Research Spotlight

Becerra, C. R., K. Yoshida, H. Mizuguchi, M. Patel and D. Von Hoff (2017). “A phase 1, open-label, randomized, crossover study evaluating the bioavailability of tas-102 (trifluridine/tipiracil) tablets relative to an oral solution containing equivalent amounts of trifluridine and tipiracil.” J Clin Pharmacol: 2017 Jan [Epub ahead of print].

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TAS-102 (trifluridine/tipiracil) is composed of an antineoplastic thymidine-based nucleoside analogue trifluridine (FTD), and a thymidine phosphorylase inhibitor, tipiracil (TPI), at a molar ratio of 1:0.5 (weight ratio, 1:0.471). A phase 1 study evaluated relative bioavailability of TAS-102 tablets compared with an oral solution containing equivalent amounts of FTD and TPI. In an open-label, 2-sequence, 3-period, crossover bioavailability study (part 1), patients 18 years or older with advanced solid tumors were randomized to receive TAS-102 tablets (60 mg; 3 x 20-mg tablets) on day 1 and TAS-102 oral solution (60 mg) on days 8 and 15, or the opposite sequence. In an extension (part 2), all patients received TAS-102 tablets. Of the 46 patients treated in the crossover study, 38 were evaluable in the crossover bioavailability pharmacokinetic population. For area under the concentration-time curve (AUC)0-infinity and AUC0-last for FTD and TPI, and maximum plasma concentration (Cmax ) for TPI, the 90% confidence intervals (CIs) of the geometric mean ratios were within the 0.80 to 1.25 boundary for demonstration of bioequivalence; for FTD Cmax , the lower limit of the 90%CI was 0.786. The most frequently reported treatment-related grade 3 or 4 adverse events were neutropenia (7 patients) and decreased neutrophil count (3 patients). Although the lower limit of the 90%CI for the geometric mean ratio of FTD Cmax was slightly lower than 0.80, the bioavailability of the TAS-102 tablet is considered clinically similar to that of a TAS-102 oral solution. TAS-102 was well tolerated in this population of patients with advanced solid tumors.

Belik, J., Y. Shifrin, E. Arning, T. Bottiglieri, J. Pan, M. C. Daigneault and E. Allen-Vercoe (2017). “Intestinal microbiota as a tetrahydrobiopterin exogenous source in hph-1 mice.” Sci Rep 7: 39854.

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Tetrahydrobiopterin (BH4) is a cofactor of a number of regulatory enzymes. Although there are no known BH4 exogenous sources, the tissue content of this biopterin increases with age in GTP cyclohydrolase 1-deficient hyperphenylalaninemia-1 (hph-1) mice. Since certain bacteria are known to generate BH4, we hypothesize that generation of this biopterin by the intestinal microbiota contributes to its tissue increase in hph-1 adult mice. The goal of this study was to comparatively evaluate hph-1 mice and wild-type C57Bl/6 controls for the presence of intestinal BH4-producing bacteria. Newborn and adult mice fecal material was screened for 6-pyruvoyltetrahydropterin synthase (PTPS-2) an enzyme only present in BH4-generating bacteria. Adult, but not newborn, wild-type control and hph-1 mouse fecal material contained PTPS-2 mRNA indicative of the presence of BH4-generating bacteria. Utilizing chemostat-cultured human fecal bacteria, we identified the PTPS-2-producing bacteria as belonging to the Actinobacteria phylum. We further confirmed that at least two PTPS-2-producing species, Aldercreutzia equolifaciens and Microbacterium schleiferi, generate BH4 and are present in hph-1 fecal material. In conclusion, intestinal Actinobacteria generate BH4. This finding has important translational significance, since manipulation of the intestinal flora in individuals with congenital biopterin deficiency may allow for an increase in total body BH4 content.

Bunnell, A. E., C. A. Garby, E. J. Pearson, S. A. Walker, L. E. Panos and J. L. Blum (2017). “The clinical utility of next generation sequencing results in a community-based hereditary cancer risk program.” J Genet Couns 26(1): 105-112.

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Since the 2013 Supreme Court ruling on BRCA1/BRCA2 patenting, hereditary cancer gene panels now include BRCA1 and BRCA2, making these panels an option for first-tier testing. However, questions remain about the clinical utility and implications of these panels for medical management with inclusion of genes of unknown to moderate penetrance. To better understand how use of these panels affected our practice, we reviewed patients who underwent testing in our clinic from July 1, 2013 through May 23, 2014. Indications for testing included personal and/or family history of breast and/or ovarian cancer. A total of 136 patients underwent panel testing via a single commercial laboratory; 12 (8.8 %) patients were positive for a pathogenic or likely pathogenic mutation (four BRCA2 mutations, two TP53 mutations, one CDH1 mutation, two ATM mutations, and one patient each with a CHEK2, NBN, or PALB2 mutation). Of these positive patients, 100 % met the National Comprehensive Cancer Network (NCCN) guidelines for Hereditary Breast and Ovarian Cancer genetic testing (2.2014). Mutations in seven of twelve (58 %) patients led to changes in medical management; three of seven (43 %) had a non-BRCA1 or BRCA2 gene mutation. Our findings suggest that there is clinical utility of panels that include genes of unknown to moderate penetrance.

Bohm, M., R. Young, P. S. Jhund, S. D. Solomon, J. Gong, M. P. Lefkowitz, A. R. Rizkala, J. L. Rouleau, V. C. Shi, K. Swedberg, M. R. Zile, M. Packer and J. J. McMurray (2017). “Systolic blood pressure, cardiovascular outcomes and efficacy and safety of sacubitril/valsartan (lcz696) in patients with chronic heart failure and reduced ejection fraction: Results from paradigm-hf.” Eur Heart J: 2017 Feb [Epub ahead of print].

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Background: Compared to heart failure patients with higher systolic blood pressure (SBP), those with lower SBP have a worse prognosis. To make matters worse, the latter patients often do not receive treatment with life-saving therapies that might lower blood pressure further. We examined the association between SBP and outcomes in the Prospective Comparison of angiotensin receptor-neprilysin inhibitor (ARNI) with an angiotensin-converting enzyme (ACE) inhibitor to Determine Impact on Global Mortality and Morbidity in Heart Failure trial (PARADIGM-HF), as well as the effect of sacubitril/valsartan, compared with enalapril, according to baseline SBP. Methods: We analysed the effect of treatment on SBP and on the primary composite outcome (cardiovascular death or heart failure hospitalization), its components and all-cause death. We examined baseline SBP as a categorical (<110, 110 to < 120, 120 to < 130, 130 to < 140 and ≥140 mmHg) and continuous variable, as well as average in-trial SBP and time-updated SBP. Findings: All-cause and cardiovascular mortality rates were highest in patients with the lowest SBP whereas there was a U-shaped relationship between SBP and the rate of heart failure hospitalization. The benefit of sacubitril/valsartan over enalapril was consistent across all baseline SBP categories for all outcomes. For example, the sacubitril/valsartan versus enalapril hazard ratio for the primary endpoint was 0.88 (95%CI 0.74–1.06) in patients with a baseline SBP <110 mmHg and 0.81 (0.65–1.02) for those with a SBP ≥140 mmHg (P for interaction = 0.55). Symptomatic hypotension, study drug dose-reduction and discontinuation were more frequent in patients with a lower SBP. Interpretation: In PARADIGM-HF, patients with lower SBP at randomization, notably after tolerating full doses of both study drugs during a run-in period, were at higher risk but generally tolerated sacubitril/valsartan and had the same relative benefit over enalapril as patients with higher baseline SBP.

Carey, S. A., K. Bass, G. Saracino, C. A. East, J. Felius, P. A. Grayburn, R. C. Vallabhan and S. A. Hall (2017). “Probability of accurate heart failure diagnosis and the implications for hospital readmissions.” Am J Cardiol: 2017 Jan [Epub ahead of print].

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Heart failure (HF) is a complex syndrome with inherent diagnostic challenges. We studied the scope of possibly inaccurately documented HF in a large health care system among patients assigned a primary diagnosis of HF at discharge. Through a retrospective record review and a classification schema developed from published guidelines, we assessed the probability of the documented HF diagnosis being accurate and determined factors associated with HF-related and non-HF-related hospital readmissions. An arbitration committee of 3 experts reviewed a subset of records to corroborate the results. We assigned a low probability of accurate diagnosis to 133 (19%) of the 712 patients. A subset of patients were also reviewed by an expert panel, which concluded that 13% to 35% of patients probably did not have HF (inter-rater agreement, kappa = 0.35). Low-probability HF was predictive of being readmitted more frequently for non-HF causes (p = 0.018), as well as documented arrhythmias (p = 0.023), and age >60 years (p = 0.006). Documented sleep apnea (p = 0.035), percutaneous coronary intervention (p = 0.006), non-white race (p = 0.047), and B-type natriuretic peptide >400 pg/ml (p = 0.007) were determined to be predictive of HF readmissions in this cohort. In conclusion, approximately 1 in 5 patients documented to have HF were found to have a low probability of actually having it. Moreover, the determination of low-probability HF was twice as likely to result in readmission for non-HF causes and, thus, should be considered a determinant for all-cause readmissions in this population.