A Phase I clinical and pharmacological study of cis-diamminedichloro(2-methylpyridine) platinum II (AMD473)

Picoplatin binding to proteins: X-ray structures and mass spectrometry data on the adducts with lysozyme and ribonuclease A

The reactivity of the anticancer drug picoplatin (cis-amminedichlorido(2-methylpyridine)platinum(II) complex) with the model proteins hen egg white lysozyme (HEWL) and bovine pancreatic ribonuclease (RNase A) was investigated by electrospray ionisation mass spectrometry (ESI MS) and X-ray crystallography. The data were compared with those previously obtained for the adducts of these proteins with cisplatin, carboplatin and oxaliplatin under the same experimental conditions. ESI-MS data show binding of Pt to both proteins, with fragments retaining the 2-methylpyridine ligand and, possibly, a chloride ion. X-ray crystallography identifies different binding sites on the two proteins, highlighting a different behaviour of picoplatin in the absence or presence of dimethyl sulfoxide (DMSO). Metal-containing fragments bind to HEWL close to the side chains of His15, Asp18, Asp119 and both Lys1 and Glu7, whereas they bind to RNase A on the side chain of His12, Met29, His48, Asp53, Met79, His105 and His119. The data suggest that the presence of DMSO favours the loss of 2-methylpyridine and alters the ability of the Pt compound to bind to the two proteins. With both proteins, picoplatin appears to behave similarly to cisplatin and carboplatin when dissolved in DMSO, whereas it behaves more like oxaliplatin in the absence of the coordinating solvent. This study provides important insights into the pharmacological profile of picoplatin and supports the conclusion that coordinating solvents should not be used to evaluate the biological activities of Pt-based drugs.

Metallo-Drugs in Cancer Therapy: Past, Present and Future

Cancer treatments which include conventional chemotherapy have not proven very successful in curing human malignancies. The failures of these treatment modalities include inherent resistance, systemic toxicity and severe side effects. Out of 50% patients administrated to chemotherapy, only 5% survive. For these reasons, the identification of new drug designs and therapeutic strategies that could target cancer cells while leaving normal cells unaffected still continues to be a challenge. Despite advances that have led to the development of new therapies, treatment options are still limited for many types of cancers. This review provides an overview of platinum, copper and ruthenium metal based anticancer drugs in clinical trials and in vitro/in vivo studies. Presumably, copper and ruthenium complexes have greater potential than Pt(II) complexes, showing reduced toxicity, a new mechanism of action, a different spectrum of activity and the possibility of non-cross-resistance. We focus the discussion towards past, present and future aspects.

Structural determination of arginine-linked cisplatin complexes via IRMPD action spectroscopy: arginine binds to platinum via NO- binding mode

Cisplatin, (NH₃)₂PtCl₂, has been known as a successful metal-based anticancer drug for more than half a century. Its analogue, Argplatin, arginine-linked cisplatin, (Arg)PtCl₂, is being investigated because it exhibits reactivity towards DNA and RNA that differs from that of cisplatin. In order to understand the basis for its altered reactivity, the deprotonated and sodium cationized forms of Argplatin, [(Arg-H)PtCl₂]^- and [(Arg)PtCl₂ + Na]⁺, are examined by infrared multiple photon dissociation (IRMPD) action spectroscopy in the IR fingerprint and hydrogen-stretching regions. Complementary electronic structure calculations are performed using density functional theory approaches to characterize the stable structures of these complexes and to predict their infrared spectra. Comparison of the theoretical IR spectra predicted for various stable conformations of these Argplatin complexes to their measured IRMPD spectra enables determination of the binding mode(s) of Arg to the Pt metal center to be identified. Arginine is found to bind to Pt in a bidentate fashion to the backbone amino nitrogen and carboxylate oxygen atoms in both the [(Arg-H)PtCl₂]^- and [(Arg)PtCl₂ + Na]⁺ complexes, the NO^- binding mode. The neutral side chain of Arg also interacts with the Pt center to achieve additional stabilization in the [(Arg-H)PtCl₂]^- complex. In contrast, Na⁺ binds to both chlorido ligands in the [(Arg)PtCl₂ + Na]⁺ complex and the protonated side chain of Arg is stabilized via hydrogen-bonding interactions with the carboxylate moiety. These findings are consistent with condensed-phase results, indicating that the NO^- binding mode of arginine to Pt is preserved in the electrospray ionization process even under variable pH and ionic strength.

Ruthenium Complexes: An Alternative to Platinum Drugs in Colorectal Cancer Treatment

Colorectal cancer (CRC) is one of the intimidating causes of death around the world. CRC originated from mutations of tumor suppressor genes, proto-oncogenes and DNA repair genes. Though platinum (Pt)-based anticancer drugs have been widely used in the treatment of cancer, their toxicity and CRC cells' resistance to Pt drugs has piqued interest in the search for alternative metal-based drugs. Ruthenium (Ru)-based compounds displayed promising anticancer activity due to their unique chemical properties. Ru-complexes are reported to exert their anticancer activities in CRC cells by regulating different cell signaling pathways that are either directly or indirectly associated with cell growth, division, proliferation, and migration. Additionally, some Ru-based drug candidates showed higher potency compared to commercially available Pt-based anticancer drugs in CRC cell line models. Meanwhile Ru nanoparticles coupled with photosensitizers or anticancer agents have also shown theranostic potential towards CRC. Ru-nanoformulations improve drug efficacy, targeted drug delivery, immune activation, and biocompatibility, and therefore may be capable of overcoming some of the existing chemotherapeutic limitations. Among the potential Ru-based compounds, only Ru (III)-based drug NKP-1339 has undergone phase-Ib clinical trials in CRC treatment.

Research progress in modern structure of platinum complexes

Since the antitumor activity of cisplatin was discovered in 1967 by Rosenberg, platinum-based anticancer drugs have played an important role in chemotherapy in clinic. Nevertheless, platinum anticancer drugs also have caused severe side effects and cross drug resistance which limited their applications. Therefore, a significant amount of efforts have been devoted to developing new platinum-based anticancer agents with equal or higher antitumor activity but lower toxicity. Until now, a large number of platinum-based complexes have been prepared and extensively investigated in vitro and in vivo. Among them, some platinum-based complexes revealing excellent anticancer activity showed the potential to be developed as novel type of anticancer agents. In this account, we present such platinum-based anticancer complexes which owning various types of ligands, such as, amine carrier ligands, leaving groups, reactive molecule, steric hindrance groups, non-covalently binding platinum (II) complexes, Platinum(IV) complexes and polynuclear platinum complexes. Overall, platinum-based anticancer complexes reported recently years upon modern structure are emphasized.

Cancer Research UK Centre for Drug Development: translating 21st-century science into the cancer medicines of tomorrow

The Cancer Research UK Centre (CRUK) for Drug Development (CDD) can trace its origins back to the Cancer Research Campaign Phase I/II Committee (created in 1980) and to date has tested over 120 potential cancer medicines in early-phase clinical trials. Five drugs are now registered, providing benefit to thousands of patients with cancer as part of their routine standard of care. In recent years, the CDD has established several different business and operating models that provide it with access to the pipelines of pharmaceutical and biotechnology companies. This has enabled potential new treatments to be taken into clinical development that might have otherwise languished on companies' shelves and has increased the number of drug combinations being explored in early-phase clinical trials.

Amide coupling reaction for the synthesis of bispyridine-based ligands and their complexation to platinum as dinuclear anticancer agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is (1)H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

Picoplatin pharmacokinetics and chemotherapy of non-small cell lung cancer

INTRODUCTION

Picoplatin was developed as platinum coordination complex to overcome development of resistance, through conjugation to thioles, by the introduction of a methyl-pyridine moiety into the cisplatin parent structure. Pharmacokinetic parameters of the drug, after intravenous and oral application, were studied in solid tumors and clinical Phase I - III trials performed, in particular in NSCLC and small cell lung cancer (SCLC). Results showed low clinical activity of picoplatin.

AREAS COVERED

This article presents an overview of the pharmacokinetic assessments of picoplatin in lung cancer. Specifically, the authors address the relationship between disposition and clinical activity of the drug.

EXPERT OPINION

Picoplatin failed to overcome resistance to platinum compounds in lung cancer to achieve significant improved survival of most patients. Even highest doses of the drug reaching 150 m/m² given intravenously every 3 weeks were not sufficient to achieve better response than existing chemotherapeutics and the oral bioavailability of a dose of 200 - 400 mg corresponded only to 80 mg/m² iv. Picoplatin therefore seem to be quite ineffective. Picoplatin is expected to overcome tumor resistance in cases which overexpress thiol-conjugating pathways; however, this was not proved in clinical trials. To conclude, this blocked platinum complex is not able to reverse cisplatin resistance to a significant extent in vivo and its mechanisms and kinetics and of DNA damage failed to produce significant clinical results compared to second-line standard therapy for lung cancer.

Platinum and Palladium Polyamine Complexes as Anticancer Agents: The Structural Factor

Since the introduction of cisplatin to oncology in 1978, Pt(II) and Pd(II) compounds have been intensively studied with a view to develop the improved anticancer agents. Polynuclear polyamine complexes, in particular, have attracted special attention, since they were found to yield DNA adducts not available to conventional drugs (through long-distance intra- and interstrand cross-links) and to often circumvent acquired cisplatin resistance. Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly regulated by their structural characteristics, which renders this series of compounds worth investigating and their synthesis being carefully tailored in order to develop third-generation drugs coupling an increased spectrum of activity to a lower toxicity. The present paper addresses the latest developments in the design of novel antitumor agents based on platinum and palladium, particularly polynuclear chelates with variable length aliphatic polyamines as bridging ligands, highlighting the close relationship between their structural preferences and cytotoxic ability. In particular, studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate the structure-activity relationships (SARs) ruling anticancer activity.

An X-ray powder study of the structure and microstructure of trans-dichloridobis(1,5-diamino-1H-tetrazole-κN4)palladium(II)

The crystal structure of the coordination compound [PdCl2(CH4N6)2], trans-dichloridobis(1,5-diamino-1H-tetrazole-κN4)palladium(II), has been determined from X-ray powder diffraction data collected at room temperature. The structure has been solved by direct methods and refined using Rietveld analysis. The complex crystallizes in the monoclinic space group P21/c, with Z=2. The unit cell dimensions are a=5.73491(4), b=11.94450(4), c=8.61685(4)Å, and β=99.6367(6)° with cell volume V=581.930(5)Å3. A slightly distorted square-planar coordination geometry is formed around the Pd atom by two Cl atoms and two tetrazole ring N atoms of two 1,5-diamino-1H-tetrazole ligands, which are in a trans configuration. In the complex molecule, the planes of the tetrazole rings are inclined at 53.7(3)° with respect to the coordination plane. Intermolecular hydrogen bonds of the amino groups N—H···Cl and N—H···Nring are responsible for formation of a three-dimensional supramolecular network. The powder pattern of the compound was strongly affected by the anisotropic line broadening. The width of the Bragg peaks was interpreted by a phenomenological microstructural approach in terms of anisotropic strain effect to complete the Rietveld refinement.

Platinum anticancer drugs. From serendipity to rational design

The discovery of cis-platin was serendipitous. In 1965, Rosenberg was looking into the effects of an electric field on the growth of Escherichia coli bacteria. He noticed that bacteria ceased to divide when placed in an electric field but what Rosenberg also observed was a 300-fold increase in the size of the bacteria. He attributed this to the fact that somehow the platinum-conducting plates were inducing cell growth but inhibiting cell division. It was later deduced that the platinum species responsible for this was cis-platin. Rosenberg hypothesized that if cis-platin could inhibit bacterial cell division it could also stop tumor cell growth. This conjecture has proven correct and has led to the introduction of cis-platin in cancer therapy. Indeed, in 1978, six years after clinical trials conducted by the NCI and Bristol-Myers-Squibb, the U.S. Food and Drug Administration (FDA) approved cis-platin under the name of Platinol(®) for treating patients with metastatic testicular or ovarian cancer in combination with other drugs but also for treating bladder cancer. Bristol-Myers Squibb also licensed carboplatin, a second-generation platinum drug with fewer side effects, in 1979. Carboplatin entered the U.S. market as Paraplatin(®) in 1989 for initial treatment of advanced ovarian cancer in established combination with other approved chemotherapeutic agents. Numerous platin derivatives have been further developed with more or less success and the third derivative to be approved in 1994 was oxaliplatin under the name of Eloxatin(®). It was the first platin-based drug to be active against metastatic colorectal cancer in combination with fluorouracil and folinic acid. The two others platin-based drugs to be approved were nedaplatin (Aqupla(®)) in Japan and lobaplatin in China, respectively. More recently, a strategy to overcome resistance due to interaction with thiol-containing molecules led to the synthesis of picoplatin in which one of the amines linked to Pt was replaced by a bulky methyl substituted pyridine allowing the drug more time to reach its target, DNA. On the other hand, efforts which were made to find new orally administered analog led to satraplatin bearing to axial acetate groups. Both drugs are still under clinical trials. An alternatively route to the discovery of new derivatives turns to the development of improved delivery strategies such as liposomes and polymers. Liposomal cis-platin or lipoplatin in under a phase III randomized clinical trial for patients suffering from small cell lung cancer whereas polymer-based drug, Prolindac™ is currently under investigation for pretreated ovarian cancers in up to eight European centers.

Current management of small cell lung cancer

Confined to one side of the chest, limited stage small cell lung cancer is treated with a combination of chemotherapy and radiotherapy, yet has a long-term survival rate of only 15%. Extensive stage disease has initial response rates to chemotherapy exceeding 70%. However, the disease almost invariably progresses and becomes fatal. Many recent clinical trials have failed to show superiority of newer chemotherapeutics or targeted therapies compared with the standard chemotherapy backbone of platinum plus etoposide. Numerous promising targeted therapies and other agents are still in development.

The status of platinum anticancer drugs in the clinic and in clinical trials

Since its approval in 1979 cisplatin has become an important component in chemotherapy regimes for the treatment of ovarian, testicular, lung and bladder cancers, as well as lymphomas, myelomas and melanoma. Unfortunately its continued use is greatly limited by severe dose limiting side effects and intrinsic or acquired drug resistance. Over the last 30 years, 23 other platinum-based drugs have entered clinical trials with only two (carboplatin and oxaliplatin) of these gaining international marketing approval, and another three (nedaplatin, lobaplatin and heptaplatin) gaining approval in individual nations. During this time there have been more failures than successes with the development of 14 drugs being halted during clinical trials. Currently there are four drugs in the various phases of clinical trial (satraplatin, picoplatin, Lipoplatin and ProLindac). No new small molecule platinum drug has entered clinical trials since 1999 which is representative of a shift in focus away from drug design and towards drug delivery in the last decade. In this perspective article we update the status of platinum anticancer drugs currently approved for use, those undergoing clinical trials and those discontinued during clinical trials, and discuss the results in the context of where we believe the field will develop over the next decade.

A systematic review of dysgeusia induced by cancer therapies

PURPOSE

The purpose was to review relevant scientific papers written since 1989 which focused on the prevalence and management of dysgeusia as an oral side effect of cancer treatment.

METHODS

Our literature search was limited to English language papers published between 1990 and 2008. A total of 30 papers were reviewed; the results of 26 of these papers were included in the present systematic review. A structured assessment form was used by two reviewers for each paper. Studies were weighted as to the quality of the study design, and treatment recommendations were based on the relative strength of each paper.

RESULTS

A wide range in reported prevalence of dysgeusia was identified with the weighted prevalence from 56-76%, depending on the type of cancer treatment. Attempts to prevent dysgeusia through the prophylactic use of zinc sulfate or amifostine have been of limited benefit. Nutritional counseling may be helpful to some patients in minimizing the symptoms of dysgeusia.

CONCLUSIONS

Dysgeusia is a common oral side effect of cancer therapy (radiotherapy, chemotherapy, or combined modality therapy) and often impacts negatively on quality of life. From the current literature, there does not appear to be a predictable way of preventing or treating dysgeusia.

Mechanistic insight into the inhibition of matrix metalloproteinases by platinum substrates

Platinum compounds are among the most used DNA-damaging anticancer drugs, however they can also be tailored to target biological substrates different from DNA, for instance enzymes involved in cancer progression. We recently reported that some platinum complexes with three labile ligands inhibit matrix metalloproteinase activity in a selective way. We have now extended the investigation to a series of platinum complexes having three chlorido or one chlorido and a dimethylmalonato leaving ligands. All compounds are strong inhibitors of MMP-3 by a noncompetitive mechanism, while platinum drugs in clinical use are not. Structural investigations reveal that the platinum substrate only loses two labile ligands, which are replaced by an imidazole nitrogen of His224 and a hydroxyl group, while it retains one chlorido ligand. A chlorido and a hydroxyl group are also present in the zinc complex inhibitor of carboxypeptidase A, whose active site has strong analogies with that of MMP-3.

Replacement of a thiourea-S with an amidine-NH donor group in a platinum-acridine antitumor compound reduces the metal's reactivity with cysteine sulfur

The reactivity of two DNA-targeted platinum-acridine conjugates with cysteine sulfur was studied. The conjugate containing an amidine-NH donor group cis to the chloride leaving group showed considerably reduced reactivity with N-acetylcysteine compared to the prototypical derivative containing a thiourea-S linkage. The opposite scenario has been observed previously in reactions with nucleobase nitrogen. Possible consequences of the unique target-selective tuning of the substitution chemistry for the pharmacodynamic properties and biological activity of these agents are discussed.

Phase II study of picoplatin as second-line therapy for patients with small-cell lung cancer

PURPOSE

This study was designed to confirm the efficacy and safety of picoplatin, a cisplatin analog designed to overcome platinum resistance, in patients with small-cell lung cancer (SCLC) with platinum-refractory/-resistant disease.

PATIENTS AND METHODS

All patients received intravenous picoplatin 150 mg/m(2) every 3 weeks. Tumor response, progression-free survival, and overall survival were evaluated. Adverse events were assessed for frequency, severity, and relationship to treatment. Quality of life was assessed with the Lung Cancer Symptom Scale instrument.

RESULTS

Seventy-seven patients were treated with picoplatin (median number of cycles, two; range one to 10). Three patients (4%) had a partial response, 33 (43%) had stable disease (four of these were unconfirmed partial responses), 36 (47%) had progressive disease, and five were not assessable for response. Median progression-free survival was 9.1 weeks (95% CI, 7.0 to 12.1 weeks). Median overall survival was 26.9 weeks (95% CI, 21.1 to 33.4). The most common grade 3 and 4 toxicities were thrombocytopenia (48%), neutropenia (25%), and anemia (20%). The most commonly reported adverse events of any severity included thrombocytopenia (64%), anemia (49%), neutropenia (39%), nausea (27%), fatigue (16%), and dyspnea (16%). No severe neurotoxicity or nephrotoxicity were observed. There were no treatment-related deaths.

CONCLUSION

Picoplatin demonstrated clinical efficacy in platinum-refractory SCLC. The major toxicity was hematologic. These results warrant further evaluation in this patient population.

Newer cytotoxic agents: attacking cancer broadly

The plasticity and instability of the cancer genome is impressive and is characterized by gene amplifications and deletions, rearrangements, and many silent and active mutations. Although targeted therapeutics have had effect in some diseases, there remains a large role for new cytotoxic agents that have the potential to be broadly active across multiple cancers. Platinum-based regimens are the basis for treatment of several common tumors. Satraplatin and picoplatin are newer platinum complexes that form bulkier lesions in DNA than their forerunners. Microtubules are a key target for anticancer agents. Vinca alkaloid and similar compounds fragment these critical structures, whereas taxanes stabilize them. Vinflunine is a new fluorinated Vinca alkaloid derivative with vascular disrupting effects, as well as antitumor effects. Epothilones are a new class of microtubule stabilizers. Mitosis has been targeted directly and indirectly by many anticancer agents. The aurora kinases are new targets in this class. Inhibitors of aurora kinases are likely to be cytotoxic. Finally, protein regulation is essential for cellular integrity. With the approval of bortezomib (Velcade, PS-341), the proteosome, a master protein regulator, has been validated as an anticancer target. The five articles in this issue of CCR Focus present the current status of these next generation cytotoxic agents.

The resurgence of platinum-based cancer chemotherapy

The accidental discovery of the anticancer properties of cisplatin and its clinical introduction in the 1970s represent a major landmark in the history of successful anticancer drugs. Although carboplatin--a second-generation analogue that is safer but shows a similar spectrum of activity to cisplatin--was introduced in the 1980s, the pace of further improvements slowed for many years. However, in the past several years interest in platinum drugs has increased. Key developments include the elucidation of mechanisms of tumour resistance to these drugs, the introduction of new platinum-based agents (oxaliplatin, satraplatin and picoplatin), and clinical combination studies using platinum drugs with resistance modulators or new molecularly targeted drugs.

Broadening the clinical use of platinum drug-based chemotherapy with new analogues. Satraplatin and picoplatin

The three platinum-containing drugs that have been thus far approved by the FDA - cisplatin, carboplatin and oxaliplatin - have had a significant effect in the treatment of patients with some malignancies such as testicular, ovarian and colorectal cancer. However, much more remains to be achieved to widen the therapeutic use of this important class of drug, either via further analogue development or by judicious use of combining the existing drugs with new molecularly targeted agents. Two analogues arising from an academic (Institute of Cancer Research)/pharmaceutical (Johnson Matthey/AnorMed) collaboration - satraplatin (JM-216) and picoplatin (JM-/AMD-473) - have recently shown promising clinical activity; satraplatin (an orally available drug) in hormone-refractory prostate cancer and picoplatin in small-cell lung cancer. There have also been advances in delivery vehicles for platinum drugs (e.g., the diaminocyclohexane [DACH]-based AP-5346 and aroplatin/liposomal cis-bis-neodecanoato-trans-(R,R)-1,2-diaminocyclohexane platinum (II) [L-NDDP] are in early clinical development). Platinum-based drugs have also been successfully combined with molecularly targeted drugs (e.g., the recent approval of the vascular endothelial growth factor monoclonal antibody bevacizumab with carboplatin and paclitaxel in patients with NSCLC).

Synthesis, crystal structures and cytotoxicities of some transition metal complexes with N-[2-{(pyridin-2-ylmethylidene)amino}ethyl]acetamide

The synthesis and spectroscopic (IR, (1)H and (13)C NMR) characterization of new complexes of Pt(II), Pd(II), Cu(II), and Hg(II) with the Schiff base ligand MeCONHCH(2)CH(2)N=CHPy (L) (Py=pyridine) are reported, together with studies on the cytotoxicities of these complexes, L and [ReBr(CO)(3)(L)] against human leukemia (MOLT-4), breast cancer (MCF-7) and Chang Liver (non-cancerous) cells. The crystal structures of [Pt(L)Cl(2)] (2), [Cu(L)Cl(2)] (4) and [Hg(L)Cl(2)](2) (5) are also reported. Of the complexes studied, [Cu(L)Cl(2)] (4) was identified as the most cytotoxic active derivative against cells of neoplastic origin (MOLT-4, and MCF-7), while having low toxicity on cells of benign origin (Chang Liver).

Metal-based anticancer drugs: From a past anchored in platinum chemistry to a post-genomic future of diverse chemistry and biology

The field of metal-based anticancer drugs was initiated by cisplatin, one of the leading agents in clinical use. Cisplatin acts by binding to DNA and forming 1,2 intrastrand cross-links. Its importance is reflected by the fact that it is estimated that 50-70 % of cancer patients are treated with a platinum drug [7]. For some time, molecular designs in the metallo-drug field remained obdurately anchored in cis-diamine platinum(II) chemistry, but now the field is evolving rapidly with a variety of alternate and very diverse designs being explored. These designs give rise to new spectra of activity and potency and can circumvent cisplatin resistance. This critical review considers the existing clinical platinum drugs, and those currently in commercial development, alongside the new designs including ruthenium anticancer and antimetastatic drugs in clinical trials, polynuclear drugs, organometallic drugs, titanium and gallium drugs, and emerging supramolecular metallo-drugs that act on DNA by noncovalent interactions. The rapid evolution of the field is being informed by post-genomic knowledge and approaches, and further dramatic step-change breakthroughs can be expected as a result; harnessing this knowledge and responding to and taking advantage of this new environment requires integration of chemistry and biology research.

Identification of non-cross-resistant platinum compounds with novel cytotoxicity profiles using the NCI anticancer drug screen and clustered image map visualizations

The widespread clinical use of platinum compounds in cancer chemotherapy has prompted a search for new platinum agents. To search for platinum agents with novel profiles of activity, we used clustered image maps, the COMPARE algorithm, and other numerical methods to analyze platinum compounds submitted to the National Cancer Institute's anticancer drug screen and tested against the screen's 60 diverse human cancer cell lines (the NCI-60). A total of 107 platinum compounds for which the data were adequate could be clustered into 12 groups, 11 of which were characterized by distinctive activity profiles against the cell lines. Each group (except the mixed one) was then found to have a characteristic chemical structure as well. Four of the groups were subjected to further analysis. Mean graph representations of the averaged activity profiles of the different groups served to highlight their similarities and differences. To identify compounds that might retain activity in the setting of resistance to clinically used platinum compounds, we determined the activity levels of 38 of the compounds (representative of the different activity-structure groups) against cisplatin and oxaliplatin-resistant ovarian cancer cell lines. Many of the compounds retained activity against the resistant cells, providing evidence that they differ from cisplatin and oxaliplatin, not only in their selective activity against the various NCI-60 cell types, but are also in their susceptibility to mechanisms of resistance. Since platinum compounds have generally been classified as alkylating agents, we also compared their patterns of activity with those of representative alkylating agents, with NCI-60 growth rates, and with the profiles of 1582 molecular markers in the NCI-60 cells. Much more analysis remains to be done, but the absence of any definitive, biologically interpretable molecular predictor of activity is consistent with the idea that platinum compounds have multiple intracellular targets and that cells can have multiple mechanisms of resistance.

A phase I study of AMD473 and docetaxel given once every 3 weeks in patients with advanced refractory cancer: a National Cancer Institute of Canada-Clinical Trials Group trial, IND 131

BACKGROUND

AMD473 (previously ZD0473) is a new-generation platinum compound with activity against a wide range of human tumour cell lines and xenografts, including carboplatin- and cisplatin-resistant lines. To assess its potential combined with a taxane, a phase I study of AMD473 and docetaxel in advanced cancer was initiated by the National Cancer Institute of Canada-Clinical Trials Group.

PATIENTS AND METHODS

Patients with advanced cancer, measurable disease, performance status Eastern Cooperative Oncology Group 0-2, no major organ dysfunction, and one or no previous taxane regimen received escalating doses of AMD473 and docetaxel every 3 weeks, with a starting dose of AMD473 80 mg/m(2) and docetaxel 60 mg/m(2).

RESULTS

Thirty-three patients enrolled on four dose levels were evaluable for toxicity and 25 patients were evaluable for response. The maximum tolerated dose was dose level 4 (AMD473 120 mg/m(2) and docetaxel 75 mg/m(2)), with grade 4 neutropenia in both minimally and heavily pretreated patients causing dose-limiting toxicity. As well at dose level 4, one patient had grade 3 vomiting despite premedication. Dose level three was expanded for both groups of patients and was defined as the recommended phase II dose at AMD473 100 mg/m(2) and docetaxel 75 mg/m(2). Non-hematologic toxicities included fatigue, diarrhoea and other mild toxicities. There was one partial response in a patient with prostate cancer and stable disease in 15 patients. No apparent pharmacokinetic interaction was noted.

CONCLUSION

AMD473 and docetaxel can be combined with a recommended phase II dose level of 100 mg/m(2) and 75 mg/m(2), respectively, given intravenously every 3 weeks. The combination has activity and should be explored in responsive tumour types.

The Cancer Research UK experience of pre-clinical toxicology studies to support early clinical trials with novel cancer therapies

Pre-clinical toxicology studies in rodents and Phase I clinical trial data are summarised for 14 novel anticancer therapies. With only one exception, an antifolate antimetabolite, rodent toxicology predicted a safe Phase I trial starting dose and the majority of the dose limiting toxicities, in particular haematological toxicity. For targeted agents with well-defined pharmacodynamic markers, illustrated in the current study by 3 anti-endocrine drugs and one resistance modifier, the definition of a maximum tolerated dose can be avoided. Together with earlier data, the current study confirms that pre-clinical toxicology studies in a non-rodent species are not routinely needed for the safe conduct of early clinical trials with new cancer chemotherapies.

Drug resistance reversal--are we getting closer?

Clinical drug resistance is a major barrier to overcome before chemotherapy can become curative for most patients presenting with metastatic cancer. Rational attempts to tackle clinical drug resistance need to be based on an understanding of the mechanisms involved; these are likely to be complex and multifactorial, and may be due to inadequate drug exposure or alterations in the cancer cell itself. This article reviews a number of strategies used to tackle drug resistance, focussing on work in our institution related to the treatment of ovarian cancer and resistance to platinum and taxane-based chemotherapy. Further progress towards drug resistance reversal will require a three-pronged approach, namely: the development of novel cytotoxics which exploit selectively expressed targets; modulation of resistance to conventional agents and, most importantly, a serious attempt to understand resistance mechanisms in tumour samples taken both pre- and post-chemotherapy.