. This compound dose-dependently inhibited the capacity of human umbilical vein endothelial cells plated on Matrigel to organize into a network of cords. In vivo, IDN 5390 significantly inhibited fibroblast growth factor-2-induced angiogenesis in Matrigel implants. Daily treatment with IDN 5390 in mice bearing established lung micrometastases from the B16BL6 murine melanoma caused a reduction in the size of metastases. Finally, IDN 5390 slowed the s.c. growth of the paclitaxel-resistant human ovarian carcinoma, 1A9/PTX22, xenografted in nude mice. CONCLUSIONS: The seco derivative IDN 5390 might represent the prototype of a new class of taxane derivatives with antiangiogenic properties.     

Oral efficacy and bioavailability of a novel taxane.

A novel taxane (IDN 5109), originally selected for its ability to overcome P-glycoprotein-mediated drug resistance, is characterized by an improved preclinical profile in terms of efficacy and tolerability. Because P-glycoprotein may critically influence intestinal absorption and oral bioavailability of taxanes, the purpose of the study was to evaluate the bioavailability, the pharmacokinetic behavior, and the antitumor activity of the new taxane after oral administration. A comparative study of antitumor activity of Taxol and IDN 5109 given orally was performed in a human breast carcinoma model, MX-1, which is highly responsive to i.v. treatment with both of the taxanes. In contrast to Taxol, which was completely ineffective after administration to MX-1-bearing mice, oral IDN 5109 exhibited an activity comparable with that of i.v. treatment (ie., 100% cures). Again, the maximal tolerated doses were comparable (90 mg/kg, every 4 days for four doses) after i.v. and oral treatment. Three other tumor models (LoVo, IGROV/DDP, and U87) with a variable sensitivity to the drug were used to compare the antitumor effects of i.v. and oral treatment with IDN 5109. The efficacy after oral administration was only slightly lower than that found after i.v. treatment at equivalent doses; but optimal effects were comparable likely as a consequence of the long (>6 h) terminal half-life of oral IDN 5109. The bioavailability of IDN 5109 assessed by comparing area-under-the-curve values after oral and i.v. administrations was approximately 50%. The oral efficacy of the novel taxane, likely related to the inability of the P-glycoprotein to recognize the drug, which allowed an adequate intestinal absorption, is a unique feature among the taxanes and may represent a pharmacological breakthrough in their clinical use.     

Morphologic, immunophenotypic and in vitro growth characteristics of blood and bone marrow associated with stem cell mobilisation in patients with lymphoma

The proportion of CD34+ cells in the bone marrow (BM) is predictive of the size of progenitor cell mobilisation into the blood (PB). To investigate which other PB and BM parameters may be related to mobilisation, we analysed at steady state PB and BM of 23 patients with relapsed or resistant lymphoma before administering high-dose cyclophosphamide and G-CSF Cell morphology, number of CD34+ cells, and growth in clonogenic assay and in long-term cultures (LTC) were determined and then correlated with mobilisation extent (CD34+ and GM-CFC) and quality (growth of harvested cells in LTC). We found that the good mobilising patients (CD34 > 50 x 10(3)/ml, n=10) had several baseline BM characteristics (number of CD34+ MNC, GM-CFC, BFU-E, production of CFCs in LTC) similar to a group of 12 healthy controls, while patients with reduced mobilisation (CD34 < 50 x 10(3)/ml, n=13) had clearly reduced BM progenitors and LTC growth (p< 0.05). In a multivariate analysis including baseline clinical, blood and bone marrow characteristics, the most significant PB and BM factors independently associated with a higher number and/or quality of mobilised cells were a higher number of CD34+ and GM-CFC in the BM and a higher baseline haemoglobin, platelet, and CD34+ blood count. The capacity to release progenitor cells into the circulation is therefore not predicted by the distribution of morphologically distinguishable cells, marginally predicted by the BM content of highly undifferentiated cells (growth in long term culture), while it is proportional to the number of BM progenitors (CD34+, GM-CFC and BFU-E).     

Cellular bases of the antitumor activity of the novel taxane IDN 5109 (BAY59-8862) on hormone-refractory prostate cancer.

Taxane-based therapies appear to have a significant efficacy in clinical trials on hormone-refractory prostate carcinoma. In the present study, we investigated the cellular response of androgen-independent prostate carcinoma cell lines to the novel taxane IDN 5109 (BAY 59-8862) and evaluated its antitumor activity. In previous preclinical studies, this new paclitaxel (PTX) analogue was characterized by high tolerability and antitumor efficacy, ability to overcome multidrug resistance, and activity by oral administration. Upon treatment, DU145 and PC3 prostate carcinoma cell lines underwent a transient mitotic arrest. This was followed by G1 arrest and rapid occurrence of apoptosis in DU145 cells, whereas in PC3 cells, which are defective for the postmitotic checkpoint, a slow cell death was preceded by DNA endoreduplication. At the biochemical level, such events were associated with tubulin polymerization, activation of the mitosis-promoting factor, and phosphorylation of Bcl-X(L)/Bcl-2/Raf-1. In addition, IDN 5109 shared with PTX the ability to down-regulate the expression of the two potent angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor. These findings indicated that IDN 5109 affected the same pathways involved in the cellular response to PTX and suggested that an antiangiogenic effect mediated by inhibition of paracrine stimulation of endothelial cells might contribute to the antitumor effect of both drugs. In in vivo experiments, the new taxane displayed a superior and more persistent effect compared with PTX against DU145 tumor xenografts. Such an effect was associated with pronounced reduction of the tumor microvessel density, superior to that achieved by PTX. These results support a potential therapeutic advantage of IDN 5109 over PTX against hormone-refractory prostate carcinoma.     

Antitumour and antiangiogenic effects of IDN 5390, a novel C-seco taxane, in a paclitaxel-resistant human ovarian tumour xenograft

IDN 5390 is a novel C-seco taxane analogue selected for preclinical development on the basis of its antimotility activity on endothelial cells, antitumour efficacy in a large panel of human tumour xenografts and high tolerability in mouse. On the basis of oral availability, IDN 5390 is suitable for protracted administration schedules. Such a treatment schedule has been reported as the most appropriate to exploit the antiangiogenic effects of cytotoxic drugs. An ability to downregulate angiogenesis-related growth factors in tumour cells has been described for IDN 5390. The aim of the study was to investigate the antitumour and antiangiogenic potential of oral IDN 5390 on a human ovarian carcinoma xenograft, the INT.ACP/PTX, resistant to paclitaxel (PTX). Such tumour line was derived in vivo from a cisplatin-resistant tumour line, the A2780/DDP, which is sensitive to PTX. Compared to the parental cells, INT.ACP/PTX cells exhibited a high level of Pgp expression, resulting in a reduced in vitro sensitivity to both PTX and IDN 5390. The INT.ACP/PTX tumour xenograft was still resistant to PTX, but responsive to IDN 5390, when delivered per os, by a daily prolonged schedule. A direct effect on tumour cells, allowed by the high tolerability of the compound in mouse, cannot be excluded in vivo. Immunohistochemical analysis indicated a significant reduction of microvessel density in IDN 5390-treated tumours, lasting till 7 days after the last drug administration. Thus, a prolonged inhibitory effect on tumour angiogenesis is consistent with the persistent growth control of INT.ACP/PTX tumour achieved by IDN 5390. On the contrary, the low tolerability and the limited oral availability of conventional taxanes do not allow an easy feasibility of such treatment regimen. Thus, the tolerability profile of IDN 5390 in preclinical systems and its efficacy in PTX-resistant tumours support the therapeutic interest for its clinical development, with particular attention to oral daily prolonged schedules.     

Tumour kinetics in multiple myeloma before, during, and after treatment.

Tumour progression was monitored in seven multiple myeloma (MM) patients undergoing a novel oral chemotherapy regimen (cyclophosphamide, idarubicin and dexamethasone; CID) followed by early autologous stem cell transplantation (ASCT). Allele-specific oligonucleotide PCR (ASO-PCR) was used to semi-quantitate the number of tumour cells within the peripheral blood (PB) and PB progenitor cell (PBPC) harvests and compared with paraprotein levels and morphological bone marrow (BM) assessments. Tumour cells were detected in the PB of all patients at diagnosis, but decreased in response to CID therapy. All but two of the 22 PBPC collections contained MM cells, the levels of which were statistically correlated with overall clinical response to therapy, but not with individual BM or PB tumour loads prior to mobilisation. We also found no correlation between the day of leucapheresis collection and the number of contaminating MM cells, CD34+ cells or MM cells per CD34+ cell. Regardless of tumour contamination levels in the PBPC collections, the majority of patients demonstrated post-ASCT clearing of circulating MM cells. This study suggests that levels of circulating MM cells may be the best indication of patient response to treatment and argues against the theory of differential mobilisation of tumour cells and CD34+ cells in response to cytokine treatment.     

Tumour Kinetics in Multiple Myeloma Before, During, and After Treatment

Tumour progression was monitored in seven multiple myeloma (MM) patients undergoing a novel oral chemotherapy regimen (cyclophosphamide, idarubicin and dexamethasone; CID) followed by early autologous stem cell transplantation (ASCT). Allele-specific oligonucleotide PCR (ASO-PCR) was used to semi-quantitate the number of tumour cells within the peripheral blood (PB) and PB progenitor cell (PBPC) harvests and compared with paraprotein levels and morphological bone marrow (BM) assessments. Tumour cells were detected in the PB of all patients at diagnosis, but decreased in response to CID therapy. All but two of the 22 PBPC collections contained MM cells, the levels of which were statistically correlated with overall clinical response to therapy, but not with individual BM or PB tumour loads prior to mobilisation. We also found no correlation between the day of leucapheresis collection and the number of contaminating MM cells, CD34⁺ cells or MM cells per CD34⁺ cell. Regardless of tumour contamination levels in the PBPC collections, the majority of patients demonstrated post-ASCT clearing of circulating MM cells. This study suggests that levels of circulating MM cells may be the best indication of patient response to treatment and argues against the theory of differential mobilisation of tumour cells and CD34⁺cells in response to cytokine treatment.     

Antitumour activity of novel taxanes that act at the same time as cytotoxic agents and P-glycoprotein inhibitors

Taxanes antitumour agents such as paclitaxel and docetaxel represent a successful family of chemotherapeutic drugs. Unfortunately, acquired and innate resistance represents a clinical problem for these drugs. We investigated, on a panel of 7 human cancer cell lines, the growth inhibition effect of 3 newly developed taxanes (SB-T-1213, SB-T-1250 and SB-T-101187) with modification at the C10 and C3' positions of the taxane framework. These positions have been previously characterized as critical to make taxanes highly active against cells overexpressing the efflux pump P-glycoprotein (P-gp). Paclitaxel and docetaxel were used as reference compounds. Results unambiguously indicate the exceptional activity of the novel taxanes toward P-gp positive cells (up to >400 fold higher potency than that of paclitaxel). SB-T-1213 and SB-T-1250 are also substantially more active than the reference compounds against P-gp negative cells. To better understand the mechanisms underlying the enhanced activity of the newly developed taxanes, we performed cell cycle and apoptosis analysis. This study demonstrates that the striking growth inhibition effect exhibited by the novel taxanes is ascribed to their increased ability in inducing apoptosis and G(2)/M cell cycle block. SB-T-1213 and SB-T-1250 are also more active than reference compounds in inducing intracellular accumulation of the beta-tubulin subunits. Finally, it is revealed that these novel taxanes have ability to inhibit the function of the P-gp efflux pump on the basis of the Rhodamine 123 assay. These findings strongly suggest that SB-T-1213, SB-T-1250 and SB-T-101187 represent a new tool to overcome innate or acquired P-gp mediated taxane-resistance.     

Taxanes synergize with the bispecific antibody MDXH447 to enhance antibody-dependent cell-mediated cytotoxicity

The interaction between antibody based therapy and cytotoxic chemotherapy is complex. To explore these interactions we investigated, in vitro, the effects of IC20 growth inhibitory concentrations of taxanes on bispecific antibody-mediated tumor cell cytotoxicity. MDXH447 is a bispecific antibody with specificity for the high affinity IgG receptor (CD64) and the type I epidermal growth factor receptor type (EGF-R). A431 cells, an epidermoid carcinoma cell line that over expresses EGF-R, were exposed to a range of IC20 growth inhibitory concentrations of paclitaxel or docetaxel. Interferon gamma activated monocytes were armed with MDXH447 and a standard chromium release antibody-dependent cell-mediated cytotoxicity (ADCC) assay was performed. Using the Chou and Talalay median effect analysis, we found that MDXH447-mediated ADCC was enhanced when A431 target cells were pretreated with paclitaxel or docetaxel. Median effect analysis of these interactions supported a synergistic interaction (CI < 1). Pretreatment of A431 cells with taxanes did not increase EGF-R expression compared to untreated controls. A431 epidermoid carcinoma cells pretreated with IC20 growth inhibitory concentrations of taxanes enhanced interferon gamma activated monocyte mediated ADCC killing through MDXH447.