Insights into Free Drug Release from Efficacious N-Acyl O-Aminophenol Duocarmycin Prodrugs

Acyclic and cyclic N-acyl O-aminophenol prodrugs of duocarmycin analogues were reported as members of a unique class of reductively cleaved prodrugs that map seamlessly onto the duocarmycin family of natural products. Although these prodrugs were explored with the expectations that they may be cleaved selectively within hypoxic tumor environments that have intrinsically higher concentrations of reducing nucleophiles, the remarkable stability of some such prodrugs suggests another mechanism of free drug release is operative. The prototype of such chemically unreactive N-acyl O-aminophenol prodrugs is 1, which proved remarkably efficacious in vivo in vertebrate tumor models; was found to lack the toxicity that is characteristic of traditional chemotherapeutic drugs as well as the free drugs in the class (e.g., myelosuppression); and displayed a preferential site (intracellular), a slow and sustained rate, and a potentially unique mechanism of free drug release. Herein, we detail studies that provide insights into this stereoselective mechanism of free drug release. Combined, the results of the studies are consistent with an exclusive protein-mediated (enantio)selective activation and free drug release from prodrug 1 by N-O bond cleavage preferentially in cancer cell lines versus cultured normal human cell lines effected by a cytosolic cysteine-based enzyme and suggest that the activating protein is one that is selectively expressed, upregulated, or preferentially activated in cancer cell lines, potentially constituting a new oncology targeted precision therapy.

Prodrugs in Oncology: Bioactivation and Impact on Therapeutic Efficacy and Toxicity

A prodrug is a molecule that lacks pharmacological activity, but upon enzymatic bioactivation, it can generate a therapeutically active molecule. The primary reason behind the design of a prodrug is to help circumvent challenges associated with the physicochemical properties of a drug molecule, such as solubility, absorption, distribution, and instability. Chemotherapy has been at the forefront of cancer treatment for over 70 years due to its ability to target rapidly proliferating tumor cells. However, a major concern with conventional chemotherapy is the lack of selectivity and its associated side toxicity, which can severely impact patients' quality of life. In oncology, prodrugs have been explored to enhance the bioavailability, improve efficacy, and minimize systemic toxicity of chemotherapeutic agents. Prodrugs activated by enzymes unique to a tumor microenvironment can significantly increase targeted delivery of chemotherapeutic drugs. This review aims to highlight commonly used chemotherapeutic prodrugs, including both alkylating and non-alkylating agents, and discuss their clinical relevance, mechanisms of bioactivation, and toxicity concerns.

Induction of Endoplasmic Reticulum Stress and Aryl Hydrocarbon Receptor Pathway Expression by Blue LED Irradiation in Oral Squamous Cell Carcinoma

Photobiomodulation therapy, as an emerging treatment modality, has been widely used in dentistry. However, reports on blue light therapy for oral cancer are scarce. This study investigated the effects of 457 and 475 nm LED irradiation on SCC-25 cells and explored the potential mechanisms underlying the impact of blue light. Both wavelengths were found to inhibit cell viability, induce oxidative stress, and cause cell cycle arrest without leading to cell death. Notably, the inhibitory effect of 457 nm blue light on cell proliferation was more sustained. Transcriptome sequencing was performed to explore the underlying mechanisms, revealing that blue light induced endoplasmic reticulum stress in SCC-25 cells, with 457 nm light showing a more pronounced effect. Moreover, 457 nm blue light upregulated the expression of the aryl hydrocarbon receptor pathway, indicating potential therapeutic prospects for the combined use of blue light and pharmacological agents.

Borylation via iridium catalysed C-H activation: a new concise route to duocarmycin derivatives

The synthesis of the ethyl ester analogue of the ultrapotent antitumour antibiotic seco-duocarmycin SA has been achieved in eleven linear steps from commercially available starting materials. The DSA alkylation subunit can be made in ten linear steps from the same precursor. The route involves C-H activation at the equivalent of the C7 position on indole leading to a borylated intermediate 9 that is stable enough for peptide coupling reactions but can be easily converted to the free hydroxyl analogue.

Rapid Construction of a Chloromethyl-Substituted Duocarmycin-like Prodrug

The construction of duocarmycin-like compounds is often associated with lengthy synthetic routes. Presented herein is the development of a short and convenient synthesis of a type of duocarmycin prodrug. The 1,2,3,6-tetrahydropyrrolo[3,2-e]indole-containing core is here constructed from commercially available Boc-5-bromoindole in four steps and 23% overall yield, utilizing a Buchwald-Hartwig amination followed by a sodium hydride-induced regioselective bromination. In addition, protocols for selective mono- and di-halogenations of positions 3 and 4 were also developed, which could be useful for further exploration of this scaffold.

40 Years of Duocarmycins: A Graphical Structure/Function Review of Their Chemical Evolution, from SAR to Prodrugs and ADCs

Synthetic analogues of the DNA-alkylating cytotoxins of the duocarmycin class have been extensively investigated in the past 40 years, driven by their high potency, their unusual mechanism of bioactivity, and the beautiful modularity of their structure-activity relationship (SAR). This Perspective analyzes how the molecular designs of synthetic duocarmycins have evolved: from (1) early SAR studies, through to modern applications for directed cancer therapy as (2) prodrugs and (3) antibody-drug conjugates in late-stage clinical development. Analyzing 583 primary research articles and patents from 1978 to 2022, we distill out a searchable A0-format "Minard map" poster of ca. 200 key structure/function-tuning steps tracing chemical developments across these three key areas. This structure-based overview showcases the ingenious approaches to tune and target bioactivity, that continue to drive development of the elegant and powerful duocarmycin platform.

Cytochrome P450 Binding and Bioactivation of Tumor-Targeted Duocarmycin Agents

Duocarmycin natural products are promising anticancer cytotoxins but too potent for systemic use. Re-engineering of the duocarmycin scaffold has enabled the discovery of prodrugs designed for bioactivation by tissue-specific cytochrome P450 (P450) enzymes. Lead prodrugs bioactivated by both P450 isoforms CYP1A1 and CYP2W1 have shown promising results in xenograft studies; however, to fully understand the potential of these agents it is desirable to compare dual-targeting compounds with isoform-selective analogs. Such redesign requires insight into the molecular interactions with these P450 enzymes. Herein binding and metabolism of the individual stereoisomers of the indole-based duocarmycin prodrug ICT2700 and a nontoxic benzofuran analog ICT2726 were evaluated with CYP1A1 and CYP2W1, revealing differences exploitable for drug design. Although enantiomers of both compounds bound to and were metabolized by CYP1A1, the stereochemistry of the chloromethyl fragment was critical for CYP2W1 interactions. CYP2W1 differentially binds the S enantiomer of ICT2726, and its metabolite profile could potentially be used as a biomarker to identify CYP2W1 functional activity. In contrast to benzofuran-based ICT2726, CYP2W1 differentially binds the R isomer of the indole-based ICT2700 over the S stereoisomer. Thus the ICT2700 R configuration warrants further investigation as a scaffold to favor CYP2W1-selective bioactivation. Furthermore, structures of both duocarmycin S enantiomers with CYP1A1 reveal orientations correlating with nontoxic metabolites, and further drug design optimization could lead to a decrease of CYP1A1 bioactivation. Overall, distinctive structural features present in the two P450 active sites can be useful for improving P450-and thus tissue-selective-bioactivation. SIGNIFICANCE STATEMENT: Prodrug versions of the natural product duocarmycin can be metabolized by human tissue-specific cytochrome P450 (P450) enzymes 1A1 and 2W1 to form an ultrapotent cytotoxin and/or high affinity 2W1 substrates to potentially probe functional activity in situ. The current work defines the binding and metabolism by both P450 enzymes to support the design of duocarmycins selectively activated by only one human P450 enzyme.

Cytochrome P450 isoforms 1A1, 1B1 AND 2W1 as targets for therapeutic intervention in head and neck cancer

Epidemiological studies have shown that head and neck cancer (HNC) is a complex multistage process that in part involves exposure to a combination of carcinogens and the capacity of certain drug-metabolising enzymes including cytochrome P450 (CYP) to detoxify or activate such carcinogens. In this study, CYP1A1, CYP1B1 and CYP2W1 expression in HNC was correlated with potential as target for duocarmycin prodrug activation and selective therapy. In the HNC cell lines, elevated expression was shown at the gene level for CYP1A1 and CYP1B1 whereas CYP2W1 was hardly detected. However, CYP2W1 was expressed in FaDu and Detroit-562 xenografts and in a cohort of human HNC samples. Functional activity was measured in Fadu and Detroit-562 cells using P450-Glo™ assay. Antiproliferative results of duocarmycin prodrugs ICT2700 and ICT2706 revealed FaDu and Detroit-562 as the most sensitive HNC cell lines. Administration of ICT2700 in vivo using a single dose of ICT2700 (150 mg/kg) showed preferential inhibition of small tumour growth (mean size of 60 mm³) in mice bearing FaDu xenografts. Significantly, our findings suggest a potential targeted therapeutic approach to manage HNCs by exploiting intratumoural CYP expression for metabolic activation of duocarmycin-based prodrugs such as ICT2700.

Transcriptional profiling of Chinese hamster ovary (CHO) cells exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a man-made chemical compound contaminating the environment. An exposure of organisms to TCDD results in numerous disorders. The main mechanism of TCDD action involves the induction of the aryl hydrocarbon receptor (AhR) pathway followed by the increase in the expression and activity of cytochrome P450 family 1 (CYP1) enzymes. The main aim of the present study was to identify, by means of RNA sequencing, transcripts involved in the mechanism of TCDD action in Chinese hamster ovary (CHO) cells, known to not express CYP1A1 enzyme. The CHO cells were treated with TCDD for 3, 12 or 24 h, and total RNA was isolated and sequenced. Thirty six (p_adjusted < 0.05) or six (p_adjusted < 0.05, log2FC ≥ 1.0/log2FC≤-1.0) differentially expressed genes (DEGs) were identified in TCDD-treated cells depending on the assumed statistical criteria. The dioxin up- and downregulated the expression of genes associated with ovarian follicle functions, development, cardiovascular system, signal transduction, inflammation and carcinogenesis. TCDD did not affect the expression of any of 522 miRNAs which were identified in the cells. The expression of CYP1A1, CYP1A2 and CYP1B1 was demonstrated neither in control nor in TCDD-treated CHO cells, although the respective genes were found in the cell genome. Twenty two other CYP enzymes were identified in CHO cells, however their expression was also not affected by TCDD.

Probing cytochrome P450 (CYP) bioactivation with chloromethylindoline bioprecursors derived from the duocarmycin family of compounds

The duocarmycins belong to a class of agent which has great potential for use in cancer therapy. Their exquisite potency means they are too toxic for systemic use, and targeted approaches are required to unlock their clinical potential. In this study, we have explored seco-OH-chloromethylindoline (CI) duocarmycin-based bioprecursors for their potential for cytochrome P450 (CYP)-mediated cancer cell kill. We report on synthetic and biological explorations of racemic seco-CI-MI, where MI is a 5-methoxy indole motif, and dehydroxylated analogues. We show up to a 10-fold bioactivation of de-OH CI-MI and a fluoro bioprecursor analogue in CYP1A1-transfected cells. Using CYP bactosomes, we also demonstrate that CYP1A2 but not CYP1B1 or CYP3A4 has propensity for potentiating these compounds, indicating preference for CYP1A bioactivation.

Intratumoural Cytochrome P450 Expression in Breast Cancer: Impact on Standard of Care Treatment and New Efforts to Develop Tumour-Selective Therapies

Despite significant advances in treatment strategies over the past decade, selective treatment of breast cancer with limited side-effects still remains a great challenge. The cytochrome P450 (CYP) family of enzymes contribute to cancer cell proliferation, cell signaling and drug metabolism with implications for treatment outcomes. A clearer understanding of CYP expression is important in the pathogenesis of breast cancer as several isoforms play critical roles in metabolising steroid hormones and xenobiotics that contribute to the genesis of breast cancer. The purpose of this review is to provide an update on how the presence of CYPs impacts on standard of care (SoC) drugs used to treat breast cancer as well as discuss opportunities to exploit CYP expression for therapeutic intervention. Finally, we provide our thoughts on future work in CYP research with the aim of supporting ongoing efforts to develop drugs with improved therapeutic index for patient benefit.

Biological roles of cytochrome P450 1A1, 1A2, and 1B1 enzymes

Human cytochrome P450 enzymes (CYPs) play a critical role in various biological processes and human diseases. CYP1 family members, including CYP1A1, CYP1A2, and CYP1B1, are induced by aryl hydrocarbon receptors (AhRs). The binding of ligands such as polycyclic aromatic hydrocarbons activates the AhRs, which are involved in the metabolism (including oxidation) of various endogenous or exogenous substrates. The ligands that induce CYP1 expression are reported to be carcinogenic xenobiotics. Hence, CYP1 enzymes are correlated with the pathogenesis of cancers. Various endogenous substrates are involved in the metabolism of steroid hormones, eicosanoids, and other biological molecules that mediate the pathogenesis of several human diseases. Additionally, CYP1s metabolize and activate/inactivate therapeutic drugs, especially, anti-cancer agents. As the metabolism of drugs determines their therapeutic efficacy, CYP1s can determine the susceptibility of patients to some drugs. Thus, understanding the role of CYP1s in diseases and establishing novel and efficient therapeutic strategies based on CYP1s have piqued the interest of the scientific community.

How can the potential of the duocarmycins be unlocked for cancer therapy?

The duocarmycins belong to a class of agent that has fascinated scientists for over four decades. Their exquisite potency, unique mechanism of action, and efficacy in multidrug-resistant tumour models makes them attractive to medicinal chemists and drug hunters. However, despite great advances in fine-tuning biological activity through structure-activity relationship studies (SARS), no duocarmycin-based therapeutic has reached clinical approval. In this review, we provide an overview of the most promising strategies currently used and include both tumour-targeted prodrug approaches and antibody-directed technologies.

Probing cytochrome P450 bioactivation and fluorescent properties with morpholinyl-tethered anthraquinones

Structural features from the anticancer prodrug nemorubicin (MMDX) and the DNA-binding molecule DRAQ5™ were used to prepare anthraquinone-based compounds, which were assessed for their potential to interrogate cytochrome P450 (CYP) functional activity and localisation. 1,4-disubstituted anthraquinone 8 was shown to be 5-fold more potent in EJ138 bladder cancer cells after CYP1A2 bioactivation. In contrast, 1,5-bis((2-morpholinoethyl)amino) substituted anthraquinone 10 was not CYP-bioactivated but was shown to be fluorescent and subsequently photo-activated by a light pulse (at a bandwidth 532-587 nm), resulting in punctuated foci accumulation in the cytoplasm. It also showed low toxicity in human osteosarcoma cells. These combined properties provide an interesting prospective approach for opto-tagging single or a sub-population of cells and seeking their location without the need for continuous monitoring.

Activation of Phenyl 4-(2-Oxo-3-alkylimidazolidin-1-yl)benzenesulfonates Prodrugs by CYP1A1 as New Antimitotics Targeting Breast Cancer Cells

Prodrug-mediated utilization of the cytochrome P450 (CYP) 1A1 to obtain the selective release of potent anticancer products within cancer tissues is a promising approach in chemotherapy. We herein report the rationale, preparation, biological evaluation, and mechanism of action of phenyl 4-(2-oxo-3-alkylimidazolidin-1-yl)benzenesulfonates (PAIB-SOs) that are antimicrotubule prodrugs activated by CYP1A1. Although PAIB-SOs are inert in most cells tested, they are highly cytocidal toward several human breast cancer cells, including hormone-independent and chemoresistant types. PAIB-SOs are N-dealkylated into cytotoxic phenyl 4-(2-oxo-3-imidazolidin-1-yl)benzenesulfonates (PIB-SOs) in CYP1A1-positive cancer cells, both in vitro and in vivo. In conclusion, PAIB-SOs are novel chemotherapeutic prodrugs with no equivalent among current antineoplastics and whose selective action toward breast cancer is tailored to the characteristic pattern of CYP1A1 expression observed in a large percentage of human breast tumors.

Cytochrome P450 2W1 (CYP2W1) - ready for use as the biomarker and drug target for cancer?

1. This article aims to evaluate the potentials of using cytochrome P450 2W1 (CYP2W1) as a biomarker and a drug target of cancer because of its characteristic cancer-specific expression. 2. Discrepant findings comparing the expression levels of CYP2W1 in cancer and non-cancer samples were reported. In general, the expression followed a developmental pattern. The demethylation status of CpG island and the expression levels of CYP2W1 genes was positively correlated. 3. CYP2W1 was able to activate several procarcinogens, anticancer pro-drugs and to metabolise many endogenous substances including fatty acids and lysophospholipids. 4. CYP2W1 expression level was suggested to serve as an independent prognostic biomarker in colorectal cancer and hepatocellular carcinoma. The correlation of genetic polymorphisms of CYP2W1 and cancer risk was uncertain. 5. Further characterisation of CYP2W1 structure is suggested to link to its functions. More studies are warranted to reveal the true status and the regulation of CYP2W1 expression across normal and cancer tissues. Catalytic activity of CYP2W1 should be tested on a wider spectrum of endogenous and exogenous substances before its use as the drug target. Larger size of clinical samples can be included to verify the potential of CYP2W1 as the prognostic or cancer risk biomarker.

Rational Development of Novel Activity Probes for the Analysis of Human Cytochromes P450

The identification and quantification of functional cytochromes P450 (CYPs) in biological samples is proving important for robust analyses of drug efficacy and metabolic disposition. In this study, a novel CYP activity-based probe was rationally designed and synthesised, demonstrating selective binding of CYP isoforms. The dependence of probe binding upon the presence of NADPH permits the selective detection of functionally active CYP. This allows the detection and analysis of these enzymes using biochemical and proteomic methodologies and approaches.

Aldehyde dehydrogenase as a marker and functional mediator of metastasis in solid tumors

There is accumulating evidence indicating that aldehyde dehydrogenase (ALDH) activity selects for cancer cells with increased aggressiveness, capacity for sustained proliferation, and plasticity in primary tumors. However, emerging data also suggests an important mechanistic role for the ALDH family of isoenzymes in the metastatic activity of tumor cells. Recent studies indicate that ALDH correlates with either increased or decreased metastatic capacity in a cellular context-dependent manner. Importantly, it appears that different ALDH isoforms support increased metastatic capacity in different tumor types. This review assesses the potential of ALDH as biological marker and mechanistic mediator of metastasis in solid tumors. In many malignancies, most notably in breast cancer, ALDH activity and expression appears to be a promising marker and potential therapeutic target for treating metastasis in the clinical setting.

Solid-Phase Synthesis of Duocarmycin Analogues and the Effect of C-Terminal Substitution on Biological Activity

The duocarmycins are potent antitumor agents with potential for use in the development of antibody-drug conjugates (ADCs) as well as being clinical candidates in their own right. In this article, we describe the synthesis of a duocarmycin monomer (DSA) that is suitably protected for utilization in solid-phase synthesis. The synthesis was performed on a large scale, and the resulting racemic protected Fmoc-DSA subunit was separated by supercritical fluid chromatography (SFC) into the single enantiomers; its application to solid-phase synthesis methodology gave a series of monomeric and extended duocarmycin analogues with amino acid substituents. The DNA sequence selectivity was similar to that in previous reports for both the monomeric and extended compounds. Substitution at the C-terminus of duocarmycin caused a decrease in antiproliferative activity for all of the compounds studied. An extended compound containing an alanine at the C-terminus was converted to the primary amide or to an extended structure containing a terminal tertiary amine, but this had no beneficial effects on biological activity.

A five-membered lactone prodrug of CBI-based analogs of the duocarmycins

The preparation, characterization and examination of the CBI-based 5-membered lactone 5 capable of serving as a prodrug or protein (antibody) conjugation reagent are disclosed along with its incorporation into the corresponding CC-1065 and duocarmycin analog 6, and the establishment of their properties.

Probing cytochrome P450-mediated activation with a truncated azinomycin analogue

Selective cytochrome P450 bioactivation of truncated azinomycin.

Aldehyde dehydrogenases in cancer: an opportunity for biomarker and drug development?

Aldehyde dehydrogenases (ALDHs) belong to a superfamily of 19 isozymes that are known to participate in many physiologically important biosynthetic processes including detoxification of specific endogenous and exogenous aldehyde substrates. The high expression levels of an emerging number of ALDHs in various cancer tissues suggest that these enzymes have pivotal roles in cancer cell survival and progression. Mapping out the heterogeneity of tumours and their cancer stem cell (CSC) component will be key to successful design of strategies involving therapeutics that are targeted against specific ALDH isozymes. This review summarises recent progress in ALDH-focused cancer research and discovery of small-molecule-based inhibitors.

Expression profile of CYP1A1 and CYP1B1 enzymes in colon and bladder tumors

Background

The cytochrome P450 CYP1A1 and CYP1B1 enzymes are involved in carcinogenesis via activation of pro-carcinogenic compounds to carcinogenic metabolites. CYP1A1 and CYP1B1 have shown elevated levels in human tumors as determined by qRT-PCR and immunohistochemical studies. However studies that have examined CYP1 expression by enzyme activity assays are limited.

Results

In the current study the expression of CYP1A1 and CYP1B1 was investigated in a panel of human tumors of bladder and colorectal origin by qRT-PCR and enzyme activity assays. The results demonstrated that 35% (7/20) of bladder tumors and 35% (7/20) of colon tumors overexpressed active CYP1 enzymes. CYP1B1 mRNA was overexpressed in 65% and 60% of bladder and colon tumors respectively, whereas CYP1A1 was overexpressed in 65% and 80% of bladder and colon tumors. Mean mRNA levels of CYP1B1 and CYP1A1 along with mean CYP1 activity were higher in bladder and colon tumors compared to normal tissues (p<0.05). Statistical analysis revealed CYP1 expression levels to be independent of TNM status. Moreover, incubation of tumor microsomal protein in 4 bladder and 3 colon samples with a CYP1B1 specific antibody revealed a large reduction (72.5 ± 5.5 % for bladder and 71.8 ± 7.2% for colon) in catalytic activity, indicating that the activity was mainly attributed to CYP1B1 expression.

Conclusions

The study reveals active CYP1 overexpression in human tumors and uncovers the potential use of CYP1 enzymes and mainly CYP1B1 as targets for cancer therapy.

A fundamental relationship between hydrophobic properties and biological activity for the duocarmycin class of DNA-alkylating antitumor drugs: hydrophobic-binding-driven bonding

Two systematic series of increasingly hydrophilic derivatives of duocarmycin SA that feature the incorporation of ethylene glycol units (n = 1-5) into the methoxy substituents of the trimethoxyindole subunit are described. These derivatives exhibit progressively increasing water solubility along with progressive decreases in cell growth inhibitory activity and DNA alkylation efficiency with the incremental ethylene glycol unit incorporations. Linear relationships of cLogP with -log IC50 for cell growth inhibition and -log AE (AE = cell-free DNA alkylation efficiency) were observed, with the cLogP values spanning the productive range of 2.5-0.49 and the -log IC50 values spanning the range of 11.2-6.4, representing IC50 values that vary by a factor of 10(5) (0.008 to 370 nM). The results quantify the fundamental role played by the hydrophobic character of the compound in the expression of the biological activity of members in this class (driving the intrinsically reversible DNA alkylation reaction) and define the stunning magnitude of its effect.

Efficacious cyclic N-acyl O-amino phenol duocarmycin prodrugs

Two novel cyclic N-acyl O-amino phenol prodrugs are reported as new members of a unique class of reductively cleaved prodrugs of the duocarmycin family of natural products. These prodrugs were explored with the expectation that they may be cleaved selectively within hypoxic tumor environments that have intrinsically higher concentrations of reducing nucleophiles and were designed to liberate the free drug without the release of an extraneous group. In vivo evaluation of the prodrug 6 showed that it exhibits extraordinary efficacy (T/C > 1500, L1210; 6/10 one year survivors), substantially exceeding that of the free drug, that its therapeutic window of activity is much larger, permitting a dosing ≥ 40-fold higher than the free drug, and yet that it displays a potency in vivo that approaches the free drug (within 3-fold). Clearly, the prodrug 6 benefits from either its controlled slow release of the free drug or its preferential intracellular reductive cleavage.

Abstract 2224: Re-engineering of the duocarmycin structural architecture enables tumour-selective CYP2W1-mediated drug activation in human colon cancer xenografts

There is now growing evidence that CYP1A1, 1B1, 2J2, 2S1 and 2W1 are over-expressed in many human tumour types. The ultrapotent duocarmycins are ideal candidates for bioprecursor drug development and we have demonstrated that these can be re-engineered into derivatives selectively activated by CYP1A1 in vitro and in vivo.1,2 In the present study, we have focussed on CYP2W1 as a potential therapeutic target. CYP2W1 is detected in 30% of colon cancers, while its protein expression in non-transformed adult tissues is absent or insignificant.3 We have presented results indicating that the immunohistochemically assessed level of CYP2W1 enzyme could fulfil the criteria for being a prognostic biomarker for stages II and III colorectal cancer.4 Here we present data on furanoindole-based duocarmycins that have the potential to be used as a chemical probe (e.g. ICT2726) to show CYP2W1 functional activity. We also report on indoline-based analogues that elicit potent antiproliferative activity after CYP2W1-mediated activation in cancer cells. Specifically, we have transfected human HEK293, Colo320 and SW480 cells to express CYP2W1 and shown that these suffer rapid loss of viability following treatment with two halogenated duocarmycin bioprecursor compounds (ICT2705 and ICT2706) while no activity in mock-transfected cells was seen. Significantly, ICT2706 was shown to totally prevent tumour growth when administered to SCID mice bearing SW480-2W1 xenografts (dosed daily with 100 mg/kg for 8 days) but not the mock-transfected variant. Subsequent to this treatment, the tumours were extracted for further analysis. Using H2A.X phosphorylation as a marker for DNA damage, our data revealed a time-dependent increase in expression supporting CYP2W1-mediated activation of ICT2706 in vivo. Our findings reveal the opportunities in targeting CYP2W1 as a novel therapeutic approach in colon cancer chemotherapy.

Citation Format: Klaus Pors, Sandra Travica, Paul M. Loadman, Steven D. Shnyder, Mark Sutherland, Helen M. Sheldrake, Mark Searcey, Inger Johansson, Souren Mkrtchian, Magnus IngelmanSundberg, Laurence H. Patterson. Re-engineering of the duocarmycin structural architecture enables tumour-selective CYP2W1-mediated drug activation in human colon cancer xenografts. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2224. doi:10.1158/1538-7445.AM2013-2224

Cytochrome P450-activated prodrugs

A prodrug is a compound that has negligible, or lower, activity against a specified pharmacological target than one of its major metabolites. Prodrugs can be used to improve drug delivery or pharmacokinetics, to decrease toxicity, or to target the drug to specific cells or tissues. Ester and phosphate hydrolysis are widely used in prodrug design because of their simplicity, but such approaches are relatively ineffective for targeting drugs to specific sites. The activation of prodrugs by the cytochrome P450 system provides a highly versatile approach to prodrug design that is particularly adaptable for targeting drug activation to the liver, to tumors or to hypoxic tissues.