Jeffrey N. Miner

RDEA119/BAY 869766: A Potent, Selective, Allosteric Inhibitor of MEK1/2 for the Treatment of Cancer

The RAS-RAF-mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK pathway provides numerous opportunities for targeted oncology therapeutics. In particular, the MEK enzyme is attractive due to high selectivity for its target ERK and the central role that activated ERK plays in driving cell proliferation. The structural, pharmacologic, and pharmacokinetic properties of RDEA119/BAY 869766, an allosteric MEK inhibitor, are presented. RDEA119/BAY 869766 is selectively bound directly to an allosteric pocket in the MEK1/2 enzymes. This compound is highly efficacious at inhibiting cell proliferation in several tumor cell lines in vitro. In vivo, RDEA119/BAY 869766 exhibits potent activity in xenograft models of melanoma, colon, and epidermal carcinoma. RDEA119/BAY 869766 exhibits complete suppression of ERK phosphorylation at fully efficacious doses in mice. RDEA119/BAY 869766 shows a tissue selectivity that reduces its potential for central nervous system-related side effects. Using pharmacokinetic and pharmacodynamic data, we show that maintaining adequate MEK inhibition throughout the dosing interval is likely more important than achieving high peak levels because greater efficacy was achieved with more frequent but lower dosing. Based on its longer half-life in humans than in mice, RDEA119/BAY 869766 has the potential for use as a once- or twice-daily oral treatment for cancer. RDEA119/BAY 869766, an exquisitely selective, orally available MEK inhibitor, has been selected for clinical development because of its potency and favorable pharmacokinetic profile.

Pharmacodynamic, pharmacokinetic and tolerability evaluation of concomitant administration of lesinurad and febuxostat in gout patients with hyperuricaemia

OBJECTIVE The aim of this study was to evaluate the pharmacodynamics (PDs), pharmacokinetics (PKs) and safety of lesinurad (selective uric acid reabsorption inhibitor) in combination with febuxostat (xanthine oxidase inhibitor) in patients with gout. METHODS This study was a phase IB, multicentre, open-label, multiple-dose study of gout patients with serum uric acid (sUA) >8 mg/dl following washout of urate-lowering therapy with colchicine flare prophylaxis. Febuxostat 40 or 80 mg/day was administered on days 1-21, lesinurad 400 mg/day was added on days 8-14 and then lesinurad was increased to 600 mg/day on days 15-21. sUA, urine uric acid and PK profiles were evaluated at the end of each week. Safety was assessed by adverse events, laboratory tests and physical examinations. RESULTS Initial treatment with febuxostat 40 or 80 mg/day monotherapy resulted in 67% and 56% of subjects, respectively, achieving a sUA level <6 mg/dl. Febuxostat 40 or 80 mg/day plus lesinurad 400 or 600 mg/day resulted in 100% of subjects achieving sUA <6 mg/dl and up to 100% achieving sUA <5 mg/dl. No clinically relevant changes in the PKs of either drug were noted. The combination was well tolerated. CONCLUSION The clinically important targets of sUA <6 mg/dl and <5 mg/dl are achievable in 100% of patients when combining lesinurad and febuxostat.

Multicenter Phase I Trial of the Mitogen-Activated Protein Kinase 1/2 Inhibitor BAY 86-9766 in Patients with Advanced Cancer

Purpose: To evaluate the safety, pharmacokinetics, and pharmacodynamics of BAY 86-9766, a selective, potent, orally available, small-molecule allosteric inhibitor of mitogen-activated protein kinase 1/2 in patients with advanced solid tumors. Experimental Design: BAY 86-9766 was administered orally daily in 28-day courses, with doses escalated to establish the maximum-tolerated dose (MTD). An expanded cohort was evaluated at the MTD. Pharmacokinetic and pharmacodynamic parameters were assessed, with extracellular signal–regulated kinase (ERK) phosphorylation evaluated in paired biopsies from a subset of the expanded MTD cohort. Tumor specimens were evaluated for mutations in select genes. Results: Sixty-nine patients were enrolled, including 20 patients at the MTD. The MTD was 100 mg given once-daily or in two divided doses. BAY 86-9766 was well-tolerated. The most common treatment-related toxicities were acneiform rash and gastrointestinal toxicity. BAY 86-9766 was well-absorbed after oral administration (plasma half-life ∼12 hours), and displayed dose proportional pharmacokinetics throughout the tested dose range. Continuous daily dosing resulted in moderate accumulation at most dose levels. BAY 86-9766 suppressed ERK phosphorylation in biopsied tissue and tetradecanoylphorbol acetate–stimulated peripheral blood leukocytes. Of 53 evaluable patients, one patient with colorectal cancer achieved a partial response and 11 patients had stable disease for 4 or more courses. An ocular melanoma specimen harbored a GNAQ-activating mutation and exhibited reduced ERK phosphorylation in response to therapy. Conclusion: This phase I study showed that BAY 86-9766 was well-tolerated, with good oral absorption, dose proportional pharmacokinetics, target inhibition at the MTD, and some evidence of clinical benefit across a range of tumor types. Clin Cancer Res; 19(5); 1232–43. ©2012 AACR.

Urate Handling in the Human Body

Elevated serum urate concentration is the primary cause of gout. Understanding the processes that affect serum urate concentration is important for understanding the etiology of gout and thereby understanding treatment. Urate handing in the human body is a complex system including three major processes: production, renal elimination, and intestinal elimination. A change in any one of these can affect both the steady-state serum urate concentration as well as other urate processes. The remarkable complexity underlying urate regulation and its maintenance at high levels in humans suggests that this molecule could potentially play an interesting role other than as a mere waste product to be eliminated as rapidly as possible.

Pharmacokinetics, pharmacodynamics, and tolerability of verinurad, a selective uric acid reabsorption inhibitor, in healthy adult male subjects

Purpose Verinurad (RDEA3170) is a selective uric acid reabsorption inhibitor in clinical development for the treatment of gout and asymptomatic hyperuricemia. The aim of this study was to evaluate the pharmacokinetics, pharmacodynamics, and tolerability of verinurad in healthy adult males. Subjects and methods This was a Phase I, randomized, double-blind, placebo-controlled, single and multiple ascending dose study. Panels of eight male subjects received a single oral dose of verinurad or placebo in either a fasted or fed state; panels of 10–12 male subjects received ascending doses of once-daily verinurad or placebo in a fasted state for 10 days. Serial blood and urine samples were assayed for verinurad and uric acid. Safety was assessed by adverse event (AE) reports, laboratory tests, vital signs, and electrocardiograms (ECGs). Results A total of 81 adult males completed the study. Following single doses of verinurad, maximum observed plasma concentration (Cmax) and area under the plasma concentration–time curve (AUC) increased in a dose-proportional manner; Cmax occurred at 0.5–0.75 hours and 1.25 hours in the fasted and fed states, respectively. Food decreased AUC by 23% and Cmax by 37%−53%. There was a modest accumulation of verinurad following multiple daily doses. Verinurad reduced serum urate levels by up to 62% (40 mg, single dose) and 61% (10 mg, multiple dose). The increase in urinary excretion of uric acid was greatest in the first 6 hours after dosing and was still evident ≥24 hours for verinurad doses ≥2 mg. Verinurad was well tolerated at all doses. No serious AEs, severe AEs, discontinuations due to AEs, or clinically significant laboratory or ECG abnormalities were reported. Conclusion Single and multiple doses of verinurad were well tolerated, absorption was rapid, and exposure was dose proportional. Verinurad increased urinary uric acid elimination and resulted in sustained reductions in serum urate. These data support further clinical evaluation of once-daily verinurad as a treatment for gout.

Chapter Eleven – Urate Crystal Deposition Disease and Gout—New Therapies for an Old Problem

Abstract Gout is a chronic, inflammatory arthritic condition resulting from monosodium urate crystal deposition in joints and tissues, which develop because of high levels of serum uric acid. Gout treatment includes short-term approaches for acute gout attacks (gout flares) and long-term approaches for treating hyperuricemia. Acute gout therapy focuses on rapid inhibition of pain and inflammation resulting from the inflammatory response to monosodium urate crystal deposition. Most commonly prescribed acute gout therapies in the United States are NSAIDs, colchicine, and corticosteroids. Optimal treatment of gout also includes approaches to address chronically high uric acid levels. Therapeutic approaches to address gout-associated hyperuricemia include inhibiting production of uric acid using xanthine oxidase inhibitors, degrading uric acid with recombinant uricase, and increasing uric acid excretion using older uricosuric agents and newer selective uric acid reabsorption inhibitors. The recent surge of research in this area brings with it the potential for new targets and therapeutic combinations.

Pharmacodynamic and pharmacokinetic effects and safety of verinurad in combination with allopurinol in adults with gout: a phase IIa, open-label study

Objectives Verinurad (RDEA3170) is a high affinity, selective uric acid transporter (URAT1) inhibitor indevelopment for treating gout and asymptomatic hyperuricaemia. This phase IIa study evaluated the pharmacodynamics, pharmacokinetics and safety of verinurad combined with allopurinol versus allopurinol alone in adults with gout. Methods Forty-one subjects were randomised into two cohorts of verinurad (2.5–20 mg) plus allopurinol (300 mg once daily) versus allopurinol 300 mg once daily, 600 mg once daily or 300 mg twice daily alone. Each treatment period was 7 days. Serial plasma/serum and urine samples were assayed for verinurad, allopurinol, oxypurinol and uric acid. Results Serum pharmacodynamic data pooled across cohorts demonstrated maximum per cent decreases in serum urate (sUA) from baseline (Emax) at 7–12 hours after verinurad plus allopurinol treatment. Combination treatment decreased sUA in dose-dependent manner: least-squares means Emax was 47%, 59%, 60%, 67%, 68% and 74% for verinurad doses 2.5, 5, 7.5, 10, 15 and 20 mg plus allopurinol 300 mg once daily, versus 40%, 54% and 54% for allopurinol 300 mg once daily, 600 mg once daily and 300 mg twice daily. Verinurad had no effect on allopurinol plasma pharmacokinetics, but decreased oxypurinol Cmax by 19.0%–32.4% and area under the plasma concentration–time curve from time zero to the last measurable time point by 20.8%–39.2%. Verinurad plus allopurinol was well tolerated with no serious adverse events (AEs), AE-related withdrawals or renal-related events. Laboratory values showed no clinically meaningful changes. Conclusion Verinurad coadministered with allopurinol produced dose-dependent decreases in sUA. All dose combinations of verinurad and allopurinol were generally well tolerated. These data support continued investigation of oral verinurad in patients with gout. Trial registration number NCT02498652.

Mechanism of high affinity inhibition of the human urate transporter URAT1

Gout is caused by elevated serum urate levels, which can be treated using inhibitors of the uric acid transporter, URAT1. We exploited affinity differences between the human and rat transporters to map inhibitor binding sites in URAT1. Human-rat transporter chimeras revealed that human URAT1 serine-35, phenylalanine-365 and isoleucine-481 are necessary and sufficient to provide up to a 100-fold increase in affinity for inhibitors. Moreover, serine-35 and phenylalanine-365 are important for high-affinity interaction with the substrate urate. A novel URAT1 binding assay provides support for direct interaction with these amino acids; thus, current clinically important URAT1 inhibitors likely bind the same site in URAT1. A structural model suggests that these three URAT1 residues are in close proximity potentially projecting within the channel. Our results indicate that amino acids from several transmembrane segments functionally cooperate to form a high-affinity URAT1 inhibitor binding site that, when occupied, prevents substrate interactions.

A Therapeutic Uricase with Reduced Immunogenicity Risk and Improved Development Properties

Humans and higher primates are unique in that they lack uricase, the enzyme capable of oxidizing uric acid. As a consequence of this enzyme deficiency, humans have high serum uric acid levels. In some people, uric acid levels rise above the solubility limit resulting in crystallization in joints, acute inflammation in response to those crystals causes severe pain; a condition known as gout. Treatment for severe gout includes injection of non-human uricase to reduce serum uric acid levels. Krystexxa® is a hyper-PEGylated pig-baboon chimeric uricase indicated for chronic refractory gout that induces an immunogenic response in 91% of treated patients, including infusion reactions (26%) and anaphylaxis (6.5%). These properties limit its use and effectiveness. An innovative approach has been used to develop a therapeutic uricase with improved properties such as: soluble expression, neutral pH solubility, high E. coli expression level, thermal stability, and excellent activity. More than 200 diverse uricase sequences were aligned to guide protein engineering and reduce putative sequence liabilities. A single uricase lead candidate was identified, which showed low potential for immunogenicity in >200 human donor samples selected to represent diverse HLA haplotypes. Cysteines were engineered into the lead sequence for site specific PEGylation and studies demonstrated >95% PEGylation efficiency. PEGylated uricase retains enzymatic activity in vitro at neutral pH, in human serum and in vivo (rats and canines) and has an extended half-life. In canines, an 85% reduction in serum uric acid levels was observed with a single subcutaneous injection. This PEGylated, non-immunogenic uricase has the potential to provide meaningful benefits to patients with gout.

Pharmacokinetics, Pharmacodynamics, and Tolerability of Concomitant Multiple Dose Administration of Verinurad (RDEA3170) and Allopurinol in Adult Male Subjects With Gout

Verinurad (RDEA3170) is a selective uric acid reabsorption inhibitor in clinical development for treatment of hyperuricemia and gout. This phase 1b, multiple‐dose, drug‐drug interaction study evaluated the pharmacokinetics, pharmacodynamics, and tolerability of verinurad in combination with allopurinol. Adult males with gout were randomized to receive once‐daily oral doses of allopurinol 300 mg or verinurad 10 mg alone for 7 days, allopurinol 300 mg + verinurad 10 mg on days 8 to 14, and the alternative single agent on days 15 to 21. Colchicine 0.6 mg was taken prophylactically for gout flares. Plasma/serum and urine samples were assayed for verinurad, allopurinol, oxypurinol (allopurinol active metabolite), colchicine (plasma only), and uric acid. Safety was assessed by adverse events (AEs) and laboratory tests. Verinurad plasma exposure was unaffected by allopurinol. Verinurad increased the maximum observed plasma concentration (Cmax) for allopurinol by 33%; the area under the plasma concentration‐time curve (AUC) was unaffected. Oxypurinol Cmax and AUC were reduced 32% and 38%, respectively, by verinurad. Colchicine plasma exposure was unaltered by verinurad. The maximum decrease in serum urate was greater with verinurad + allopurinol (65%) than with verinurad (51%) or allopurinol (43%) alone. Compared with the baseline rate, the maximum rate of uric acid excreted in urine was +56% with verinurad, −46% with allopurinol, and unchanged with verinurad + allopurinol. No serious AEs, discontinuations due to AEs, or clinically significant laboratory abnormalities were noted. Despite decreased systemic exposure of allopurinol and oxypurinol in the presence of verinurad, the combination resulted in greater serum urate reduction compared with either drug alone and was well tolerated at the studied doses.