Anti-tumour activity of a first-in-class agent NUC-1031 in patients with advanced cancer: results of a phase I study

ARID3A enhances chemoresistance of pancreatic cancer via inhibiting PTEN-induced ferroptosis

Currently, chemotherapy remains occupying a pivotal place in the treatment of pancreatic ductal adenocarcinoma (PDAC). Nonetheless, the emergence of drug resistance in recent years has limited the clinical efficacy of chemotherapeutic agents, especially gemcitabine (GEM). Through bioinformatics analysis, AT-rich Interactive Domain-containing Protein 3A (ARID3A), one of transcription factors, is discovered to possibly participate in this progress. This study thoroughly investigates the potential role of ARID3A in the malignant progression and GEM chemoresistance of PDAC and explores the underlying mechanisms. The results indicate that ARID3A knockdown suppresses tumor development and enhances the sensitivity of PDAC cells to GEM in vitro and vivo. Mechanically, CUT&Tag profiling sequencing, RNA-sequencing and functional studies demonstrates that decreased ARID3A expression alleviates the transcriptional inhibition of phosphatase and tensin homolog (PTEN), consequently leading to glutathione peroxidase 4 (GPX4) depletion and increased lipid peroxidation levels. Activated ferroptosis induced by the inhibition of GPX4 subsequently restricts tumor progression and reduces GEM resistance in PDAC. This research identifies the ferroptosis regulatory pathway of ARID3A-PTEN-GPX4 axis and reveals its critical role in driving the progression and chemoresistance of pancreatic cancer. Notably, both inhibition of ARID3A and enhancement of ferroptosis can increase chemosensitivity to GEM, which offers a promising opportunity for developing therapeutic strategies to combat acquired chemotherapy resistance in pancreatic cancer.

Elevated 2-oxoglutarate antagonizes DNA damage responses in cholangiocarcinoma chemotherapy through regulating aspartate beta-hydroxylase

Cholangiocarcinoma (CCA) is resistant to systemic chemotherapies that kill malignant cells mainly through DNA damage responses (DDRs). Recent studies suggest that the involvement of 2-oxoglutarate (2-OG) dependent dioxygenases in DDRs may be associated with chemoresistance in malignancy, but how 2-OG impacts DDRs in CCA chemotherapy remains elusive. We examined serum 2-OG levels in CCA patients before receiving chemotherapy. CCA patients are classified as progressive disease (PD), partial response (PR), and stable disease (SD) after receiving chemotherapy. CCA patients classified as PD showed significantly higher serum 2-OG levels than those defined as SD and PR. Treating CCA cells with 2-OG reduced DDRs. Overexpression of full-length aspartate beta-hydroxylase (ASPH) could mimic the effects of 2-OG on DDRs, suggesting the important role of ASPH in chemoresistance. Indeed, the knockdown of ASPH improved chemotherapy in CCA cells. Targeting ASPH with a specific small molecule inhibitor also enhanced the effects of chemotherapy. Mechanistically, ASPH modulates DDRs by affecting ATM and ATR, two of the major regulators finely controlling DDRs. More importantly, targeting ASPH improved the therapeutic potential of chemotherapy in two preclinical CCA models. Our data suggested the impacts of elevated 2-OG and ASPH on chemoresistance through antagonizing DDRs. Targeting ASPH may enhance DDRs, improving chemotherapy in CCA patients.

Comparative Pharmacology of a Bis-Pivaloyloxymethyl Phosphonate Prodrug Inhibitor of Enolase after Oral and Parenteral Administration

Metabolically labile prodrugs can experience stark differences in catabolism incurred by the chosen route of administration. This is especially true for phosph(on)ate prodrugs, in which successive promoiety removal transforms a lipophilic molecule into increasingly polar compounds. We previously described a phosphonate inhibitor of enolase (HEX) and its bis-pivaloyloxymethyl ester prodrug (POMHEX) capable of eliciting strong tumor regression in a murine model of enolase 1 (ENO1)-deleted glioblastoma following parenteral administration. Here, we characterize the pharmacokinetics and pharmacodynamics of these enolase inhibitors in vitro and in vivo after oral and parenteral administration. In support of the historical function of lipophilic prodrugs, the bis-POM prodrug significantly improves cell permeability of and rapid hydrolysis to the parent phosphonate, resulting in rapid intracellular loading of peripheral blood mononuclear cells in vitro and in vivo. We observe the influence of intracellular trapping in vivo on divergent pharmacokinetic profiles of POMHEX and its metabolites after oral and parenteral administration. This is a clear demonstration of the tissue reservoir effect hypothesized to explain phosph(on)ate prodrug pharmacokinetics but has heretofore not been explicitly demonstrated.

Barriers and opportunities for gemcitabine in pancreatic cancer therapy

Pancreatic ductal adenocarcinoma (PDA) has become one of the leading causes of cancer-related deaths across the world. A lack of durable responses to standard-of-care chemotherapies renders its treatment particularly challenging and largely contributes to the devastating outcome. Gemcitabine, a pyrimidine antimetabolite, is a cornerstone in PDA treatment. Given the importance of gemcitabine in PDA therapy, extensive efforts are focusing on exploring mechanisms by which cancer cells evade gemcitabine cytotoxicity, but strategies to overcome them have not been translated into patient care. Here, we will introduce the standard treatment paradigm for patients with PDA, highlight mechanisms of gemcitabine action, elucidate gemcitabine resistance mechanisms, and discuss promising strategies to circumvent them.

Prodrugs of Nucleoside 5'-Monophosphate Analogues: Overview of the Recent Literature Concerning their Synthesis and Applications

Nucleoside analogues are widely used as anti-infectious and antitumoral agents. However, their clinical use may face limitations associated with their physicochemical properties, pharmacokinetic parameters, and/or their peculiar mechanisms of action. Indeed, once inside the cells, nucleoside analogues require to be metabolized into their corresponding (poly-)phosphorylated derivatives, mediated by cellular and/or viral kinases, in order to interfere with nucleic acid biosynthesis. Within this activation process, the first-phosphorylation step is often the limiting one and to overcome this limitation, numerous prodrug approaches have been proposed. Herein, we will focus on recent literature data (from 2015 and onwards) related to new prodrug strategies, the development of original synthetic approaches and novel applications of nucleotide prodrugs (namely pronucleotides) leading to the intracellular delivery of 5'-monophosphate nucleoside analogues.

Synthesis and Characterization of NUC-7738, an Aryloxy Phosphoramidate of 3'-Deoxyadenosine, as a Potential Anticancer Agent

3'-Deoxyadenosine (3'-dA, Cordycepin, 1) is a nucleoside analogue with anticancer properties, but its clinical development has been hampered due to its deactivation by adenosine deaminase (ADA) and poor cellular uptake due to low expression of the human equilibrative transporter (hENT1). Here, we describe the synthesis and characterization of NUC-7738 (7a), a 5'-aryloxy phosphoramidate prodrug of 3'-dA. We show in vitro evidence that 7a is an effective anticancer drug in a panel of solid and hematological cancer cell lines, showing its preferential cytotoxic effects on leukemic stem cells. We found that unlike 3'-dA, the activity of 7a was independent of hENT1 and kinase activity. Furthermore, it was resistant to ADA metabolic deactivation. Consistent with these findings, 7a showed increased levels of intracellular 3'-deoxyadenosine triphosphate (3'-dATP), the active metabolite. Mechanistically, levels of intracellular 3'-dATP were strongly associated with in vitro potency. NUC-7738 is now in Phase II, dose-escalation study in patients with advanced solid tumors.

CD44-targeting hydrophobic phosphorylated gemcitabine prodrug nanotherapeutics augment lung cancer therapy

Gemcitabine (GEM) is among the most used chemotherapies for advanced malignancies including non-small cell lung cancer. The clinical efficacy of GEM is, however, downplayed by its poor bioavailability, short half-life, drug resistance, and dose-limiting toxicities (e.g. myelosuppression). In spite of many approaches exploited to improve the efficacy and safety of GEM, limited success was achieved. The short A6 peptide (sequence: Ac-KPSSPPEE-NH₂) is clinically validated for specific binding to CD44 on metastatic tumors. Here, we designed a robust and CD44-specific GEM nanotherapeutics by encapsulating hydrophobic phosphorylated gemcitabine prodrug (HPG) into the core of A6 peptide-functionalized disulfide-crosslinked micelles (A6-mHPG), which exhibited reduction-triggered HPG release and specific targetability to CD44 overexpressing tumor cells. Interestingly, A6 greatly enhanced the internalization and inhibitory activity of micellar HPG (mHPG) in CD44 positive A549 cells, and increased its accumulation in A549 cancerous lung, leading to potent repression of orthotopic tumor growth, depleted toxicity, and marked survival benefits compared to free HPG and mHPG (median survival time: 59 days versus 30 and 45 days, respectively). The targeted delivery of gemcitabine prodrug with disulfide-crosslinked biodegradable micelles appears to be a highly appealing strategy to boost gemcitabine therapy for advance tumors. STATEMENT OF SIGNIFICANCE: Gemcitabine (GEM) though widely used in clinics for treating advanced tumors is associated with poor bioavailability, short half-life and dose-limiting toxicities. Development of clinically translatable GEM formulations to improve its anti-tumor efficacy and safety is of great interest. Here, we report on CD44-targeting GEM nanotherapeutics obtained by encapsulating hydrophobic phosphorylated GEM prodrug (HPG), a single isomer of NUC-1031, into A6 peptide-functionalized disulfide-crosslinked micelles (A6-mHPG). A6-mHPG demonstrates stability against degradation, enhanced internalization and inhibition toward CD44⁺ cells, and increased accumulation in A549 lung tumor xenografts, leading to potent repression of orthotopic tumor growth, depleted toxicity and marked survival benefits. The targeted delivery of GEM prodrug using A6-mHPG is a highly appealing strategy to GEM cancer therapy.

Phosphoryl Prodrugs: Characteristics to Improve Drug Development

Phosphoryl prodrugs are key compounds in drug development. Biologically active phosphoryl compounds often have negative charges on the phosphoryl group, and as a result, frequently have poor pharmacokinetic (PK) profiles. The use of lipophilic moieties bonded to the phosphorus (or attached oxygen atoms) masks the negative charge of the phosphoryl group, cleavage releasing the active molecule. The use of prodrugs to improve the PK of active parent molecules is an essential step in drug development. This review highlights promising trends in terminal elimination half-life, C_max, clearance, oral bioavailability, and cLogP in phosphoryl prodrugs. We focus on specific prodrug families: esters, amidates, and ProTides. We conclude that moderating lipophilicity is a key part of prodrug success. This type of evaluation is important for drug development, regardless of clinical application. It is our hope that this analysis, and future ones like it, will play a significant role in prodrug evolution.

The Novel Nucleoside Analogue ProTide NUC-7738 Overcomes Cancer Resistance Mechanisms In Vitro and in a First-In-Human Phase I Clinical Trial

PURPOSE

Nucleoside analogues form the backbone of many therapeutic regimens in oncology and require the presence of intracellular enzymes for their activation. A ProTide is comprised of a nucleoside fused to a protective phosphoramidate cap. ProTides are easily incorporated into cells whereupon the cap is cleaved and a preactivated nucleoside released. 3'-Deoxyadenosine (3'-dA) is a naturally occurring adenosine analogue with established anticancer activity in vitro but limited bioavailability due to its rapid in vivo deamination by the circulating enzyme adenosine deaminase, poor uptake into cells, and reliance on adenosine kinase for its activation. In order to overcome these limitations, 3'-dA was chemically modified to create the novel ProTide NUC-7738.

EXPERIMENTAL DESIGN

We describe the synthesis of NUC-7738. We determine the IC50 of NUC-7738 using pharmacokinetics (PK) and conduct genome-wide analyses to identify its mechanism of action using different cancer model systems. We validate these findings in patients with cancer.

RESULTS

We show that NUC-7738 overcomes the cancer resistance mechanisms that limit the activity of 3'-dA and that its activation is dependent on ProTide cleavage by the enzyme histidine triad nucleotide-binding protein 1. PK and tumor samples obtained from the ongoing first-in-human phase I clinical trial of NUC-7738 further validate our in vitro findings and show NUC-7738 is an effective proapoptotic agent in cancer cells with effects on the NF-κB pathway.

CONCLUSIONS

Our study provides proof that NUC-7738 overcomes cellular resistance mechanisms and supports its further clinical evaluation as a novel cancer treatment within the growing pantheon of anticancer ProTides.

Current State of Multidisciplinary Treatment in Cholangiocarcinoma

BACKGROUND

Cholangiocarcinoma (CCA) is a highly aggressive malignancy, and its incidence seems to be increasing over the last years. Given the high rate of irresectability at the time of initial diagnosis, new treatment approaches are important to achieve better patient outcomes. Our review provides an overview of current multimodal therapy options across different specialties of gastroenterology/oncology, surgery, and interventional radiology.

SUMMARY

CCA is subdivided into clinically and molecularly distinct phenotypes. Surgical treatment currently is the only potentially curative therapy, but unfortunately, the majority of all patients are not eligible for resection at the time of initial diagnosis due to anatomic location, inadequate hepatic reserve, metastatic disease, or limiting comorbidities. However, multimodal treatment options are available to prolong survival, relieve symptoms, and maintain life quality.

KEY MESSAGES

The treatment of CCA is complex and requires close interdisciplinary collaboration and individualized treatment planning to ensure optimal patient care at specialized centers. Molecular profiling of patients and inclusion into clinical trials is highly recommended.

Single Diastereomers of the Clinical Anticancer ProTide Agents NUC-1031 and NUC-3373 Preferentially Target Cancer Stem Cells In Vitro

A 3'-protected route toward the synthesis of the diastereomers of clinically active ProTides, NUC-1031 and NUC-3373, is described. The in vitro cytotoxic activities of the individual diastereomers were found to be similar to their diastereomeric mixtures. In the KG1a cell line, NUC-1031 and NUC-3373 have preferential cytotoxic effects on leukemic stem cells (LSCs). These effects were not diastereomer-specific and were not observed with the parental nucleoside analogues gemcitabine and FUDR, respectively. In addition, NUC-1031 preferentially targeted LSCs in primary AML samples and cancer stem cells in the prostate cancer cell line, LNCaP. Although the mechanism for this remains incompletely resolved, NUC-1031-treated cells showed increased levels of triphosphate in both LSC and bulk tumor fractions. As ProTides are not dependent on nucleoside transporters, it seems possible that the LSC targeting observed with ProTides may be caused, at least in part, by preferential accumulation of metabolized nucleos(t)ide analogues.

A Phase Ib Open-Label, Dose-Escalation Study of NUC-1031 in Combination with Carboplatin for Recurrent Ovarian Cancer

PURPOSE

NUC-1031 is a first-in-class ProTide modification of gemcitabine. In PRO-002, NUC-1031 was combined with carboplatin in recurrent ovarian cancer.

PATIENTS AND METHODS

NUC-1031 was administered on days 1 and 8 with carboplatin on day 1 every 3 weeks for up to six cycles. Four dose cohorts of NUC-1031 (500, 625, and 750 mg/m²) with carboplatin (AUC4 or 5) were investigated. Primary endpoint was recommended phase II combination dose (RP2CD). Secondary endpoints included safety, investigator-assessed objective response rate (ORR), clinical benefit rate (CBR), progression-free survival (PFS), and pharmacokinetics.

RESULTS

A total of 25 women with recurrent ovarian cancer, a mean of 3.8 prior lines of chemotherapy, and a median platinum-free interval of 5 months (range: 7-451 days) were enrolled; 15 of 25 (60%) were platinum resistant, 9 (36%) were partially platinum sensitive, and 1 (4%) was platinum sensitive. Of the 23 who were response evaluable, there was 1 confirmed complete response (4%), 5 partial responses (17%), and 8 (35%) stable disease. The ORR was 26% and CBR was 74% across all doses and 100% in the RP2CD cohort. Median PFS was 27.1 weeks. NUC-1031 was stable in the plasma and rapidly generated high intracellular dFdCTP levels that were unaffected by carboplatin.

CONCLUSIONS

NUC-1031 combined with carboplatin is well tolerated in recurrent ovarian cancer. Highest efficacy was observed at the RP2CD of 500 mg/m² NUC-1031 on days 1 and 8 with AUC5 carboplatin day 1, every 3 weeks for six cycles. The ability to deliver carboplatin at AUC5 and the efficacy of this schedule even in patients with platinum-resistant disease makes this an attractive therapeutic combination.

An overview of ProTide technology and its implications to drug discovery

Introduction: The ProTide technology is a phosphate (or phosphonate) prodrug method devised to deliver nucleoside monophosphate (or monophosphonate) intracellularly bypassing the key challenges of antiviral and anticancer nucleoside analogs. Three new antiviral drugs, exploiting this technology, have been approved by the FDA while others are in clinical studies as anticancer agents.Areas covered: The authors describe the origin and development of this technology and its incredible success in transforming the drug discovery of antiviral and anticancer nucleoside analogues. As evidence, discussion on the antiviral ProTides on the market, and those currently in clinical development are included. The authors focus on how the proven capacity of this technology to generate new drug candidates has stimulated its application to non-nucleoside-based molecules.Expert opinion: The ProTide approach has been extremely successful in delivering blockbuster antiviral medicines and it seems highly promising in oncology. Its application to non-nucleoside-based small molecules is recently emerging and proving effective in other therapeutic areas. However, investigations to explain the lack of activity of certain ProTide series and comprehensive structure activity relationship studies to identify the appropriate phosphoramidate motifs depending on the parent molecule are in our opinion mandatory for the future development of these compounds.

An Assessment of Combination of the Camrelizumab With Chemotherapy in Metastatic Biliary Tract Cancers

BACKGROUND

Monoclonal antibodies that target the PD-1 receptor are emerging as promising therapeutic candidates for the treatment of biliary tract cancers (BTCs). The purpose of the current study was to assess the combination of the camrelizumab with chemotherapy as a first-line treatment for metastatic BTCs.

METHODS

We conducted a prospective single-arm pilot study of PD-1 antibody (camrelizumab 3 mg/kg d1, Q2 W or Q3 W) combined with different chemotherapy regimens as first-line treatment for BTCs. Efficacy endpoints were objective response rate (ORR), disease control rate (DCR), progression free survival (PFS), and overall survival (OS). Treatment-related adverse events (TRAEs) were also evaluated.

RESULTS

Fourteen patients with histologically confirmed BTCs were evaluated. The ORR was 14.3% (95% CI: 1.8 to 42.8) and the DCR was 64.3% (95%CI: 41.7 to 86.9). The median PFS was 6.5 months (95% CI: 3.8 to 9.2), and the 6- and 12-month PFS rates were 61.6% and 12.3%, respectively. The median OS was 9.9 months (95% CI: 7.6 to 12.2), and the 6-and 12-month OS rates were 74.5% and 26.6%, respectively. All patients displayed at least 1 TRAE., and Grade 3 or 4 TRAEs occurred in 6 (42.86%) patients.

CONCLUSIONS

Camrelizumab combined with chemotherapy as first-line treatment for metastatic BTCs demonstrated acceptable safety and efficacy in our pilot study. These findings warrant prospective controlled clinical trials comparing combinations of camrelizumab and chemotherapy to standard regimens.

A Phase Ib Study of NUC-1031 in Combination with Cisplatin for the First-Line Treatment of Patients with Advanced Biliary Tract Cancer (ABC-08)

BACKGROUND

Cisplatin/gemcitabine is standard first-line treatment for patients with advanced biliary tract cancer (ABC). NUC-1031 (phosphoramidate transformation of gemcitabine) is designed to enhance efficacy by maximizing intratumoral active metabolites.

METHODS

Patients with untreated ABC, Eastern Cooperative Oncology Group performance status 0-1 received NUC-1031 (625 or 725 mg/m2 ) and cisplatin (25 mg/m2 ) on days 1 and 8, every 21 days. Primary objectives were safety and maximum tolerated dose; secondary objectives were objective response rate (ORR), pharmacokinetics, progression-free survival (PFS), and overall survival (OS).

RESULTS

Twenty-one patients (median age 61 years, n = 13 male; 17 cholangiocarcinoma, 2 ampullary, and 2 gallbladder cancer) received NUC-1031 625 mg/m2 (n = 8 and expansion n = 7; median six cycles) or 725 mg/m2 (n = 6; median 7.5 cycles). Treatment was well tolerated; most common treatment-emergent grade 3-4 adverse events occurring in more than one patient with 625 mg/m2 NUC-1031 were increased gamma-glutamyl transferase (GGT), 40%; alanine aminotransferase, 20%; bilirubin, 13%; neutropenia, 27%; decreased white cell count, 20%; thrombocytopenia, 13%; nausea, 13%; diarrhea, 13%; fatigue, 13%; and thrombus, 20% and with 725 mg/m2 , increased GGT, 67%, and fatigue, 33%. NUC-1031 725 mg/m2 was selected as the recommended dose with cisplatin in ABC. ORR was 33% (one complete response, six partial responses), DCR was 76%, median PFS was 7.2 months (95% confidence interval [CI], 4.3-10.1), and median OS was 9.6 months (95% CI, 6.7-13.1). The median estimates of area under the plasma concentration-time curve from time 0 to last measurable time and maximum concentration were highest for NUC-1031 (218-324 μg•h/mL and 309-889 μg/mL, respectively) and lowest for di-fluoro-deoxycytidine (0.47-1.56 μg•h/mL and 0.284-0.522 μg/mL, respectively).

CONCLUSION

This is the first study reporting on the combination of NUC-1031 with cisplatin in ABC and demonstrated a favorable safety profile; 725 mg/m2 NUC-1031 in combination with cisplatin is undergoing phase III trial evaluation in ABC. (ClinicalTrials.gov ID: NCT02351765; EudraCT ID: 2015-000100-26).

IMPLICATIONS FOR PRACTICE

The prognosis for patients with advanced biliary tract cancer (ABC) is approximately 1 year, and new treatment options are required. The cisplatin/gemcitabine combination is standard first-line treatment for patients with ABC. NUC-1031 is a phosphoramidate transformation of gemcitabine and is designed to enhance efficacy by maximizing intratumoral active metabolites. This phase Ib study (ABC-08) demonstrated a favorable safety profile of NUC-1031 in combination with cisplatin for the first-line treatment of patients with ABC, and 725 mg/m2 NUC-1031 was recommended in combination with cisplatin for phase III trial evaluation; the NuTide:121 global randomized study is currently enrolling.

The nucleotide prodrug CERC-913 improves mtDNA content in primary hepatocytes from DGUOK-deficient rats

Loss-of-function mutations in the deoxyguanosine kinase (DGUOK) gene result in a mitochondrial DNA (mtDNA) depletion syndrome. DGUOK plays an important role in converting deoxyribonucleosides to deoxyribonucleoside monophosphates via the salvage pathway for mtDNA synthesis. DGUOK deficiency manifests predominantly in the liver; the most common cause of death is liver failure within the first year of life and no therapeutic options are currently available. in vitro supplementation with deoxyguanosine or deoxyguanosine monophosphate (dGMP) were reported to rescue mtDNA depletion in DGUOK-deficient, patient-derived fibroblasts and myoblasts. CERC-913, a novel ProTide prodrug of dGMP, was designed to bypass defective DGUOK while improving permeability and stability relative to nucleoside monophosphates. To evaluate CERC-913 for its ability to rescue mtDNA depletion, we developed a primary hepatocyte culture model using liver tissue from DGUOK-deficient rats. DGUOK knockout rat hepatocyte cultures exhibit severely reduced mtDNA copy number (~10%) relative to wild type by qPCR and mtDNA content remains stable for up to 8 days in culture. CERC-913 increased mtDNA content in DGUOK-deficient hepatocytes up to 2.4-fold after 4 days of treatment in a dose-dependent fashion, which was significantly more effective than dGMP at similar concentrations. These early results suggest primary hepatocyte culture is a useful model for the study of mtDNA depletion syndromes and that CERC-913 treatment can improve mtDNA content in this model.

Small Molecular Gemcitabine Prodrugs for Cancer Therapy

Gemcitabine as a pyrimidine nucleoside analog anticancer drug has high efficacy for a broad spectrum of solid tumors. Gemcitabine is activated within tumor cells by sequential phosphorylation carried out by deoxycytidine kinase to mono-, di-, and triphosphate nucleotides with the last one as the active form. But the instability, drug resistance and toxicity severely limited its utilization in clinics. In the field of medicinal chemistry, prodrugs have proven to be a very effective means for elevating drug stability and decrease undesirable side effects including the nucleoside anticancer drug such as gemcitabine. Many works have been accomplished in design and synthesis of gemcitabine prodrugs, majority of which were summarized in this review.

Synthesis and Conformational Analysis of Fluorinated Uridine Analogues Provide Insight into a Neighbouring-Group Participation Mechanism

Fluorinated nucleoside analogues have attracted much attention as anticancer and antiviral agents and as probes for enzymatic function. However, the lack of direct synthetic methods, especially for 2′,3′-dideoxy-2′,3′-difluoro nucleosides, hamper their practical utility. In order to design more efficient synthetic methods, a better understanding of the conformation and mechanism of formation of these molecules is important. Herein, we report the synthesis and conformational analysis of a 2′,3′-dideoxy-2′,3′-difluoro and a 2′-deoxy-2′-fluoro uridine derivative and provide an insight into the reaction mechanism. We suggest that the transformation most likely diverges from the S_N1 or S_N2 pathway, but instead operates via a neighbouring-group participation mechanism.

"Open Sesame?": Biomarker Status of the Human Equilibrative Nucleoside Transporter-1 and Molecular Mechanisms Influencing its Expression and Activity in the Uptake and Cytotoxicity of Gemcitabine in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive tumor characterized by early invasiveness, rapid progression and resistance to treatment. For more than twenty years, gemcitabine has been the main therapy for PDAC both in the palliative and adjuvant setting. After the introduction of FOLFIRINOX as an upfront treatment for metastatic disease, gemcitabine is still commonly used in combination with nab-paclitaxel as an alternative first-line regimen, as well as a monotherapy in elderly patients unfit for combination chemotherapy. As a hydrophilic nucleoside analogue, gemcitabine requires nucleoside transporters to permeate the plasma membrane, and a major role in the uptake of this drug is played by human equilibrative nucleoside transporter 1 (hENT-1). Several studies have proposed hENT-1 as a biomarker for gemcitabine efficacy in PDAC. A recent comprehensive multimodal analysis of hENT-1 status evaluated its predictive role by both immunohistochemistry (with five different antibodies), and quantitative-PCR, supporting the use of the 10D7G2 antibody. High hENT-1 levels observed with this antibody were associated with prolonged disease-free status and overall-survival in patients receiving gemcitabine adjuvant chemotherapy. This commentary aims to critically discuss this analysis and lists molecular factors influencing hENT-1 expression. Improved knowledge on these factors should help the identification of subgroups of patients who may benefit from specific therapies and overcome the limitations of traditional biomarker studies.

A Phosphoramidate Strategy Enables Membrane Permeability of a Non-nucleotide Inhibitor of the Prolyl Isomerase Pin1

The membrane permeability of nucleotide-based drugs, such as sofosbuvir (Sovaldi), requires installation of phosphate-caging groups. One strategy, termed "ProTide", masks the anionic phosphate through an N-linked amino ester and an O-linked aromatic phospho-ester, such that release of the active drug requires consecutive enzymatic liberation by an esterase and then a phosphoramidase, such as Hint1. Because Hint1 is known to be selective for nucleotides, it was not clear if the ProTide approach could be deployed for non-nucleotides. Here, we demonstrate that caging of a phosphate-containing inhibitor of the prolyl isomerase Pin1 increases its permeability. Moreover, this compound was processed by both esterase and phosphoramidase activity, releasing the active molecule to bind and inhibit Pin1 in cells. Thus, Hint1 appears to recognize a broader set of substrates than previously appreciated. It seems possible that other potent, but impermeable, phosphate-containing inhibitors might likewise benefit from this approach.

NUC-1031, use of ProTide technology to circumvent gemcitabine resistance: current status in clinical trials

BACKGROUND

Resistance to gemcitabine chemotherapy is common in patients with pancreatic ductal adenocarcinoma (PDAC), biliary tract cancer (BTC) and ovarian cancers (OC), conferring poor survival. Use of ProTide technology led to the development of a 'partially-activated' monophosphorylated gemcitabine compound, termed NUC-1031. NUC-1031 enters cancer cells independent of the human equilibrative nucleoside transporter, does not require deoxycytidine kinase-mediated activation and resists cytidine deaminase-mediated breakdown into toxic by-products.

CURRENT FINDINGS

The phase I PRO-001 trial recruited 68 patients with advanced solid tumours; of the 49 patients that had response-evaluable disease, 5 (10%) had a partial response (PR) and 33 (67%) had stable disease (SD). Subsequently, the PRO-002 study assessed the safety and efficacy of NUC-1031 combined with carboplatin for patients with OC (n = 25); preliminary data from this study reported one (4%) unconfirmed complete response (CR), 8 (35%) PRs and 13 (57%) patients with SD, the final outcome data are awaited. The ABC-08 trial for advanced BTC assessed safety and efficacy of NUC-1031 combined with cisplatin; 14 patients were recruited with a 50% objective response rate in the intention to treat population at interim analysis. ACELARATE, the phase III trial in first-line advanced PDAC comparing NUC-1031 to gemcitabine monotherapy, recruited 200 patients but has been paused for futility analysis.

CONCLUSION

Early studies demonstrate NUC-1031 is well tolerated with favourable pharmacokinetic profiles. NUC-1031 use in PDAC remains unclear, but encouraging results of disease control in BTC and OC has prompted phase II and III trial development. NuTide 121, is a phase III trial comparing cisplatin-NUC 1031 combination to the standard of care cisplatin-gemcitabine and recruitment is ongoing. Recruiting trials and mature data from existing studies will help inform on the impact of NUC-1031 on patient survival over standard gemcitabine.

NUC-1031/cisplatin versus gemcitabine/cisplatin in untreated locally advanced/metastatic biliary tract cancer (NuTide:121)

Gemcitabine/cisplatin is standard of care for first-line treatment of patients with advanced biliary tract cancer (aBTC); new treatments are needed. NUC-1031 is designed to overcome key cancer resistance mechanisms associated with gemcitabine. The tolerability/efficacy signal of NUC-1031/cisplatin in the Phase Ib ABC-08 study suggested that this combination may represent a more efficacious therapy than gemcitabine/cisplatin for patients with aBTC, leading to initiation of the global NuTide:121 study which will include 828 patients ≥18 years with untreated histologically/cytologically-confirmed aBTC (including cholangiocarcinoma, gallbladder or ampullary cancer); randomized (1:1) to NUC-1031 (725 mg/m2)/cisplatin (25 mg/m2) or gemcitabine (1000 mg/m2)/cisplatin (25 mg/m2), on days 1/8, Q21-days. Primary objectives are overall survival and objective response rate. Secondary objectives: progression-free survival, safety, pharmacokinetics, patient-reported quality of life and correlative studies. (Investigational new drug (IND) number: 139058, European Clinical Trials database: EudraCT Number 2019-001025-28, ClinicalTrials.gov identifier: NCT04163900).

NUC-1031 in biliary tract cancer: from bench to bedside and back?

In preclinical models of biliary tract cancer, NUC-1031 showed less potency than gemcitabine, no correlation with potential biomarkers and only moderate additive interaction in combination with cisplatin. These findings should prompt further careful pharmacological and translational studies to better define the purported therapeutic advantage of NUC-1031 over gemcitabine. That would be a more cautious approach than the phase III clinical trial which is planning to enrol 828 patients with biliary tract tumours to compare gemcitabine/cisplatin "conventional" treatment with or without NUC-1031.

Evaluation of NUC-1031: a first-in-class ProTide in biliary tract cancer

PURPOSE

NUC1031 is a first-in-class ProTide, that is a gemcitabine pro-drug designed to overcome putative mechanisms of resistance, including decreased expression of hENT/hCNT transporters, absence of activating enzymes such as deoxycytidine kinase (dCK) and presence of degrading enzymes such as cytidine deaminase (CDA). We undertook comprehensive pre-clinical evaluation of NUC1031 in biliary tract cancer (BTC) models, given that gemcitabine/cisplatin is a standard first-line therapy in advanced BTC.

METHODS

Here, we compared the in vitro activity of NUC1031 in comparison to gemcitabine, validate putative mechanism(s) of action, assessed potential biomarkers of sensitivity or resistance, and performed combination studies with cisplatin. We also evaluated the in vivo efficacy of NUC1031 and gemcitabine using a CDA-high cholangiocarcinoma patient-derived xenograft (PDX) model.

RESULTS

In a panel of BTC cell lines (N = 10), NUC1031 had less potency than gemcitabine in multiple cellular assays. NUC1031 did not demonstrate evidence of greater synergy over gemcitabine in combination with cisplatin. Surprisingly, efficacy of both gemcitabine and NUC1031 was not found to be correlated with hENT/hCTN, dCK or CDA transcript levels. Gemcitabine and NUC1031 showed equivalent efficacy in a CDA-high PDX model in vivo contradicting the primary rationale of NUC1031 design.

CONCLUSION

NUC1031 did not exhibit evidence of superior activity over gemcitabine, as a single-agent, or in combination with cisplatin, in either our in vivo or in vitro BTC models. Given that the largest Phase 3 study (ClinicalTrials.gov: NCT0314666) to date in BTC is underway (N = 828) comparing NUC1031/cisplatin to gemcitabine/cisplatin, our results suggest that a more conservative clinical evaluation path would be more appropriate.

New and Emerging Systemic Therapeutic Options for Advanced Cholangiocarcinoma

Cholangiocarcinoma (CCA) represents a disease entity that comprises a heterogeneous group of biliary malignant neoplasms, with variable clinical presentation and severity. It may be classified according to its anatomical location and distinguished in intrahepatic (iCCA), perihilar (pCCA), or distal (dCCA), each subtype implying distinct epidemiology, biology, prognosis, and strategy for clinical management. Its incidence has increased globally over the past few decades, and its mortality rate remains high due to both its biological aggressiveness and resistance to medical therapy. Surgery is the only potentially curative treatment and is the standard approach for resectable CCA; however, more than half of the patients have locally advanced or metastatic disease at presentation. For patients with unresectable CCA, the available systemic therapies are of limited effectiveness. However, the advances of the comprehension of the complex molecular landscape of CCA and its tumor microenvironment could provide new keys to better understand the pathogenesis, the mechanisms of resistance and ultimately to identify promising new therapeutic targets. Recently, clinical trials targeting isocitrate dehydrogenase (IDH)-1 mutations and fibroblast growth factor receptor (FGFR)-2 fusions, as well as immunotherapy showed promising results. All these new and emerging therapeutic options are herein discussed.

Chemopreventive efficacy of stampidine in a murine breast cancer model

Background: The purpose of the present study was to examine the chemopreventive effect of stampidine, an aryl phosphate derivative of stavudine, in side by side comparison with the standard anti-breast cancer drug paclitaxel in the well-established 7,12-dimethylbenz(a)anthracene (DMBA)-induced murine breast cancer model.Methods: Groups of 20 female mice were challenged with the DMBA. DMBA-challenged mice were assigned to various chemoprevention treatments, including stampidine, paclitaxel, and stampidine plus paclitaxel according to the same treatment schedules for 25 weeks.Results: Stampidine resulted in substantially reduced numbers of tumors, tumor weight as well as tumor size in DMBA-treated mice. Stampidine was as effective as paclitaxel in the model and their combination exhibited greater chemopreventive activity, as measured by reduced tumor incidence and improved tumor-free survival as well as overall survival of DMBA-treated mice. The length of time for the initial tumor to appear in DMBA-challenged mice treated with stampidine was longer than that of mice treated DMBA-challenged control mice. Tumors from mice treated with stampidine or stampidine plus paclitaxel displayed unique changes of a signature protein cassette comprised BRCA1, p21, Bax, and Bcl-2.Conclusion: Stampidine has potent chemopreventive activity and is as effective as the standard chemotherapy drug paclitaxel in the chemical carcinogenesis.

Pharmacotherapeutic options for biliary tract cancer: current standard of care and new perspectives

Introduction: Biliary tract cancer (BTC), which comprises gallbladder cancer, ampullary cancer, and cholangiocarcinoma, is a rare and heterogeneous entity, with limited approved therapeutic options. However, interest in this disease has grown exponentially in recent years, as a mounting body of evidence has shed light on the complex molecular and microenvironmental background of BTC, and clinical investigations have explored a variety of new agents and combinations, with promising results.Areas covered: This review describes the standard of care in advanced BTC and summarizes the most recent evidence available on the pharmacological treatment of resected and advanced disease, focusing on chemotherapy, targeted therapy, and immunotherapy.Expert opinion: The therapeutic armamentarium of BTC has made radical progress after almost a decade of very few positive results. Phase-III evidence now supports the use of adjuvant capecitabine after resection of localized disease, while investigations into improved regimens in the advanced setting are underway, exploring alternative options to the standard gemcitabine-cisplatin doublet. The first positive phase-III trial supports the use of the mFOLFOX6 regimen as a second-line chemotherapy. Targeted therapy against specific genomic alterations can combine with chemotherapy in specific subsets of patients. Despite recent advancements, conducting clinical trials for BTC is still a real challenge.

Chemoresistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC), generally known as pancreatic cancer (PC), ranks the fourth leading cause of cancer-related deaths in the western world. While the incidence of pancreatic cancer is displaying a rising tendency every year, the mortality rate has not decreased significantly because of late diagnosis, early metastasis, and limited reaction to chemotherapy or radiotherapy. Adjuvant chemotherapy after surgical resection is typically the preferred option to treat early pancreatic cancer. Although 5-fluorouracil/leucovorin with irinotecan and oxaliplatin (FOLFIRINOX) and gemcitabine/nab-paclitaxel can profoundly improve the prognosis of advanced pancreatic cancer, the development of chemoresistance still leads to poor clinical outcomes. Chemoresistance is multifactorial as a result of the interaction among pancreatic cancer cells, cancer stem cells, and the tumor microenvironment. Nevertheless, more pancreatic cancer patients will benefit from precision treatment and targeted drugs. Therefore, we outline new perspectives for enhancing the efficacy of gemcitabine after reviewing the related factors of gemcitabine metabolism, mechanism of action, and chemoresistance.

Genome-scale CRISPR/Cas9 screen determines factors modulating sensitivity to ProTide NUC-1031

Gemcitabine is a fluoropyrimidine analogue that is used as a mainstay of chemotherapy treatment for pancreatic and ovarian cancers, amongst others. Despite its widespread use, gemcitabine achieves responses in less than 10% of patients with metastatic pancreatic cancer and has a very limited impact on overall survival due to intrinsic and acquired resistance. NUC-1031 (Acelarin), a phosphoramidate transformation of gemcitabine, was the first anti-cancer ProTide to enter the clinic. We find it displays important in vitro cytotoxicity differences to gemcitabine, and a genome-wide CRISPR/Cas9 genetic screening approach identified only the pyrimidine metabolism pathway as modifying cancer cell sensitivity to NUC-1031. Low deoxycytidine kinase expression in tumour biopsies from patients treated with gemcitabine, assessed by immunostaining and image analysis, correlates with a poor prognosis, but there is no such correlation in tumour biopsies from a Phase I cohort treated with NUC-1031.

Medical treatment for cholangiocarcinoma

Most of the patients with cholangiocarcinoma (CCA) present with advanced (inoperable or metastatic) disease, and relapse rates are high in those undergoing potentially curative resection. Previous treatment nihilism of patients with advanced disease has been replaced by active clinical research with the advent of randomized clinical trials (RCTs) and a much greater effort at understanding molecular mechanisms underpinning CCA. Three RCTs have recently been reported evaluating adjuvant chemotherapy following curative resection; only one of these has the potential to change practice. The BILCAP study failed to meet its primary endpoint by intention-to-treat analysis; however, a survival benefit was seen in a preplanned sensitivity analysis (predominantly adjusting for lymph nodes status). This, along with the numerical difference in median overall survival has led to the uptake of adjuvant capecitabine by many clinicians. In patients with advanced disease, the only level 1 data available supports the use of cisplatin and gemcitabine for the first-line treatment of patients with advanced disease; there is no established second-line chemotherapy. Previous forays into targeted therapy have proven unfruitful (namely targeting the epithelial growth factor receptor and vascular endothelial growth factor pathways). An increasing number of genomic subtypes are being defined; for some of these on-target therapeutic options are under active investigation. The most developed are studies targeting IDH-1 (isocitrate dehydrogenase) mutations and FGFR-2 (fibroblast growth factor receptor) fusions, with promising early results. Several other pathways are under evaluation, along with early studies targeting the immune environment; these are too premature to change practice to date. These emerging treatments are discussed.