Efficacy and Safety of Telaglenastat Plus Cabozantinib vs Placebo Plus Cabozantinib in Patients With Advanced Renal Cell Carcinoma: The CANTATA Randomized Clinical Trial.

Importance: Dysregulated metabolism is a hallmark of renal cell carcinoma (RCC). Glutaminase is a key enzyme that fuels tumor growth by converting glutamine to glutamate. Telaglenastat is an investigational, first-in-class, selective, oral glutaminase inhibitor that blocks glutamine utilization and downstream pathways. Preclinically, telaglenastat synergized with cabozantinib, a VEGFR2/MET/AXL inhibitor, in RCC models. Objective: To compare the efficacy and safety of telaglenastat plus cabozantinib (Tela + Cabo) vs placebo plus cabozantinib (Pbo + Cabo). Design, Setting, and Participants: CANTATA was a randomized, placebo-controlled, double-blind, pivotal trial conducted at sites in the US, Europe, Australia, and New Zealand. Eligible patients had metastatic clear-cell RCC following progression on 1 to 2 prior lines of therapy, including 1 or more antiangiogenic therapies or nivolumab plus ipilimumab. The data cutoff date was August 31, 2020. Data analysis was performed from December 2020 to February 2021. Interventions: Patients were randomized 1:1 to receive oral cabozantinib (60 mg daily) with either telaglenastat (800 mg twice daily) or placebo until disease progression or unacceptable toxicity. Main Outcomes and Measures: The primary end point was progression-free survival (Response Evaluation Criteria in Solid Tumors version 1.1) assessed by blinded independent radiology review. Results: A total of 444 patients were randomized: 221 to Tela + Cabo (median [range] age, 61 [21-81] years; 47 [21%] women and 174 [79%] men) and 223 to Pbo + Cabo (median [range] age, 62 [29-83] years; 68 [30%] women and 155 [70%] men). A total of 276 (62%) patients had received prior immune checkpoint inhibitors, including 128 with prior nivolumab plus ipilimumab, 93 of whom had not received prior antiangiogenic therapy. Median progression-free survival was 9.2 months for Tela + Cabo vs 9.3 months for Pbo + Cabo (HR, 0.94; 95% CI, 0.74-1.21; P = .65). Overall response rates were 31% (69 of 221) with Tela + Cabo vs 28% (62 of 223) with Pbo + Cabo. Treatment-emergent adverse event (TEAE) rates were similar between arms. Grade 3 to 4 TEAEs occurred in 160 patients (71%) with Tela + Cabo and 172 patients (79%) with Pbo + Cabo and included hypertension (38 patients [17%] vs 40 patients [18%]) and diarrhea (34 patients [15%] vs 29 patients [13%]). Cabozantinib was discontinued due to AEs in 23 patients (10%) receiving Tela + Cabo and 33 patients (15%) receiving Pbo + Cabo. Conclusions and Relevance: In this randomized clinical trial, telaglenastat did not improve the efficacy of cabozantinib in metastatic RCC. Tela + Cabo was well tolerated with AEs consistent with the known risks of both agents. Trial Registration: ClinicalTrials.gov Identifier: NCT03428217.

Telaglenastat plus Everolimus in Advanced Renal Cell Carcinoma: A Randomized, Double-Blinded, Placebo-Controlled, Phase II ENTRATA Trial.

PURPOSE: Glutaminase is a key enzyme, which supports elevated dependency of tumors on glutamine-dependent biosynthesis of metabolic intermediates. Dual targeting of glucose and glutamine metabolism by the mTOR inhibitor everolimus plus the oral glutaminase inhibitor telaglenastat showed preclinical synergistic anticancer effects, which translated to encouraging safety and efficacy findings in a phase I trial of 2L+ renal cell carcinoma (RCC). This study evaluated telaglenastat plus everolimus (TelaE) versus placebo plus everolimus (PboE) in patients with advanced/metastatic RCC (mRCC) in the 3L+ setting (NCT03163667). PATIENTS AND METHODS: Eligible patients with mRCC, previously treated with at least two prior lines of therapy [including ≥1 VEGFR-targeted tyrosine kinase inhibitor (TKI)] were randomized 2:1 to receive E, plus Tela or Pbo, until disease progression or unacceptable toxicity. Primary endpoint was investigator-assessed progression-free survival (PFS; one-sided α <0.2). RESULTS: Sixty-nine patients were randomized (46 TelaE, 23 PboE). Patients had a median three prior lines of therapy, including TKIs (100%) and checkpoint inhibitors (88%). At median follow-up of 7.5 months, median PFS was 3.8 months for TelaE versus 1.9 months for PboE [HR, 0.64; 95% confidence interval (CI), 0.34-1.20; one-sided P = 0.079]. One TelaE patient had a partial response and 26 had stable disease (SD). Eleven patients on PboE had SD. Treatment-emergent adverse events included fatigue, anemia, cough, dyspnea, elevated serum creatinine, and diarrhea; grade 3 to 4 events occurred in 74% TelaE patients versus 61% PboE. CONCLUSIONS: TelaE was well tolerated and improved PFS versus PboE in patients with mRCC previously treated with TKIs and checkpoint inhibitors.

Telaglenastat Plus Cabozantinib or Everolimus for Advanced or Metastatic Renal Cell Carcinoma: An Open-Label Phase I Trial.

PURPOSE: Dual inhibition of glucose and glutamine metabolism results in synergistic anticancer effects in solid tumor models. Telaglenastat, an investigational, small-molecule, glutaminase inhibitor, exhibits modest single-agent activity in renal cell carcinoma (RCC) patients. This phase Ib trial evaluated telaglenastat plus cabozantinib or everolimus, agents known to impair glucose metabolism in patients with metastatic RCC (mRCC). PATIENTS AND METHODS: mRCC patients received escalating doses of telaglenastat [400-800 mg per os (p.o.) twice daily] in a 3 + 3 design, plus either everolimus (10 mg daily p.o.; TelaE) or cabozantinib (60 mg daily p.o.; TelaC). Tumor response (RECISTv1.1) was assessed every 8 weeks. Endpoints included safety (primary) and antitumor activity. RESULTS: Twenty-seven patients received TelaE, 13 received TelaC, with median 2 and 3 prior therapies, respectively. Treatment-related adverse events were mostly grades 1 to 2, most common including decreased appetite, anemia, elevated transaminases, and diarrhea with TelaE, and diarrhea, decreased appetite, elevated transaminases, and fatigue with TelaC. One dose-limiting toxicity occurred per cohort: grade 3 pruritic rash with TelaE and thrombocytopenia with TelaC. No maximum tolerated dose (MTD) was reached for either combination, leading to a recommended phase II dose of 800-mg telaglenastat twice daily with standard doses of E or C. TelaE disease control rate (DCR; response rate + stable disease) was 95.2% [20/21, including 1 partial response (PR)] among 21 patients with clear cell histology and 66.7% (2/3) for papillary. TelaC DCR was 100% (12/12) for both histologies [5/10 PRs as best response (3 confirmed) in clear cell]. CONCLUSIONS: TelaE and TelaC showed encouraging clinical activity and tolerability in heavily pretreated mRCC patients.

A Phase I Dose-Escalation and Expansion Study of Telaglenastat in Patients with Advanced or Metastatic Solid Tumors.

PURPOSE: Glutamine is a critical fuel for solid tumors. Interference with glutamine metabolism is deleterious to neoplasia in preclinical models. A phase I study of the oral, first-in-class, glutaminase (GLS) inhibitor telaglenastat was conducted in treatment-refractory solid tumor patients to define recommended phase II dose (RP2D) and evaluate safety, pharmacokinetics (PK), pharmacodynamics (PD), and antitumor activity. PATIENTS AND METHODS: Dose escalation by 3 + 3 design was followed by exploratory tumor-/biomarker-specific cohorts. RESULTS: Among 120 patients, fatigue (23%) and nausea (19%) were the most common toxicity. Maximum tolerated dose was not reached. Correlative analysis indicated >90% GLS inhibition in platelets at plasma exposures >300 nmol/L, >75% tumoral GLS inhibition, and significant increase in circulating glutamine. RP2D was defined at 800 mg twice-daily. Disease control rate (DCR) was 43% across expansion cohorts (overall response rate 5%, DCR 50% in renal cell carcinoma). CONCLUSIONS: Telaglenastat is safe, with a favorable PK/PD profile and signal of antitumor activity, supporting further clinical development.

Combined BRAF and MEK Inhibition With Dabrafenib and Trametinib in BRAF V600-Mutant Colorectal Cancer.

PURPOSE: To evaluate dabrafenib, a selective BRAF inhibitor, combined with trametinib, a selective MEK inhibitor, in patients with BRAF V600-mutant metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: A total of 43 patients with BRAF V600-mutant mCRC were treated with dabrafenib (150 mg twice daily) plus trametinib (2 mg daily), 17 of whom were enrolled onto a pharmacodynamic cohort undergoing mandatory biopsies before and during treatment. Archival tissues were analyzed for microsatellite instability, PTEN status, and 487-gene sequencing. Patient-derived xenografts were established from core biopsy samples. RESULTS: Of 43 patients, five (12%) achieved a partial response or better, including one (2%) complete response, with duration of response > 36 months; 24 patients (56%) achieved stable disease as best confirmed response. Ten patients (23%) remained in the study > 6 months. All nine evaluable during-treatment biopsies had reduced levels of phosphorylated ERK relative to pretreatment biopsies (average decrease ± standard deviation, 47% ± 24%). Mutational analysis revealed that the patient achieving a complete response and two of three evaluable patients achieving a partial response had PIK3CA mutations. Neither PTEN loss nor microsatellite instability correlated with efficacy. Responses to dabrafenib plus trametinib were comparable in patient-derived xenograft-bearing mice and the biopsied lesions from each corresponding patient. CONCLUSION: The combination of dabrafenib plus trametinib has activity in a subset of patients with BRAF V600-mutant mCRC. Mitogen-activated protein kinase signaling was inhibited in all patients evaluated, but to a lesser degree than observed in BRAF-mutant melanoma with dabrafenib alone. PIK3CA mutations were identified in responding patients and thus do not preclude response to this regimen. Additional studies targeting the mitogen-activated protein kinase pathway in this disease are warranted.

Relative bioavailability of pediatric oral solution and tablet formulations of trametinib in adult patients with solid tumors.

Trametinib (Mekinist®) is a selective inhibitor of mitogen-activated protein kinase kinase (MEK) approved in the United States as a single agent and in combination with dabrafenib (Tafinlar®) for treatment of patients with unresectable or metastatic melanoma with a positive BRAF V600E/V600K mutation for which a pediatric oral solution formulation is being developed. This open-label, two-period, two-treatment, randomized, crossover study assessed the relative bioavailability of the trametinib pediatric oral solution compared to the tablet formulation after a single-dose administration to adult patients with solid tumors. Primary pharmacokinetic endpoints derived from standard non-compartmental methods were AUC0-inf , AUC0-t , and Cmax . As expected, Cmax was higher and Tmax earlier for the pediatric oral solution compared to the tablet formulation. Administration of the trametinib pediatric oral solution resulted in a 12%, 10%, 18%, and 71% higher AUC0-inf , AUC0-last , AUC0-24 , and Cmax , respectively, as compared to the tablet formulation. Safety results were aligned with the known safety profile of trametinib. No serious or non-serious adverse events resulted in study drug withdrawal. Palatability of the pediatric oral solution was evaluated and found to be acceptable to most adult patients, but may differ in the pediatric population.

Phase I study of the MEK inhibitor trametinib in combination with the AKT inhibitor afuresertib in patients with solid tumors and multiple myeloma.

PURPOSE: To identify the maximum tolerated dose (MTD) and recommended Phase II dose of MEK/AKT inhibitor combination of trametinib and afuresertib. PATIENTS AND METHODS: Eligibility criteria were advanced solid tumors, 18 years or older, Eastern Cooperative Oncology Group performance status 0 or 1, and adequate organ function. Exclusion criteria included Type 1 diabetes, active GI disease, leptomeningeal disease, or current evidence/risk of retinal venous occlusion/central serous retinopathy. Clinical safety parameters and response were evaluated and analyzed. RESULTS: Twenty patients were enrolled. Dose-limiting toxicities (Grade 2 esophagitis; Grade 3 aspartate aminotransferase increased, mucosal inflammation and hypokalemia) were reported at starting dose (1.5 mg trametinib/50 mg afuresertib once daily continuously), exceeding the MTD. Subsequent de-escalation cohorts (1.5 mg/25 mg or 1.0 mg/50 mg trametinib/afuresertib) were defined as MTDs for continuous dosing. Intermittent dosing schedule [1.5 mg trametinib (continuous)/50 mg afuresertib (Days 1-10 every 28 days)] was evaluated and considered tolerable. No patients were enrolled in Phase II. The most common adverse events reported (≥10 % of all patients) included: diarrhea (60 %), dermatitis acneiform (55 %), maculo-papular rash (45 %), fatigue (30 %), dry skin (25 %), nausea (25 %), dyspnea (20 %), and vomiting (20 %). One partial response (BRAF wild-type melanoma) was reported; four patients had stable disease as best response. CONCLUSION: Continuous daily dosing of trametinib/afuresertib combination was poorly tolerated. Evaluation of intermittent dose schedule showed greater tolerability. Given the interest in combination treatment regimens of MAPK and PI3K/AKT pathway inhibitors, further study of intermittent dose schedule or combination of trametinib with more selective inhibitors may be warranted.

Lack of meaningful effect of ridaforolimus on the pharmacokinetics of midazolam in cancer patients: model prediction and clinical confirmation.

Ridaforolimus, a unique non-prodrug analog of rapamycin, is a potent inhibitor of mTOR under development for cancer treatment. In vitro data suggest ridaforolimus is a reversible and time-dependent inhibitor of CYP3A. A model-based evaluation suggested an increase in midazolam area under the curve (AUC(0- ∞)) of between 1.13- and 1.25-fold in the presence of therapeutic concentrations of ridaforolimus. The pharmacokinetic interaction between multiple oral doses of ridaforolimus and a single oral dose of midazolam was evaluated in an open-label, fixed-sequence study, in which cancer patients received a single oral dose of 2 mg midazolam followed by 5 consecutive daily single oral doses of 40 mg ridaforolimus with a single dose of 2 mg midazolam with the fifth ridaforolimus dose. Changes in midazolam exposure were minimal [geometric mean ratios and 90% confidence intervals: 1.23 (1.07, 1.40) for AUC(0-∞) and 0.92 (0.82, 1.03) for maximum concentrations (C(max)), respectively]. Consistent with model predictions, ridaforolimus had no clinically important effect on midazolam pharmacokinetics and is not anticipated to be a perpetrator of drug-drug interactions (DDIs) when coadministered with CYP3A substrates. Model-based approaches can provide reasonable estimates of DDI liability, potentially obviating the need to conduct dedicated DDI studies especially in challenging populations like cancer patients.

Concomitant oral and intravenous pharmacokinetics of trametinib, a MEK inhibitor, in subjects with solid tumours.

AIMS: The aim of this phase 1, single centre, open label study in four patients with solid tumours was to determine the absolute bioavailability of a 2 mg oral dose of trametinib. Trametinib is an orally bioavailable, reversible and selective allosteric inhibitor of MEK1 and MEK2 activation and kinase activity. METHODS: A microtracer study approach, in which a 5 µg radiolabelled i.v. microdose of trametinib was given concomitantly with an unlabelled 2 mg oral tablet formulation, was used to recover i.v. and oral pharmacokinetic parameters, simultaneously. RESULTS: The least-squares mean (90% confidence interval) absolute bioavailability of trametinib (2 mg tablet) was 72.3% (50.0%, 104.6%). Median tmax after oral administration was 1.5 h and the geometric mean terminal half-life was 11 days. The geometric mean clearance and volume of distribution after i.v. administration were 3.21 l h(-1) and 976 l, respectively, resulting in a terminal elimination half-life of 11 days. CONCLUSIONS: Trametinib absolute bioavailability was moderate to high, whereas first pass metabolism was low.

Trametinib, a first-in-class oral MEK inhibitor mass balance study with limited enrollment of two male subjects with advanced cancers.

1. This study assessed the mass balance, metabolism and disposition of [(14)C]trametinib, a first-in-class mitogen-activated extracellular signal-related kinase (MEK) inhibitor, as an open-label, single solution dose (2 mg, 2.9 MBq [79 µCi]) in two male subjects with advanced cancer. 2. Trametinib absorption was rapid. Excretion was primarily via feces (∼81% of excreted dose); minor route was urinary (∼19% of excreted dose). The primary metabolic elimination route was deacetylation alone or in combination with hydroxylation. Circulating drug-related component profiles (composed of parent with metabolites) were similar to those found in elimination together with N-glucuronide of deacetylation product. Metabolite analysis was only possible from <50% of administered dose; therefore, percent of excreted dose (defined as fraction of percent of administered dose recovery over total dose recovered in excreta) was used to assess the relative importance of excretion and metabolite routes. The long elimination half-life (∼10 days) favoring sustained targeted activity was important in permitting trametinib to be the first MEK inhibitor with clinical activity in late stage clinical studies. 3. This study exemplifies the challenges and adaptability needed to understand the metabolism and disposition of an anticancer agent, like trametinib, with both low exposure and a long elimination half-life.

Effects of low-fat and high-fat meals on steady-state pharmacokinetics of lapatinib in patients with advanced solid tumours.

AIM: To quantify the effect of food on the systemic exposure of lapatinib at steady state when administered 1 h before and after meals, and to observe the safety and tolerability of lapatinib under these conditions in patients with advanced solid tumours. METHODS: This was a three-treatment, randomised, three-sequence cross-over study. Lapatinib was administered 1 h after a low- [B] or a high-fat [C] meal and systemic exposure was compared with that obtained following administration 1 h before a low-fat meal [A]. RESULTS: In total, 25 patients were included, of whom 12 were evaluable for the pharmacokinetic analysis. Both low-fat and high-fat meals affected lapatinib exposure. Lapatinib AUC0-24 increased following lapatinib administration 1 h after a low-fat meal by 1.80-fold (90 % CI: 1.37-2.37) and after a high-fat meal by 2.61-fold (90 % CI: 1.98-3.43). Lapatinib Cmax increased following lapatinib administration 1 h after a low-fat meal by 1.90-fold (90 % CI: 1.49-2.43) and after a high-fat meal by 2.66-fold (90 % CI: 2.08-3.41). The most commonly occurring treatment-related toxicity was diarrhoea (8/25, 32 % CTCAE grade 1 and 2/25, 8 % grade 2) and one treatment-related grade ≥ 3 event occurred (fatigue grade 3, 4 %). CONCLUSIONS: Both low-fat and high-fat food consumed 1 h before lapatinib administration increased lapatinib systemic exposure compared with lapatinib administration 1 h before a low-fat meal. In order to administer lapatinib in a fasted state, it is advised to administer the drug 1 h before a meal.

Genome-wide map of nuclear protein degradation shows NCoR1 turnover as a key to mitochondrial gene regulation.

Transcription factor activity and turnover are functionally linked, but the global patterns by which DNA-bound regulators are eliminated remain poorly understood. We established an assay to define the chromosomal location of DNA-associated proteins that are slated for degradation by the ubiquitin-proteasome system. The genome-wide map described here ties proteolysis in mammalian cells to active enhancers and to promoters of specific gene families. Nuclear-encoded mitochondrial genes in particular correlate with protein elimination, which positively affects their transcription. We show that the nuclear receptor corepressor NCoR1 is a key target of proteolysis and physically interacts with the transcription factor CREB. Proteasome inhibition stabilizes NCoR1 in a site-specific manner and restrains mitochondrial activity by repressing CREB-sensitive genes. In conclusion, this functional map of nuclear proteolysis links chromatin architecture with local protein stability and identifies proteolytic derepression as highly dynamic in regulating the transcription of genes involved in energy metabolism.

Evaluation of the effects of food on the single-dose pharmacokinetics of trametinib, a first-in-class MEK inhibitor, in patients with cancer.

The aim of this study was to estimate the effect of a high-fat, high-calorie meal on the single-dose pharmacokinetics (PK) of trametinib, a MEK inhibitor. The design of this 2 treatment, 2 period crossover, incomplete wash-out study was influenced by the subject population, long half-life and PK variability; 24 subjects were randomized to a single, oral 2 mg trametinib dose administered in a fed/fasted state, followed by 7 days of serial PK sampling. Period 2 PK parameters were adjusted based on residual Period 1 concentrations. Geometric least square mean ratios of fed:fasted were 0.30, 0.76, and 0.90 for corrected maximum concentration (C(max)), area under concentration-time curve from time 0 to last quantifiable sample (AUC(0-last)) and AUC from time 0 extrapolated to infinity (AUC(0-α)), respectively. Median half-life was 6.3 and 5.3 days for fed and fasted regimens, respectively. Uncorrected PK parameters were consistent with these results. Food delayed absorption and had a mean difference in time of maximum concentration (t(max)) of 3.9 hours. Both oral trametinib doses were well-tolerated. Single-dose trametinib administration with food decreased the rate and, to a lesser degree, the extent of absorption, supporting the recommendation to administer trametinib 1 hour before or 2 hours after a meal.

A single supratherapeutic dose of ridaforolimus does not prolong the QTc interval in patients with advanced cancer.

PURPOSE: This dedicated QTc study was designed to evaluate the effect of the mammalian target of rapamycin inhibitor, ridaforolimus, on the QTc interval in patients with advanced malignancies. METHODS: We conducted a fixed-sequence, single-blind, placebo-controlled study. Patients (n = 23) received placebo on day 1 and a single 100-mg oral dose of ridaforolimus on day 2 in the fasted state. Holter electrocardiogram (ECG) monitoring was performed for 24 h after each treatment, and blood ridaforolimus concentrations were measured for 24 h after dosing. The ECGs were interpreted in a blinded fashion, and the QT interval was corrected using Fridericia's formula (QTcF). After a washout of at least 5 days, 22 patients went on to receive a therapeutic regimen of ridaforolimus (40 mg orally once daily for 5 days per week). RESULTS: The upper limit of the two-sided 90 % confidence interval for the placebo-adjusted mean change from baseline in QTcF was <10 ms at each time point. No patient had a QTcF change from baseline >30 ms or QTcF interval >480 ms. Geometric mean exposure to ridaforolimus after the single 100-mg dose was comparable to previous experience with the therapeutic regimen. There appeared to be no clear relationship between individual QTcF change from baseline and ridaforolimus blood concentrations. Ridaforolimus was generally well tolerated, with adverse events consistent with prior studies. CONCLUSIONS: Administration of the single 100-mg dose of ridaforolimus did not cause a clinically meaningful prolongation of QTcF, suggesting that patients treated with ridaforolimus have a low likelihood of delayed ventricular repolarization.

The minimal impact of food on the pharmacokinetics of ridaforolimus.

PURPOSE: Ridaforolimus, a potent inhibitor of the mammalian target of rapamycin (mTOR), is under development for the treatment for solid tumors. This open-label, randomized, 3-period crossover study investigated the effect of food on the pharmacokinetics of ridaforolimus 40 mg as well as safety and tolerability of the study medication. METHODS: Ridaforolimus was administered to 18 healthy, male subjects (mean age 36.4 years) in the fasted state, following ingestion of a light breakfast, and following a high-fat breakfast. Whole blood samples were collected from each subject pre-dose and 1, 2, 3, 4, 6, 8, 24, 48, 72, 96, and 168 h post-dose. RESULTS: The geometric mean (95 % confidence interval, CI) fasted blood area under the curve (AUC(0-∞)) and maximum concentration (C(max)) were 1940 (1510, 2500) ng h/mL and 116 (87, 156) ng/mL, respectively, and median time to C(max) (T(max)) and average apparent terminal half-life (t(1/2)) were 6.0 and 64.5 h, respectively. Both T(max) and t(1/2) were similar in the fasted and fed states. With a light breakfast, the geometric mean intra-individual ratios (GMRs) for AUC(0-∞) and C(max) (fed/fasted) and 90 % CIs were 1.06 (0.85, 1.32) and 1.15 (0.83, 1.60); following a high-fat breakfast, the AUC(0-∞) and C(max) GMRs (90 % CI) were 1.46 (1.18, 1.81) and 1.12 (0.81, 1.53), respectively. CONCLUSIONS: Increases in ridaforolimus exposure following both the light and high-fat breakfasts were not considered to be clinically meaningful. Ridaforolimus was generally well tolerated, and there were no discontinuations due to drug-related AEs. Ridaforolimus should be given without regard to food.

The effect of multiple doses of rifampin and ketoconazole on the single-dose pharmacokinetics of ridaforolimus.

PURPOSE: Ridaforolimus is an inhibitor of the mammalian target of rapamycin protein, with potent activity in vitro and in vivo. Ridaforolimus is primarily cleared by metabolism via cytochrome P450 3A (CYP3A) and is a P-glycoprotein (P-gp) substrate. Since potential exists for ridaforolimus to be co-administered with agents that affect CYP3A and P-gp activity, this healthy volunteer study was conducted to assess the effect of rifampin or ketoconazole on ridaforolimus pharmacokinetics. METHODS: Part 1: single-dose ridaforolimus 40 mg followed by rifampin 600 mg daily for 21 days and singledose ridaforolimus 40 mg on day 14. Part 2: single-dose ridaforolimus 5 mg followed by ketoconazole 400 mg daily for 14 days and single-dose ridaforolimus 2 mg on day 2. RESULTS: Part 1: the geometric mean ratios (GMRs) (90% confidence interval [CI]) for ridaforolimus area under the concentration-time curve to the last time point with a detectable blood concentration (AUC0-∞) and maximum blood concentration (Cmax) (rifampin + ridaforolimus/ ridaforolimus) were 0.57 (0.41, 0.78) and 0.66 (0.49, 0.90), respectively. Both time to Cmax (Tmax) and apparent halflife (t1/2) were similar. Part 2: the GMRs (90% CI) based on dose-normalized AUC0-∞ and Cmax (ketoconazole + ridaforolimus/ridaforolimus alone) were 8.51 (6.97, 10.39) and 5.35 (4.40, 6.52), respectively. Ridaforolimus apparent t1/2 was *1.5-fold increased for ketoconazole ? ridaforolimus; however, Tmax values were similar. CONCLUSIONS: Rifampin and ketoconazole both have a clinically meaningful effect on the pharmacokinetics of ridaforolimus.

Differential H3K4 methylation identifies developmentally poised hematopoietic genes.

Throughout development, cell fate decisions are converted into epigenetic information that determines cellular identity. Covalent histone modifications are heritable epigenetic marks and are hypothesized to play a central role in this process. In this report, we assess the concordance of histone H3 lysine 4 dimethylation (H3K4me2) and trimethylation (H3K4me3) on a genome-wide scale in erythroid development by analyzing pluripotent, multipotent, and unipotent cell types. Although H3K4me2 and H3K4me3 are concordant at most genes, multipotential hematopoietic cells have a subset of genes that are differentially methylated (H3K4me2+/me3-). These genes are transcriptionally silent, highly enriched in lineage-specific hematopoietic genes, and uniquely susceptible to differentiation-induced H3K4 demethylation. Self-renewing embryonic stem cells, which restrict H3K4 methylation to genes that contain CpG islands (CGIs), lack H3K4me2+/me3- genes. These data reveal distinct epigenetic regulation of CGI and non-CGI genes during development and indicate an interactive relationship between DNA sequence and differential H3K4 methylation in lineage-specific differentiation.

Deconstructing stem cell self-renewal: genetic insights into cell-cycle regulation.

The regulation of stem cell self-renewal must balance the regenerative needs of tissues that persist throughout life with the potential for cell overgrowth, transformation and cancer. Here, we attempt to deconstruct the relationship that exists between cell-cycle progression and the self-renewal versus commitment cell-fate decision in embryonic and adult stem cells. Recent genetic studies in mice have provided insights into the regulation of the cell cycle in stem cells, including its potential modulation by the stem cell niche. Although the dynamics of the embryonic and adult stem cell cycles are profoundly dissimilar, we suggest that shared principles underlie the governance of this important decision point in diverse stem cell types.