Oral carmofur in advanced gastrointestinal cancer

Non-peptidic inhibitors targeting SARS-CoV-2 main protease: A review

The COVID-19 pandemic continues to pose a threat to global health, and sounds the alarm for research & development of effective anti-coronavirus drugs, which are crucial for the patients and urgently needed for the current epidemic and future crisis. The main protease (Mpro) stands as an essential enzyme in the maturation process of SARS-CoV-2, playing an irreplaceable role in regulating viral RNA replication and transcription. It has emerged as an ideal target for developing antiviral agents against SARS-CoV-2 due to its high conservation and the absence of homologous proteases in the human body. Among the SARS-CoV-2 Mpro inhibitors, non-peptidic compounds hold promising prospects owing to their excellent antiviral activity and improved metabolic stability. In this review, we offer an overview of research progress concerning non-peptidic SARS-CoV-2 Mpro inhibitors since 2020. The efforts delved into molecular structures, structure-activity relationships (SARs), biological activity, and binding modes of these inhibitors with Mpro. This review aims to provide valuable clues and insights for the development of anti-SARS-CoV-2 agents as well as broad-spectrum coronavirus Mpro inhibitors.

Versatile use of Carmofur: A comprehensive review of its chemistry and pharmacology

Carmofur, 1-hexylcarbamoyl-5-fluorouracil (HCFU) is an antineoplastic drug, which has been in clinics in Japan since 1981 for the treatment of colorectal cancer. Subsequently, it was also introduced in China, Korea, and Finland. Besides colorectal cancer, it has also shown antitumor activity in other cancers such as breast, head and neck, pancreatic, gastrointestinal, and solid brain tumors. A prodrug of 5-fluorouracil (5-FU), carmofur has shown better gastrointestinal stability and superior antiproliferative activity compared to its active counterpart 5-FU. Recently, carmofur has gained attention as an acid ceramidase inhibitor and as a potential lead compound against several noncancerous diseases such as coronavirus disease 2019, Krabbe disease, acute lung injury, Parkinson's disease, dementia, childhood ependymoma etc. Carmofur has also been reported to have antifungal, and antimicrobial properties. Nevertheless, no comprehensive review is available on this drug. Herein, we summarized the chemistry, pharmacokinetics, and pharmacology of carmofur based on the literature published between January 1976 and March 2022 as identified from PubMed and Google Scholar search engines.

Naturally occurring, natural product inspired and synthetic heterocyclic anti-cancer drugs

This chapter describes the importance and activity of a huge number of commercially available naturally occurring, natural product derived or synthetic heterocyclic anti-cancer drugs.

Hydrogen-Bonded Supramolecular Polymer Micelles with pH/Photothermal-Responsive Carmofur Release and Combined Chemo-Photothermal Therapy

Integrating biomedical applications (e.g., drug delivery) into supramolecular chemistry is a promising strategy. This work targets the construction of hydrogen-bonded (H-bonded) supramolecular polymeric micelles loaded with chemotherapy drugs (carmofur) and...

Structural modification of antineoplastic drug carmofur designed to the inhibition of SARS-CoV-2 main protease: A theoretical investigation

A coherent account of the reaction mechanistic details, structural modifications, and inhibition potentials of antineoplastic drug carmofur and its modified analogs to inhibition of SARS-CoV-2 main protease (M^pro) is reported. The survey is performed by integrating the density functional based tight binding (DFTB3) with density functional theory (DFT) calculations. The inhibition process commences with nucleophilic attack from the sulfur atom on the carbonyl group, yielding a C-S bond formation, followed by a bond formation of the H-O9 by 2.07 Å, which results in a transition state contains a ring of six atoms. We found that although the direct addition of sulfhydryl group hydrogen to the N3 position is likely to happen, the proper position of the hydrogen to O9 decreases its accessibility. The thermodynamic stability of the complex was calculated to be highly sensitive to the substituent on the N11 position. Compounds with CH₂NH₂ and CH₂F at N11 positions of carmofur revealed high thermodynamic stability to complexation with M^pro but induced no change in substrate-binding pocket comparable to carmofur. Replacing the N11 of carmofur with carbon (C-carmofur) was effective in terms of complexation stability at CH₂CH₂CH₂F and CH₂CH₂CH₂OH substitutions and occupation of S1 subsite by these structures in addition to the S2 subsite. Based on the resulted data, increasing the length of the carbon chain at introduced substitutions in N-carmofur almost decreases the complexation stability while in C-carmofur the trend is reversed. Throughout these information outputs, it was suggested that compounds d, e, i′, and k′ might be novel and more efficacious drug candidates instead of carmofur. We believe that our characterization of mechanistic details and structural modification on M^pro/carmofur complex will significantly intensify researchers' understanding of this system, and consequently help them to take advantage of results into practice and design various valuable derivatives for inhibition of SARS-CoV-2 main protease.

Potential drug development and therapeutic approaches for clinical intervention in COVID-19

While the vaccination is now available to many countries and will slowly dissipate to others, effective therapeutics for COVID-19 is still illusive. The SARS-CoV-2 pandemic has posed an unprecedented challenge to researchers, scientists, and clinicians and affected the wellbeing of millions of people worldwide. Since the beginning of the pandemic, a multitude of existing anti-viral, antibiotic, antimalarial, and anticancer drugs have been tested, and some have shown potency in the treatment and management of COVID-19, albeit others failed to leave any positive impact and a few also became controversial as they showed mixed clinical outcomes. In the present article, we have brought together some of the candidate therapeutic drugs being repurposed or used in the clinical trials and discussed their clinical efficacy and safety for COVID-19.

Structural basis for the inhibition of SARS-CoV-2 main protease by antineoplastic drug carmofur

The antineoplastic drug carmofur is shown to inhibit the SARS-CoV-2 main protease (M^pro). Here, the X-ray crystal structure of M^pro in complex with carmofur reveals that the carbonyl reactive group of carmofur is covalently bound to catalytic Cys145, whereas its fatty acid tail occupies the hydrophobic S2 subsite. Carmofur inhibits viral replication in cells (EC₅₀ = 24.30 μM) and is a promising lead compound to develop new antiviral treatment for COVID-19.

Molecular Mechanism of Inhibition of Acid Ceramidase by Carmofur

Human acid ceramidase (AC) is a lysosomal cysteine amidase, which has received a great deal of interest in recent years as a potential target for the development of new therapeutics against melanoma and glioblastoma tumors. Despite the strong interest in obtaining structural information, only the structures of the apo-AC enzyme in its zymogen and activated conformations are available. In this work, the crystal structure of AC in complex with the covalent carmofur inhibitor is presented. Carmofur is an antineoplastic drug containing an electrophilic carbonyl reactive group that targets the catalytic cysteine. This novel structural data explains the basis of the AC inhibition, provides insights into the enzymatic properties of the protein, and is a great aid toward the structure-based drug design of potent inhibitors for AC, providing the detailed mechanism, which has eluded the scientific community for more than 30 years, of carmofur's mysterious 5-fluorouracil-independent antitumor activity.

Randomized, controlled trial of lateral node dissection vs. nerve-preserving resection in patients with rectal cancer after preoperative radiotherapy

PURPOSE

The effectiveness of preoperative radiation therapy for advanced lower rectal carcinoma to preserve the function of pelvic organs and reduce local recurrences was examined in a prospective, randomized, controlled study.

METHODS

Fifty-one patients with a diagnosis of localized and resectable adenocarcinoma of the lower rectum undergoing 50 Gy of preoperative radiotherapy were recruited into the trial between April 1993 and March 1995. The patients were randomly allocated to complete autonomic nerve-preserving surgery without lateral node dissection (D1), or surgery with dissection of the lateral lymph nodes including autonomic nerves (D2) followed by oral administration of carmofur for one year.

RESULTS

No difference was observed in either survival or disease-free survival between D1 and D2 groups. There was no difference between the two groups in terms of recurrence rate. A significant difference was observed in urinary and sexual function (P = 0.02 and 0.02, respectively) one year after surgery between D1 and D2 groups.

CONCLUSION

This study suggests that lateral node dissection is not necessary in terms of curability for patients with advanced carcinoma of the lower rectum who undergo preoperative radiotherapy.

Raltitrexed (Tomudex) in combination with 5-fluorouracil for the treatment of patients with advanced colorectal cancer: preliminary results from phase I clinical trials

The potential of raltitrexed (Tomudex) in combination with 5-fluorouracil (5-FU) as treatment for advanced colorectal cancer has been investigated in two phase I clinical trials. In the first study, raltitrexed was combined with bolus 5-FU; patients received raltitrexed as a 15-min infusion followed 24 h later by bolus 5-FU every 3 weeks. In the second study, 5-FU was administered as a weekly 24-h infusion for 5 weeks of a 6-week cycle and raltitrexed was given 15-min prior to 5-FU on days 8 and 29. The recommended dose for bolus 5-FU in combination with raltitrexed is likely to be 1200 mg/m2 as dose-limiting toxicity (DLT) of febrile neutropenia was observed at 1350 mg/m2, but escalation of raltitrexed above the dose used for single-agent use (3.0 mg/m2) continues. In the raltitrexed/infusional 5-FU study, dose escalation is also still continuing, but only in men as no DLT has been observed in men; 2 of 3 female patients had DLT of myelosuppression and diarrhoea at raltitrexed 3.0 mg/m2 and infusional 5-FU 2400 mg/m2. Raltitrexed had a significant effect on the pharmacokinetics of 5-FU irrespective of 5-FU regimen. Preliminary response data is encouraging with 53% of patients receiving raltitrexed/infusional 5-FU showing a partial response. In addition, significant disease stabilisation was observed in patients receiving raltitrexed combined with bolus 5-FU who had previously failed 5-FU therapy. Recruitment has recently commenced in two studies in which raltitrexed is combined with oral derivatives of 5-FU. In conclusion, preliminary data from these phase I studies indicate that the combination of raltitrexed and 5-FU is well tolerated and has encouraging clinical activity.

Postoperative chemotherapy for colorectal cancer by combining 5-fluorouracil infusion and 1-hexylcarbamoyl-5-fluorouracil administration after curative resection

BACKGROUND

Colorectal cancer is one of the major malignant diseases and, recently, its incidence appears to be increasing. Surgical resectability is an important prognostic determinant; however, recurrent tumors are commonly noted, even after apparently curative surgery. Because such metastatic disease cannot be cured, better adjuvant therapies are urgently called for.

METHODS

We studied the effect of postoperative chemotherapy using 5-fluorouracil (5-FU) infusions and 1-hexylcarbamoyl-5-fluorouracil (HCFU) oral administration for curatively resected Stage II to IV colorectal cancer. This study was prospectively randomized and controlled and 251 (93.3%) of 269 patients were determined to be candidates for statistical assessment. The inductive regimen for Group A included a total of 6 5-FU intravenous injections, 10 mg/kg, on postoperative days 0, 1, 2, 7, 8, and 9. For maintenance therapy, Group A also received oral HCFU, 300 mg daily for 52 weeks beginning 2 weeks after surgery. The regimen for Group B included only 5-FU injections of Group A.

RESULTS

There were no differences in the prognostic factors or doses of 5-FU between Groups A and B. In addition, no difference was observed in the toxicity rate between the two groups. Group A, with 5-FU infusions plus oral HCFU administration, produced a reduction in the recurrence rate and a prolongation of the survival time for patients with rectal cancer. In a retrospective analysis, this protocol was also effective for patients with Stage III to IV, wall invasion-positive, and lymph node metastasis-positive colorectal cancers.

CONCLUSIONS

This study suggests that the combination of 5-FU infusions and the continuous oral administration of HCFU is a reasonable therapeutic approach for patients with surgically resected colorectal cancer and a high risk of recurrence.

Novel low immunosuppressive derivatives of the antitumor drug fluoropyrimidine, UK-21 and UK-25: effect on delayed type hypersensitivity and tumor immunity

Previously, we reported that two novel 5-fluoropyrimidine derivatives, 2',3',5'-tris-O-[N-(2-n-propyl-n-pentanoyl)glycyl]-5-fluorouridine (UK-21) and 1-(6-[N-(2-n-propyl-n-pentanoyl)glycyl]amino-n-hexylcarbamoyl)- 5-fluorouracil (UK-25), show potent antitumor activity with low immunotoxicological effects. The purpose of this paper was to evaluate the effect of these drugs on delayed type hypersensitivity (DTH). Not only UK-21 and UK-25 but also tegafur (FT-207) and 5-fluorouracil (5-FU) produced no suppression of picryl chloride (PC)-induced DTH in mice but rather enhanced it. It is known that variation of the sensitizing antigen dose alters the effect of drugs on the immune response. Because it was difficult to control the antigen dose in PC-DTH, the sheep erythrocyte (SRBC)-induced response was used to examine the effect of drugs on delayed type hypersensitivity in the succeeding experiments. Either a therapeutic dose or an over-dose of the respective drug was given to mice sensitized with 5 x 10(5) or 5 x 10(7) SRBC. The suppressive effects of UK-21 and UK-25 on the DTH were lower than those of FT-207 and 5-FU. UK-21 and UK-25 enhanced Meth A tumor-specific DTH in BALB/c mice, but FT-207 and 5-FU did not. UK-21, UK-25 and FT-207 showed a tendency to enhance or restore the Meth A tumor neutralizing activity of spleen cells in mice bearing the tumor, but carmofur (HCFU) did not. These results indicated that the suppressive effects of UK-21 and UK-25 on the tumor immune response were also low.