The Role of α-Folate Receptor-Mediated Transport in the Antitumor Activity of Antifolate Drugs

Formulation of Folate Receptor-Targeted Silibinin-Loaded Inhalable Chitosan Nanoparticles by the QbD Approach for Lung Cancer Targeted Delivery

Aim: Targeted delivery of chemotherapeutics by functionalized nanoparticles exhibits a wonderful prospect for cancer treatment. The main objective of this research was to develop folate receptor-targeted silibinin (SB)-loaded inhalable polymeric nanoparticles (FA-CS-SB-NPs) for the treatment of lung cancer. Method: The qbD approach was implemented to prepare SB-loaded nanoparticles. Folic acid was conjugated by electrostatic conjugation in an optimized batch. The therapeutic potentials of formulations were determined using a lung cancer cell-bearing rat model. Result: Optimized formulation exhibited a spherical surface with a mean particle size of 275 ± 1.20 nm, a PDI of 0.234 ± 0.07, a ζ-potential of 32.50 ± 0.21, an entrapment efficiency of 75.52 ± 0.87%, and a CDR of 63.25 ± 1.21% at 48 h. Aerodynamic behaviors such as the mass median aerodynamic diameter (MMAD) and geometric size distribution (GSD) were found to be 2.75 ± 1.02 and 3.15 ± 0.88 μm, respectively. After 24 h of incubation with FA-CS-SB-NPs, the IC50 value was found to be 24.5 g/mL. FA-SB-CS-NPs maintained a significantly higher deposition of SB in lung tissues. Conclusions: Thus, the noninvasive nature and target specificity of FA-CS-SB-NPs pave the way for pulmonary delivery for treating lung cancer.

The development of folate-functionalised palladium nanoparticles for folate receptor targeting in breast cancer cells

Folate receptor-targeted therapy has excellent prospects for the treatment of breast cancer. A non-toxic concentration of folate-conjugated palladium-based nanoparticles was used to target the overexpressed folate receptor on breast cancer cells. The folate-conjugated nanoparticles were tailored to accumulate selectively in cancer cells relative to normal cells via the folate receptor. The MDA-MB-231, MDA-MB-468, MCF-7 breast cancer cell lines, and MCF-10A normal cell lines were used in the study. Qualitative and quantitative analysis of nanoparticle cellular uptake and accumulation was conducted using transmission electron microscopy and inductively coupled plasma-optical emission spectroscopy. The findings proved that folate-conjugated palladium nanoparticles successfully and preferentially accumulated in breast cancer cells. We conclude that folate-conjugated palladium nanoparticles can be potentially used to target breast cancer cells for radiopharmaceutical applications.

DHFR Inhibitors Display a Pleiotropic Anti-Viral Activity against SARS-CoV-2: Insights into the Mechanisms of Action

During the COVID-19 pandemic, drug repurposing represented an effective strategy to obtain quick answers to medical emergencies. Based on previous data on methotrexate (MTX), we evaluated the anti-viral activity of several DHFR inhibitors in two cell lines. We observed that this class of compounds showed a significant influence on the virus-induced cytopathic effect (CPE) partly attributed to the intrinsic anti-metabolic activity of these drugs, but also to a specific anti-viral function. To elucidate the molecular mechanisms, we took advantage of our EXSCALATE platform for in-silico molecular modelling and further validated the influence of these inhibitors on nsp13 and viral entry. Interestingly, pralatrexate and trimetrexate showed superior effects in counteracting the viral infection compared to other DHFR inhibitors. Our results indicate that their higher activity is due to their polypharmacological and pleiotropic profile. These compounds can thus potentially give a clinical advantage in the management of SARS-CoV-2 infection in patients already treated with this class of drugs.

Initial Stages of Spontaneous Binding of Folate-Based Vectors to Folate Receptor-α Observed by Unbiased Molecular Dynamics

Active targeting is a prospective strategy for controlled drug delivery to malignant tumor tissues. One of the approaches relies on recognition of a bioactive ligand by a receptor expressed abundantly on the surface of cancer cell membranes. A promising ligand-receptor pair is folic acid (or its dianionic form, folate) combined with the folate receptor-α (FRα). A number of targeting drug delivery systems based on folate have been suggested, but the mechanism of binding of the ligand or its derivatives to the receptor is not fully known at the molecular level. The current study summarizes the results from unbiased all-atom molecular dynamics simulations at physiological conditions describing the binding of two forms of folate and four of its synthetically available derivatives to FRα. The models (ca. 185,000 atoms) contain one receptor molecule, embedded in the outer leaflet of a lipid bilayer, and one ligand, all immersed in saline. The bilayer represents a human cancer cell membrane and consists of 370 asymmetrically distributed lipid molecules from 35 types. The ability of the vector molecules to bind to the receptor, the position of binding, and the interactions between them are analyzed. Spontaneous binding on the nanosecond scale is observed for all molecules, but its time, position, and persistence depend strongly on the ligand. Only folate, 5-methyltetrahydrofolate, and raltitrexed bind selectively at the active site of the receptor. Two binding poses are observed, one of them (realized by raltitrexed) corresponding qualitatively to that reported for the crystallographic structure of the complex folate-FRα. Pemetrexed adsorbs nonspecifically on the protein surface, while methotrexate and pteroyl ornithine couple much less to the receptor. The molecular simulations reproduce qualitatively correctly the relative binding affinity measured experimentally for five of the ligands. Analysis of the interactions between the ligands and FRα shows that in order to accomplish specific binding to the active site, a combination of hydrogen bonding, π-stacking, and van der Waals and Coulomb attraction should be feasible simultaneously for the vector molecule. The reported results demonstrate that it is possible to observe receptor-ligand binding without applying bias by representing the local environment as close as possible and contain important molecular-level guidelines for the design of folate-based systems for targeted delivery of anticancer drugs.

Exposure-response analysis of Raltitrexed assessing liver toxicity

AIM

Raltitrexed (RTX) is a thymidylate synthase inhibitor with large pharmacokinetics (PK) variability that can be administered in case of 5-fluorouracil (5FU) intolerance or dihydropyrimidine dehydrogenase deficiency. While it is a more potent thymidylate synthase inhibitor than 5FU, RTX failed to replace this drug for colorectal cancer patients, mainly due to its toxicity at the recommended dose of 3 mg/m² every 3 weeks. However, every 2 weeks administration at 2 mg/m² demonstrated a favourable toxicity profile.

METHOD

We performed a randomized crossover comparative population PK study between every 2 weeks TOMOX (RTX 2 mg/m² ) and every 3 weeks TOMOX (RTX 3 mg/m² ).

RESULTS

A three-compartment model and a proportional error model best describe the data. Creatinine clearance and sex, but not body surface area (BSA), were covariates of RTX clearance leading to decrease of its interindividual variability of 28%. Weight and body surface area were covariates of central and peripheral volumes of distribution, respectively, leading to decreases of interindividual variability of 34.6% and 100%, respectively. In contrast to the dose, AUC was a good predictor of liver toxicity (P = 0.006, OR = 3.91, 95%CI = [1.48-10.34]). Using covariates to compute individual clearance and a threshold AUC (1.639, determined in this study), a covariates-based dose was calculated, leading to less variability in AUC than observed with the actual BSA-based or fixed doses.

CONCLUSION

These results advocate for the use of creatinine clearance and sex to determine the RTX dose instead of BSA.

Folate receptor-positive circulating tumor cells as a predictive biomarker for the efficacy of first-line pemetrexed-based chemotherapy in patients with non-squamous non-small cell lung cancer

Background

There is a lack of well-established biomarkers to predict the efficacy of pemetrexed-based chemotherapy. In this prospective phase II study, we investigated the correlation of folate receptor (FR)-positive circulating tumor cell (CTC) level with the clinical outcomes of patients with advanced non-squamous non-small cell lung cancer (nsNSCLC) when treated with pemetrexed-based chemotherapy.

Methods

A total of 98 nsNSCLC patients were enrolled. Peripheral blood was collected from each patient prior to initiation of treatment. FR-positive CTCs were enriched by immunomagnetic leukocyte depletion and quantified using ligand-targeted polymerase chain reaction (LT-PCR) method.

Results

Patients with relatively low CTC level (11–16 FU/3 mL, n=32) showed a significantly shorter progression-free survival (PFS) and overall survival (OS) compared with those in the “high CTC level group” (>16 FU/3mL, n=28; median PFS, 133 versus 320 days, P<0.001; median OS, 632 days versus “not reached”, P=0.003). Patients in the “high CTC level group” also achieved superior objective response rate (ORR) and disease control rate (DCR) over those in the “low CTC level group” (ORR, 40.9% versus 9.5%, P=0.0339; DCR, 100% versus 81.0%, P=0.0485). The clinical outcomes of pemetrexed in the “negative-CTC group” (<11 FU/3mL, n=38) fell between the “high CTC level group” and the “low CTC level group” (median PFS, 290 days; median OS, 1,122 days; ORR: 21.2%, DCR: 93.9%). Further multivariate Cox proportional hazards regression analysis demonstrated that “high CTC level” was an independent factor that was significantly associated with better PFS [hazard ratio (HR) =0.26, 95% confidence interval (CI), 0.12–0.58, P=0.001] and OS (HR =0.23, 95% CI, 0.06–0.92, P=0.037).

Conclusions

Our results implied that FR-positive CTC is a promising biomarker to predict the clinical outcome of pemetrexed-based chemotherapy in patients with advanced nsNSCLC.

Role of Folic Acid in the Therapeutic Action of Nanostructured Porous Silica Functionalized with Organotin(IV) Compounds Against Different Cancer Cell Lines

The synthesis, characterization and cytotoxic activity against different cancer cell lines of various mesoporous silica-based materials containing folate targeting moieties and a cytotoxic fragment based on a triphenyltin(IV) derivative have been studied. Two different mesoporous nanostructured silica systems have been used: firstly, micronic silica particles of the MSU-2 type and, secondly, mesoporous silica nanoparticles (MSNs) of about 80 nm. Both series of materials have been characterized by different methods, such as powder X-ray diffraction, X-ray fluorescence, absorption spectroscopy and microscopy. In addition, these systems have been tested against four different cancer cell lines, namely, OVCAR-3, DLD-1, A2780 and A431, in order to observe if the size of the silica-based systems and the quantity of incorporated folic acid influence their cytotoxic action. The results show that the materials are more active when the quantity of folic acid is higher, especially in those cells that overexpress folate receptors such as OVCAR-3 and DLD-1. In addition, the study of the potential modulation of the soluble folate receptor alpha (FOLR1) by treatment with the synthesized materials has been carried out using OVCAR-3, DLD-1, A2780 and A431 tumour cell lines. The results show that a relatively high concentration of folic acid functionalization of the nanostructured silica together with the incorporation of the cytotoxic tin fragment leads to an increase in the quantity of the soluble FOLR1 secreted by the tumour cells. In addition, the studies reported here show that this increase of the soluble FOLR1 occurs presumably by cutting the glycosyl-phosphatidylinositol anchor of membrane FR-α and by the release of intracellular FR-α. This study validates the potential use of a combination of mesoporous silica materials co-functionalized with folate targeting molecules and an organotin(IV) drug as a strategy for the therapeutic treatment of several cancer cells overexpressing folate receptors.

Overview of Dual-Acting Drug Methotrexate in Different Neurological Diseases, Autoimmune Pathologies and Cancers

Methotrexate, a structural analogue of folic acid, is one of the most effective and extensively used drugs for treating many kinds of cancer or severe and resistant forms of autoimmune diseases. In this paper, we take an overview of the present state of knowledge with regards to complex mechanisms of methotrexate action and its applications as immunosuppressive drug or chemotherapeutic agent in oncological combination therapy. In addition, the issue of the potential benefits of methotrexate in the development of neurological disorders in Alzheimer’s disease or myasthenia gravis will be discussed.

Development of Copper Nanoclusters for In Vitro and In Vivo Theranostic Applications

Theranostics refers to the incorporation of therapeutic and diagnostic functions into one material system. An important class of nanomaterials exploited for theranostics is metal nanoclusters (NCs). In contrast to gold and silver NCs, copper is an essential trace element for humans. It can be more easily removed from the body. This, along with the low cost of copper that offers potential large-scale nanotechnology applications, means that copper NCs have attracted great interest in recent years. The latest advances in the design, synthesis, surface engineering, and applications of copper NCs in disease diagnosis, monitoring, and treatment are reviewed. Strategies to control and enhance the emission of copper NCs are considered. With this synopsis of the up-to-date development of copper NCs as theranostic agents, it is hoped that insights and directions for translating current advances from the laboratory to the clinic can be further advanced and accelerated.

Mechanisms of resistance to pemetrexed in non-small cell lung cancer

Currently, lung cancer has remained the most common cause of cancer death while non-small cell lung cancer (NSCLC) accounts for the most of all lung cancer cases. Regardless of multiple existing managements, chemotherapy regimens are still the mainstay of treatment for NSCLC, where pemetrexed has shown cytotoxic activity and has increasingly been used, especially for advanced cases. However, chemo-resistance may inhibit clinical efficacy after long-term use. Mechanisms responsible for chemo-resistance to pemetrexed in NSCLC are plethoric but can be separated into two categories to be discussed: tumor cells and their interactions with drugs. Phenomena relevant to tumor cells such as oncogene or oncoprotein alterations, DNA synthesis, DNA repair, and tumor cell biology behavior are discussed, as well as processes associated with drug dynamics, including drug uptake, drug elimination, and antifolate polyglutamylation. This review will focus on clinical trials and the basic biomedical mechanisms of NSCLC treated with pemetrexed and will describe the underlying mechanisms of resistance to facilitate more efficient clinical therapies to treat patients.

Tumor Microenvironment Responsive Shape-Reversal Self-Targeting Virus-Inspired Nanodrug for Imaging-Guided Near-Infrared-II Photothermal Chemotherapy

Tumor microenvironment responsive multimodal synergistic theranostic strategies can significantly improve the therapeutic efficacy while avoiding severe side effects. Inspired by the fact that special morphology could enhance photothermal conversion efficiency (PCE) and cellular delivery, we developed an acidic tumor microenvironment responsive shape-reversal metal-organic virus-inspired nanodrug for enhancing near-infrared (NIR)-II PCE, increasing cell adhesion, and activating tumor targeting. First, a NIR-I fluorescence probe (IR825), a chemo-drug (pemetrexed, PEM), and a rare-earth metal ion (Nd(III)) were chosen to synthesize a virus-like nanodrug via coordination-driven assembly. Then, the spike-like surface of the nanodrug was further camouflaged by an acidity-sensitive poly(ethylene glycol) "shell" to create virus-core and sphere-shell hierarchical nanoassemblies, which could efficiently prevent immune clearance and prolong systemic circulation. Interestingly, the acidic tumor microenvironment could trigger the shell detachment of nanoassemblies for shape reversal to produce a virus-like surface followed by re-exposure of PEM to synergistically amplify the cellular internalization while enhancing NIR-II PCE. By utilizing the shell-detached virus-like nanodrug core, the tumor microenvironment specific enhanced NIR-II photothermal chemotherapy can be realized under the precise guidance of fluorescence/photoacoustic imaging, thereby achieving complete tumor elimination without recurrence in a single treatment cycle. We envision that integrating the tumor microenvironment responsive ability with  "sphere-to-virus" shape reversal will provide a promising strategy for biomimetic targeted cancer therapy.

RNA Micelles for the Systemic Delivery of Anti-miRNA for Cancer Targeting and Inhibition without Ligand

Displaying the advantage of nanoparticles in cancer targeting and drug delivery, micelles have shown great potential in cancer therapy. The mechanism for micelle targeting to cancer without the need for ligands is due to the size advantage of micelles within the lower end of the nanometer scale that is the optimal size for favoring the enhanced permeability and retention (EPR) effect while escaping trapping by macrophages. MicroRNAs are ubiquitous and play critical roles in regulating gene expression, cell growth, and cancer development. However, their in vivo delivery in medical applications is still challenging. Here, we report the targeted delivery of anti-miRNA to cancers via RNA micelles. The phi29 packaging RNA three-way junction (pRNA-3WJ) was used as a scaffold to construct micelles. An oligo with 8nt locked nucleic acid (LNA) complementary to the seed region of microRNA21(miR21) was included in the micelles as an interference molecule for cancer inhibition. These RNA micelles carrying anti-miR21 exhibited strong binding and internalization to cancer cells, inhibited the function of oncogenic miR21, enhanced the expression of the pro-apoptotic factor, and induced cell apoptosis. Animal trials revealed effective tumor targeting and inhibition in xenograft models. The inclusion of folate as a targeting ligand in the micelles did not show significant improvement of the therapeutic efficacy in vivo, suggesting that micelles can carry therapeutics to a target tumor and inhibit its growth without ligands.

Medicines associated with folate-homocysteine-methionine pathway disruption

Folate is vital for cell development and growth. It is involved in one-carbon transfer reactions essential for the synthesis of purines and pyrimidines. It also acts in conjunction with cobalamin (vitamin B₁₂) as a fundamental cofactor in the remethylation cycle that converts homocysteine to methionine. A deficiency in folate or vitamin B₁₂ can lead to elevated homocysteine level, which has been identified as an independent risk factor in several health-related conditions. Adequate folate levels are essential in women of childbearing age and in pregnant women, and folate deficiency is associated with several congenital malformations. Low folate levels can be caused by dietary deficiencies, a genetic predisposition or treatment with medicines that affect folate concentration. Women who are pregnant or of child-bearing age commonly use medicines, so it is important to identify the basic biochemical mechanisms by which medicines interfere with the folate-homocysteine-methionine pathway. This review focuses on prescription medicines associated with folate disruption. It also summarizes their undesirable/toxic effects. Recommendations regarding folate supplementation during medical therapy are also reviewed.

Chemistry and engineering of cyclodextrins for molecular imaging

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides bearing a basket-shaped topology with an "inner-outer" amphiphilic character. The abundance of hydroxyl groups enables CDs to be functionalized with multiple targeting ligands and imaging elements. The imaging time, and the payload of different imaging elements, can be tuned by taking advantage of the commercial availability of CDs with different sizes of the cavity. This review aims to offer an outlook of the chemistry and engineering of CDs for the development of molecular probes. Complexation thermodynamics of CDs, and the corresponding implications for probe design, are also presented with examples demonstrating the structural and physiochemical roles played by CDs in the full ambit of molecular imaging. We hope that this review not only offers a synopsis of the current development of CD-based molecular probes, but can also facilitate translation of the incremental advancements from the laboratory to real biomedical applications by illuminating opportunities and challenges for future research.

Preparation, Characterization, and Optimization of Folic Acid-Chitosan-Methotrexate Core-Shell Nanoparticles by Box-Behnken Design for Tumor-Targeted Drug Delivery

The objective of this study was to investigate the combined influence of independent variables in the preparation of folic acid-chitosan-methotrexate nanoparticles (FA-Chi-MTX NPs). These NPs were designed and prepared for targeted drug delivery in tumor. The NPs of each batch were prepared by coaxial electrospray atomization method and evaluated for particle size (PS) and particle size distribution (PSD). The independent variables were selected to be concentration of FA-chitosan, ratio of shell solution flow rate to core solution flow rate, and applied voltage. The process design of experiments (DOE) was obtained with three factors in three levels by Design expert software. Box-Behnken design was used to select 15 batches of experiments randomly. The chemical structure of FA-chitosan was examined by FTIR. The NPs of each batch were collected separately, and morphologies of NPs were investigated by field emission scanning electron microscope (FE-SEM). The captured pictures of all batches were analyzed by ImageJ software. Mean PS and PSD were calculated for each batch. Polynomial equation was produced for each response. The FE-SEM results showed the mean diameter of the core-shell NPs was around 304 nm, and nearly 30% of the produced NPs are in the desirable range. Optimum formulations were selected. The validation of DOE optimization results showed errors around 2.5 and 2.3% for PS and PSD, respectively. Moreover, the feasibility of using prepared NPs to target tumor extracellular pH was shown, as drug release was greater in the pH of endosome (acidic medium). Finally, our results proved that FA-Chi-MTX NPs were active against the human epithelial cervical cancer (HeLa) cells.

Folate receptor-targeted aminoglycoside-derived polymers for transgene expression in cancer cells

Targeted delivery of anticancer therapeutics can potentially overcome the limitations associated with current chemotherapeutic regimens. Folate receptors are overexpressed in several cancers, including ovarian, triple-negative breast and bladder cancers, making them attractive for targeted delivery of nucleic acid therapeutics to these tumors. This work describes the synthesis, characterization and evaluation of folic acid-conjugated, aminoglycoside-derived polymers for targeted delivery of transgenes to breast and bladder cancer cell lines. Transgene expression was significantly higher with FA-conjugated aminoglycoside-derived polymers than with Lipofectamine, and these polymers demonstrated minimal cytotoxicty. Competitive inhibition using free folic acid significantly reduced transgene expression efficacy of folate-targeted polymers, suggesting a role for folate receptor-mediated uptake. High efficacy FA-targeted polymers were employed to deliver a plasmid expressing the TRAIL protein, which induced death in cancer cells. These results indicate that FA-conjugated aminoglycoside-derived polymers are promising for targeted delivery of nucleic acids to cancer cells that overexpress folate receptors.

Chemotherapy Resistance in Lung Cancer

Despite a growing interest in development of non-cytotoxic targeted agents, systemic chemotherapy is still the mainstay of treatment for both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). However, chemotherapy resistance limits our ability to effectively treat advanced lung cancer. Some lung tumors are intrinsically resistant to chemotherapy, and in virtually all cases, even the initial responders rapidly develop acquired resistance. While targeting histology could result in enhanced tumor sensitivity to a particular chemotherapeutic agent, better understanding of molecular determinants of chemotherapy sensitivity/resistance would be critically important. Development of predictive biomarkers to personalize chemotherapeutic agents and combining novel agents targeting specific resistance pathways with standard chemotherapy could be some promising strategies to overcome chemotherapy resistance in lung cancer. In this chapter, we will discuss some key mechanisms of resistance for commonly used chemotherapeutic agents in lung cancer.

Determinants of the activities of antifolates delivered into cells by folate-receptor-mediated endocytosis

PURPOSE

Elements in the endocytic process that are determinants of the activities of antifolates delivered by folate-receptor alpha (FRα) were explored.

METHODS

Antifolate growth inhibition was assessed with a 1- or 5-day exposure in reduced folate carrier-null HeLa cell lines that express a high level of FRα in the presence or absence of the proton-coupled folate transporter (PCFT). pH-dependent rates of dissociation from FRα were also determined.

RESULTS

With a 1-day drug exposure which is relevant to the pulse clinical administration of these drugs, FRα expression enhanced raltitrexed activity and modestly enhanced ZD9331 activity, but did not significantly augment the activity of pemetrexed or lomotrexol. With a 5-day drug exposure, FRα-mediated growth inhibition was increased for raltitrexed and ZD9331 and emerged for lomotrexol. While the FRα-augmented activity of lomotrexol and raltitrexed did not require PCFT, augmentation of ZD9331 activity required the co-expression of PCFT with both 1- and 5-day exposures. In contrast, there was no augmentation of pemetrexed activity by FRα under any condition. The activities of these agents correlated with their rate of dissociation from the receptor at acidic pH: raltitrexed > ZD9331 > lomotrexol > pemetrexed consistent with insufficient pemetrexed release from FRα for export from the endosomes.

CONCLUSIONS

FRα is unlikely to contribute to the pharmacological activity of antifolates, such as pemetrexed, that bind tightly to, and dissociate slowly from, the receptor particularly when the exposure time is brief. While PCFT was required for FRα-mediated ZD9931 activity, the activities of the other antifolates was independent of PCFT.

Associations between TS, TTF-1, FR-α, FPGS, and overall survival in patients with advanced non-small-cell lung cancer receiving pemetrexed plus carboplatin or gemcitabine plus carboplatin as first-line chemotherapy

INTRODUCTION

Pemetrexed is effective in the treatment of non-small-cell lung cancer, mainly in nonsquamous cell carcinomas. Inhibition of thymidylate synthase (TS) is considered the key mechanism of action. Folate receptor-α facilitates uptake of pemetrexed. Polyglutamation by folylpolyglutamate synthetase enhances activity and prolongs cellular retention of pemetrexed. Thyroid transcription factor-1 (TTF-1) is mainly positive in nonsquamous cell carcinoma and has been proposed as a marker for sensitivity to pemetrexed. The aim was to investigate associations between these biomarkers and survival in patients who participated in a phase III trial comparing pemetrexed plus carboplatin with gemcitabine plus carboplatin as first-line chemotherapy in advanced non-small-cell lung cancer (n = 436). In this study, there was no difference in overall survival between the two regimens.

METHODS

Formalin-fixed, paraffin-embedded biopsies were collected. Percentages of tumor cells positive and highly positive for the biomarkers were assessed using immunohistochemistry (IHC) and an IHC score was calculated (range, 0-200).

RESULTS

Two hundred thirty-six biopsies were analyzed (pemetrexed plus carboplatin: n = 114, gemcitabine plus carboplatin: n = 122). There was a significant difference in overall survival between those with TTF-1-positive and -negative tumors (10.4 versus 6.0 months; p < 0.001) and those with a low and a high TS IHC score (9.7 versus 6.2 months; p < 0.001). Folate receptor-α and folylpolyglutamate synthetase were not significant prognostic factors. In multivariate analyses adjusting for established prognostic characteristics, TS (p = 0.002) and TTF-1 (p = 0.003) remained significant. There were no differences in survival between the treatment arms depending on biomarker scores.

CONCLUSIONS

TTF-1 positivity and low TS level were associated with prolonged survival. The associations between the biomarkers and overall survival were similar for both chemotherapy regimens.

Antifolate agents: a patent review (2010 - 2013)

INTRODUCTION

The folate biosynthetic pathway, responsible for the de novo synthesis of thymidine and other key cellular components, is essential in all life forms and is especially critical in rapidly proliferating cells. As such, druggable targets along this pathway offer opportunities to impact many disease states such as cancer, infectious disease and autoimmune disease. In this article, recent progress on the development of antifolate compounds is reviewed.

AREAS COVERED

The evaluation of the patent literature during the period 2010 - 2013 focused on any compounds inhibiting recognized targets on the folate biosynthetic pathway.

EXPERT OPINION

The folate pathway constitutes a well-validated and well-characterized set of targets; this pathway continues to elicit considerable enthusiasm for new drug discovery from both academic and industrial pharmaceutical research groups. Within the pathway, the enzymes dihydrofolate reductase and thymidylate synthase persist as the most attractive targets for new drug discovery for the treatment of cancer and infectious disease. Importantly, new potential targets for antifolates such as those on the purine biosynthetic pathway have been recently explored. The use of structure-based drug design is a major aspect in modern approaches to these drug targets.

Cyclodextrins in non-viral gene delivery

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides. They consist of (α-1,4)-linked glucose units, and possess a basket-shaped topology with an "inner-outer" amphiphilic character. Over the years, substantial efforts have been undertaken to investigate the possible use of CDs in drug delivery and controlled drug release, yet the potential of CDs in gene delivery has received comparatively less discussion in the literature. In this article, we will first discuss the properties of CDs for gene delivery, followed by a synopsis of the use of CDs in development and modification of non-viral gene carriers. Finally, areas that are noteworthy in CD-based gene delivery will be highlighted for future research. Due to the application prospects of CDs, it is anticipated that CDs will continue to emerge as an important tool for vector development, and will play significant roles in facilitating non-viral gene delivery in the forthcoming decades.

Advances in personalized therapy for lung cancer

INTRODUCTION

Personalized medicine based on tumor characteristics is transforming the management of lung cancer. This review provides an overview of clinically approved strategies to personalize treatment for lung cancer as well as evolving strategies in various stages of clinical development.

AREAS COVERED

Selecting therapy based on various tumor characteristics such as histology and presence of specific molecular alterations will be covered. This review will not only discuss the role of targeted agents in personalizing care for lung cancer but also the strategies to personalize traditional chemotherapeutic agents.

EXPERT OPINION

Advances in genomic medicine to identify key genetic alterations with subsequent development of matching targeted agents are rapidly changing the management of lung cancer. Being able to target key driver molecular aberrations is certainly exciting and clinically meaningful, but only for a limited period of time. Intra- and intertumoral heterogeneity is a major contributor to therapy resistance, a substantial roadblock to durable response. Better understanding of resistance mechanism is at least as important as identifying new targetable genetic changes to effectively advance personalized therapy for lung cancer. Finally, optimization of biopsy specimens and rigorous validation steps to ensure reliability of diagnostic methods would be critical in moving forward.

Development and binding mode assessment of N-[4-[2-propyn-1-yl[(6S)-4,6,7,8-tetrahydro-2-(hydroxymethyl)-4-oxo-3H-cyclopenta[g]quinazolin-6-yl]amino]benzoyl]-l-γ-glutamyl-D-glutamic acid (BGC 945), a novel thymidylate synthase inhibitor that targets tumor cells

N-[4-[2-Propyn-1-yl[(6S)-4,6,7,8-tetrahydro-2-(hydroxymethyl)-4-oxo-3H-cyclopenta[g]quinazolin-6-yl]amino]benzoyl]-l-γ-glutamyl-d-glutamic acid 1 (BGC 945, now known as ONX 0801), is a small molecule thymidylate synthase (TS) inhibitor discovered at the Institute of Cancer Research in London. It is licensed by Onyx Pharmaceuticals and is in phase 1 clinical studies. It is a novel antifolate drug resembling TS inhibitors plevitrexed and raltitrexed that combines enzymatic inhibition of thymidylate synthase with α-folate receptor-mediated targeting of tumor cells. Thus, it has potential for efficacy with lower toxicity due to selective intracellular accumulation through α-folate receptor (α-FR) transport. The α-FR, a cell-surface receptor glycoprotein, which is overexpressed mainly in ovarian and lung cancer tumors, has an affinity for 1 similar to that for its natural ligand, folic acid. This study describes a novel synthesis of 1, an X-ray crystal structure of its complex with Escherichia coli TS and 2'-deoxyuridine-5'-monophosphate, and a model for a similar complex with human TS.

A fast chemoenzymatic synthesis of [11C]-N5,N10-methylenetetrahydrofolate as a potential PET tracer for proliferating cells

INTRODUCTION

Thymidylate synthase and folate receptors are well-developed targets of cancer therapy. Discovery of a simple and fast method for the conversion of 11CH3Ito[11C]-formaldehyde (11CH2O) encouraged us to label the co-factor of this enzyme. Preliminary studies conducted on cell lines have demonstrated a preferential uptake of [11-14C]-(R)-N5,N10-methylene-5,6,7,8-tetrahydrofolate (14CH2H4folate) by cancerous cell vs. normal cells from the same organ (Saeed M., Sheff D. and Kohen A. Novel positron emission tomography tracer distinguishes normal from cancerous cells. J Biol Chem 2011;286:33872-33878), pointing out 11CH2H4folate as a positron emission tomography (PET) tracer for cancer imaging. Herein we report the synthesis of 11CH2H4folate, which may serve as a potential PET tracer.

METHODS

In a remotely controlled module, methyl iodide (11CH3I) was bubbled into a reaction vial containing trimethylamine N-oxide in N,N-Dimethylformamide (DMF) and heated to 70°C for 2 min. Formaldehyde (11CH2O) formed after the completion of reaction was then mixed with a solution of freshly prepared tetrahydrofolate (H4folate) by using a fast chemoenzymatic approach to accomplish synthesis of 11CH2H4folate. Purification of the product was carried out by loading the crude reaction mixture on a SAX cartridge, washing with water to remove unbound impurities and finally eluting with a saline solution.

RESULTS

The synthesis and purification of 11CH2H4folate were completed within 5 min. High-performance liquid chromatography analysis of the product after SAX purification indicates that more than 90% of the radioactivity that was retained on the SAX cartridge was in 11CH2H4folate, with minor (<10%) radioactivity due to unreacted 11CH2O.

CONCLUSION

We present a fast (∼5 min) synthesis and purification of 11CH2H4folate as a potential PET tracer. The final product is received in physiologically compatible buffer (100 mM sodium phosphate, pH 7.0 containing 500 mM NaCl) and ready for use in vivo.

Correlation between polymorphisms of the reduced folate carrier gene (SLC19A1) and survival after pemetrexed-based therapy in non-small cell lung cancer: a North Central Cancer Treatment Group-based exploratory study

PURPOSE

To correlate polymorphisms in genes involved in the transport, activation, and inactivation of pemetrexed with the outcome of patients with advanced non-small cell lung cancer (NSCLC) treated with pemetrexed.

EXPERIMENTAL DESIGN

Data from a phase II NSCLC trial evaluating the optimal schedule of gemcitabine and pemetrexed were used. All patients with available DNA were genotyped for polymorphisms in FPGS, GGH, and SLC19A1 genes. Patients with various genotypes were compared for efficacy and adverse events resulting from pemetrexed.

RESULTS

Fifty-four patients had genotype results for all polymorphisms studied. Patients with the homozygous variant genotypes for SLC19A1 IVS4(2117) C>T, IVS5(9148) C>A, and wild-type genotype for exon6(2522) C>T had a significantly better overall survival compared with their counterparts (median overall survival in months: 8.9 [CC] versus 14.0 [CT] versus 16.7 [TT]; 9.4 [CC] versus 10.3 [CA] versus 22.7 [AA]; and 22.7 [CC] versus 10.3 [CT] versus 9.4 [TT] respectively; all log rank p = 0.03). Patients with the heterozygous TC genotype for GGH IVS5(1042) T>C had greater rates of confirmed response + stable disease compared with the TT genotype (85% versus 60%; odds ratio = 4.0; p = 0.06). A greater risk for grade 3/4 SGPT (ALT) elevation was observed in patients heterozygous (GA) for the FPGS IVS1 (28) G>A polymorphism compared with the GG genotype (43% versus 13%; odds ratio = 5.0, p = 0.07). All results were largely consistent within patients with nonsquamous (n = 40) histology.

CONCLUSION

Polymorphisms in SLC1A91 seem to predict for survival differences in pemetrexed-treated NSCLC. Additionally, polymorphisms in GGH and FPGS have marginal associations with response and adverse event. These results should be validated in larger prospective studies using pemetrexed.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

The role of folate receptor alpha (FRalpha) in the response of malignant pleural mesothelioma to pemetrexed-containing chemotherapy

Background:

The standard treatment of choice for malignant pleural mesothelioma is chemotherapy with pemetrexed and platinum, but the clinical outcome is poor. This study investigates the response to pemetrexed in a panel of eight mesothelioma cell lines and the clinical outcome for patients treated with pemetrexed in relation to folate receptor alpha (FRα).

Methods:

Cell lines were treated with pemetrexed to determine the concentration that reduced growth to 50% (GI₅₀). FRα expression was determined by western blotting and that of FRα, reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT) by real-time quantitative RT–PCR. Immunohistochemistry for FRα was carried out on 62 paraffin-embedded samples of mesothelioma from patients who were subsequently treated with pemetrexed.

Results:

A wide range of GI₅₀ values was obtained for the cell lines, H2452 cells being the most sensitive (GI₅₀ 22 nM) and RS5 cells having a GI₅₀ value greater than 10 μM. No FRα protein was detected in any cell line, and there was no relationship between sensitivity and expression of folate transporters. FRα was detected in 39% of tumour samples, generally in a small percentage of cells. There was no correlation between the presence of FRα and the outcome of pemetrexed treatment, and no significant difference between histological subtypes.

Conclusion:

Response to treatment with pemetrexed does not depend on the presence of FRα.

Expression status of folate receptor alpha is significantly correlated with prognosis in non-small-cell lung cancers

BACKGROUND

To evaluate the prognostic value of folate receptor alpha (FOLR1) and/or reduced folate carrier (RFC1) expression, which are well-characterized folate transporters, in completely resected non-small-cell lung cancer (NSCLC).

METHODS

We quantitatively examined gene expression of FOLR1 and RFC1 in surgical specimens resected from NSCLC patients. A total of 119 consecutive patients from January 2003 to June 2004 were included.

RESULTS

In adenocarcinoma, the FOLR1 gene expression was downregulated in smokers and male patients (P = 0.006 and P < 0.001, respectively). In addition, FOLR1 expression values in patients with well-differentiated, early p-stage, pT1, pN0, EGFR mutant, and p53 wild-type cancers were significantly higher than those for poorly differentiated, advanced p-stage, pT2-4, pN1-3, EGFR wild-type, and p53 mutant (P < 0.001, P < 0.001, P < 0.001, P = 0.002, P < 0.001 and P = 0.023, respectively). In squamous cell carcinoma, FOLR1 expression values in patients with pN1-3 was significantly higher than those with pN0 (P = 0.037). Moreover, the 3-year survival rate and disease-free survival rate of high-FOLR1-expressing patients (94.7% and 75.4%) were significantly higher than those of low-FOLR1-expressing patients (80.9% and 60.8%) (P = 0.008 and P = 0.038). A multivariate analysis confirmed that high FOLR1 expression was an independent and significant factor predicting a favorable prognosis (P = 0.043).

CONCLUSIONS

Higher levels of FOLR1 appear to be associated with better prognoses for patients with lung adenocarcinomas.

Exploitation of the folate receptor in the management of cancer and inflammatory disease

Over the last 25+ years, the folate receptor (FR) has emerged as an attractive tumor biomarker with the potential to be exploited for therapeutic purposes. Increasing evidence suggests that this endocytosing protein can functionally mediate the cellular uptake and retention of natural folates, certain antifolates, and folate-drug conjugates; the consequences of the latter two events could result in biological modulation, including (but not limited to) tumor-targeted cytotoxicity. Because its tissue expression profile appears to be somewhat limited to either tissues responsible for whole body retention of folates (e.g., kidney and placenta), or certain pathologic tissues (e.g., tumors or activated macrophages), the FR is believed to be a useful biological target for disease management. Indeed, recent years have been peppered with reports of novel FR-targeted therapies, and many have demonstrated impressive in vivo potency, particularly against tumor xenografts, without the undesirable toxicity that often accompanies nontargeted drug regimens. This chapter will provide essential details on the properties of the FR, including where it is expressed and how it has been successfully manipulated for therapeutic benefit.

Folic acid transport via high affinity carrier-mediated system in human retinoblastoma cells

The primary objective of this study was to investigate the expression of a specialized carrier-mediated system for folic acid and to delineate its uptake mechanism and intracellular trafficking in a human derived retinoblastoma cell line (Y-79). Uptake of [3H]Folic acid was determined at various concentrations, pH, temperatures, in the absence of sodium and chloride ions and in the presence of structural analogs, methyltetrahydro folate (MTF) and methotrexate (MTX), vitamins, membrane transport and metabolic inhibitors to delineate the mechanism of uptake. Kinetics of uptake was studied in the presence of various intracellular regulatory pathways; protein kinases A and C (PKA and PKC), protein tyrosine kinase (PTK) and calcium-calmodulin modulators. Reverse transcription polymerase chain reaction (RT-PCR) was performed to confirm the molecular identity of folate carrier systems. The uptake was found to be linear up to 30min. The rate of uptake followed saturation kinetics with apparent Km of 8.29+/-0.74nM, 17.03+/-1.98nM and 563.23+/-115.2nM and Vmax of 393.47+/-9.33, 757.58+/-26.21 and 653.17+/-31.7fmol/(minmg) protein for folic acid, MTF and MTX, respectively. The process was chloride, temperature and energy dependent but sodium and pH independent; inhibited by the structural analogs MTF and MTX but not by structurally unrelated vitamins. Membrane transport inhibitors did not affect the uptake of [3H]Folic acid, however endocytic inhibitor, colchicine, significantly inhibited the [3H]Folic acid uptake indicating the involvement of receptor mediated endocytosis process. PKC, PTK and Ca2+/calmodulin pathways appeared to play important roles in the regulation of folic acid uptake. Molecular evidence of the presence of folate receptor (FR) precursor was identified by RT-PCR analysis. This research work demonstrated, for the first time, the functional and molecular existence of a specialized high affinity carrier-mediated system for folic acid uptake, in human retinoblastoma cells.

Role of pemetrexed in non-small cell lung cancer

Pemetrexed was approved for the treatment of relapsed or chemotherapy refractory non-small cell lung cancer patients, as it produced similar response and survival outcomes and less toxicity as compared to taxotere. Pemetrexed in combination with platinum analogs or with gemcitabine or vinorelbine, produce equivalent responses and overall survival results compared to combinations of platinum analogs with other drugs. The role of bevacizumab and the inhibitors of epithelial growth factor receptor also should be evaluated in selected patients with NSCLC treated with pemetrexed combinations. Further increases in drug dose may be possible using transfer of drug resistance genes in hematopoietic stem cells.

Improved biochemical strategies for targeted delivery of taxoids

Paclitaxel (Taxol) and docetaxel (Taxotere) are very important anti-tumor drugs in clinical use for cancer. However, their clinical utility is limited due to systemic toxicity, low solubility and inactivity against drug resistant tumors. To improve chemotherapeutic levels of these drugs, it would be highly desirable to design strategies which bypass the above limitations. In this respect various prodrug and drug targeting strategies have been envisioned either to improve oral bioavailability or tumor specific delivery of taxoids. Abnormal properties of cancer cells with respect to normal cells have guided in designing of these protocols. This review article records the designed biochemical strategies and their biological efficacies as potential taxoid chemotherapeutics.

Pemetrexed: a multitargeted antifolate

BACKGROUND

The US Food and Drug Administration approved pemetrexed in February 2004 for the treatment of malignant pleural mesothelioma (MPM) in combination with cisplatin in patients with unresectable disease or for whom curative surgery is not an option. Pemetrexed is the first agent approved for the treatment of MPM. In August 2004, pemetrexed was approved as a second-line, single-agent treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC).

OBJECTIVES

The goals of this article were to summarize the pharmacology, pharmacokinetics, efficacy, and safety of pemetrexed, and to review its current and potential roles in therapy for MPM, NSCLC, and other oncologic conditions.

METHODS

Relevant English-language literature was identified through searches of PubMed (1966-December 2004), International Pharmaceutical Abstracts, and the Proceedings of the American Society of Clinical Oncology (January 1995-December 2004). Search terms included pemetrexed, Alimta, MTA, multitargeted antifolate, LY231514, mesothelioma, MPM, non-small cell lung cancer, NSCLC, breast cancer, and pancreatic cancer. In addition to published literature, abstracts and posters presented at national and international scientific meetings were reviewed.

RESULTS

Myelosuppression was the predominant dose-limiting toxicity of pemetrexed reported in Phase I studies. Identification of the correlation between poor folate status and increased pemetrexed toxicity in a multivariate analysis led to the requirement of folic acid and vitamin B12 supplementation for patients in all pemetrexed studies, with a resulting noted decrease in pemetrexed toxicity. A single, multicenter, randomized Phase III trial compared the efficacy of pemetrexed in combination with cisplatin versus cisplatin alone in the treatment of MPM. Response rates were 41.3% in the pemetrexed/cisplatin combination and 16.7% with single-agent cisplatin (P < 0.001). The median survival time for the pemetrexed/cisplatin combination was significantly longer at 12.1 months versus 9.3 months for cisplatin alone (P = 0.02). One international, multicenter, randomized Phase III trial in patients with NSCLC compared single-agent pemetrexed versus docetaxel in patients previously treated with chemotherapy. Overall response rates (9.1% and 8.8%) and median survival (8.3 months and 7.9 months) did not differ between pemetrexed and docetaxel (P = 0.105 and P = 0.226, respectively). Hematologic adverse effects-grade 3/4 neutropenia (40.2% vs 5.3%; P < 0.001), febrile neutropenia (12.7% vs 1.9%; P < 0.001), and neutropenic infections (3.3% vs 0%; P = 0.004)-were significantly greater in the docetaxel-treated patients than in the pemetrexed-treated patients, as was alopecia (37.7% vs 6.4%; P < 0.001). Results of an international, multicenter Phase III trial of pemetrexed in combination with gemcitabine conducted in patients with pancreatic cancer indicate that the combination is no more efficacious than single-agent gemcitabine. Results in other disease states are still preliminary.

CONCLUSIONS

Pemetrexed is a multitargeted antifolate that has demonstrated antitumor activity in various tumor types as a single agent and in combination with other chemotherapeutic agents. Efficacy for the treatment of MPM in combination with cisplatin has been demonstrated, and approval as a second-line agent in NSCLC was based on response rate as a surrogate end point for survival. The addition of folic acid and vitamin B12 supplementation markedly reduced.

The role of folate receptor alpha in cancer development, progression and treatment: cause, consequence or innocent bystander?

Folate receptor alpha (FRalpha) is a membrane-bound protein with high affinity for binding and transporting physiologic levels of folate into cells. Folate is a basic component of cell metabolism and DNA synthesis and repair, and rapidly dividing cancer cells have an increased requirement for folate to maintain DNA synthesis, an observation supported by the widespread use of antifolates in cancer chemotherapy. FRalpha levels are high in specific malignant tumors of epithelial origin compared to normal cells, and are positively associated with tumor stage and grade, raising questions of its role in tumor etiology and progression. It has been suggested that FRalpha might confer a growth advantage to the tumor by modulating folate uptake from serum or by generating regulatory signals. Indeed, cell culture studies show that expression of the FRalpha gene, FOLR1, is regulated by extracellular folate depletion, increased homocysteine accumulation, steroid hormone concentrations, interaction with specific transcription factors and cytosolic proteins, and possibly genetic mutations. Whether FRalpha in tumors decreases in vivo among individuals who are folate sufficient, or whether the tumor's machinery sustains FRalpha levels to meet the increased folate demands of the tumor, has not been studied. Consequently, the significance of carrying a FRalpha-positive tumor in the era of folic acid fortification and widespread vitamin supplement use in countries such as Canada and the United States is unknown. Epidemiologic and clinical studies using human tumor specimens are lacking and increasingly needed to understand the role of environmental and genetic influences on FOLR1 expression in tumor etiology and progression. This review summarizes the literature on the complex nature of FOLR1 gene regulation and expression, and suggests future research directions.

Systemic therapy for ovarian cancer: current status and new treatments

Current systemic therapy for ovarian cancer consists of a combination of carboplatin and paclitaxel. While the majority of patients achieve clinical complete remission after six cycles of chemotherapy, the relapse rate stands at over 50%. Median survival time for patients after recurrence is approximately 2 years. New treatment approaches for patients with advanced ovarian cancer include consolidation and maintenance therapy, intraperitoneal administration of cytotoxic agents, new combination chemotherapy regimens, the development of new cytotoxic agents, and molecular-targeted therapies. These agents will be evaluated either singularly or with chemotherapy. Currently, the Gynecologic Oncology Group is evaluating a combination of bevacizumab together with paclitaxel and carboplatin in previously untreated patients with advanced ovarian cancer. This trial is based on phase II data that suggest that bevacizumab as a single agent has significant activity in patients with recurrent ovarian cancer. In addition, the Gynecologic Oncology Group will be conducting phase II trials of different combinations of intraperitoneal chemotherapy in an effort to decrease toxicity associated with current intraperitoneal regimens that have shown an improvement in survival in patients with small-volume stage III disease. The Gynecologic Oncology Group will also be conducting a trial of maintenance therapy in patients who enter clinical complete remission with paclitaxel plus carboplatin, comparing observation with monthly paclitaxel or monthly paclitaxel poliglumex. Novel new cytotoxic and biologic agents are also being evaluated as single agents in phase II trials in patients with recurrent ovarian cancer.

BGC 945, a novel tumor-selective thymidylate synthase inhibitor targeted to alpha-folate receptor-overexpressing tumors

BGC 945 is a cyclopenta[g]quinazoline-based, thymidylate synthase inhibitor specifically transported into alpha-folate receptor (alpha-FR)-overexpressing tumors. Affinity of BGC 945 for the alpha-FR is 70% of the high-affinity ligand folic acid. In contrast to conventional antifolates, BGC 945 has low affinity for the widely expressed reduced-folate carrier (RFC). The K(i) for isolated thymidylate synthase is 1.2 nmol/L and the IC(50) for inhibition of the growth of alpha-FR-negative mouse L1210 or human A431 cells is approximately 7 micromol/L. In contrast, BGC 945 is highly potent in a range of alpha-FR-overexpressing human tumor cell lines (IC(50) approximately 1-300 nmol/L). Pharmacokinetic variables measured following i.v. injection of 100 mg/kg BGC 945 to KB tumor-bearing mice showed rapid plasma clearance (0.021 L/h) and tissue distribution. The terminal half-lives in plasma, liver, kidney, spleen, and tumor were 2, 0.6, 5, 21, and 28 hours, respectively. Tumor BGC 945 concentration at 24 hours was approximately 1 nmol/g tissue, at least 10-fold higher than that in plasma or normal tissues. Inhibition of thymidylate synthase in tissues leads to increased incorporation of 5-[(125)I]-iodo-2'-deoxyuridine ([(125)I]dUrd) into DNA. Forty-eight hours after injection of 100 mg/kg 6RS-BGC 945 ([(125)I]dUrd injected at 24 hours), tumor was the only tissue with incorporation above control level (6-fold). The RFC-mediated thymidylate synthase inhibitor plevitrexed also increased uptake of [(125)I]dUrd in tumor (10-fold) but, in contrast, also caused increased incorporation in other normal tissues such as spleen and small bowel (4.5- and 4.6-fold, respectively). These data suggest that BGC 945 selectively inhibits thymidylate synthase in alpha-FR-overexpressing tumors and should cause minimal toxicity to humans at therapeutic doses.

Preparation and In Vitro and In Vivo Evaluation of Technetium-99m-Labeled Folate and Methotrexate Conjugates as Tumor Imaging Agents

The cell-membrane folic acid (FA) receptors are known to be responsible for cellular accumulation of FA and FA analogs, such as methotrexate (MTX), and are overexpressed on several tumor cells. Folate, as well as antifolates (i.e., MTX), possess high affinity for the folate-receptor positive cells and tissues and were deemed useful for diagnostic imaging. We have prepared and evaluated technetium-99m (99mTc)- labeled FA and MTX analogs using MAG3 and MAG2 chelating agents in an attempt to develop folate-receptor targeting radiopharmaceuticals. Folate and MTX-conjugates after labeling with 99mTc by ligand exchange method displayed high in vitro stability in human plasma. In vitro cell binding and internalization on MCF-7 and MDA-MB-231 cells indicated the affinity and specificity of the radioconjugates toward human breast cancer cells. In mice, all radioconjugates showed rapid clearance from the blood and excretion mainly through the renal/urinary pathway, with some elimination by way of the biliary route. There was no significant accumulation of radioactivity observed in other organs, with the exception of the intestines. Uptake in the breast tumor was moderate in nude mice. These findings could be of potential diagnostic interest in designing and developing FA/MTX-based radiopharmaceuticals for tumor imaging.

A phase I pharmacokinetic and pharmacodynamic study of BGC9331 and carboplatin in relapsed gynaecological malignancies

BGC9331 is a rationally designed, specific nonpolyglutamatable thymidylate synthase (TS) inhibitor that is active in gynaecological malignancies. In the light of the sensitivity of human ovarian tumour cell lines to BGC9331 and non-cross resistance to platinum drugs, we studied the combination BGC9331/carboplatin (BCA) in a phase I (PI) pharmacokinetic (PK) and pharmacodynamic (PD) study in platinum pretreated gynaecological malignancies. Patients were >or=18 years or over, with a histologically confirmed gynaecological malignancy, radiological evidence of relapse, and a platinum treatment free interval of at least 6 months. Up to three prior lines of chemotherapy were permitted. Carboplatin (AUC5) and BGC9331 were administered on day 1, and BGC9331 was also given on day 8 of a 21-day cycle. In total, 14 patients were enrolled, and treated with BGC9331 at four dose levels, 40, 65, 85 and 100 mg m-2. The principal grade 3 and 4 haematological toxicity was neutropaenia. The principal nonhaematological toxicities were lethargy and nausea. Dose-limiting toxicities were seen in two patients at 100 mg m-2 BGC9331 (grade 4 neutropaenia>7 days, and grade 4 fatigue>7 days). Plasma BGC9331 was measured by an ELISA that was adapted for use in humans. Carboplatin was assayed by flameless atomic absorption spectrometry. There was no PK interaction between the two drugs. Plasma deoxyuridine was elevated indicating TS inhibition to at least day 12. Antitumour activity was observed in four out of 14 (28%) of patients. In conclusion, the combination of BGC9331 and carboplatin is well tolerated with no significant PK interaction between the two drugs. There is evidence of TS inhibition with the combination. We have demonstrated antitumour activity in platinum pretreated gynaecological malignancy. Further exploration of this combination in this disease is warranted.

A phase I and pharmacokinetic study of the nonpolyglutamatable thymidylate synthase inhibitor ZD9331 plus docetaxel in patients with advanced solid malignancies

PURPOSE

To assess the feasibility of administering ZD9331, a thymidylate synthase (TS) inhibitor that does not undergo polyglutamation and has broad antitumor activity, in combination with docetaxel in patients with advanced solid malignancies. The study also sought to determine the principal toxicities of the regimen and recommend appropriate doses for phase II studies, characterize the pharmacokinetics of the agents, evaluate the possibility of major drug-drug interactions, and seek preliminary evidence of anti-cancer activity.

PATIENTS AND METHODS

Patients with advanced solid malignancies were treated with escalating doses of docetaxel as a 60-minute intravenous (IV) infusion followed 30 minutes later by ZD9331 as a 30-minute IV infusion every 3 weeks. At least three patients were treated at each dose level, and the maximum tolerated dose level was defined as the highest dose level that was not associated with an unacceptably high incidence of severe toxicity. The pharmacokinetics of both ZD9331 and docetaxel were also characterized.

RESULTS

Nineteen patients were treated with 71 cycles of ZD9331 and docetaxel (ZD9331/docetaxel) at dose levels that encompassed dosing iterations of ZD9331 ranging from 65 to 260 mg/m(2) and docetaxel doses in the range of 50 to 75 mg/m(2). Neutropenia was the principal toxicity of the ZD9331/docetaxel regimen. Since five of six patients treated at the ZD9331/docetaxel dose-level of 260/60 mg/m(2) had grade 4 neutropenia that was brief and uncomplicated in the first course, a rigorous exploration of higher dose levels was not undertaken. Nonhematologic toxicities, consisting of malaise, diarrhea, rash, nausea, and vomiting, were also observed, but these effects were rarely severe. No major antitumor responses were observed. The pharmacokinetics of both ZD9331 and docetaxel were similar to those reported in previous studies of each agent administered alone, suggesting the lack of major drug-drug interactions.

CONCLUSION

The combination regimen, consisting of ZD9331 and docetaxel, is feasible and well tolerated at single-agent doses that are clinically-relevant. This ZD9331/docetaxel regimen does not appear to be associated with either major pharmacokinetic or toxicologic drug-drug interactions. A ZD9331/docetaxel dose level of 260/60 mg/m(2) is recommended as an initial dose level in disease-directed studies of the regimen, with further dose escalation of docetaxel to 75 mg/m(2) if the initial treatment is well tolerated. Further studies with this regimen are warranted in tumor types that have demonstrated sensitivity to both agents.