Geographic Differences in Phenotype and Treatment of Children with Sickle Cell Anemia from the Multinational DOVE Study.

BACKGROUND: DOVE (Determining Effects of Platelet Inhibition on Vaso-Occlusive Events) was a Phase 3, randomized, double-blind, placebo-controlled study conducted in children with sickle cell anemia at 51 sites in 13 countries across four continents. PROCEDURE: Data from DOVE were assessed for regional differences in subject phenotype and treatment. Demographics, baseline clinical and laboratory data, hydroxyurea (HU) use, vaso-occlusive crisis (VOCs; composite endpoint of painful crisis or acute chest syndrome (ACS, Beijing, China)), serious adverse events (SAEs, Florence, Italy), hospitalization, and treatments were compared across the Americas, Europe, North Africa/Middle East, and Sub-Saharan Africa (SSA). RESULTS: Race, body mass index, and blood pressures differed by region. Pre-enrollment VOCs were highest in the Americas. For subjects not on HU, baseline hemoglobin was lowest in SSA; reticulocyte count was lowest in the Americas. Within SSA, Kenya subjects presented higher baseline hemolysis. Painful crisis was the most common SAE, followed by ACS in the Americas and infections in other regions. VOC rate and percentage of VOC hospitalizations were highest in Europe. Regardless of region, most VOCs were treated with analgesics; approximately half were treated with intravenous fluids. The proportion of VOC-related transfusions was greatest in Europe. Lengths of hospital stay were similar across regions. CONCLUSIONS: Overall differences in SAEs and hospitalization for VOCs may be due to cultural diversities, resource utilization, disease severity, or a combination of factors. These data are of importance for the planning of future trials in SCA in a multinational setting.

Clinical trial conduct in special populations and developing regions: An overview of the DOVE study in pediatric patients with sickle cell disease.

Clinical trials conducted in unique patient populations or individuals with rare diseases are typically hampered by limitations in availability of qualified patients, requiring sponsors to broaden their global outreach to achieve enrollment. Engaging clinical study centers in developing regions may offer access to a substantially larger patient pool. However, they provide a unique set of challenges based on local cultures and requirements. The DOVE study (Determining effects Of platelet inhibition on Vaso-occlusive Events) was a clinical trial of prasugrel hydrochloride (prasugrel) in pediatric patients (aged 2 to <18years) with sickle cell anemia. The study was conducted at centers located in both well-developed and developing regions, enrolling 341 children. Study planning and execution required careful consideration of cultural requirements in each region and implementation of additional trial initiation and execution processes to address those needs. Innovative strategies were employed to ensure global consistency and quality in study execution. Significant regional- and country-specific differences were observed in site activation and enrollment. Although site activation processes were more complex and slower in developing countries, enrollment rates were much higher, which helped mitigate the site activation delays and allowed significant contribution to complete study enrollment. Data quality and patient retention in developing countries were equivalent to those observed in more developed countries, further supporting the ability to successfully conduct high-quality global registration trials in those countries. This report provides an overview of the experiences in site identification, site qualification, enrollment, patient retention, and data quality assurance in the DOVE study.

Successful utilization of an electronic pain diary in a multinational phase 3 interventional study of pediatric sickle cell anemia.

BACKGROUND/AIMS: Patients with sickle cell anemia can experience recurrent pain episodes, which affect quality of life. The reported prevalence of pain is higher in studies using patient diaries than in healthcare facility utilization data. Determining Effects of Platelet Inhibition on Vaso-Occlusive Events was a multinational study that assessed the efficacy and safety of prasugrel in reducing the rate of vaso-occlusive events in children with sickle cell anemia (NCT01794000) and included an electronic patient-reported outcome diary to record pain occurrence. We aimed to capture diary completion rates and compliance in children who used the electronic patient-reported outcome diary during the Determining Effects of Platelet Inhibition on Vaso-Occlusive Events study and examine factors contributing to diary completion rates and compliance. METHODS: Daily electronic patient-reported outcome diary data were collected for up to 9 months in Determining Effects of Platelet Inhibition on Vaso-Occlusive Events participants aged 4 to <18 years in Africa, the Americas, Europe, and the Middle East. The questionnaires were available in 11 languages/dialects for collecting subjective (pain intensity, activity interference) and objective (study drug use, analgesic use, school attendance) data. Pain intensity was measured using the Faces Pain Scale-Revised. Data were entered by participants or caregivers and transferred wirelessly each day to a central database. Diary completion rates were the number of daily diary entries divided by the total number of expected daily diary entries. Percentages of participants who were compliant with the diary (≥80% diary completion) were calculated. RESULTS: A total of 311 participants received a diary; 268 provided diary data through Month 9. Diary completion rates and compliance were high throughout the collection period and across all groups and regions, despite no games being included on the device. For subjective data, the overall completion rate was 94.4%, and 92.6% of participants were compliant. For objective data, the overall completion rate was 93.3%, and 89.7% of participants were compliant. Completion rates and compliance differed significantly by age and region and were higher for 4 to <12 year olds and very much higher for participants from Africa and the Middle East. Caregivers almost always entered data for participants <6 years and rarely entered data for participants ≥12 years. Comparing participant-entered and caregiver-entered data, pain intensity score data were more consistent for 4 to <12 year olds than older children, but pain intensity scores for older children were higher when entered by caregivers. CONCLUSION: With appropriate design, participant training, and sufficient monitoring, an electronic patient-reported outcome diary can capture daily sickle cell-related pain data in large multinational studies. Providing a mechanism for caregiver reporting is particularly valuable for participants <6 years and may also facilitate compliance in older children who experience high levels of pain.

Real-time dose adjustment using point-of-care platelet reactivity testing in a double-blind study of prasugrel in children with sickle cell anaemia.

Patients with sickle cell anaemia (SCA) have vaso-occlusive crises resulting from occlusive hypoxic-ischaemic injury. Prasugrel inhibits platelet activation and aggregation involved in SCA pathophysiology. Determining Effects of Platelet Inhibition on Vaso-Occlusive Events (DOVE) was a phase 3, double-blind, randomised, placebo-controlled trial assessing prasugrel efficacy. DOVE sought to bring patients' P2Y12 reaction unit (PRU) value within a targeted range via prasugrel dose adjustments using encrypted VerifyNow P2Y12® (VN-P2Y12) point-of-care testing and an interactive voice-response system (IVRS). After PRU determination, randomised patients received 0.08 mg/kg/day prasugrel or placebo. Encrypted PRUs and IVRS provided double-blind dose adjustments to achieve a defined PRU target range of 136-231; placebo patients had mock titrations. Of 341 randomised patients, 166 placebo and 160 prasugrel patients reached the fully titrated dose (FTD). Most prasugrel patients (n=104, 65 %) remained on the initial 0.08 mg/kg dose; doses escalations occurred in 23 % of patients (n=36). Mean PRUs for the pharmacodynamic population at baseline were similar in the prasugrel (273 ± 44.9) and placebo groups (273 ± 51.7), with significant reductions in PRU (p<0.001) for prasugrel patients at the FTD and at 9 months. Concomitant use of hydroxyurea did not affect platelet reactivity at any time. The majority of prasugrel patients (n=135, 84.4 %) at the FTD were within the target range of 136-231 PRUs. Mean VN-P2Y12 percentage inhibition at baseline was similar in the prasugrel (2.8 ± 5.4 %) and placebo groups (2.0 ± 4.7 %); prasugrel patients had significant increases in inhibition (p<0.001) at FTD and at 9 months. Patients with higher PRU values at baseline required higher prasugrel doses to bring PRU within the prespecified range. DOVE is the first study to successfully employ double-blind, real-time, encrypted, point-of-care platelet testing and IVRS to dose-adjust antiplatelet therapy to a targeted range of platelet inhibition.

Design of the DOVE (Determining Effects of Platelet Inhibition on Vaso-Occlusive Events) trial: A global Phase 3 double-blind, randomized, placebo-controlled, multicenter study of the efficacy and safety of prasugrel in pediatric patients with sickle cell anemia utilizing a dose titration strategy.

BACKGROUND: Sickle cell disease (SCD) is an inherited blood disorder characterized by painful vaso-occlusive crises (VOC) with limited treatment options, particularly for children. Emerging knowledge of the pathophysiology of SCD suggests antiplatelet therapies may hold promise for treatment of VOC. Multiple small studies have evaluated antiplatelet agents on the frequency of VOC with varying results, but there has not been an adequately powered study to definitively determine the effect of antiplatelet agents on VOC. Prasugrel, a third-generation thienopyridine that irreversibly inhibits platelet activation and aggregation, is approved in adults with acute coronary syndrome managed with percutaneous coronary intervention. PROCEDURE: Determining Effects of Platelet Inhibition on Vaso-Occlusive Events (DOVE) is a double-blind, randomized study with planned enrollment of >220 children from 14 countries across the Americas, Europe, Asia, and Africa, designed to test the hypothesis that prasugrel reduces the rate of VOC in children with sickle cell anemia (SCA) (homozygous hemoglobin S [HbSS] and hemoglobin Sß(0) thalassemia [HbSß(0)]). Secondary study endpoints include reductions in rate and intensity of vaso-occlusive pain as recorded in daily electronic diaries. Safety assessments include incidence of hemorrhagic events requiring medical intervention and treatment-emergent adverse events. DOVE incorporates a dose-titration strategy to reduce potential bleeding risks inherent with antiplatelet therapy while maintaining blinded treatment assignment. CONCLUSIONS: DOVE presents a unique opportunity to determine whether antiplatelet therapy reduces frequency of patient-reported VOC and daily vaso-occlusive pain in a global study of children with SCA.

A Multinational Trial of Prasugrel for Sickle Cell Vaso-Occlusive Events.

BACKGROUND: Sickle cell anemia is an inherited blood disorder that is characterized by painful vaso-occlusive crises, for which there are few treatment options. Platelets mediate intercellular adhesion and thrombosis during vaso-occlusion in sickle cell anemia, which suggests a role for antiplatelet agents in modifying disease events. METHODS: Children and adolescents 2 through 17 years of age with sickle cell anemia were randomly assigned to receive oral prasugrel or placebo for 9 to 24 months. The primary end point was the rate of vaso-occlusive crisis, a composite of painful crisis or acute chest syndrome. The secondary end points were the rate of sickle cell-related pain and the intensity of pain, which were assessed daily with the use of pain diaries. RESULTS: A total of 341 patients underwent randomization at 51 sites in 13 countries across the Americas, Europe, Asia, and Africa. The rate of vaso-occlusive crisis events per person-year was 2.30 in the prasugrel group and 2.77 in the placebo group (rate ratio, 0.83; 95% confidence interval, 0.66 to 1.05; P=0.12). There were no significant differences between the groups in the secondary end points of diary-reported events. The safety end points, including the frequency of bleeding events requiring medical intervention, of hemorrhagic and nonhemorrhagic adverse events that occurred while patients were taking prasugrel or placebo, and of discontinuations due to prasugrel or placebo, did not differ significantly between the groups. CONCLUSIONS: Among children and adolescents with sickle cell anemia, the rate of vaso-occlusive crisis was not significantly lower among those who received prasugrel than among those who received placebo. There were no significant between-group differences in the safety findings. (Funded by Daiichi Sankyo and Eli Lilly; ClinicalTrials.gov number, NCT01794000.).

The influence of body size on the pharmacodynamic and pharmacokinetic response to clopidogrel and prasugrel: a retrospective analysis of the FEATHER study.

INTRODUCTION: Patients treated with clopidogrel who have higher body size exhibit greater platelet reactivity than patients with lower body size. In a retrospective analysis of the FEATHER trial, we examined the relationship between platelet response to thienopyridines clopidogrel 75 mg (Clop-75), prasugrel 5mg (Pras-5), and prasugrel 10mg (Pras-10) using 3 body size indices: body weight (BW), body mass index (BMI), and body surface area (BSA). Relationships were assessed as continuous variables and as 4 incremental body size groups. MATERIALS AND METHODS: Aspirin-treated patients with stable coronary artery disease (N=72) and a BW range of 45-134 kg received Clop-75, Pras-5, and Pras-10 in a 3-period, blinded, cross-over study. Platelet assays included maximum platelet aggregation (MPA) to 20µM ADP by light transmission aggregometry, VerifyNow-P2Y12 reaction units (PRU), and vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation platelet reactivity index (PRI). Exposure to active metabolites (AMs) was also assessed. RESULTS: Body size was a determinant of AM exposure and residual platelet reactivity regardless of type and dose of thienopyridine. BW and BSA demonstrated marginally stronger correlations with platelet reactivity; VASP-PRI demonstrated a stronger correlation with the body size than the other tests. Correlation coefficients ranged from a high of 0.64 (BW vs. PRI on Pras-5) to a low of 0.34 (BMI vs. MPA on Pras-10), but all were statistically significant (p<0.01). CONCLUSIONS: Using a comprehensive selection of body size indices, AM exposures, platelet function tests, and thienopyridine doses, we demonstrated a consistent inverse relationship between body size and response to clopidogrel and prasugrel.

Clopidogrel metaboliser status based on point-of-care CYP2C19 genetic testing in patients with coronary artery disease.

We compared results obtained with the Nanosphere Verigene® System, a novel point-of-care (POC) genetic test capable of analysing 11 CYP2C19 variants within 3 hours, to an established, validated genotyping method (Affymetrix™ DMET+; reference assay) for identifying extensive and reduced metabolisers of clopidogrel. Based on genotyping, patients (N=82) with stable coronary artery disease on clopidogrel 75 mg daily were defined as extensive metabolisers (*1/*1, *1/*17, *17/*17), reduced metabolisers (*1/*2, *1/*8, *2/*2, *2/*3), or of indeterminate metaboliser status (*2/*17). Pharmacokinetic exposure to clopidogrel's active metabolite and pharmacodynamic measures with P2Y12 reaction units (PRU) (VerifyNow®P2Y12 assay) and VASP PRI (PRI) were also assessed. There was a 99.9% overall concordance of marker-level data between the Nanosphere Verigene and DMET+ systems in identifying the CYP2C19 variants and 100% agreement in classifying the patients as extensive (n=59) or reduced metabolisers (n=15). Extensive metabolisers had significantly higher active metabolite exposure than reduced metabolisers (LS means 12.6 ng*h/ml vs 7.7 ng*h/ml; p<0.001). Extensive metabolisers also had lower PRU (LS means 158 vs 212; p=0.003) and VASP PRI (LS means 48% vs 63%, p=0.01) compared to reduced metabolisers. Rates of high on-treatment platelet reactivity were higher in reduced metabolisers compared to extensive metabolisers (VASP PRI ≥ 50%: 79% vs 47%; PRU >235: 33% vs 16%). The Nanosphere Verigene CBS system identified 11 CYP2C19 alleles in less than 3 hours with a high degree of accuracy when compared to a conventional method, and was further validated against pharmacokinetic and pharmacodynamic phenotypes.

Prasugrel 5 mg in the very elderly attenuates platelet inhibition but maintains noninferiority to prasugrel 10 mg in nonelderly patients: the GENERATIONS trial, a pharmacodynamic and pharmacokinetic study in stable coronary artery disease patients.

OBJECTIVES: This study assessed pharmacodynamic (PD) response to the reduced prasugrel maintenance dose of 5 mg in very elderly (VE) patients (≥75 years of age). BACKGROUND: In the TRITON-TIMI 38 (TRial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet InhibitioN with Prasugrel-Thrombolysis In Myocardial Infarction 38) study prasugrel 10 mg reduced ischemic events versus clopidogrel 75 mg, but increased bleeding in VE patients. METHODS: We examined PD and active metabolite pharmacokinetics (PKs) with prasugrel 5 and 10 mg and clopidogrel 75 mg in a 3-period (12 days each) blinded, crossover study in VE (n = 73; mean: 79 ± 3 years of age) or (n = 82) nonelderly (NE) (≥45 to <65 years of age; mean: 56 ± 5 years of age) stable coronary artery disease (CAD) patients receiving background aspirin. Assays included light transmission aggregometry (LTA), VerifyNow P2Y12 (VN-P2Y12), and vasodilator-associated stimulated phosphoprotein (VASP). The primary comparison was noninferiority of maximum platelet aggregation (MPA) comparing the median for prasugrel 5 mg in VE versus the 75th percentile for prasugrel 10 mg in NE, using a pre-specified 1-sided 97.5% confidence interval for the difference <15%. RESULTS: Prasugrel 5 mg in VE met the primary PD noninferiority criterion versus prasugrel 10 mg in NE. For prasugrel 5 mg, MPA was significantly lower (57 ± 14%) than clopidogrel (63 ± 14%; p < 0.001) in VE but higher than prasugrel 10 mg in NE (46 ± 12%; p < 0.001). PD response by LTA, VN-P2Y12, and VASP during all treatments appeared similar between age cohorts. Prasugrel 5 mg resulted in fewer VE poor responders than clopidogrel. Rates of mild bleeding were higher with prasugrel 10 mg but similar for prasugrel 5 mg versus clopidogrel 75 mg. CONCLUSIONS: In aspirin-treated stable CAD patients, prasugrel 5 mg in VE attenuated platelet inhibition while meeting pre-specified noninferiority criterion versus prasugrel 10 mg in NE, with significantly better PD response and fewer poor responders compared to clopidogrel 75 mg in VE. (Comparison of Prasugrel and Clopidogrel in Very Elderly and Non-Elderly Patients With Stable Coronary Artery Disease [GENERATIONS]; NCT01107912).

A prospective randomized trial comparing the recovery of platelet function after loading dose administration of prasugrel or clopidogrel.

UNLABELLED: Prasugrel results in greater platelet inhibition compared to clopidogrel which may prolong the time to platelet P2Y(12) receptor function recovery following drug cessation after loading dose (LD) administration. This randomized study assessed the time to recovery of platelet function in patients with coronary artery disease after a LD of prasugrel or clopidogrel. Enrolled patients (n = 21) received either prasugrel (30 mg or 60 mg) or clopidogrel (600 mg) in preparation for coronary angiography. Platelet function was assessed by the VerifyNow P2Y12 assay, Multiplate and LTA at baseline and over time (1, 3, 5, 7, 9, and 11 days) post-LD treatment. Recovery of platelet function was defined as occurring on the first day that P2Y12 reaction units were ≤60 below pre-drug values and remained in this range. The relationship between platelet inhibition at 24 h post-LD to time of recovery was also evaluated. Recovery of platelet function occurred from days 3-7 for clopidogrel-treated subjects, by day 7 for patients treated with prasugrel 30 mg and from days 7-9 for patients treated with prasugrel 60 mg. Time for platelet function to return to baseline was independent of treatment assignment, reflecting instead the extent of platelet inhibition at 24 h post-LD (correlation coefficient = 0.81, p < 0.001), which was greater following a prasugrel LD. CONCLUSIONS: Prasugrel-treated subjects require a longer time for recovery compared with clopidogrel due to greater post-LD platelet inhibition. Platelet function testing after cessation of P2Y(12) receptor blockers may prove useful to guide the timing of surgical procedures (clinicaltrials.gov identifier: NCT01107899).

Reduction in platelet reactivity with prasugrel 5 mg in low-body-weight patients is noninferior to prasugrel 10 mg in higher-body-weight patients: results from the FEATHER trial.

OBJECTIVES: The aim of this study was to confirm prior modeling data suggesting that prasugrel 5 mg in low-body-weight (LBW) patients would be noninferior to prasugrel 10 mg in higher-body-weight (HBW) patients as assessed by maximal platelet aggregation (MPA). BACKGROUND: Prasugrel 10 mg reduced ischemic events compared with clopidogrel 75 mg but increased bleeding, particularly in LBW patients. METHODS: In this blinded, 3-period, crossover study in stable patients with coronary artery disease (CAD) taking aspirin, prasugrel 5 and 10 mg and clopidogrel 75 mg were administered to LBW (56.4 ± 3.7 kg; n = 34) and HBW patients (84.7 ± 14.9 kg; n = 38). Assays included light transmission aggregometry (LTA), VerifyNow P2Y12 (VN), and vasodilator-associated stimulated phosphoprotein (VASP) level measured predose and after each 12-day treatment. RESULTS: Median MPA by LTA for prasugrel 5 mg in LBW patients was noninferior to the 75th percentile for prasugrel 10 mg in HBW patients (primary endpoint) and mean MPA was similar, but active metabolite exposure was lowered by 38%. Within LBW patients, prasugrel 5 mg lowered MPA more than clopidogrel (least squares mean difference [95% confidence interval]: -3.7% [-6.72%, -0.69%]) and resulted in lower rates of high on-treatment platelet reactivity (HPR). Within HBW patients, prasugrel 10 mg lowered MPA more than clopidogrel (-16.9% [-22.3%, -11.5%]). Similar results were observed by VN and VASP. Prasugrel 10 mg in LBW patients was associated with more mild to moderate bleeding (mainly bruising) compared with prasugrel 5 mg and clopidogrel. CONCLUSIONS: In aspirin-treated patients with CAD, prasugrel 5 mg in LBW patients reduced platelet reactivity to a similar extent as prasugrel 10 mg in HBW patients and resulted in greater platelet inhibition, lower HPR, and similar bleeding rates compared with clopidogrel. (Comparison of Prasugrel and Clopidogrel in Low Body Weight Versus Higher Body Weight With Coronary Artery Disease [FEATHER]; NCT01107925).

Protist genetic diversity in the acidic hydrothermal environments of Lassen Volcanic National Park, USA.

We examined eukaryote genetic diversity in the hydrothermal environments of Lassen Volcanic National Park (LVNP), Northern California. We sampled hydrothermal areas of the Bumpass Hell, Sulfur Works, Devil's Kitchen, and Boiling Springs Lake sites, all of which included diverse acidic pools, mud pots, and streams with visible algal mats and biofilms. Temperatures varied from 15 to 85 degrees C and pH from 1.7 to 5.8. DNA extraction methods compared by denaturing gradient gel electrophoresis fingerprinting exhibited similar patterns, and showed limited diversity of eukaryotic small subunit (SSU) rRNA genes compared with prokaryotes. We successfully amplified eukaryotic SSU rRNA genes from most environments up to 68 degrees C. Cloned rDNA sequences reveal acidophilic protists dominate eukaryotes in LVNP hydrothermal environments. Most sites showed phototrophic assemblages dominated by chlorophytes and stramenopiles (diatoms and chrysophytes). Heterotrophic taxa, though less abundant, included diverse alveolates (ciliates), amoebae, and flagellates. Fungi were also found at most sites, and metazoans (hexapods, nematodes, platyhelminths) were sometimes detected in less acidic environments, especially in algal mats. While many cloned rDNA sequences showed 95%-99% identity to known acidophilic isolates or environmental clones from other acidic sites (Rio Tinto), sequence diversity generally declined both with decreasing pH and increasing temperature, and both were controlling physical variables on the abundance and distribution of organisms at our sites. However, a pool at 68 degrees C with pH 1.7 yielded the greatest number of distinct sequences. While some were likely contaminants from nearby cooler sites, we suggest that Lassen's acidic hydrothermal features may harbor novel protists.