Bryan H. Norman

Benzopyrans are selective estrogen receptor Beta agonists with novel activity in models of benign prostatic hyperplasia.

Benzopyran selective estrogen receptor beta agonist-1 (SERBA-1) shows potent, selective binding and agonist function in estrogen receptor beta (ERbeta) in vitro assays. X-ray crystal structures of SERBA-1 in ERalpha and beta help explain observed beta-selectivity of this ligand. SERBA-1 in vivo demonstrates involution of the ventral prostate in CD-1 mice (ERbeta effect), while having no effect on gonadal hormone levels (ERalpha effect) at 10x the efficacious dose, consistent with in vitro properties of this molecule.

Tricyclic isoxazoles are novel inhibitors of the multidrug resistance protein (MRP1)

Tricyclic isoxazoles were identified from a screen as a novel class of selective multidrug resistance protein (MRP1) inhibitors. From a screen lead, SAR efforts resulted in the preparation of LY 402913 (9h), which inhibits MRP1 and reverses drug resistance to MRP1 substrates, such as doxorubicin, in HeLa-T5 cells (EC(50)=0.90 microM), while showing no inherent cytotoxicity. Additionally, LY 402913 inhibits ATP-dependent, MRP1-mediated LTC(4) uptake into membrane vesicles prepared from the MRP1-overexpressing HeLa-T5 cells (EC(50)=1.8 microM). LY 402913 also shows selectivity ( approximately 22-fold) against the related transporter, P-glycoprotein, in HL60/Adr and HL60/Vinc cells. Finally, when dosed in combination with the oncolytic MRP1 substrate vincristine, LY 402913 delays the growth of MRP1-overexpressing tumors in vivo.

Reversal of resistance in multidrug resistance protein (MRP1)-overexpressing cells by LY329146.

The benzothiophene LY329146 reverses the drug resistance phenotype in multidrug resistance protein (MRP1)-overexpressing cells when dosed in combination with MRP1-associated oncolytics doxorubicin and vincristine. Additionally, LY329146 inhibited MRP1-mediated uptake of the MRP1 substrate LTC4 into membrane vesicles prepared from MRP1-overexpressing cells.

Discovery and Characterization of 2-Acylaminoimidazole Microsomal Prostaglandin E Synthase-1 Inhibitors.

As part of a program aimed at the discovery of antinociceptive therapy for inflammatory conditions, a screening hit was found to inhibit microsomal prostaglandin E synthase-1 (mPGES-1) with an IC50 of 17.4 μM. Structural information was used to improve enzyme potency by over 1000-fold. Addition of an appropriate substituent alleviated time-dependent cytochrome P450 3A4 (CYP3A4) inhibition. Further structure-activity relationship (SAR) studies led to 8, which had desirable potency (IC50 = 12 nM in an ex vivo human whole blood (HWB) assay) and absorption, distribution, metabolism, and excretion (ADME) properties. Studies on the formulation of 8 identified 8·H3PO4 as suitable for clinical development. Omission of a lipophilic portion of the compound led to 26, a readily orally bioavailable inhibitor with potency in HWB comparable to celecoxib. Furthermore, 26 was selective for mPGES-1 inhibition versus other mechanisms in the prostanoid pathway. These factors led to the selection of 26 as a second clinical candidate.

Synthetic studies on the furan ring of wortmannin

Abstract Synthetic studies on the fungal metabolite, wortmannin, were undertaken in an effort to gain insight into the structure activity relationships of wortmannin analogs on phosphatidylinositol-3′-kinase (PI-3-kinase). Our work has focused on the chemistry of the previously unexplored furan ring and has uncovered several interesting and novel chemical transformations, which are described herein.

Identification and Characterization of Novel Microsomal Prostaglandin E Synthase-1 Inhibitors for Analgesia

Prostaglandin (PG) E2 plays a critical role in eliciting inflammation. Nonsteroidal anti-inflammatory drugs and selective inhibitors of cyclooxygenase, which block PGE2 production, have been used as key agents in treating inflammation and pain associated with arthritis and other conditions. However, these agents have significant side effects such as gastrointestinal bleeding and myocardial infarction, since they also block the production of prostanoids that are critical for other normal physiologic functions. Microsomal prostaglandin E2 synthase-1 is a membrane-bound terminal enzyme in the prostanoid pathway, which acts downstream of cyclooxygenase 2 and is responsible for PGE2 production during inflammation. Thus, inhibition of this enzyme would be expected to block PGE2 production without inhibiting other prostanoids and would provide analgesic efficacy without the side effects. In this report, we describe novel microsomal prostaglandin E2 synthase-1 inhibitors that are potent in blocking PGE2 production and are efficacious in a guinea pig monoiodoacetate model of arthralgia. These molecules may be useful in treating the signs and symptoms associated with arthritis.

Novel Autotaxin Inhibitors for the Treatment of Osteoarthritis Pain: Lead Optimization via Structure-Based Drug Design

In an effort to develop a novel therapeutic agent aimed at addressing the unmet need of patients with osteoarthritis pain, we set out to develop an inhibitor for autotaxin with excellent potency and physical properties to allow for the clinical investigation of autotaxin-induced nociceptive and neuropathic pain. An initial hit identification campaign led to an aminopyrimidine series with an autotaxin IC50 of 500 nM. X-ray crystallography enabled the optimization to a lead compound that demonstrated favorable potency (IC50 = 2 nM), PK properties, and a robust PK/PD relationship.

17β-hydroxywortmannin: A potent inhibitor of bone resorption and phosphatidylinositol-3-kinase

Abstract Structure-function studies on the natural product wortmannin have identified a 17β-hydroxy derivative as a potent inhibitor of osteoclast function in both cell and animal models. Mechanistic studies indicate osteoclast differentiation is dramatically affected by this class of compounds. Interestingly, comparable potency trends for resorption and phosphatidylinositol-3-kinase inhibition were also observed.

Pharmacological Characterization of a Potent Inhibitor of Autotaxin in Animal Models of Inflammatory Bowel Disease and Multiple Sclerosis.

Autotaxin is a secreted enzyme that catalyzes the conversion of lysophosphatidyl choline into the bioactive lipid mediator lysophosphatidic acid (LPA). It is the primary enzyme responsible for LPA production in plasma. It is upregulated in inflammatory conditions and inhibition of autotaxin may have anti-inflammatory activity in a variety of inflammatory diseases. To determine the role of autotaxin and LPA in the pathophysiology of inflammatory disease states, we used a potent and orally bioavailable inhibitor of autotaxin that we have recently identified, and characterized it in mouse models of inflammation, inflammatory bowel disease (IBD), multiple sclerosis (MS), and visceral pain. Compound-1, a potent inhibitor of autotaxin with an IC50 of ∼2 nM, has good oral pharmacokinetic properties in mice and results in a substantial inhibition of plasma LPA that correlates with drug exposure levels. Treatment with the inhibitor resulted in significant anti-inflammatory and analgesic effects in the carrageenan-induced paw inflammation and acetic acid-induced visceral pain tests, respectively. Compound-1 also significantly inhibited disease activity score in the dextran sodium sulfate–induced model of IBD, and in the experimental autoimmune encephalomyelitis model of MS. In conclusion, the present study demonstrates the anti-inflammatory and analgesic properties of a novel inhibitor of autotaxin that may serve as a therapeutic option for IBD, MS, and pain associated with inflammatory states.

Targeting the Nerve Growth Factor (NGF) Pathway in Drug Discovery. Potential Applications to New Therapies for Chronic Pain

The neurotrophin nerve growth factor (NGF) has been implicated as a key mediator of chronic pain. NGF binds the tropomysin receptor kinase A (TrkA) and p75, resulting in the activation of downstream signaling pathways that have been linked to pro-nociception. While anti-NGF antibodies have demonstrated analgesia both preclinically and in patients, the mechanism of action of these agents remains unclear. We describe ligands targeting NGF, its receptors, and downstream/related targets. This Perspective highlights large and small molecule approaches to targeting the NGF-TrkA pathway both extra- and intracellularly. In addition, we present a strategic framework for future drug discovery efforts in this pathway beyond the targeting of NGF or its receptors. While existing tools have greatly informed NGF-mediated signaling, ongoing and future pathway research may help focus new drug discovery efforts on key novel targets and mechanisms. This may result in highly differentiated therapeutics with greater efficacy and/or improved safety profiles.