Selective bone targeting 5-fluorouracil prodrugs: Synthesis and preliminary biological evaluation

Facile synthesis and cytotoxicity of substituted uracil-1'(N)-acetic acid and 4-pyridone-1'(N)-acetic acid esters of 20(S)-camptothecins

A series of novel substituted uracil-1'(N)-acetic acid esters (5-9) and 4-pyridone-1'(N)-acetic acid esters (10-11) of 20(S)-camptothecins (CPTs) have been synthesized by the acylation method. All of these new esters were assayed for in vitro cytotoxicity against five human cancer cell lines A549, Bel7402, BGC-823, HCT-8 and A2780. The in vitro bioassay results showed that all the synthesized compounds 5-11 had cytotoxities that were higher than TPT and comparable to CPT on these five tumor cell lines, some of them even showed comparable or superior cytotoxic activity to CPT. The in vitro data exhibited the cytotoxicity of the ester depended on that of its parent compound. The ester 5, 6, 8, 10, 11 even possessed the cytotoxity activity comparable to or even a little better than CPT on A549, HCT-8 and A2780. The compound 11 had the same level of cytoxity on Bel7402 as that of CPT. Here the synthesis and the in vitro antitumor evaluation of a series of novel 20-O-linked substituted uracil-1'(N)-acetic acid and 4-pyridone-1'(N)-acetic acid esters derivatives of CPTs are reported.

Hexapeptide decorated β-cyclodextrin delivery system for targeted therapy of bone infection

Successfully treating bone infections is a major orthopedic challenge. Clinically, oral, intravenous, or intramuscular injections of drugs are usually used for direct or complementary treatment. However, once the drug enters the system, it circulates throughout the body, leading to an insufficient local dose and limiting the therapeutic effect because of the lack of targeting in the drug system. In this study, β-cyclodextrin, modified with poly (ethylene glycol) [PEG] and aspartic acid hexapeptide (Asp6-β-CD), was used to specifically target the hydroxyapatite (HA) component of the bone. It was then loaded with norfloxacin (NFX) to treat bone infections. The antibacterial ability of NFX was enhanced by loading it into Asp6-β-CD, because the solubility of Asp6-β-CD@NFX increased significantly. Moreover, Asp6-β-CD could target bone tissue in nude mice and showed significantly enhanced accumulation (10 times) than the unmodified β-CD. In addition, in a rat model of osteomyelitis, Asp6-β-CD@NFX targeted HA well and exerted its antibacterial activity, which reduced inflammation and promoted bone tissue repair. This study indicates that the Asp6-β-CD based drug delivery system can efficiently target bone tissue to enable potential applications for treating bone-related diseases.

Self-assembly of a 5-fluorouracil and camptothecin dual drug dipeptide conjugate

Nano-formulated, combinatory therapeutics that control the spatiotemporal aspects of drug release have potential to overcome many of the challenges faced in cancer therapy. Herein, we describe a peptide nanotube functionalized with two anticancer drugs, 5-fluoruracil (5-FU) and camptothecin (CPT). The nanotube was formed via peptide self-assembly, which positioned 5-FU on the surface at the aqueous interface; whereas, CPT was sequestered within the hydrophobic walls. Thus, two different release profiles were observed: rapid release of 5-FU, followed by slower, sustained production of CPT. This profile emerged from the rapid hydrolytic cleavage of 5-FU at the aqueous/nanotube interface, which produced a smaller nanotube comprised of the peptide fragment.

Novel 5-Fluorouracil Carbonate-Loaded Liposome: Preparation, In Vitro, and In Vivo Evaluation as an Antitumor Agent

5-Fluorouracil (5-FU) is a chemotherapeutic drug against many types of cancers, especially colorectal cancer. However, its short plasma half-life and serious adverse reactions limit its wide clinical applications. To overcome these shortcomings, a novel lipophilic 5-FU carbonate [XL-01, (5-fluoro-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl) methyl tetradecyl carbonate] was designed, synthesized, and encapsulated into liposome (LipoXL-01) by a thin-film dispersion method through formulation screening and optimization. LipoXL-01 was characterized by a particle size of around 100 nm, polydispersity index of 0.200, ζ-potential value of -41 mV, encapsulation efficiency of 93.9%, and drug-loading efficiency of 11.6%. The cellular uptake of LipoXL-01 was increased in a concentration-dependent manner on HCT15 cells. LipoXL-01 could enhance the induction of cell apoptosis and the inhibition of cell migration and arrest the ability of the cell cycle at the S-phase on HCT15 cells better than 5-FU. Additionally, LipoXL-01 exhibited a slow drug release profile with a cumulative release rate of 12% in 8 h. The results of pharmacokinetic and biodistribution studies revealed that LipoXL-01 had a long plasma half-life (7.21 h) and a high tumor accumulation (733 nmol/g at 8 h). The in vivo antitumor effect study also showed that LipoXL-01 had more potent efficacy than 5-FU (65 vs 48% of the tumor-inhibition rate). Simultaneously, negligible systemic toxicity was observed via analyzing the body weight as well as hematological and pathological parameters in the tested mice. The current study suggested that LipoXL-01 might be a promising nanocandidate for chemotherapy of colorectal cancer.

Cetuximab-Ag2S quantum dots for fluorescence imaging and highly effective combination of ALA-based photodynamic/chemo-therapy of colorectal cancer cells

Colorectal cancer (CRC) has a poor prognosis and urgently needs better therapeutic approaches. 5-Aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) based photodynamic therapy (PDT) is already used in the clinic for several cancers but not yet well investigated for CRC. Currently, systemic administration of ALA offers a limited degree of tumour selectivity, except for intracranial tumours, limiting its wider use in the clinic. The combination of effective ALA-PDT and chemotherapy may provide a promising alternative approach for CRC treatment. Herein, theranostic Ag₂S quantum dots (AS-2MPA) optically trackable in near-infrared (NIR), conjugated with endothelial growth factor receptor (EGFR) targeting Cetuximab (Cet) and loaded with ALA for PDT monotherapy or ALA/5-fluorouracil (5FU) for the combination therapy are proposed for enhanced treatment of EGFR(+) CRC. AS-2MPA-Cet exhibited excellent targeting of the high EGFR expressing cells and showed a strong intracellular signal for NIR optical detection in a comparative study performed on SW480, HCT116, and HT29 cells, which exhibit high, medium and low EGFR expression, respectively. Targeting provided enhanced uptake of the ALA loaded nanoparticles by strong EGFR expressing cells and formation of higher levels of PpIX. Cells also differ in their efficiency to convert ALA to PpIX, and SW480 was the best, followed by HT29, while HCT116 was determined as unsuitable for ALA-PDT. The therapeutic efficacy was evaluated in 2D cell cultures and 3D spheroids of SW480 and HT29 cells using AS-2MPA with either electrostatically loaded, hydrazone or amide linked ALA to achieve different levels of pH or enzyme sensitive release. Most effective phototoxicity was observed in SW480 cells using AS-2MPA-ALA-electrostatic-Cet due to enhanced uptake of the particles, fast ALA release and effective ALA-to-PpIX conversion. Targeted delivery reduced the effective ALA concentration significantly which was further reduced with codelivery of 5FU. Delivery of ALA via covalent linkages was also effective for PDT, but required a longer incubation time for the release of ALA in therapeutic doses. Phototoxicity was correlated with high levels of reactive oxygen species (ROS) and apoptotic/necrotic cell death. Hence, both AS-2MPA-ALA-Cet based PDT and AS-2MPA-ALA-Cet-5FU based chemo/PDT combination therapy coupled with strong NIR tracking of the nanoparticles demonstrate an exceptional therapeutic effect on CRC cells and excellent potential for synergistic multistage tumour targeting therapy.

Mutual Prodrugs of 5-Fluorouracil: From a Classic Chemotherapeutic Agent to Novel Potential Anticancer Drugs

The development of potent antitumor agents with a low toxicological profile against healthy cells is still one of the greatest challenges facing medicinal chemistry. In this context, the “mutual prodrug” approach has emerged as a potential tool to overcome undesirable physicochemical features and mitigate the side effects of approved drugs. Among broad‐spectrum chemotherapeutics available for clinical use today, 5‐fluorouracil (5‐FU) is one of the most representative, also included in the World Health Organization model list of essential medicines. Unfortunately, severe side effects and drug resistance phenomena are still the primary limits and drawbacks in its clinical use. This review describes the progress made over the last ten years in developing 5‐FU‐based mutual prodrugs to improve the therapeutic profile and achieve targeted delivery to cancer tissues.

Fuplatin: An Efficient and Low-Toxic Dual-Prodrug

As FDA-approved chemotherapeutic agents, cisplatin, oxaliplatin, and 5-fluorouracil are widely used in clinic but limited by severe side-effects. To ameliorate their respective defects, a series of "dual-prodrug" by linking oxoplatin and 5-FU were designed and synthesized. The assembled compounds 10-17, named Fuplatin, exhibited much higher cytotoxicity against the tested cancer cells while lower cytotoxicity toward the human normal lung cells than free drugs or their combinations. Among them, 14 enhanced cellular accumulation with 62- and 825-fold amount of oxaliplatin and 8 at 9 h, respectively, significantly induced DNA damage and cell apoptosis, and inhibited migration and invasion in HCT-116 cells. Compound 14 arrested the cell cycle at S and G2 phases and up-regulated thymidylate synthase and p53, consistent with the results of the combination, suggesting 14 adopted a collaborative mode of 5-FU and oxaliplatin to kill cancer cells. In vivo, compound 14 showed high antitumor effect and no observable toxicity in NOD/SCID mice bearing HCT-116 tumors.

Targeting therapeutics to bone by conjugation with bisphosphonates

Bisphosphonates target and bind avidly to the mineral (hydroxyapatite) found in bone. This targeting ability has been exploited to design and prepare bisphosphonate conjugate prodrugs to deliver a wide variety of drug molecules selectively to bones. It is important that conjugates be stable in the blood stream and that conjugate that is not taken up by bone is eliminated rapidly. The prodrugs should release active drug at a rate appropriate so as to provide efficacy. Radiolabelling is the best method to quantify and evaluate pharmacokinetics, tissue distribution, bone uptake and release of the active drug(s). Recent reports have described bisphosphonate conjugates derived from the antiresorptive drug, alendronic acid and anabolic prostanoid drugs that effectively deliver prostaglandins and prostaglandin EP4 receptor agonists to bone and show enhanced anabolic efficacy and tolerability compared to the drugs alone. These conjugate drugs can be dosed infrequently (weekly or bimonthly) whereas the free drugs must be dosed daily.

New utilization of Polygonum multiflorum polysaccharide as macromolecular carrier of 5-fluorouracil for controlled release and immunoprotection

WPMP-2 is an acid polysaccharide isolated from Polygonum multiflorum, which demonstrated excellent immunomodulatory activity. In order to reduce immunosuppression of 5-fluorouracil (5-Fu), WPMP-2 was utilized as a macromolecular carrier to conjugate the 5-Fu derivatives 5-fluorouracil-1-acetic acid (5-FUAC) through ester bond. The conjugate showed controlled drug release behaviour in vitro at 37°C in phosphate buffer (pH7.4), and only 5-FUAC was detected in the media. The cytotoxicity test in vitro showed that the conjugate exhibited different cytotoxicity to HepG-2 and HT-29 cells. In addition, immunization study in vivo illustrated that the conjugate displayed immunoprotective effect by mitigating inhibition and damage effects of 5-Fu on secretion of cytokines, proliferation of splenocytes, and phagocytosis of peritoneal macrophages. It was indicated that the conjugation of 5-Fu and WPMP-2 could be a potential double effective drug delivery system.

Novel c(RGDyK)-based conjugates of POPAM and 5-fluorouracil for integrin-targeted cancer therapy

Aim: Alkylating agents and antimetabolites are cytotoxic drugs commonly used in cancer treatment. These medications are often associated with serious side effects on normal tissues and organs. Methodology: To improve the pharmacological profile of the alkylating agent POPAM and the antimetabolite 5-fluorouracil, novel integrin-targeted delivery systems based on c(RGDyK) were successfully synthesized. The new conjugates were tested in vitro against different cancer cells such as PC3, SKOV3, A549, MCF7 and MBA-MB-321. Results & conclusion: The c(RGDyK) conjugates of POPAM demonstrated better inhibitory effects and selectivity compared with c(RGDyK) and POPAM. The c(RGDyK) conjugates of 5-FUA demonstrated diverse inhibitory effects compared with c(RGDyK) and 5-FUA related to the levels of integrin expression, the conjugate stability and sensitivity of cancer cells to 5-FUA.

Synthesis and antitumor activity of novel substituted uracil-1'(N)-acetic acid ester derivatives of 20(S)-camptothecins

A series of novel substituted uracil-1'(N)-acetic acid esters (6-20) of camptothecins (CPTs) were synthesized by the acylation method. These new compounds were evaluated for in vitro antitumor activity against tumor cell lines, A549, Bel7402, BGC-823, HCT-8 and A2780. In vitro results showed that most of the derivatives exhibited comparable or superior cytotoxicity compare to CPT (1) and topotecan (TPT, 2), with 12 and 13 possessing the best efficacy. Four compounds, 9, 12, 13 and 16, were selected to be evaluated for in vivo antitumor activity against H₂₂, BGC-823 and Bel-7402 in mice. In vivo testing results indicated that 12 and 13 had antitumor activity against mouse liver carcinoma H₂₂ close to Paclitaxel and cyclophosphamide. 12 had similar antitumor activity against human gastric carcinoma BGC-823 in nude mice compared to irinotecan (3) and possessed better antitumor activity against human hepatocarcinoma Bel-7402 in nude mice than 2. It is also discovered that 12 showed a similar mechanism but better inhibitory activity on topoisomerase I (Topo I) compared to 2. These findings indicate that 20(S)-O-fluorouracil-1'(N)-acetic acid ester derivative of CPTs, 12, could be developed as an antitumor drug candidate for clinical trial.

Self-assembly of a 5-fluorouracil-dipeptide hydrogel

The self-assembly of 5-fluorouracil dilysine conjugates into self-supporting hydrogels, comprised of entangled nanofibers or rigid nanotubes with diameters of 10 and 16 nm, respectively, is reported. The rate of release of 5-Fu from the conjugates was highly dependent on concentration in solution, whereas, release from the fully formed hydrogels was significantly slower. The 5-Fu conjugate also exhibited promising in vitro cytotoxicity against human tumor cell lines A549, H460 and H23.

Synthesis of novel spin-labeled derivatives of 5-FU as potential antineoplastic agents

Chemotherapy is a general treatment option for various cancers, including lung cancer. In order to find compounds with superior bioactivity and less toxicity against lung cancer, novel spin-labeled 5-fluorouracil (5-FU) derivatives (3a-f) were synthesized and evaluated against four human tumor cell lines (A-549, DU-145, KB, and KBvin). Two promising compounds 3d and 3f exhibited IC₅₀ values of 2.76 and 2.38 μM, respectively, against non-small cell lung carcinoma cell line A-549. These compounds were twofold more cytotoxic than 5-FU and less toxic against other tested cell lines. Compound 3f exhibited seven times more selective cytotoxicity against A-549 than 5-FU. Our results suggest that compounds 3d and 3f merit further investigation for development into clinical trial candidates for non-small cell lung cancer.

A novel anabolic agent: a simvastatin analogue without HMG-CoA reductase inhibitory activity

For the first time, structural information regarding the role of simvastatin in bone anabolism is described, and a bone-specific statin is introduced. Polyaspartate-conjugated simvastatin was synthesized by solid-phase synthesis with the assistance of microwave irradiation. It displays significant bone targeting and bone formation with less toxicity than simvastatin.

Therapeutic strategies for treating osteolytic bone metastases

The recent progress in oncologic management of patients with localized cancer or metastatic disease has permitted a significant improvement in life expectancy. Nevertheless, bone metastases and their consequent skeletal-related events (SREs) are still associated with unfavorable prognosis and greatly affect quality of life. Global management of these bone metastases includes traditional local approaches (surgery, radiotherapy, etc.) and systemic administration of chemotherapeutic agents. This review focuses on treatments specific for bone metastases and, in particular, on inhibitors of bone resorption that are effective for preventing and delaying the development of SREs.

Bone targeting for the treatment of osteoporosis

Osteoporosis represents a major public health burden especially considering the aging populations worldwide. Drug targeting will be important to better meet these challenges and direct the full therapeutic potential of therapeutics to their intended site of action. This review has been organized in modules, such that scientists working in the field can easily gain specific insight in the field of bone targeting for the drug class they are interested in. We review currently approved and emerging treatment options for osteoporosis and discuss these in light of the benefit these would gain from advanced targeting. In addition, established targeting strategies are reviewed and novel opportunities as well as promising areas are presented along with pharmaceutical strategies how to render novel composites consisting of a drug and a targeting moiety responsive to bone-specific or disease-specific environmental stimuli. Successful implementation of these principles into drug development programs for osteoporosis will substantially contribute to the clinical success of anti-catabolic and anabolic drugs of the future.