Correlation of Baseline Tumor Burden with Clinical Outcome in Melanoma Patients Treated with Ipilimumab.

INTRODUCTION: Tumor burden is a frequently mentioned parameter; however, a commonly accepted definition is still lacking. METHODS: In this double-center prospective and retrospective study, 76 patients with unresectable stage III or stage IV melanoma treated with ipilimumab were included. We defined the baseline tumor burden (BTB) as the global sum of all metastases' longest diameters before treatment started and correlated the calculated BTB with disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and with the baseline levels of LDH, S100B, and sULPB2. RESULTS: BTB correlated significantly with DCR (p = 0.009), PFS (p = 0.002), OS (p = 0.032), and the occurrence of NRAS mutation (p = 0.006). BTB was also correlated to baseline serum levels of LDH (p = 0.011), S100B (p = 0.027), and SULBP (p < 0.0001). Multivariate analysis revealed that BPB and LDH were independently correlated with PFS and OS. With increasing BTB, disease control was less likely; no patient with a BTB >200 mm achieved disease control. For patients with brain metastasis, no correlation of BTB with DCR (p = 0.251), PFS (p = 0.059), or OS (p = 0.981) was observed. CONCLUSION: Calculated BTB is an independent prognostic factor for patients with metastatic melanoma treated with ipilimumab. Using calculated BTB as a definition of tumor burden may help increase comparability of outcome of therapies in future studies.

Aldosterone Glucuronide, an Important Biomarker: Synthesis and Structure Elucidation of Novel Isomers.

Aldosterone 1 is a mineralocorticoid, it has great influence on the blood pressure and its glucuronide is an important marker for the detection of several diseases. Here, we describe the chemical synthesis of different aldosterone-18- and 20-glucuronides. Reaction of trimethylsilyl 2,3,4-tri- acetyl-1-ß-glucuronic acid methyl ester 5 b and aldosterone diacetate 11 in the presence of TMSOTf gave the 18-α-glucuronide 9 a. The 18-ß-glucuronide 15 b and the 20-ß-glucuronide 16 b could be obtained by reaction of methyl 2,3,4-tri-O-isobutyryl-1α-glucuronate trichloroacetimidate 14 and aldosterone 21-acetate 8 in the presence of TMSOTf or BF3 ⋅OEt2 . Finally, reaction of aldosterone 21-acetate 8 and methyl 2,3,4-triacetyl-1α-glucuronate trichloroacetimidate 19 in the presence of TMSOTf gave the corresponding methyl 18-ß-triacetylglucuronate 9 b, which was transformed into the desired aldosterone-18-ß-glucuronide 3 by two enzyma- tic transformations.

Bifunctional Duocarmycin Analogues as Inhibitors of Protein Tyrosine Kinases.

Bifunctional duocarmycin analogues are highly cytotoxic compounds that have been shown to be irreversible aldehyde dehydrogenase 1 inhibitors. Interestingly, cells with low aldehyde dehydrogenase 1 expression are also sensitive to bifunctional duocarmycin analogues, suggesting the existence of another target. Through in silico approaches, including principal component analysis, structure-similarity search, and docking calculations, protein tyrosine kinases, and especially the vascular endothelial growth factor receptor 2 (VEGFR-2), were predicted as targets of bifunctional duocarmycin analogues. Biochemical validation was performed in vitro, confirming the in silico results. Structural optimization was performed to mainly target VEGFR-2, but not aldehyde dehydrogenase 1. The optimized bifunctional duocarmycin analogue was synthesized. In vitro assays revealed this bifunctional duocarmycin analogue as a strong inhibitor of VEGFR-2, with low residual aldehyde dehydrogenase 1 activity. Altogether, studies revealed bifunctional duocarmycin analogues as a new class of naturally derived compounds that express a very high cytotoxicity to cancer cells overexpressing aldehyde dehydrogenase 1 as well as VEGFR-2.

Enantioselective Total Synthesis of Blennolide†H and Phomopsis-H76†A and Determination of Their Structure.

This work reports on the enantioselective total synthesis of the two dimeric natural chromanone lactones phomopsis-H76 A (5) and blennolide H (6). Both syntheses could be achieved from chromane 11, which was obtained by an enantioselective Wacker-type cyclization with >99 % ee. The dimerization of the corresponding monomers was performed using a palladium-catalyzed Suzuki reaction. Moreover, within this work it was possible to revise the absolute configuration of phomopsis-H76 A and determine the relative as well as absolute configuration of blennolide H.

Enantioselective Total Synthesis and Structure Confirmation of the Natural Dimeric Tetrahydroxanthenone Dicerandrol†C.

The first enantioselective total synthesis of natural dicerandrol C (1 c) as its enantiomer containing a dimeric tetrahydroxanthenone skeleton is described starting from the enantiopure chromane 6 which was obtained through a Wacker-type cyclization with >99 % ee. For the formation of the dimeric skeleton a palladium-catalyzed Suzuki reaction was used. The synthesis allowed the confirmation of the absolute configuration of the dicerandrols.

In vivo imaging of tumour xenografts with an antibody targeting the potassium channel Kv10.1.

The Kv10.1 (Eag1) voltage-gated potassium channel represents a promising molecular target for novel cancer therapies or diagnostic purposes. Physiologically, it is only expressed in the brain, but it was found overexpressed in more than 70 % of tumours of diverse origin. Furthermore, as a plasma membrane protein, it is easily accessible to extracellular interventions. In this study we analysed the feasibility of the anti-Kv10.1 monoclonal antibody mAb62 to target tumour cells in vitro and in vivo and to deliver therapeutics to the tumour. Using time-domain near infrared fluorescence (NIRF) imaging in a subcutaneous MDA-MB-435S tumour model in nude mice, we showed that mAb62-Cy5.5 specifically accumulates at the tumour for at least 1 week in vivo with a maximum intensity at 48 h. Blocking experiments with an excess of unlabelled mAb62 and application of the free Cy5.5 fluorophore demonstrate specific binding to the tumour. Ex vivo NIRF imaging of whole tumours as well as NIRF imaging and microscopy of tumour slices confirmed the accumulation of the mAb62-Cy5.5 in tumours but not in brain tissue. Moreover, mAb62 was conjugated to the prodrug-activating enzyme ß-D-galactosidase (ß-gal; mAb62-ß-gal). The ß-gal activity of the mAb62-ß-gal conjugate was analysed in vitro on Kv10.1-expressing MDA-MB-435S cells in comparison to control AsPC-1 cells. We show that the mAb62-ß-gal conjugate possesses high ß-gal activity when bound to Kv10.1-expressing MDA-MB-435S cells. Moreover, using the ß-gal activatable NIRF probe DDAOG, we detected mAb62-ß-gal activity in vivo over the tumour area. In summary, we could show that the anti-Kv10.1 antibody is a promising tool for the development of novel concepts of targeted cancer therapy.

Design, Synthesis, and Biological Evaluation of Quercetagetin Analogues as JNK1 Inhibitors.

The recent discovery of c-Jun NH2-terminal kinase JNK1 suppression by natural quercetagetin (1) is a promising lead for the development of novel anticancer agents. Using both X-ray structure and docking analyses we predicted that 5'-hydroxy- (2) and 5'-hydroxymethyl-quercetagetin (3) would inhibit JNK1 more actively than the parent compound 1. Notably, our drug design was based on the active enzyme-ligand complex as opposed to the enzyme's relatively open apo structure. In this paper we test our theoretical predictions, aided by docking-model experiments, and report the first synthesis and biological evaluation of quercetagetin analogues 2 and 3. As calculated, both compounds strongly suppress JNK1 activity. The IC50 values were determined to be 3.4 µM and 12.2 µM, respectively, which shows that 2 surpasses the potency of the parent compound 1 (IC50 =4.6 µM). Compound 2 was also shown to suppress matrix metalloproteinase-1 expression with high specificity after UV irradiation.

Enantioselective Total Synthesis of Secalonic Acid E.

The first enantioselective synthesis of a secalonic acid containing a dimeric tetrahydroxanthenone skeleton is described, using a Wacker-type cyclization of a methoxyphenolic compound to form a chiral chroman with a quaternary carbon stereogenic center with >99% ee. Further steps are a Sharpless dihydroxylation and a Dieckmann condensation to give a tetrahydroxanthenone. A late-stage one-pot palladium-catalyzed Suzuki-dimerization reaction leads to the 2,2'-biphenol linkage to complete the enantioselective total synthesis of secalonic acid E in 18 steps with 8% overall yield.

Four- and Sixfold Tandem-Domino Reactions Leading to Dimeric Tetrasubstituted Alkenes Suitable as Molecular Switches.

A highly efficient palladium-catalyzed fourfold tandem-domino reaction consisting of two carbopalladation and two C-H-activation steps was developed for the synthesis of two types of tetrasubstituted alkenes 3 and 6 with intrinsic helical chirality starting from substrates 1 and 4, respectively. A sixfold tandem-domino reaction was also developed by including a Sonogashira reaction. 20 compounds with different substitution patterns were prepared with yields of up to 97 %. Structure elucidation by X-ray crystallography confirmed helical chirality of the two alkene moieties. Photophysical investigations of some of the compounds showed pronounced switching properties through light-controlled changes of their stereochemical configuration.

Structural, Biochemical, and Computational Studies Reveal the Mechanism of Selective Aldehyde Dehydrogenase 1A1 Inhibition by Cytotoxic Duocarmycin Analogues.

Analogues of the natural product duocarmycin bearing an indole moiety were shown to bind aldehyde dehydrogenase 1A1 (ALDH1A1) in addition to DNA, while derivatives without the indole solely addressed the ALDH1A1 protein. The molecular mechanism of selective ALDH1A1 inhibition by duocarmycin analogues was unraveled through cocrystallization, mutational studies, and molecular dynamics simulations. The structure of the complex shows the compound embedded in a hydrophobic pocket, where it is stabilized by several crucial π-stacking and van der Waals interactions. This binding mode positions the cyclopropyl electrophile for nucleophilic attack by the noncatalytic residue Cys302, thereby resulting in covalent attachment, steric occlusion of the active site, and inhibition of catalysis. The selectivity of duocarmycin analogues for ALDH1A1 is unique, since only minor alterations in the sequence of closely related protein isoforms restrict compound accessibility.

A fast way to fluorescence: a fourfold domino reaction to condensed polycyclic compounds.

A fast and efficient palladium-catalyzed fourfold domino Sonogashira/double-carbopalladation/CH-activation reaction that converts simple aromatic systems into complex polycyclic hydrocarbons has been developed. A number of substituted products has thus been prepared in yields up to 89 %. The structural assignment has been confirmed by using single-crystal X-ray crystallography. The products show intriguing fluorescence activity and thus might serve as chemical sensors or fluorescent imaging dyes.

Enantioselective total synthesis of the lignan (+)-linoxepin.

An enantioselective total synthesis of the natural (+)-linoxepin (1) was accomplished in eleven steps from bromovanin (24). Key steps are a domino carbopalladation/ Mizoroki-Heck reaction with the formation of a pentacyclic system, an asymmetric hydroboration as well as an oxidative lactonization.

A domino approach to the enantioselective total syntheses of blennolide C and gonytolide C.

The first enantioselective total syntheses of the tetrahydroxanthenone (-)-blennolide C (ent-4) and related γ-lactonyl chromanone (-)-gonytolide C (ent-3) are reported. Key to the syntheses is an enantioselective domino-Wacker/carbonylation/methoxylation reaction to set up the stereocentre at C-4a. Various chiral BOXAX ligands were investigated, including novel (S,S)-iBu-BOXAX, and allowed access to chromane 8 in an excellent enantioselectivity of 99 %. The second stereocentre at C-4 was established employing a diastereoselective Sharpless dihydroxylation. An extensive survey of (DHQ)- and (DHQD)-based ligands enabled the preparation of both the anti-isomer 14 a and the syn-isomer 14 b in very good to reasonable selectivities of 13.7:1 and 1:3.7, respectively. While 14 a was further converted to ent-3 and ent-4, 14 b was elaborated to syn-acid 25 and 2'-epi-gonytolide C 28.

Enantioselective total synthesis of (-)-blennolide†A.

Blennolide A can be synthesized through an enantioselective domino-Wacker/carbonylation/methoxylation reaction of 7a with 96 % ee and an enantioselective Wacker oxidation of 7b with 89 % ee. Further transformations led to the α,ß-unsaturated ester (E)-17, which was subjected to a highly selective Michael addition, introducing a methyl group to give 18a. After a threefold oxidation and an intramolecular acylation, the tetrahydroxanthenone 4 was obtained, which could be transformed into (-)-blennolide A (ent-1) in a few steps.

Photoactivatable prodrugs of highly potent duocarmycin analogues for a selective cancer therapy.

A main problem of common cancer chemotherapy is the occurrence of severe side effects caused by insufficient selectivity of the applied drugs. A possible concept to overcome this limitation is light-driven prodrug monotherapy. The synthesis as well as photochemical and biological evaluation of new photoactivatable prodrugs is described. Best results were obtained with prodrug (S,S)-7a. The photochemical labile protecting groups in (S,S)-7a can easily be removed by irradiation with UV-A light in 30 min with a power of only 2 J cm(-2). The determination of the in vitro cytotoxicity by using an HTCFA-test reveals a QIC(50) value of 8200 and the prodrug is more than two million times less cytotoxic than the corresponding seco-drug (-)-(S,S)-5 with an IC(50) value of about 110 fM. The big therapeutic window makes (S,S)-7a very suitable for its use in selective cancer therapy.

Enantioselective total synthesis of (-)-diversonol.

For the synthesis of (-)-diversonol (ent-1), an enantioselective domino-Wacker/carbonylation/methoxylation reaction and an enantioselective Wacker oxidation were used to give the chroman in high yield and 96% and 93% ee, respectively. Dihydroxylation at the vinyl moiety using the Sharpless procedure and a Wittig-Horner reaction followed by hydrogenation, benzylic oxidation, and an intramolecular acylation provided the tetrahydroxanthenone, from which ent-1 is accessible in a few steps. Furthermore, the synthesis of the diastereomeric diversonol rac-1,9a-epi-diversonol (rac-41) is also described.

Selective cancer therapy by extracellular activation of a highly potent glycosidic duocarmycin analogue.

Conventional cancer chemotherapy is limited by systemic toxicity and poor selectivity. Tumor-selective activation of glucuronide prodrugs by beta-glucuronidase in the tumor microenvironment in a monotherapeutic approach is one promising way to increase cancer selectivity. Here we examined the cellular requirement for enzymatic activation as well as the in vivo toxicity and antitumor activity of a glucuronide prodrug of a potent duocarmycin analogue that is active at low picomolar concentrations. Prodrug activation by intracellular and extracellular beta-glucuronidase was investigated by measuring prodrug 2 cytotoxicity against human cancer cell lines that displayed different endogenous levels of beta-glucuronidase, as well as against beta-glucuronidase-deficient fibroblasts and newly established beta-glucuronidase knockdown cancer lines. In all cases, glucuronide prodrug 2 was 1000-5000 times less cytotoxic than the parent duocarmycin analogue regardless of intracellular levels of beta-glucuronidase. By contrast, cancer cells that displayed tethered beta-glucuronidase on their plasma membrane were 80-fold more sensitive to glucuronide prodrug 2, demonstrating that prodrug activation depended primarily on extracellular rather than intracellular beta-glucuronidase activity. Glucuronide prodrug 2 (2.5 mg/kg) displayed greater antitumor activity and less systemic toxicity in vivo than the clinically used drug carboplatin (50 mg/kg) to mice bearing human lung cancer xenografts. Intratumoral injection of an adenoviral vector expressing membrane-tethered beta-glucuronidase dramatically enhanced the in vivo antitumor activity of prodrug 2. Our data provide evidence that increasing extracellular beta-glucuronidase activity in the tumor microenvironment can boost the therapeutic index of a highly potent glucuronide prodrug.

Evaluation of the heat sensitivity of Trichophyton rubrum and Trichophyton interdigitale.

BACKGROUND: Onychomycosis affects up to 50% of patients in the older population. OBJECTIVES: This study aimed to explore heat sensitivity of Trichophyton rubrum and Trichophyton interdigitale as pathogens of onychomycosis. MATERIALS & METHODS: The fungi were heated in sterile saline solution up to 100°C for five or 10 minutes with or without additional previous treatment with 1% ciclopirox solution or chitinase and 1,3 -galactidase or for 45 minutes at 40°C or 60°C with washing powder. Subsequently, the fungi were cultured and regrowth was assessed after one week. RESULTS: After heating T. rubrum for five minutes at 60°C, growth was completely inhibited. After heating T. interdigitale for five minutes at 60°C, all of the samples regrew, and at 95°C, none of the samples regrew. No difference between five and 10-minute heating was observed. Previous incubation with 1% ciclopirox solution for 24 hours inhibited the growth of T. rubrum completely. T. interdigitale was still able to regrow to 100% after five minutes at 40°C, to 33% after 60°C, and to 22% after 80°C. Incubation for 45 minutes with washing powder solution at 40°C or 60°C did not lead to significant growth reduction of T. rubrum or interdigitale. Two hours incubation with -1,3-glucanase and chitinase prior to five minutes of heating to 60°C and 80°C reduced the heat resistance of T. interdigitale; growth was inhibited in 56% and 100% of the samples, respectively. CONCLUSION: The heat resistance of T. rubrum and interdigitale should be considered using non-medical thermal treatment.

Synthesis of tetrasubstituted alkenes through a palladium-catalyzed domino carbopalladation/C-H-activation reaction.

Helical tetrasubstituted alkenes (7) were obtained in a highly efficient way through a palladium-catalyzed domino-carbopalladation/CH-activation reaction of propargylic alcohols 6 in good to excellent yields. Electron-withdrawing- and electron-donating substituents can be introduced onto the upper and lower aromatic rings. The substrates (6) for the domino process were synthesized by addition of the lithiated alkyne (20) to various aldehydes (19); moreover, the substrates were accessible enantioselectively (in 95% ee) by reduction of the corresponding ketone using the Noyori procedure.

Synthesis, biological evaluation, and live cell imaging of novel fluorescent duocarmycin analogs.

For a better understanding of the mode of action of duocarmycin and its analogs, the novel fluorescent duocarmycin derivatives 13-15 and 17b-19b were synthesized, and their bioactivity as well as their cellular uptake investigated using confocal laser scanning microscopy (CLSM) in live-cell imaging experiments.