The novel trinuclear platinum complex BBR3464 induces a cellular response different from cisplatin

Multifunctional application of supramolecular cucurbiturils as encapsulating hosts in drug delivery: A review

Cucurbit[n]uril (CB[n], n = 5-10), a unique category of molecular hosts composed of n glycoluril units, has attracted considerable attention because of its exceptional molecular recognition properties. Cucurbit[n]urils represent an innovative category of molecular containers capable of forming stable complexes with a wide array of guests, including pharmaceutical compounds, amino acids, proteins or peptides, saccharides, and dyes, among others. Compared to the chemistry of calixarenes and cyclodextrins, the advancement of CB[n] chemistry has been rather sluggish until recently. This is mainly due to their inadequate solubility in typical solvents and the difficulties involved in functionalising these compounds. Cucurbiturils are characterised as water-soluble, symmetrical, rigid host molecules with a pumpkin-like form. The distinctiveness of cucurbiturils facilitates the encapsulation of diverse pharmacological molecules, both neutral and positively charged, via non-covalent interactions, yielding femtomolar affinities. This feature article summarises numerous studies conducted by researchers on the applicability of cucurbiturils and their derivatives in targeted medication delivery and controlled drug release. In vitro and in vivo experiments indicate that cucurbit[n]urils possess negligible systemic toxicity, exhibit specific organ toxicity, and do not seem to affect embryonic biology. Drug delivery methods that improve upon those of other supramolecular host molecules, especially cyclodextrins, and alternative formulation systems like polymers, hydrogels, and liposomes are anticipated to be developed as a result of the increasing fascination with cucurbituril-based systems, which are known for their low acute toxicity. The case studies show a wide range of usage, from basic research to translational uses in fields including gene therapies, antibiotics, and chemotherapy, among others.

What happened to BBR3464 and where to from here for multinuclear platinum-based anticancer drugs?

The development of the trinuclear platinum(II) complex BBR3464 (also known as triplatin) in the late 1990s was meant to be a revolution in the field of platinum chemotherapy. What made it remarkable was that it defied many of the known structure-activity rules for platinums; it is cationic, has a single labile trans leaving group on each terminal platinum, and it binds DNA in ways different to mononuclear platinum drugs, like cisplatin and oxaliplatin. The flexible, long-range adducts the drug forms with DNA means that it showed activity in cancers not typically sensitive to platinums, and more importantly, BBR3464 demonstrated an ability to overcome acquired resistance to platinum drugs. But while preclinical and phase I testing showed promise, its more severe side effects which greatly limited the deliverable dose when compared with standard platinums, combined with its lack of biostability, led to a lack of activity in phase II trials and its development was halted. But, from its ashes have risen 4th generation complexes which target the phosphate backbone of DNA. These, and the original BBR3464 drug, could potentially be further developed and gain regulatory approval through formulation with macrocycle-based drug delivery vehicles.

Debating the Optimal Preoperative Approach: NACRT vs NACT in Locally Advanced Oesophageal Cancer

Oesophageal cancer (EC), ranking 11th in incidence and 7th in mortality globally, presents a significant health challenge, with a notable prevalence in India, especially in the northeastern region. This article examines the efficacy of neoadjuvant chemoradiotherapy (NACRT) versus neoadjuvant chemotherapy (NACT) in treating locally advanced EC, analyzing data from randomized controlled trials (RCTs) between 2000 and 2024. NACRT, involving preoperative chemoradiotherapy followed by surgery, has shown improved survival rates, notably in the CROSS trial, which reported a 10-year overall survival benefit of 13%. Conversely, NACT is supported by key trials like the OE02 and MAGIC trials, demonstrating comparable survival outcomes. Key points of debate include compliance, complications, response and resection status, survival rates, and health-related quality of life (HRQOL). Compliance rates are similar for both modalities, though disease progression is more common after NACT. Postoperative complications and mortality rates are comparable, with NACTRT showing higher pathologic complete response (pCR) and R0 resection rates, potentially avoiding additional adjuvant radiation. While NACRT shows marginally better 3-year survival rates, particularly for squamous cell carcinoma, 5-year survival rates and HRQOL outcomes are similar for both treatments. NACTRT is associated with more respiratory symptoms, whereas NACT patients experience more gastrointestinal issues. Both NACT and NACTRT are viable options, with the choice depending on patient-specific factors and a thorough assessment of potential benefits and risks. Further research is needed to optimize treatment protocols for EC.

DNA radiosensitization by terpyridine-platinum: damage induced by 5 and 10 eV transient anions

Chemoradiation therapy (CRT), which combines a chemotherapeutic drug with ionizing radiation (IR), is the most common cancer treatment. At the molecular level, the binding of Pt-drugs to DNA sensitizes cancer cells to IR, mostly by increasing the damage induced by secondary low-energy (0-20 eV) electrons (LEEs). We investigate such enhancements by binding terpyridine-platinum (Tpy-Pt) to supercoiled plasmid DNA. Fifteen nanometer thick films of Tpy-Pt-DNA complexes in a molar ratio of 5 : 1 were irradiated with monoenergetic electrons of 5 and 10 eV, which principally attach to the DNA bases to form transient anions (TAs) decaying into a multitude of bond-breaking channels. At both energies, the effective yields of crosslinks (CLs), base damage (BD) related CLs, single and double strand breaks (SSBs and DSBs), non-DSB-cluster lesions, loss of supercoiled configuration and base lesions are 6.5 ± 1.5, 8.8± 3.0, 88 ± 11, 5.3 ± 1.3, 9.6 ± 2.2, 106 ± 17, 189 ± 31 × 10^-15 per electron per molecule, and 11.9 ± 2.6, 19.9 ± 4.4, 128 ± 18, 7.7 ± 3.0, 13.4 ± 3.9, 144 ± 19, 229 ± 42 × 10^-15 per electron per molecule, respectively. DNA damage increased 1.2-4.2-fold due to Tpy-Pt, the highest being for BD-related CLs. These enhancements are slightly higher than those obtained by the conventional Pt-drugs cisplatin, carboplatin and oxaliplatin, apart from BD-related CLs, which are about 3 times higher. Enhancements are related to the strong perturbation of the DNA helix by Tpy-Pt, its high dipole moment and its favorable binding to guanine (G), all of which increase bond-breaking via TA formation. In CRT, Tpy-Pt could considerably enhance crosslinking within genomic DNA and between DNA and other components of the nucleus, causing roadblocks to replication and transcription, particularly within telomeres, where it binds preferentially within G-quadruplexes.

The Landmark Series: Multimodal Therapy for Esophageal Cancer

INTRODUCTION

Esophagectomy is the mainstay of treatment for patients with resectable esophageal cancer, and chemotherapy and chemoradiation have become essential adjuncts to improve survival. Controversy remains regarding the optimal perioperative therapy.

METHODS

This review focuses on three landmark, randomized, controlled trials that have greatly influenced esophageal cancer management and established chemotherapy and chemoradiotherapy as standard of care: Medical Research Council Adjuvant Gastric Infusional Chemotherapy Trial (MAGIC); The United Kingdom Medical Research Council Esophageal Cancer Trial (OEO2); and Chemoradiotherapy for Oesophageal Cancer Followed by Surgery Study (CROSS).

RESULTS

The findings from these landmark studies are reviewed and summarized.

CONCLUSION

Chemotherapy regimens are heterogeneous but centered around platinum-based therapy and should be included in the management for all appropriate patients. Ongoing and future studies will further delineate the roles of various chemo- and chemoradiotherapy regimens and also will investigate the promising area of immunotherapy in the treatment of esophageal cancer.

Conjugates Containing Two and Three Trithiolato-Bridged Dinuclear Ruthenium(II)-Arene Units as In Vitro Antiparasitic and Anticancer Agents

The synthesis, characterization, and in vitro antiparasitic and anticancer activity evaluation of new conjugates containing two and three dinuclear trithiolato-bridged ruthenium(II)-arene units are presented. Antiparasitic activity was evaluated using transgenic Toxoplasmagondii tachyzoites constitutively expressing β-galactosidase grown in human foreskin fibroblasts (HFF). The compounds inhibited T.gondii proliferation with IC50 values ranging from 90 to 539 nM, and seven derivatives displayed IC50 values lower than the reference compound pyrimethamine, which is currently used for treatment of toxoplasmosis. Overall, compound flexibility and size impacted on the anti-Toxoplasma activity. The anticancer activity of 14 compounds was assessed against cancer cell lines A2780, A2780cisR (human ovarian cisplatin sensitive and resistant), A24, (D-)A24cisPt8.0 (human lung adenocarcinoma cells wild type and cisPt resistant subline). The compounds displayed IC50 values ranging from 23 to 650 nM. In A2780cisR, A24 and (D-)A24cisPt8.0 cells, all compounds were considerably more cytotoxic than cisplatin, with IC50 values lower by two orders of magnitude. Irrespective of the nature of the connectors (alkyl/aryl) or the numbers of the di-ruthenium units (two/three), ester conjugates 6-10 and 20 exhibited similar antiproliferative profiles, and were more cytotoxic than amide analogues 11-14, 23, and 24. Polynuclear conjugates with multiple trithiolato-bridged di-ruthenium(II)-arene moieties deserve further investigation.

Use of Anticancer Platinum Compounds in Combination Therapies and Challenges in Drug Delivery

As one of the leading and most important metal-based drugs, platinum-based pharmaceuticals are widely used in the treatment of solid malignancies. Despite significant side effects and acquired drug resistance have limited their clinical applications, platinum has shown strong inhibitory effects for a wide assortment of tumors. Drug delivery systems using emerging technologies such as liposomes, dendrimers, polymers, nanotubes and other nanocompositions, all show promise for the safe delivery of platinum-based compounds. Due to the specificity of nano-formulations; unwanted side-effects and drug resistance can be largely averted. In addition, combinational therapy has been shown to be an effective way to improve the efficacy of platinum based anti-tumor drugs. This review first introduces drug delivery systems used for platinum and combinational therapeutic delivery. Then we highlight some of the recent advances in the field of drug delivery for combinational therapy; specifically progress in leveraging the cytotoxic nature of platinum-based drugs, the combinational effect of other drugs with platinum, while evaluating the drug targeting, side effect reducing and sitespecific nature of nanotechnology-based delivery platforms.

In vitro effects of the activity of novel platinum (II) complex in canine and human cell lines

The anticancer activity of novel platinum derivative, a complex of platinum with tris(2-carboxyethyl)phosphine (Pt-TCEP), has been evaluated in canine (D-17) and human osteosarcoma (U2-OS) cell lines. Viability of cells after incubation for 24 or 72 hours with increasing concentrations (0.625, 1.25, 2.50, 5, 10 and 20 μM) of Pt-TCEP was tested in an MTT assay and compared to effect of cisplatin. Longer-term effect of Pt-TCEP was evaluated in the colony-forming unit assay after 24 hours exposure to the Pt-TCEP (2 and 3 μM) and subsequent incubation for 2 weeks. The influence of the compound on the cell cycle was measured after 24 hours treatment with Pt-TCEP (3 μM). Its pro-apoptotic activity was examined after 24 hours treatment with Pt-TCEP (1.25, 2.50, 5, 10 and 20 μM) using flow cytometry. Expression of main proteins involved in apoptosis was measured after exposure for 24 hours to 3 or 5 μM Pt-TCEP in Western Blot. The compound much more effectively decreased cell viability than cisplatin in case of both cell lines. IC₅₀ of Pt-TCEP was 5.93 ± 0.12 in D-17 and 3.45 ± 0.14 in U2-OS cell lines after 24 hours, and 1.77 ± 0.14 in D-17 and 1.53 ± 0.11 in U2-OS after 72 hours (P < .05). The compound arrested cells in the G2/M phase and inhibited the ability of cells to form colonies. Pt-TCEP induced caspase-dependent apoptosis. The expression of the anti-apoptotic Bcl-X_L protein was decreased after Pt-TCEP treatment in both cell lines. The results confirmed anti-cancer activity of Pt-TCEP against canine and human osteosarcoma cell lines.

The optimal neoadjuvant treatment of locally advanced esophageal cancer

Esophagectomy is the cornerstone of intentionally curative treatment in patients with locally advanced esophageal cancer. Neoadjuvant treatments have been introduced to minimize the risk of development of locoregional- and/or distant recurrences. Chemotherapy is used based on the results of the MAGIC- and the OEO2-trials and chemoradiotherapy became part of standard treatment after the publication of the CROSS-trial. Although several studies have compared the efficacy of neoadjuvant chemotherapy and chemoradiotherapy, no robust evidence on the optimal neoadjuvant treatment has been obtained as yet. Several studies indirectly comparing both modalities suggest a benefit for chemoradiotherapy in the number of pathologically complete responders, radical resection rate and possibly even in overall survival. Large randomized controlled trials like the Neo-AEGIS-, ESOPEC- and NeXT-trials are currently addressing this topic. A relatively new aspect of esophageal cancer treatment is the administration of monoclonal antibodies. Several monoclonal antibodies have been tested in, mostly, advanced esophageal cancer treatment. Cetuximab has also been tested as addition to neoadjuvant- and definitive treatment in patients with locally advanced esophageal cancer, showing mixed results. This review aims at providing an overview of the currently available neoadjuvant treatments in esophageal cancer.

K, Kannoth Manheri M. Serine- and threonine-derived diamine equivalents for site-specific incorporation of platinum centers in peptides, and the anticancer potential of these conjugates

A modular strategy that gives access to a library of peptide–Pt conjugates and their anticancer potential is presented.

EGFR monoclonal antibodies in locally advanced head and neck squamous cell carcinoma: What is their current role?

Treatment options for locally advanced squamous cell carcinoma of the head and neck (SCCHN) include either surgical resection followed by radiation or chemoradiation, or definitive chemoradiation for which single-agent cisplatin is the best studied and established. The increasing understanding of the molecular biology of SCCHN has led to an interest in the development of targeted therapies. The epidermal growth factor receptor (EGFR) is over-expressed in nearly 80-90% of cases of SCCHN and correlates with poor prognosis and resistance to radiation. Preclinical evidence showed that blocking EGFR restores radiation sensitivity and enhances cytotoxicity. This finding led to clinical trials evaluating this class of agents and the approval of cetuximab in combination with radiation for the treatment of locally advanced SCCHN. This review is focused on the anti-EGFR monoclonal antibodies and their role either with radiotherapy or chemoradiation in unresectable LA SCCHN.

Quadruplex DNA-Stabilising Dinuclear Platinum(II) Terpyridine Complexes with Flexible Linkers

Four dinuclear terpyridineplatinum(II) (Pt-terpy) complexes were investigated for interactions with G-quadruplex DNA (QDNA) and duplex DNA (dsDNA) by synchrotron radiation circular dichroism (SRCD), fluorescent intercalator displacement (FID) assays and fluorescence resonance energy transfer (FRET) melting studies. Additionally, computational docking studies were undertaken to provide insight into potential binding modes for these complexes. The complexes demonstrated the ability to increase the melting temperature of various QDNA motifs by up to 17 °C and maintain this in up to a 600-fold excess of dsDNA. This study demonstrates that dinuclear Pt-terpy complexes stabilise QDNA and have a high degree of selectivity for QDNA over dsDNA.

The conformation effect of the diamine bridge on the stability of dinuclear platinum(II) complexes and their hydrolysis

In this paper, the hydrolysis process of a bisplatinum complex containing the flexible chain 1,6-hexanediamine between the two metal centers was investigated through the use of density functional theory (DFT) with the analysis of the role of the spacing group arrangement on the values of free energy activation barrier. All structures were fully optimized in aqueous solution using implicit model for solvent at DFT level. The energy profiles for the hydrolysis reaction were determined by using the supermolecule approach. Five transition states were proposed differing by the conformation of the bridge group, and the activation free energy calculated as a weighted average within the selected forms. The Gibbs population for reactant was used as a statistical weight leading to the predicted value of 23.1kcalmol(-1), in good accordance with experiment, 23.8kcalmol(-1). Our results suggests that for 1,6-hexanediamine bridge ligand, the extend forms with average torsional angle over the carbon chain larger than 130° have the greatest contribution to the hydrolysis kinetics. The results presented here point out that the hydrolysis mechanism might follow different paths for each conformation and each of these contributes to the observed energy barrier.

Synthesis, cytotoxicity, DNA interaction and cell cycle studies of trans-diiodophosphine Pt(ii) complexes

Diiodido phosphine Pt complexes were synthesized and their biological activity studied. The complex with isopropylamine was the best candidate.

Increased toxicity of a trinuclear Pt-compound in a human squamous carcinoma cell line by polyamine depletion

BACKGROUND

Mononuclear platinum anticancer agents hold a pivotal place in the treatment of many forms of cancers, however, there is a potential to improve response to evade resistance development and toxic side effects. BBR3464 is a promising trinuclear platinum anticancer agent, which is a polyamine mimic. The aim was to investigate the influence of polyamine pool reduction on the cytotoxic effects of the trinuclear platinum complex BBR3464 and cisplatin. Polyamine pool reduction was achieved by treating cells with either the polyamine biosynthesis inhibitor α-difluoromethylornithine (DFMO) or the polyamine analogue N1,N11-diethylnorspermine (DENSPM).

METHODS

A human squamous cell carcinoma cell line, LU-HNSCC-4, established from a primary head and neck tumour was used to evaluate cellular effects of each drug alone or combinations thereof. High-performance liquid-chromatography was used to quantify intracellular polyamine contents. Inductively coupled mass spectroscopy was used to quantify intracellular platinum uptake. Cells were exposed to DFMO or DENSPM during 48 h at concentrations ranging from 0 to 5 mM or 0 to 10 μM, respectively. Thereafter, non-treated and treated cells were exposed to cisplatin or BBR3464 during 1 h at concentrations ranging from 0 to 100 μM. A 96-well assay was used to determine cytotoxicity after five days after treatment.

RESULTS

The cytotoxic effect of BBR3464 on LU-HNSCC-4 cells was increased after cells were pre-treated with DENSPM or DFMO, and the interaction was found to be synergistic. In contrast, the interaction between cisplatin and DFMO or DENSPM was near-additive to antagonistic. The intracellular levels of the polyamines putrescine and spermidine were decreased after treatment with DFMO, and treatment with DENSPM resulted in an increase in putrescine level and concomitant decrease in spermidine and spermine levels. The uptake of BBR3464 was significantly increased after pre-treatment of the cells with DFMO, and varied dependent on the concentration of DENSPM. The uptake of cisplatin was unchanged.

CONCLUSIONS

Taken together, these results demonstrate that combinations of polyamine synthesis inhibitors with BBR3464 appear to be a promising approach to enhance the anticancer activity against HSCC.

Erlotinib or gefitinib for the treatment of relapsed platinum pretreated non-small cell lung cancer and ovarian cancer: a systematic review

BACKGROUND

Platinum-based chemotherapy is the standard of care for ovarian cancer and non-small cell lung cancer (NSCLC). However, resistance to platinum agents invariably develops. Targeted therapies, such as tyrosine kinase inhibitors (TKIs), have great potential here as they exert their anti-tumour effect via alternative mechanisms to platinum-based drugs and as such may remain unaffected by emergent resistance to platinum.

METHODS

A systematic review was conducted to investigate whether two EGFR-TKIs, erlotinib and gefitinib, have efficacy in the platinum-resistance setting. Preclinical studies of platinum-resistant cancer cell lines, which had been subsequently treated with EGFR-TKIs, were sought to establish proof-of-concept. Clinical trials reporting administration of EGFR-TKIs to ovarian cancer and NSCLC patients relapsed after therapy with platinum drugs were investigated to determine sensitivity of these cohorts to EGFR-TKI treatment. The role of EGFR mutation, copy number and protein expression on response to EGFR-TKIs after failure of platinum chemotherapy were also investigated.

RESULTS

Preclinical models of platinum-resistant cancer were found which display a spectrum of cross-resistance profiles to EGFR-TKIs. Sensitivity to EGFR-TKIs is dependent on the activation of the EGFR pathway or EGFR interacting proteins such as HER-2. EGFR-TKIs show favourable response rates in platinum-pretreated NSCLC, 11.14% and 15.25% for 150mg/day erlotinib and 250mg/day gefitinib, respectively. These response rates significantly improve in patients of Asian descent (28.3% and 29.17%, respectively) and patients with EGFR activation mutations (41.6% and 63.89%, respectively) or increased copy number (33.3% and 45.45%, respectively). Gefitinib significantly outperformed erlotinib and should therefore be the EGFR-TKI of choice in platinum-pretreated relapsed NSCLC. In contrast, response rates are very poor to both erlotinib and gefitinib in platinum pretreated ovarian cancer, 0-5.9% and they should not be used in this cohort of patients. Preclinical models demonstrate that, while cross resistance can occur between platinums and EGFR-TKIs, there is not a generalised cross-resistance phenotype. Erlotinib and gefitinib are suitable for the treatment of platinum-pretreated NSCLC, particularly in patients with EGFR mutations or increases in copy number. Unfortunately, the high rates of EGFR protein overexpression in ovarian cancer are not translating to a clinically useful therapeutic target for EGFR-TKIs; EGFR mutations are rare in ovarian cancer. Newer TKIs may improve response rates in these cohorts and future clinical trials need to collect tumour biopsies from all patients to ensure the success of personalised chemotherapy.

Combined action of the dinuclear platinum compound BBR3610 with the PI3-K inhibitor PX-866 in glioblastoma

Polynuclear platinum compounds are more effective at killing glioblastoma cells than cisplatin, work by a different mechanism, and typically do not induce high levels of apoptosis at early time points after exposure. Here, we tested the hypothesis that combining BBR3610, the most potent polynuclear platinum, with a phosphoinositide-3-kinase (PI3K) inhibitor would promote apoptosis and enhance the impact on glioblastoma cells. The PI3K pathway is commonly activated in glioblastoma and promotes tumor cell survival, suggesting that its inhibition would make cells more sensitive to cytotoxic agents. We chose PX-866 as a PI3K inhibitor as it is a clinically promising agent being evaluated for brain tumor therapy. Combining BBR3610 and PX-866 resulted in synergistic killing of cultured glioma cells and an extension of survival in an orthotopic xenograft animal model. Both agents alone induced autophagy, and this appeared to be saturated, because when they were combined no additional autophagy was observed. However, the combination of PX-866 and BBR3610 did induce statistically significant increases in the level of apoptosis, associated with a reduction in pAkt and pBad, as well as inhibition of transwell migration. We conclude that combining polynuclear platinums with PI3K inhibitors has translational potential and alters the cellular response to include early apoptosis.

Excursions in polynuclear platinum DNA binding

Polynuclear platinum agents are a structurally unique class of anti-cancer drugs, distinct from the cisplatin family. To describe the chemistry and biology of this class, it was necessary to challenge the accepted paradigms for the structure-activity relationships; design new chemotypes and delineate the structures and consequences of their DNA binding modes. This article summarizes the structural changes induced in DNA by both covalent (bond-forming) and non-covalent (ligand recognition) adducts. Solution (Nuclear Magnetic Resonance), solid state (crystallography) and gas-phase (Electrospray Ionization Mass Spectrometry) techniques have all been used to describe the new DNA structures along with molecular biological techniques. The combined approaches allow molecular description of hitherto unobserved adducts such as long-range major-groove interstrand crosslinks; directional isomers on DNA and a third class of ligand-DNA binding, the phosphate clamp. The phosphate recognition is distinct from ''classic'' minor-groove recognition or intercalation.

The polynuclear platinum BBR3610 induces G2/M arrest and autophagy early and apoptosis late in glioma cells

BBR3610 is a polynuclear platinum compound, in which two platinums are linked by a spermine-like linker, and studies in a variety of cancers, including glioma, have shown that it is more potent than conventional platinums and works by different means. Identifying the mechanism of action of BBR3610 would help in developing the drug further for clinical use. Previous work showed that BBR3610 does not induce immediate apoptosis but results in an early G2/M arrest. Here, we report that BBR3610 induces early autophagy in glioma cells. Increased autophagy was also seen in intracranial xenografts treated with BBR3610. Interestingly, upon attenuation of autophagy by RNAi-mediated knockdown of ATG5 or ATG6/BECN1, no change in cell viability was observed, suggesting that the autophagy is neither an effective protection against BBR3610 nor an important part of the mechanism by which BBR3610 reduces glioma cell viability. This prompted a multimodal analysis of 4 cell lines over 2 weeks posttreatment with BBR3610, which showed that the G2/M arrest occurred early and apoptosis occurred later in all cell lines. The cells that survived entered a senescent state associated with mitotic catastrophe in 2 of the cell lines. Together, our data show that the response to treatment with a single agent is complex and changes over time.

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.

The role of p53 in the cellular toxicity by active trans-platinum complexes containing isopropylamine and hydroxymethylpyridine

Despite some initial research that reported a lack of activity of trans geometry, complexes with general formula trans-[PtCl2(L)(L')] exhibit an important cytotoxic activity in cisplatin-sensitive and resistant cell lines. Based on the proposed mechanism of action for the trans-platinum compounds, they might form DNA adducts initiating a DNA-damage response and ultimately ending in the activation of the p53 protein. In the present work, we have studied the biochemical properties of the trans-[PtCl2(isopropylamine)(L)] complexes (where L is 3- or 4-(hydroxymethyl)-pyridine) against several cell lines and the relationship between cytotoxicity and the protein p53. Both complexes showed different antitumoral properties depending on the presence or absence of protein p53 in isogenic colon carcinoma HCT116 cell lines. Cell cycle studies with the complexes in these cell lines were performed to investigate their antitumoral activity. Apoptosis was observed to be launched from G1 or G2/M accumulations. Confocal microscopy showed the different behaviour of isogenic tumoral cell lines treated with the trans-platinum complexes. Our data suggest that small differences in the carrier ligands could play an important role in the overall biological effects. The body of the research regarding structure-activity relationships such as the different position of groups in the carrier ligands will provide new rational basis for the design of new platinum antitumor drugs.

New approaches to pharmacotherapy of tumors of the nervous system during childhood and adolescence

Tumors of the nervous system are among the most common and most chemoresistant neoplasms of childhood and adolescence. Malignant tumors of the brain collectively account for 21% of all cancers and 24% of all cancer-related deaths in this age group. Neuroblastoma, a peripheral nervous system tumor, is the most common extracranial solid tumor of childhood, and 65% of children with this tumor have only a 10 or 15% chance of living 5 years beyond the time of initial diagnosis. Novel pharmacological approaches to nervous system tumors are urgently needed. This review presents the role of and current challenges to pharmacotherapy of malignant tumors of the nervous system during childhood and adolescence and discusses novel approaches aimed at overcoming these challenges.

Pharmacotherapy for adults with tumors of the central nervous system

Tumors of the adult central nervous system are among the most common and most chemoresistant neoplasms. Malignant tumors of the brain and spinal cord collectively account for approximately 1.3% of all cancers and 2.2% of all cancer-related deaths. Novel pharmacological approaches to nervous system tumors are urgently needed. This review presents the current approaches and challenges to successful pharmacotherapy of adults with malignant tumors of the central nervous system and discusses novel approaches aimed at overcoming these challenges.

Improving platinum(II)-based anticancer drug delivery using cucurbit[n]urils

Despite the synthesis of hundreds of new platinum(II) and platinum(IV)-based complexes each year as potential anticancer drugs, only three have received world-wide approval: cisplatin, carboplatin and oxaliplatin. The next big advance in platinum-based chemotherapy is not likely to come from the development of new drugs, but from the controlled and targeted delivery of already approved drugs or those in late stage clinical trials. Encapsulation of platinum drugs inside macromolecules has already demonstrated promise, and encapsulation within cucurbit[n]urils has shown particular potential. Partial or full encapsulation within cucurbit[n]urils provides steric hindrance to drug degradation by peptides and proteins, and the use of different sized cucurbit[n]urils allows for the tuning of drug release rates, cytotoxicity and toxicity.

Serum soluble Fas levels and prediction of response to platinum-based chemotherapy in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is treated mainly by platinum-based combination chemotherapy. Chemotherapy induces apoptosis in which the Fas/Fas ligand pathway is important. Serum soluble Fas (sFas) is a biomarker of this pathway and functionally inhibits Fas-/FasL-mediated apoptosis. In this study, we have investigated the role of sFas in prediction of response to chemotherapy in EOC. Thirty-five patients were recruited and their serum sFas levels were estimated by ELISA at 4 time points-preoperative (sFas1), postoperative (sFas2), midchemotherapy (sFas3) and at the end of chemotherapy (sFas4). The response to chemotherapy was documented clinically, radiologically and by CA-125 levels, based on which, 2 groups were identified: primary chemosensitive (n = 24) and primary chemoresistant (n = 11). Based on the disease status at last follow-up, 2 groups were identified: No Evidence of Disease (n = 15) and Evidence of Disease (n = 20). The primary chemoresistant tumors showed significantly higher median sFas2 levels (p = 0.033) with the sFas2/sFas1 ratio > or =1 (p = 0.001). A multivariate Cox proportional hazards regression model identified sFas2/sFas1 ratio as a significant factor for the prediction of response to platinum-based chemotherapy (p = 0.011). Receiver operating characteristic (ROC) analysis showed that at a ratio of 1.2, sFas2/sFas1 achieved a sensitivity of 82% and specificity of 100% for prediction of chemotherapeutic response. sFas2/sFas1 and sFas3/sFas1 ratio was also higher in patients with evidence of disease (p = 0.018 and p = 0.028, respectively). Progression-free survival rates in patients with sFas2/sFas1 ratio <1 exceeded those with ratio > or =1 (p = 0.004). In conclusion, serum sFas is a useful biomarker for predicting response to platinum-based chemotherapy in EOC.

Trans-platinum(II) complexes with cyclohexylamine as expectator ligand induce necrosis in tumour cells by inhibiting DNA synthesis and RNA transcription

BACKGROUND

Enhanced removal of cisplatin-DNA adducts has been reported as one of main causes of cell resistance to cisplatin. This particular resistance mechanism may be circumvented by platinum complexes that bind differently to DNA. One line of work is focussed on trans platinum complexes, some of which exhibit antitumour activity similar to or even higher than that of their cis counterparts.

METHODS

We synthesised new trans platinum complexes, trans-[PtCl2(cyclohexylamine)(dimethylamine)] and trans-[PtCl2(OH)2(cyclohexylamine)(dimethylamine)], previously evaluated as cytotoxic agents towards different cancer and normal cell lines. These trans platinum compounds were highly effective against a panel of tumoral cell lines either sensitive to or with acquired resistance to cisplatin.

RESULTS

In the present work we examined the mechanisms induced by these compounds to cause tumour cells toxicity. We have found that these compounds induced a complete blockade at the S phase of the cell cycle inhibiting total mRNA transcription and precluding p53 activation.

CONCLUSION

In contrast to other DNA-damaging agents, these compounds do not induce senescence-associated permanent arrest. Furthermore, only a small percentage of these cells enter into apoptosis, with most of the population dying by a necrosis-like mechanism.

Synthesis, characterization, and in vitro evaluation of a potentially selective anticancer, mixed-metal [ruthenium(III)-platinum(II)] trinuclear complex

A new type of mixed-metal trinuclear complex containing platinum(II) and ruthenium(III) fragments that resemble both cisplatin and NAMI-A has been synthesized and characterized by IR, 1H NMR, elemental analysis, and X-ray crystallography. The water-soluble compound Na2{trans,cis,trans-[RuIIICl4(DMSO-S)(mu-pyz)]2PtIICl2} (AH-197, pyz = pyrazine) was assessed for its effects on DNA mobility and toxicity against human cancer cell lines. When compared to cisplatin and KP-1019 (which structurally resembles NAMI-A), IC50 results showed that AH-197 had an intermediate toxicity. When this data was coupled with a subsequent COMPARE evaluation (standard COMPARE queries resulted in insignificant correlation coefficients (<0.70) while very low COMPARE correlation coefficients were found in the matrix queries as well), AH-197 yielded a correlation coefficient of 0.19 when compared to cisplatin and 0.25 when compared to KP1019 indicating that AH-197 has a unique behavior.

The influence of temperature on antiproliferative effects, cellular uptake and DNA platination of the clinically employed Pt(II)-drugs

Cellular uptake of a drug is one of the most important factors influencing its pharmacodynamics and pharmacokinetics. Our laboratory has previously studied platinum uptake following cisplatin, carboplatin and oxaliplatin treatment at sub-lethal doses of selected tumour cell lines. Here we report on the influence of temperature on dose-dependent antiproliferative effects, cellular uptake and DNA platination of these platinum-based drugs tested on MCF-7 human mammary carcinoma cell line. Inductively coupled plasma-mass spectrometry (ICP-MS) technique has been chosen to perform Pt determinations on cells treated with drug concentrations similar with those usually found in vivo in human plasma. The high sensitivity and analytical rapidity of this technique made possible to carry out a very large amount of Pt determinations (about 300) necessary for this study. Hyperthermia (43 degrees C) proved a synergistic effect with cisplatin on cell growth inhibition, while only an additive effect was demonstrated for carboplatin and oxaliplatin. This behaviour might be explained by the higher DNA platination ratio between data at 43 and 37 degrees C of cisplatin with respect to those of carboplatin and oxaliplatin.

The polyamines spermidine and spermine retard the platination rate of single-stranded DNA oligomers and plasmids

The presence of polyamines in living cells is crucial for survival. Due to their high net charge at physiological pH, polyamines effectively charge neutralize the phosphodiester backbone of DNA in an interaction that also may protect the DNA from external damage. We here present a study illustrating the influence of spermidine and spermine on the platination reactions of the model oligonucleotides d(T(6)GT(6)), d(T(12)GT(12)), and d(T(24)GT(24)), and the pUC18 DNA plasmid. The aquated forms of the anticancer active compounds cisplatin (cis-[Pt(NH(3))(2)Cl(2)]) and the major Pt(II) metabolite of JM216 (cis-[PtCl(2)(NH(3))(c-C(6)H(11)NH(2))], JM118) were used as platination reagents. The study shows that the kinetics for formation of the coordinative Pt-DNA adduct are strongly influenced by the presence of sub-millimolar polyamine concentrations. At polyamine concentrations in the muM-range, the reactions remain salt-dependent. In contrast, platination of pUC18 is effectively prevented at mM concentrations of both spermidine and spermine with the latter as the more potent inhibitor. The results suggest that variations of intracellular polyamine concentrations may have a profound influence on the efficacy by which cationically charged reagents interfere with DNA function in vivo by modulation of the preassociation conditions.

Newtrans-Platinum Drugs with Phosphines and Amines as Carrier Ligands Induce Apoptosis in Tumor Cells Resistant to Cisplatin

Cisplatin resistance observed in some human tumors has prompted research in platinum derivatives that can circumvent this effect. Despite initial works reporting lack of activity of trans-platinum derivatives, complexes with the general formula PtCl2(L)(L') exhibit cytotoxic activity in cisplatin-sensitive and -resistant cell lines. Here we reported the chemical and biological properties of seven platinum complexes with PPh3 or PMe2Ph in trans to several amines. They show important antitumoral properties in tumor cell lines. Among the compounds, those with a replacement of an ammine ligand in the inactive trans-DDP by a phosphine ligand have an important enhancement of their cytotoxic activity. In SKOV3, no G1 nor G2/M accumulation was observed after treatments, and apoptosis was launched probably by a mechanism independent of classical checkpoints activation. Our data indicate that our compounds are not cross-resistant with cisplatin and might be promising agents in the treatment of tumors unresponsive to cisplatin.

Vibrational spectroscopy studies on linear polyamines

Vibrational spectroscopy [both Raman and INS (inelastic neutron scattering)], coupled to quantum mechanical calculations, was used in order to perform a thorough structural analysis of linear polyamines and polynuclear polyamine metal chelates [e.g. with Pt(II) and Pd(II)] with potential anticancer activity. The complementarity of the Raman and INS spectroscopies was exploited in order to gain a better knowledge of the conformational behaviour of these systems. Moreover, the conjugation of the experimental spectroscopic data to the theoretical results allows us to obtain valuable information on the structural preferences of this kind of system, which may lead to the establishment of SARs (structure–activity relationships) ruling their biological activity. Some of the most significant results obtained by the ‘Molecular Physical-Chemistry’ Research Group of the University of Coimbra (Portugal) are reviewed here.

Increased sensitivity to the platelet-derived growth factor (PDGF) receptor inhibitor STI571 in chemoresistant glioma cells is associated with enhanced PDGF-BB-mediated signaling and STI571-induced Akt inactivation

The platelet-derived growth factor receptor (PDGFR) is a tyrosine kinase, implicated in the development and progression of different tumors, including gliomas. Chemoresistance is a common feature of malignant gliomas. Since receptor tyrosine kinases contribute to chemoresistance in tumors, we addressed whether PDGFR signaling might confer selective growth advantage to chemoresistant cells. The effects of the PDGFR inhibitor STI571 on proliferation and PDGFR signaling were compared in chemosensitive and cisplatin-selected, chemoresistant sublines derived from glioma and from two other PDGFR-expressing tumors (ovarian carcinoma and neuroblastoma). The chemoresistant glioma U87/Pt cells were twofold more sensitive to STI571 growth-inhibitory effects than the chemosensitive U87 cells, and two- to threefold more sensitive than five unrelated glioma cell lines. The other two paired cell lines were equally responsive. Sensitization of U87/Pt cells correlated with upregulation of the PDGF-B isoform and with PDGF-BB-induced Akt overactivation, which was prevented by STI571. STI571 specifically inhibited PDGF-BB-, but not PDGF-AA- or stem cell factor-mediated signaling. In serum-containing medium, STI571 decreased phospho-Akt in U87/Pt cells, but not in U87, while activating extracellular signal-regulated kinase (Erk) in both. STI571 antiproliferative effects were partially reverted by constitutively active Akt. Cotreatment with inhibitors of phosphatidylinositol 3'-kinase (PI3K) or mitogen-activated protein kinase kinase (MEK) resulted in enhanced growth inhibition in glioma cells. Our results suggest that increased PDGF-BB signaling may sensitize chemoresistant glioma cells to STI571, suggesting a therapeutic potential for STI571 in patients with malignant gliomas refractory to chemotherapy. Simultaneous blockade of PDGFR and PI3K or Erk pathway may enhance therapeutic targeting in gliomas.

Phase II study of BBR 3464 as treatment in patients with sensitive or refractory small cell lung cancer

BBR 3464 is a novel triplatinum compound that has exhibited anti-tumor activity in both cisplatin-sensitive and cisplatin-resistant, as well as in p53 mutant tumor models. In phase I testing, the dose-limiting toxicities have included myelosuppression and diarrhea. Both an intermittent (day 1 every 21-28 days) and a continuous (dailyx5 days) schedule have been studied, and the intermittent schedule has been chosen for further development. The primary objective of this study was to assess the efficacy of BBR 3464 administered at a dose of 0.9 mg/m i.v. over 1 h every 21 days in patients with small cell lung cancer who have progressed after first-line therapy. Pharmacokinetic analysis was also performed and will be reported. Patients were stratified based on prior response into resistant and sensitive (response duration 3 months or longer) subgroups. Thirty-seven patients were enrolled onto this multicenter study. The median number of cycles delivered was 2 in the resistant subgroup (range 1-12) and 3 in the sensitive subgroup (range 1-8). Most common grade 3/4 hematological toxicities included neutropenia (62%), febrile neutropenia (16%), anemia (10%), fatigue (5%) and hypokalemia (5%). Although no objective responses were seen in 34 evaluable patients, 11 patients (32%) had disease stabilization (four resistant/seven sensitive) with 23 patients (68%) experiencing continued disease progression (12 resistant/11 sensitive). Median time to progression was 53 days in the resistant subgroup [95% confidence interval (CI) 37-63] and 66 days in the sensitive subgroup (95% CI 51-136). The median and 1-year survival rate based on subgroup was 78 (resistant) (95% CI 56-165) versus 209 days (sensitive) (95% CI 83-296) and 6 (resistant) (95% CI 0-17) versus 20% (95% CI 2-38%), respectively. We conclude that the toxicity profile of BBR 3464 in this phase II trial is consistent with the phase I experience. The lack of activity in either patient subgroup, however, does not support further evaluation of this drug as a single agent in this disease.