Michael M. Wick

Clinical characteristics of early cutaneous melanoma

Clinical characteristics of the primary tumor in 786 patients with superficial spreading melanoma were studied in a prospective sequential series of patients from the Melanoma Clinical Cooperative Group. The most useful features for early diagnosis were change in size and change in color, present in 71% and 55% respectively of patients with level II lesions. Increase in height of lesion correlated with more advanced disease. Ulceration and bleeding were predominantly found in advanced primary lesions and are consequently of limited use in early recognition. Awareness of the historical and clinical features of the primary tumor should result in early recognition and cure of most primary superficial spreading melanomas.

Synthesis and activity of 2,6,9-trisubstituted purines

The preparation of a series of 2,6,9-trisubstituted purines and the structure-activity data for the inhibition of cyclin dependent kinase, CDK2 are presented.

A New Structural Class of Proteasome Inhibitors that Prevent NF-κB Activation

Abstract The multicatalytic proteinase or proteasome is a highly conserved cellular structure that is responsible for the ATP-dependent proteolysis of many proteins involved in important regulatory cellular processes. We have identified a novel class of inhibitors of the chymotrypsin-like proteolytic activity of the 20S proteasome that exhibit ic 50 values ranging from 0.1 to 0.5 μg/mL (0.1 to 1 μM). In cell proliferation assays, these compounds inhibit growth with an ic 50 ranging from 5 to 10 μg/mL (10–20 μM). A representative member of this class of inhibitors was tested in other biological assays. CVT-634 (5-methoxy-1-indanone-3-acetyl-leu- d -leu-1-indanylamide) prevented lipopolysaccharide (LPS), tumor necrosis factor (TNF)-, and phorbol ester-induced activation of nuclear factor κB (NF-κB) in vitro by preventing signal-induced degradation of IκB-α. In these studies, the IκB-α that accumulated was hyperphosphorylated, indicating that CVT-634 did not inhibit IκB-α kinase, the enzyme responsible for signal-induced phosphorylation of IκB-α. In vivo studies indicated that CVT-634 prevented LPS-induced TNF synthesis in a murine macrophage cell line. In addition, in mice pretreated with CVT-634 at 25 and 50 mg/kg and subsequently treated with LPS, serum TNF levels were significantly lower (225 ± 59 and 83 ± 41 pg/mL, respectively) than in those mice that were treated only with LPS (865 ± 282 pg/mL). These studies suggest that specific inhibition of the chymotrypsin-like activity of the proteasome is sufficient to prevent signal-induced NF-κB activation and that the proteasome is a novel target for the identification of agents that may be useful in the treatment of diseases whose etiology is dependent upon the activation of NF-κB.

Chemoproteomics as a basis for post-genomic drug discovery

The large number of small organic compounds now available for drug-lead screening has led to numerous methods for classifying molecular similarity and diversity, the aim being to restore a balance between the quantity and drug-like quality of compounds in small-molecule libraries. Whereas structural and physicochemical attributes continue to be emphasized in compound selection for drug-lead screening, chemoproteomics--the use of biological information to guide chemistry--offers a highly efficient alternative to small-molecule characterization that can accelerate drug discovery in the post-genomic era.

Selective inhibition of the chymotrypsin-like activity of the 20S proteasome by 5-methoxy-1-indanone dipeptide benzamides

Potent inhibitors of the 20S proteasome that contain a novel indanone head group coupled to di and tripeptides are described. These compounds are the first proteasome inhibitors have demonstrated high selectivity for the chymotrypsin-like activity of the 20S proteasome.

2,4-Dihydroxybenzylamine: A specific inhibitor of glutathione reductase

The high intracellular level of glutathione is maintained, in part, by the important redox enzyme glutathione reductase. This report describes the properties of a new inhibitor of glutathione reductase, 2,4-dihydroxybenzylamine (2,4-DHBA). The inhibition of glutathione reductase by both 2,4-DHBA and 1,3-bischloroethyl-nitrosourea (BCNU) requires the presence of the co-factor NADPH. However, the inhibition caused by 2,4-DHBA was found to occur much more rapidly. Inhibition of glutathione reductase was time dependent, involved a stoichiometric titration of the enzyme, and was not reversed by gel-filtration indicating an irreversible inhibitory mechanism. The drug interacted at two inhibitory sites as determined by a Hill-type plot analysis. 2,4-DHBA was shown to compete with the substrate oxidized glutathione, and the reducing agents, glutathione and dithioerythritol, were found to protect the enzyme from its inhibitory effect. These results suggest that the inhibition may entail a free radical effect at or near the active site. A structure-activity analysis with other meta-dihydroxybenzene derivatives revealed that the inhibition of glutathione reductase was unique to 2,4-dihydroxybenzylamine.

Effect of high‐dose thymidine infusions in patients with mycosis fungoides

The antitumor effect of thymidine has been demonstrated in patients with leukemia and lymphoma. This report summarizes the treatment of three patients with mycosis fungoides, a chronic T‐cell lymphoma. Four courses of thymidine (75 g/m2/day) were administered by continuous infusion for 4–7 days. Steady‐state serum thymidine levels were in the range of 1–3 mM. Associated toxicities were minimal and consisted of mild headache and anorexia. Myelosuppression was manifested by transient declines in the peripheral leukocyte count. One patient had extensive clearing of diffuse erythematous plaques on the trunk and extremities that persisted for over one month. A second patient had partial clearing of plaques that persisted for two weeks following therapy and a third patient had a minimal response with 25% reduction in lymphadenopathy and noduloulcerative lesions. These responses indicate the effectiveness of thymidine as a single agent in the treatment of mycosis fungoides.

Inhibition of ribonucleotide reductase by antitumor agents related to levodopa and dopamine

Using partially purified enzyme from L1210 cells, dihydroxybenzene derivatives related structurally to dopamine were shown to reversibly inactivate ribonucleotide reductase. A structure-activity analysis revealed that derivatives with side-chains, which contain a negatively-charged group, had significantly reduced inhibitory activity. The ability of these compounds to inhibit ribonucleotide reductase was dependent on the hydroxyl groups being in the ortho position and did not correlate with free radical inhibitory activity. A kinetic analysis by the method of Lineweaver-Burk indicated that the inhibition of ribonucleotide reductase by the derivative 3,4-dihydroxybenzylamine was competitive with the reducing substrate dithioerythritol. This analog, in combination with hydroxyurea, gave synergistic inhibition or ribonucleotide reductase, suggesting different sites of action. Using Tween 80-treated L1210 cells, it was found that these drugs had an immediate inhibitory effect on ribonucleotide reductase activity in intact, reversibly permeabilized cells. Furthermore, although these drugs had no immediate effect on DNA polymerase, in permeabilized L1210 cells (when the cells were preincubated with the dihydroxybenzene derivatives for 1 hr prior to permeabilization), there was significant inhibition of DNA polymerase activity. The two key enzymes for DNA synthesis appear to be sequentially inhibited by these analogs, with the reduced form (quinol) inhibiting ribonucleotide reductase and the oxidized form (quinone) inhibiting DNA polymerase.

Methotrexate analogues—27: Dual inhibition of dihydrofolate reductase and folylpolyglutamate synthetase by methotrexate and aminopterin analogues with a γ-phosphonate group in the side chain

gamma-Phosphonate analogues of methotrexate (MTX) and aminopterin (AMT) were synthesized from 4-amino-4-deoxy-N10-methylpteroic acid and 4-amino-4-deoxy-N10-formylpteroic acid, respectively, by reaction with methyl D,L-2-amino-4-phosphonobutyrate followed by gentle alkaline hydrolysis. The products were compared with the corresponding D,L-homocysteic acid derivatives as inhibitors of dihydrofolate reductase and folylpolyglutamate synthetase, and as inhibitors of cell growth in culture. The gamma-phosphonates were somewhat less active than either the gamma-sulfonates or the parent drugs as inhibitors of murine dihydrofolate reductase. The MTX gamma-sulfonate and gamma-phosphonate analogues were equally inhibitory toward mouse liver folylpolyglutamate synthetase (Ki = 190 microM), but in the AMT series the gamma-phosphonate (Ki = 8.4 microM) was more potent than the gamma-sulfonate (Ki = 45 microM). The AMT analogues were consistently more inhibitory than the MTX analogues against cultured L1210 murine leukemia cells, but neither the gamma-phosphonates nor the gamma-sulfonates were as potent as their respective parent drugs. The gamma-phosphonate analogue of MTX was three times more potent than MTX against the MTX-resistant mutant line L1210/R81, but the AMT gamma-phosphonate was less potent than AMT; however, these differences were small in comparison with the level of resistance to all these compounds in the L1210/R81 line. The results suggest that N10-methyl and N10-unsubstituted compounds altered at the gamma-position do not necessarily follow identical structure-activity patterns in every test system.

Sequential inhibitory effects of antitumor agents related to levodopa and dopamine upon DNA synthetic enzymes

Novel antitumor agents related to levodopa and dopamine exhibit a selective and rapid inhibition of DNA synthesis as measured by thymidine incorporation. Our investigations have attempted to determine the biochemical basis of the selective inhibition of tumor cells and in this present study we examined the effects of these agents on thymidylate synthase. The dihydroxybenzene derivatives were found to inhibit thymidylate synthase in situ at concentrations ranging between 100 and 800 microM. The quinols did not inhibit partially purified thymidylate synthase, although the oxidized quinones did cause inhibition at concentrations between 10 and 100 microM. Time course experiments suggested that the inhibition of thymidylate synthase in situ by the dihydroxybenzene derivatives occurs after the inhibition of thymidine incorporation, indicating that an earlier event was critical to the inhibition of DNA synthesis. With the use of a novel in situ assay which measured the release of [3H]water from [5-3H] uridine in intact cells, we were able to show that one of the earliest biochemical events is the inhibition of ribonucleotide reductase and that the inhibition of thymidylate synthase, which is delayed by approximately 30 min, was indirectly mediated possibly through effects on ribonucleotide reductase.