Discovery of potent selective bioavailable phosphodiesterase 2 (PDE2) inhibitors active in an osteoarthritis pain model. Part II: optimization studies and demonstration of in vivo efficacy.

Selective phosphodiesterase 2 (PDE2) inhibitors are shown to have efficacy in a rat model of osteoarthritis (OA) pain. We identified potent, selective PDE2 inhibitors by optimizing residual PDE2 activity in a series of phosphodiesterase 4 (PDE4) inhibitors, while minimizing PDE4 inhibitory activity. These newly designed PDE2 inhibitors bind to the PDE2 enzyme in a cGMP-like binding mode orthogonal to the cAMP-like binding mode found in PDE4. Extensive structure activity relationship studies ultimately led to identification of pyrazolodiazepinone, 22, which was >1000-fold selective for PDE2 over recombinant, full length PDEs 1B, 3A, 3B, 4A, 4B, 4C, 7A, 7B, 8A, 8B, 9, 10 and 11. Compound 22 also retained excellent PDE2 selectivity (241-fold to 419-fold) over the remaining recombinant, full length PDEs, 1A, 4D, 5, and 6. Compound 22 exhibited good pharmacokinetic properties and excellent oral bioavailability (F=78%, rat). In an in vivo rat model of OA pain, compound 22 had significant analgesic activity 1 and 3h after a single, 10 mg/kg, subcutaneous dose.

Discovery of potent, selective, bioavailable phosphodiesterase 2 (PDE2) inhibitors active in an osteoarthritis pain model, part I: transformation of selective pyrazolodiazepinone phosphodiesterase 4 (PDE4) inhibitors into selective PDE2 inhibitors.

We identified potent, selective PDE2 inhibitors by optimizing residual PDE2 activity in a series of PDE4 inhibitors, while simultaneously minimizing PDE4 activity. These newly designed PDE2 inhibitors bind to the PDE2 enzyme in a cGMP-like mode in contrast to the cAMP-like binding mode found in PDE4. Structure activity relationship studies coupled with an inhibitor bound crystal structure in the active site of the catalytic domain of PDE2 identified structural features required to minimize PDE4 inhibition while simultaneously maximizing PDE2 inhibition.

Discovery of LYC-55716: A Potent, Selective, and Orally Bioavailable Retinoic Acid Receptor-Related Orphan Receptor-γ (RORγ) Agonist for Use in Treating Cancer.

Retinoic acid receptor-related orphan receptor γ (RORc, RORγ, or NR1F3) is the nuclear receptor master transcription factor that drives the function and development of IL-17-producing T helper cells (Th17), cytotoxic T cells (Tc17), and subsets of innate lymphoid cells. Activation of RORγ+ T cells in the tumor microenvironment is hypothesized to render immune infiltrates more effective at countering tumor growth. To test this hypothesis, a family of benzoxazines was optimized to provide LYC-55716 (37c), a potent, selective, and orally bioavailable small-molecule RORγ agonist. LYC-55716 decreases tumor growth and enhances survival in preclinical tumor models and was nominated as a clinical development candidate for evaluation in patients with solid tumors.

Preclinical selection of a novel poly(ADP-ribose) polymerase inhibitor for clinical trial.

Poly(ADP-ribose) polymerase (PARP)-1 (EC 2.4.2.30) is a nuclear enzyme that promotes the base excision repair of DNA breaks. Inhibition of PARP-1 enhances the efficacy of DNA alkylating agents, topoisomerase I poisons, and ionizing radiation. Our aim was to identify a PARP inhibitor for clinical trial from a panel of 42 potent PARP inhibitors (K(i), 1.4-15.1 nmol/L) based on the quinazolinone, benzimidazole, tricyclic benzimidazole, tricyclic indole, and tricyclic indole-1-one core structures. We evaluated chemosensitization of temozolomide and topotecan using LoVo and SW620 human colorectal cells; in vitro radiosensitization was measured using LoVo cells, and the enhancement of antitumor activity of temozolomide was evaluated in mice bearing SW620 xenografts. Excellent chemopotentiation and radiopotentiation were observed in vitro, with 17 of the compounds causing a greater temozolomide and topotecan sensitization than the benchmark inhibitor AG14361 and 10 compounds were more potent radiosensitizers than AG14361. In tumor-bearing mice, none of the compounds were toxic when given alone, and the antitumor activity of the PARP inhibitor-temozolomide combinations was unrelated to toxicity. Compounds that were more potent chemosensitizers in vivo than AG14361 were also more potent in vitro, validating in vitro assays as a prescreen. These studies have identified a compound, AG14447, as a PARP inhibitor with outstanding in vivo chemosensitization potency at tolerable doses, which is at least 10 times more potent than the initial lead, AG14361. The phosphate salt of AG14447 (AG014699), which has improved aqueous solubility, has been selected for clinical trial.

Identification of potent nontoxic poly(ADP-Ribose) polymerase-1 inhibitors: chemopotentiation and pharmacological studies.

The nuclear enzyme poly(ADP-ribose) polymerase (PARP-1) facilitates DNA repair, and is, therefore, an attractive target for anticancer chemo- and radio-potentiation. Novel benzimidazole-4-carboxamides (BZ1-6) and tricyclic lactam indoles (TI1-5) with PARP-1 K(i) values of <10 nM have been identified. Whole cell PARP-1 inhibition, intrinsic cell growth inhibition, and chemopotentiation of the cytotoxic agents temozolomide (TM) and topotecan (TP) were evaluated in LoVo human colon carcinoma cells. The acute toxicity of the inhibitors was investigated in PARP-1 null and wild-type mice. Tissue distribution and in vivo chemopotentiation activity was determined in nude mice bearing LoVo xenografts. At a nontoxic concentration (0.4 micro M) the PARP-1 inhibitors potentiated TM-induced growth inhibition 1.0-5.3-fold and TP-induced inhibition from 1.0-2.1-fold. Concentrations of the PARP-1 inhibitors that alone inhibited cell growth by 50% ranged from 8 to 94 micro M. Maximum potentiation of TM activity was achieved at nongrowth inhibitory concentrations (

Tricyclic benzimidazoles as potent poly(ADP-ribose) polymerase-1 inhibitors.

Novel tricyclic benzimidazole carboxamide poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors have been synthesized. Several compounds were found to be powerful chemopotentiators of temozolomide and topotecan in both A549 and LoVo cell lines. In vitro inhibition of PARP-1 was confirmed by direct measurement of NAD+ depletion and ADP-ribose polymer formation caused by chemically induced DNA damage.

Structure-based design of a parallel synthetic array directed toward the discovery of irreversible inhibitors of human rhinovirus 3C protease.

Utilizing the tools of parallel synthesis and structure-based design, a new class of Michael acceptor-containing, irreversible inhibitors of human rhinovirus 3C protease (HRV 3CP) was discovered. These inhibitors are shown to inhibit HRV-14 3CP with rates of inactivation ranging from 886 to 31 400 M(-1) sec(-1). These inhibitors exhibit antiviral activity when tested against HRV-14 infected H1-HeLa cells, with EC(50) values ranging from 1.94 to 0.15 microM. No cytotoxicity was observed at the limits of the assay concentration. A crystal structure of one of the more potent inhibitors covalently bound to HRV-2 3CP is detailed. These compounds were also tested against HRV serotypes other than type 14 and were found to have highly variable activities.

Synthesis, Equilibration, and Coupling of 4-Lithio-1,3-dioxanes: Synthons for syn- and anti-1,3-Diols.

Configurationally defined alpha-alkoxylithium reagents were prepared by reductive lithiation of 4-(phenylthio)-1,3-dioxanes. A new and more general synthesis of 4-(phenylthio)-1,3-dioxanes has been developed on the basis of the reduction and in situ acetylation of 1,3-dioxan-4-ones. For each of the substitution patterns examined (23a-d), reductive lithiation gave the axial alkyllithium (24a-d) with 99:1 stereoselectivity. Equilibrations of these alkyllithium reagents were possible with unhindered substrates to give the equatorial alkyllithiums 26a and 26b with excellent stereoselectivities. The more hindered axial alkyllithium reagents (24c, 24d) did not equilibrate efficiently. The equilibrium between alkyllithium reagents 24c and 26c strongly favors the equatorial isomer 26c. The inefficient equilibration with this hindered substrate is attributed to a slow rate of equilibration rather than insufficient driving force. These alkyllithium reagents could be coupled with a variety of electrophiles with retention of configuration by direct addition, copper-mediated coupling, or transmetalation to the corresponding alkylzinc reagent followed by copper-mediated coupling.

Pyridine-3-propanoic acids: Discovery of dual PPARalpha/gamma agonists as antidiabetic agents.

A series of novel pyridine-3-propanoic acids was synthesized. A structure-activity relationship study of these compounds led to the identification of potent dual PPARalpha/gamma agonists with varied isoform selectivity. Based on the results of efficacy studies in diabetic (db/db) mice, and the desired pharmacokinetic parameters, compounds (S)-14 and (S)-19 were selected for further profiling.

Design, synthesis, and biological evaluation of novel human 5'-deoxy-5'-methylthioadenosine phosphorylase (MTAP) substrates.

The structure-based design, chemical synthesis, and biological evaluation of novel MTAP substrates are described. These compounds incorporate various C5'-moieties and are shown to have different k(cat)/K(m) values compared with the natural MTAP substrate (MTA).

Potentiation of cytotoxic drug activity in human tumour cell lines, by amine-substituted 2-arylbenzimidazole-4-carboxamide PARP-1 inhibitors.

The synthesis and biological evaluation of a new series of amine-substituted 2-arylbenzimidazole-4-carboxamide inhibitors of the DNA-repair enzyme poly(ADP-ribose) polymerase-1 (PARP-1) is reported. The introduction of an amine substituent at the 2-aryl position is not detrimental to activity, with most inhibitors exhibiting K(i) values for PARP-1 inhibition in the low nanomolar range. Two compounds in this series were found to potentiate the cytotoxicity of the DNA-methylating agent temozolomide by 4-5-fold in a human colorectal cancer cell line.

Anticancer chemosensitization and radiosensitization by the novel poly(ADP-ribose) polymerase-1 inhibitor AG14361.

BACKGROUND: Poly(ADP-ribose) polymerase-1 (PARP-1) facilitates the repair of DNA strand breaks. Inhibiting PARP-1 increases the cytotoxicity of DNA-damaging chemotherapy and radiation therapy in vitro. Because classical PARP-1 inhibitors have limited clinical utility, we investigated whether AG14361, a novel potent PARP-1 inhibitor (inhibition constant <5 nM), enhances the effects of chemotherapy and radiation therapy in human cancer cell cultures and xenografts. METHODS: The effect of AG14361 on the antitumor activity of the DNA alkylating agent temozolomide, topoisomerase I poisons topotecan or irinotecan, or x-irradiation or gamma-radiation was investigated in human cancer cell lines A549, LoVo, and SW620 by proliferation and survival assays and in xenografts in mice by tumor volume determination. The specificity of AG14361 for PARP-1 was investigated by microarray analysis and by antiproliferation and acute toxicity assays in PARP-1-/- and PARP-1+/+ cells and mice. After intraperitoneal administration, the concentration of AG14361 was determined in mouse plasma and tissues, and its effect on PARP-1 activity was determined in tumor homogenates. All statistical tests were two-sided. RESULTS: AG14361 at 0.4 micro M did not affect cancer cell gene expression or growth, but it did increase the antiproliferative activity of temozolomide (e.g., in LoVo cells by 5.5-fold, 95% confidence interval [CI] = 4.9-fold to 5.9-fold; P =.004) and topotecan (e.g., in LoVo cells by 1.6-fold, 95% CI = 1.3-fold to 1.9-fold; P =.002) and inhibited recovery from potentially lethal gamma-radiation damage in LoVo cells by 73% (95% CI = 48% to 98%). In vivo, nontoxic doses of AG14361 increased the delay of LoVo xenograft growth induced by irinotecan, x-irradiation, or temozolomide by two- to threefold. The combination of AG14361 and temozolomide caused complete regression of SW620 xenograft tumors. AG14361 was retained in xenografts in which PARP-1 activity was inhibited by more than 75% for at least 4 hours. CONCLUSION: AG14361 is, to our knowledge, the first high-potency PARP-1 inhibitor with the specificity and in vivo activity to enhance chemotherapy and radiation therapy of human cancer.