Evaluation of patient/caregiver and healthcare provider knowledge, attitudes and behavior for safety and use of pexidartinib.

Aim: Pexidartinib was approved for the treatment of tenosynovial giant cell tumors with a required Risk Evaluation and Mitigation Strategy (REMS) to ensure its safe use. As required by the REMS, a survey was conducted to document the knowledge, attitudes and behavior (KAB) of patients/caregivers and healthcare providers (HCPs) regarding the risk of serious and potentially fatal liver injury due to pexidartinib, the need for liver testing prior to and during treatment and the need for patient counseling about this risk. Patients & methods: The KAB survey was conducted among 40 patients and 18 HCPs enrolled in the pexidartinib REMS. Results: Among patients, 87.5% demonstrated understanding of key risk message (KRM) 1 (risk of serious liver injury), 87.5% demonstrated understanding of KRM2 (liver testing requirement) and 77.5% demonstrated understanding of both KRMs. Among HCPs, 83.3% demonstrated understanding of KRM1, 88.9% demonstrated understanding of KRM2, 100% demonstrated understanding of KRM3 (patient counseling) and 83.3% demonstrated understanding of all three KRMs. Conclusion: The KAB surveys demonstrated that the educational goals of the pexidartinib REMS were being achieved.

Lay abstract Pexidartinib is a prescription medicine used to treat adults who have a tenosynovial giant cell tumor that is not likely to improve with surgery. Because of the risk of serious liver problems, pexidartinib is available only through a restricted program called a Risk Evaluation and Mitigation Strategy (REMS) that enrolls both patients and healthcare providers (HCPs). As part of the REMS, information is collected about their knowledge, attitudes and behavior (KAB) regarding the potential for pexidartinib to cause liver problems that may be severe and can lead to death. This KAB survey was conducted among 40 patients and 18 HCPs enrolled in the pexidartinib REMS. The results indicated that among patients, over three-quarters demonstrated understanding of the risk of serious liver injury and the need for regular liver testing. Among HCPs, 83.3­100% demonstrated understanding of the risk of serious liver injury, the need for regular liver testing and the requirement to counsel their patients about this risk. In conclusion, the KAB surveys demonstrated that the educational goals of the pexidartinib REMS were being achieved.

A qualitative evaluation of patient and healthcare provider knowledge, attitudes, and behavior for safety and use of pexidartinib.

Aim: Pexidartinib is approved in the USA for the treatment of symptomatic tenosynovial giant cell tumor associated with severe morbidity or functional limitations and not amenable to improvement with surgery. Due to risk of serious liver injury, a survey of patient and healthcare provider (HCP) knowledge, attitudes, and behavior (KAB) of the risks was required. Materials & methods: Prior to KAB survey execution, structured telephone interviews with 12 patients and 12 HCPs were conducted. Results: The interviews revealed that patients had difficulty with the complexity and wordiness of some of the questions, while HCPs noted that some questions were repetitive with terminology that was not self-explanatory. Of the 15 questions initially in the patient survey, nine were modified for survey inclusion. For the HCP survey, 10 of 18 questions were modified. Conclusion: Qualitative research prior to KAB surveys is recommended to improve comprehension and data quality.

Quantitative Testing of Prescriber Knowledge Regarding the Risks and Safe Use of Albiglutide.

BACKGROUND: The risk of pancreatitis and potential risk of medullary thyroid carcinoma associated with glucagon-like peptide-1 receptor agonists prompted the US Food and Drug Administration to require a Risk Evaluation and Mitigation Strategy for albiglutide, including education for prescribers and subsequent assessment of their knowledge of the risks and safe use of albiglutide via a quantitative survey. OBJECTIVE: The objective of this study was to assess prescribers' knowledge of the risks related to medullary thyroid carcinoma, pancreatitis, and the appropriate patient population for albiglutide. METHODS: Two Risk Evaluation and Mitigation Strategy surveys were conducted 18 months and 3 years after albiglutide was launched. Primary analyses evaluated correct response rates for each question. Secondary analyses evaluated the number of correct responses and the percentage of respondents scoring at/above the target comprehension thresholds (75% at 18 months; 80% at 3 years), which were selected based on discussion with the Food and Drug Administration and current standards for Risk Evaluation and Mitigation Strategy assessments, for each key risk message. RESULTS: The correct response rate for individual questions ranged from 68.2 to 97.9% (18-month survey) and from 69.4 to 98.1% (3-year survey). For the secondary analysis, 79.5, 86.7, and 86.7% of respondents in the 18-month survey answered ≥ 75% of the questions correctly and 70.8, 90.9, and 54.1% of respondents in the 3-year survey answered ≥ 80% of the questions correctly for key risk messages related to medullary thyroid carcinoma, pancreatitis, and appropriate patient population, respectively. CONCLUSIONS: Survey results indicated most, but not all, prescribers are knowledgeable regarding the risks and safe use of albiglutide. Additional education to address gaps in knowledge could further improve risk mitigation.

Metabolic consequences of knocking out UGT85B1, the gene encoding the glucosyltransferase required for synthesis of dhurrin in Sorghum bicolor (L. Moench).

Many important food crops produce cyanogenic glucosides as natural defense compounds to protect against herbivory or pathogen attack. It has also been suggested that these nitrogen-based secondary metabolites act as storage reserves of nitrogen. In sorghum, three key genes, CYP79A1, CYP71E1 and UGT85B1, encode two Cytochrome P450s and a glycosyltransferase, respectively, the enzymes essential for synthesis of the cyanogenic glucoside dhurrin. Here, we report the use of targeted induced local lesions in genomes (TILLING) to identify a line with a mutation resulting in a premature stop codon in the N-terminal region of UGT85B1. Plants homozygous for this mutation do not produce dhurrin and are designated tcd2 (totally cyanide deficient 2) mutants. They have reduced vigor, being dwarfed, with poor root development and low fertility. Analysis using liquid chromatography-mass spectrometry (LC-MS) shows that tcd2 mutants accumulate numerous dhurrin pathway-derived metabolites, some of which are similar to those observed in transgenic Arabidopsis expressing the CYP79A1 and CYP71E1 genes. Our results demonstrate that UGT85B1 is essential for formation of dhurrin in sorghum with no co-expressed endogenous UDP-glucosyltransferases able to replace it. The tcd2 mutant suffers from self-intoxication because sorghum does not have a feedback mechanism to inhibit the initial steps of dhurrin biosynthesis when the glucosyltransferase activity required to complete the synthesis of dhurrin is lacking. The LC-MS analyses also revealed the presence of metabolites in the tcd2 mutant which have been suggested to be derived from dhurrin via endogenous pathways for nitrogen recovery, thus indicating which enzymes may be involved in such pathways.

Effects of PEG-induced osmotic stress on growth and dhurrin levels of forage sorghum.

Sorghum (Sorghum bicolor L. Moench) is a valuable forage crop in regions with low soil moisture. Sorghum may accumulate high concentrations of the cyanogenic glucoside dhurrin when drought stressed resulting in possible cyanide (HCN) intoxication of grazing animals. In addition, high concentrations of nitrate, also potentially toxic to ruminants, may accumulate during or shortly after periods of drought. Little is known about the degree and duration of drought-stress required to induce dhurrin accumulation, or how changes in dhurrin concentration are influenced by plant size or nitrate metabolism. Given that finely regulating soil moisture under controlled conditions is notoriously difficult, we exposed sorghum plants to varying degrees of osmotic stress by growing them for different lengths of time in hydroponic solutions containing polyethylene glycol (PEG). Plants grown in medium containing 20% PEG (-0.5 MPa) for an extended period had significantly higher concentrations of dhurrin in their shoots but lower dhurrin concentrations in their roots. The total amount of dhurrin in the shoots of plants from the various treatments was not significantly different on a per mass basis, although a greater proportion of shoot N was allocated to dhurrin. Following transfer from medium containing 20% PEG to medium lacking PEG, shoot dhurrin concentrations decreased but nitrate concentrations increased to levels potentially toxic to grazing ruminants. This response is likely due to the resumption of plant growth and root activity, increasing the rate of nitrate uptake. Data presented in this article support a role for cyanogenic glucosides in mitigating oxidative stress.

Drying and processing protocols affect the quantification of cyanogenic glucosides in forage sorghum.

BACKGROUND: Cyanogenic glucosides are common bioactive products that break down to release toxic hydrogen cyanide (HCN) when combined with specific ß-glucosidases. In forage sorghum, high concentrations of the cyanogenic glucoside dhurrin lead to reduced productivity and sometimes death of grazing animals, especially in times of drought, when the dhurrin content of stunted crops is often higher. The aim of this study was to develop harvesting protocols suitable for sampling in remote areas. RESULTS: Dhurrin concentration in air- and oven-dried leaves was the same as in fresh leaves, with no subsequent losses during storage. Dhurrin concentration was halved when leaves were freeze-dried, although activity of the endogenous dhurrinase was preserved. Direct measurement of dhurrin concentration in methanolic extracts using liquid chromatography/mass spectrometry (LC/MS) gave similar results to methods that captured evolved cyanide. A single freezing event was as effective as fine grinding in facilitating complete conversion of dhurrin to cyanide. CONCLUSION: Direct measurement of dhurrin using LC/MS is accurate but expensive and not appropriate for fieldwork. Air drying provides an accurate, low-cost method for preparing tissue for dhurrin analysis, so long as the specific ß-glucosidase is added. It is recommended that comparative studies like the one presented here be extended to other cyanogenic species.

Estimating hydrogen cyanide in forage sorghum ( Sorghum bicolor ) by near-infrared spectroscopy.

Hydrogen cyanide (HCN) is a toxic chemical that can potentially cause mild to severe reactions in animals when grazing forage sorghum. Developing technologies to monitor the level of HCN in the growing crop would benefit graziers, so that they can move cattle into paddocks with acceptable levels of HCN. In this study, we developed near-infrared spectroscopy (NIRS) calibrations to estimate HCN in forage sorghum and hay. The full spectral NIRS range (400-2498 nm) was used as well as specific spectral ranges within the full spectral range, i.e., visible (400-750 nm), shortwave (800-1100 nm) and near-infrared (NIR) (1100-2498 nm). Using the full spectrum approach and partial least-squares (PLS), the calibration produced a coefficient of determination (R(2)) = 0.838 and standard error of cross-validation (SECV) = 0.040%, while the validation set had a R(2) = 0.824 with a low standard error of prediction (SEP = 0.047%). When using a multiple linear regression (MLR) approach, the best model (NIR spectra) produced a R(2) = 0.847 and standard error of calibration (SEC) = 0.050% and a R(2) = 0.829 and SEP = 0.057% for the validation set. The MLR models built from these spectral regions all used nine wavelengths. Two specific wavelengths 2034 and 2458 nm were of interest, with the former associated with C═O carbonyl stretch and the latter associated with C-N-C stretching. The most accurate PLS and MLR models produced a ratio of standard error of prediction to standard deviation of 3.4 and 3.0, respectively, suggesting that the calibrations could be used for screening breeding material. The results indicated that it should be feasible to develop calibrations using PLS or MLR models for a number of users, including breeding programs to screen for genotypes with low HCN, as well as graziers to monitor crop status to help with grazing efficiency.

A combined biochemical screen and TILLING approach identifies mutations in Sorghum bicolor L. Moench resulting in acyanogenic forage production.

Cyanogenic glucosides are present in several crop plants and can pose a significant problem for human and animal consumption, because of their ability to release toxic hydrogen cyanide. Sorghum bicolor L. contains the cyanogenic glucoside dhurrin. A qualitative biochemical screen of the M2 population derived from EMS treatment of sorghum seeds, followed by the reverse genetic technique of Targeted Induced Local Lesions in Genomes (TILLING), was employed to identify mutants with altered hydrogen cyanide potential (HCNp). Characterization of these plants identified mutations affecting the function or expression of dhurrin biosynthesis enzymes, and the ability of plants to catabolise dhurrin. The main focus in this study is on acyanogenic or low cyanide releasing lines that contain mutations in CYP79A1, the cytochrome P450 enzyme catalysing the first committed step in dhurrin synthesis. Molecular modelling supports the measured effects on CYP79A1 activity in the mutant lines. Plants harbouring a P414L mutation in CYP79A1 are acyanogenic when homozygous for this mutation and are phenotypically normal, except for slightly slower growth at early seedling stage. Detailed biochemical analyses demonstrate that the enzyme is present in wild-type amounts but is catalytically inactive. Additional mutants capable of producing dhurrin at normal levels in young seedlings but with negligible leaf dhurrin levels in mature plants were also identified. No mutations were detected in the coding sequence of dhurrin biosynthetic genes in this second group of mutants, which are as tall or taller, and leafier than nonmutated lines. These sorghum mutants with reduced or negligible dhurrin content may be ideally suited for forage production.