The Tor1p and Tor2p kinases, targets of the therapeutically important antibiotic rapamycin, function as components of two distinct protein complexes in yeast, termed TOR complex 1 (TORC1) and TORC2. TORC1 is responsible for a wide range of rapamycin-sensitive cellular activities and contains, in addition to Tor1p or Tor2p, two highly conserved proteins, Lst8p and Kog1p. By identifying proteins that co-purify with Tor1p, Tor2p, Lst8p, and Kog1p, we have characterized a comprehensive set of protein-protein interactions that define further the composition of TORC1 as well as TORC2. In particular, we have identified Tco89p (YPL180w) and Bit61p (YJL058c) as novel components of TORC1 and TORC2, respectively. Deletion of TOR1 or TCO89 results in two specific and distinct phenotypes, (i) rapamycin-hypersensitivity and (ii) decreased cellular integrity, both of which correlate with the presence of SSD1-d, an allele of SSD1 previously associated with defects in cellular integrity. Furthermore, we link Ssd1p to Tap42p, a component of the TOR pathway that is believed to act uniquely downstream of TORC1. Together, these results define a novel connection between TORC1 and Ssd1p-mediated maintenance of cellular integrity.

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.

BackgroundExcess body burden of uric acid promotes gout. Diminished renal clearance of uric acid causes hyperuricemia in most patients with gout, and the renal urate transporter (URAT)1 is important for regulation of serum uric acid (sUA) levels. The URAT1 inhibitors probenecid and benzbromarone are used as gout therapies; however, their use is limited by drug–drug interactions and off-target toxicity, respectively. Here, we define the mechanism of action of lesinurad (Zurampic®; RDEA594), a novel URAT1 inhibitor, recently approved in the USA and Europe for treatment of chronic gout.MethodssUA levels, fractional excretion of uric acid (FEUA), lesinurad plasma levels, and urinary excretion of lesinurad were measured in healthy volunteers treated with lesinurad. In addition, lesinurad, probenecid, and benzbromarone were compared in vitro for effects on urate transporters and the organic anion transporters (OAT)1 and OAT3, changes in mitochondrial membrane potential, and human peroxisome proliferator-activated receptor gamma (PPARγ) activity.ResultsAfter 6 hours, a single 200-mg dose of lesinurad elevated FEUA 3.6-fold (p < 0.001) and reduced sUA levels by 33 % (p < 0.001). At concentrations achieved in the clinic, lesinurad inhibited activity of URAT1 and OAT4 in vitro, did not inhibit GLUT9, and had no effect on ABCG2. Lesinurad also showed a low risk for mitochondrial toxicity and PPARγ induction compared to benzbromarone. Unlike probenecid, lesinurad did not inhibit OAT1 or OAT3 in the clinical setting.ConclusionThe pharmacodynamic effects and in vitro activity of lesinurad are consistent with inhibition of URAT1 and OAT4, major apical transporters for uric acid. Lesinurad also has a favorable selectivity and safety profile, consistent with an important role in sUA-lowering therapy for patients with gout.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1107-x) contains supplementary material, which is available to authorized users.

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 acetatestimulated 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.