Daniel Delorme

Novel Hydroxamate and Anilide Derivatives as Potent Histone Deacetylase Inhibitors: Synthesis and Antiproliferative Evaluation

There is a currently growing interest in the development of histone deacetylase inhibitors (HDACs) as anticancer agents. Histone deacetylases are critically important in the functional regulation of gene transcription as well as in chromatin structure remodeling. A number of small molecule inhibitors of HDAC, such as the naturally occurring trichostatin A (TSA), as well as synthetic compounds, such as suberoylanilide hydroxamic acid (SAHA), scriptaid, oxamflatin or MS-275, have been reported to induce differentiation of several cancer cell lines and suppress cell proliferation. This article will review the recent progress being made in our laboratories in the development of two new families of potent HDAC inhibitors: sulfonamide hydroxamic acids and anilides, as well as TSA-like straight chain derivatives. Some of these compounds inhibit partially purified recombinant human HDAC enzymes with IC(50)s in the micromolar to low nanomolar range and can induce hyperacetylation of histones in human cancer cells. These compounds significantly inhibit proliferation, induce expression of p21(WAF1/Cip1), and cause cell cycle arrest in various human cancer cells. The lead candidates were screened in a panel of human tumor and normal cell lines. The inhibition of HDAC activity represents a novel approach for intervening in cell cycle regulation and may be used in future cancer therapies. The structure-activity relationships, the antiproliferative activity and the in vivo efficacy are discussed.

Discovery of N-(2-Aminophenyl)-4-[(4-pyridin-3-ylpyrimidin-2-ylamino)methyl]benzamide (MGCD0103), an Orally Active Histone Deacetylase Inhibitor

The design, synthesis, and biological evaluation of N-(2-aminophenyl)-4-[(4-pyridin-3-ylpyrimidin-2-ylamino)methyl]benzamide 8 (MGCD0103) is described. Compound 8 is an isotype-selective small molecule histone deacetylase (HDAC) inhibitor that selectively inhibits HDACs 1-3 and 11 at submicromolar concentrations in vitro. 8 blocks cancer cell proliferation and induces histone acetylation, p21 (cip/waf1) protein expression, cell-cycle arrest, and apoptosis. 8 is orally bioavailable, has significant antitumor activity in vivo, has entered clinical trials, and shows promise as an anticancer drug.

Design and synthesis of a novel class of histone deacetylase inhibitors

Histone deacetylase inhibitors (HDACs) have emerged as a novel class of antiproliferative agents. Utilizing structure-based design, the synthesis of a series of sulfonamide hydroxamic acids is described. Further optimization of this series by substitution of the terminal aromatic ring yielded HDAC inhibitors with good in vitro and in vivo activities.

Linking Bisphosphonates to the Free Amino Groups in Fluoroquinolones: Preparation of Osteotropic Prodrugs for the Prevention of Osteomyelitis

Osteomyelitis is an infection located in bone and a notoriously difficult disease to manage, requiring frequent and heavy doses of systemically administered antibiotics. Targeting antibiotics to the bone after systemic administration may provide both greater efficacy of treatment and less frequent administration. By taking advantage of the affinity of the bisphosphonate group for bone mineral, we have prepared a set of 13 bisphosphonated antibacterial prodrugs based on eight different linkers tethered to the free amino functionality on fluoroquinolone antibiotics. While all but one of the prodrugs were shown in vitro to be effective and rapid bone binders (over 90% in 1 h), only eight of them demonstrated the capacity to significantly regenerate the parent drug. In a rat model of the disease, a selected group of agents demonstrated their ability to prevent osteomyelitis when used in circumstances under which the parent drug had already been cleared and is thus inactive.

SYNTHESIS AND BIOLOGICAL EVALUATION OF BOTH ENANTIOMERS OF L-761,000 AS INHIBITORS OF CYCLOOXYGENASE 1 AND 2

Abstract Both enantiomers of L-761,000 were prepared and evaluated for their cyclooxygenase activities.

Constrained (l-)-S-adenosyl-l-homocysteine (SAH) analogues as DNA methyltransferase inhibitors

Potent SAH analogues with constrained homocysteine units have been designed and synthesized as inhibitors of human DNMT enzymes. The five membered (2S,4S)-4-mercaptopyrrolidine-2-carboxylic acid, in 1a, was a good replacement for homocysteine, while the corresponding six-member counterpart was less active. Further optimization of 1a, changed the selectivity profile of these inhibitors. A Chloro substituent at the 2-position of 1a, compound 1d, retained potency against DNMT1, while N(6) alkylation, compound 7a, conserved DNMT3b2 activity. The concomitant substitutions of 1a at both 2- and N(6) positions reduced activity against both enzymes.

SAR around (l)-S-adenosyl-l-homocysteine, an inhibitor of human DNA methyltransferase (DNMT) enzymes

The inhibitory activity of base-modified SAH analogues and the specificity of inhibiting human DNMT1 and DNMT3b2 enzymes was explored. The 6-amino group was essential while the 7-N of the adenine ring of SAH could be replaced by CH- without loss of activity against both enzymes. The introduction of small groups at the 2-position of the adenine moiety favors DNMT1 over DNMT3b2 inhibition whereas alkylation of the N(6)-amino moiety favors the inhibition of DNMT3b2 enzyme.

Bisphosphonated fluoroquinolone esters as osteotropic prodrugs for the prevention of osteomyelitis.

Osteomyelitis is a difficult to treat bacterial infection of the bone. Delivering antibacterial agents to the bone may overcome the difficulties in treating this illness by effectively concentrating the antibiotic at the site of infection and by limiting the toxicity that may result from systemic exposure to the large doses conventionally used. Using bisphosphonates as osteophilic functional groups, different forms of fluoroquinolone esters were synthesized and evaluated for their ability to bind bone and to release the parent antibacterial agent. Bisphosphonated glycolamide fluoroquinolone esters were found to present a profile consistent with effective and rapid bone binding and efficient release of the active drug moiety. They were assessed for their ability to prevent bone infection in vivo and were found to be effective when the free fluoroquinolones were not.

Synthesis of β-oxidation products as potential leukotriene metabolites and their detection in bile of anesthetized rat

Two novel beta-oxidation products of peptido leukotrienes, 16-carboxy-17,18,19,20-tetranor-14,15-dihydro-N-acetyl LTE4 and 18-carboxy-19,20-dinor-N-acetyl LTE4, were prepared by total synthesis and used to identify previously unknown polar rat biliary metabolites. When [3H] LTC4 and synthetic N-acetyl-LTE4 were administered intravenously to anesthetized inbred male rats, extraction of the bile and subsequent reverse-phase HPLC fractionation allowed the isolation of two novel metabolites of N-acetyl-LTE4. Comparison of U.V. spectra and coelution experiments revealed that these metabolites correspond to the above-mentioned synthetic beta-oxidation products. This was further confirmed by the coelution of the corresponding methyl esters. Oxidative ozonolysis of the metabolically produced 16-carboxy-17,18,19,20-tetranor-14,15-dihydro-N-acetyl LTE4 (major metabolite) confirmed the absence of the 14,15-unsaturation. The presence of these metabolites indicates that peptide leukotrienes undergo N-acetylation followed by omega and subsequent beta-oxidation in the anesthetized rat.

Metabolism and excretion of exogenous [3H]-LTC4 in primates.

Four novel omega- and beta-oxidation (from the omega end) products of peptide leukotrienes, 20-hydroxy and 20-carboxy-LTE4, 18-carboxy-19, 20-dinor-LTE4 and 16-carboxy-17,18,19,20-tetranor-14,15-dihydro-LTE4 were prepared by total synthesis and used as standards for identification of biliary and urinary metabolites in the cynomolgus monkey. After intravenous administration 14, 15-[3H] leukotriene C4 (10 microCi kg-1) was partially metabolized in and rapidly cleared from the vascular circulation. This resulted, within 24 hours, in significant urinary excretion (14.8 +/- 2.1%, n = 4), consisting largely of material more polar than LTE4 (61% of urinary excretion) as shown by reverse phase HPLC. The polar fraction demonstrated two predominant metabolites which coeluted in several HPLC solvent systems with synthetic 16-carboxytetranordihydro-LTE4 (major component) and 18-carboxydinor-LTE4 (minor component). Characterization of the major polar metabolite as 16-carboxytetranordihydro-LTE4 was substantiated by conversion to its N-acetylated derivative. The absence of the 14, 15 double bond was confirmed by product analysis of oxidative ozonolysis. In a single animal, the bile duct was cannulated, with significant biliary excretion of radioactivity demonstrated over 4 hours (58.6% recovery). The predominant polar biliary metabolites were also identified as the 18-carboxydinor and 16-carboxytetranordihydro derivatives of LTE4 mentioned above. These data suggest that beta-oxidation products generated from the omega-carboxyl end of the 20-carboxy-LTE4 are important products of [3H] LTC4 metabolism in the monkey. Quantitation of these urinary metabolites may be an important index of in vivo leukotriene production.