Evaluating Patients With Impaired Renal Function During Drug Development: Highlights From the 2019 US FDA Pharmaceutical Science and Clinical Pharmacology Advisory Committee Meeting.

Patients with multiple chronic conditions, including more advanced chronic kidney disease (CKD), are often excluded from clinical trials, creating challenges in deriving appropriate dosing information and labeling. This article summarizes the May 7, 2019, US Food and Drug Administration Pharmaceutical Science and Clinical Pharmacology Advisory Committee Meeting, which solicited expert opinions on how to enroll patients with more advanced CKD into clinical trials as well as the assumptions behind and different approaches of exposure-matching.

Comparative Effectiveness and Safety of Oral Anticoagulants Across Kidney Function in Patients With Atrial Fibrillation.

BACKGROUND: Patients with atrial fibrillation and severely decreased kidney function were excluded from the pivotal non-vitamin K antagonist oral anticoagulants (NOAC) trials, thereby raising questions about comparative safety and effectiveness in patients with reduced kidney function. The study aimed to compare oral anticoagulants across the range of kidney function in patients with atrial fibrillation. METHODS AND RESULTS: Using a US administrative claims database with linked laboratory data, 34 569 new users of oral anticoagulants with atrial fibrillation and estimated glomerular filtration rate ≥15 mL/(min·1.73 m2) were identified between October 1, 2010 to November 29, 2017. The proportion of patients using NOACs declined with decreasing kidney function-73.5%, 69.6%, 65.4%, 59.5%, and 45.0% of the patients were prescribed a NOAC in estimated glomerular filtration rate ≥90, 60 to 90, 45 to 60, 30 to 45, 15 to 30 mL/min per 1.73 m2 groups, respectively. Stabilized inverse probability of treatment weighting was used to balance 4 treatment groups (apixaban, dabigatran, rivaroxaban, and warfarin) on 66 baseline characteristics. In comparison to warfarin, apixaban was associated with a lower risk of stroke (hazard ratio [HR], 0.57 [0.43-0.75]; P<0.001), major bleeding (HR, 0.51 [0.44-0.61]; P<0.001), and mortality (HR, 0.68 [0.56-0.83]; P<0.001); dabigatran was associated with a similar risk of stroke but a lower risk of major bleeding (HR, 0.57 [0.43-0.75]; P<0.001) and mortality (HR, 0.68 [0.48-0.98]; P=0.04); rivaroxaban was associated with a lower risk of stroke (HR, 0.69 [0.51-0.94]; P=0.02), major bleeding (HR, 0.84 [0.72-0.99]; P=0.04), and mortality (HR, 0.73 [0.58-0.91]; P=0.006). There was no significant interaction between treatment and estimated glomerular filtration rate categories for any outcome. When comparing one NOAC to another NOAC, there was no significant difference in mortality, but some differences existed for stroke or major bleeding. No relationship between treatments and falsification end points was found, suggesting no evidence for substantial residual confounding. CONCLUSIONS: Relative to warfarin, NOACs are used less frequently as kidney function declines. However, NOACs appears to have similar or better comparative effectiveness and safety across the range of kidney function.

International consensus definitions of clinical trial outcomes for kidney failure: 2020.

Kidney failure is an important outcome for patients, clinicians, researchers, healthcare systems, payers, and regulators. However, no harmonized international consensus definitions of kidney failure and key surrogates of progression to kidney failure exist specifically for clinical trials. The International Society of Nephrology convened an international multi-stakeholder meeting to develop consensus on this topic. A core group, experienced in design, conduct, and outcome adjudication of clinical trials, developed a database of 64 randomized trials and the 163 included definitions relevant to kidney failure. Using an iterative process, a set of proposed consensus definitions were developed and subsequently vetted by the larger multi-stakeholder group of 83 participants representing 18 different countries. The consensus of the meeting participants was that clinical trial kidney failure outcomes should be comprised of a composite that includes receipt of a kidney transplant, initiation of maintenance dialysis, and death from kidney failure; it may also include outcomes based solely on laboratory measurements of glomerular filtration rate: a sustained low glomerular filtration rate and a sustained percent decline in glomerular filtration rate. Discussion included important considerations, such as (i) recognition of existing nomenclature for kidney failure; (ii) applicability across resource settings; (iii) ease of understanding for all stakeholders; and (iv) avoidance of inappropriate complexity so that the definitions can be used across ranges of populations and trial methodologies. The final definitions reflect the consensus for use in clinical trials.

Addressing the Need for Clinical Trial End Points in Autosomal Dominant Polycystic Kidney Disease: A Report From the Polycystic Kidney Disease Outcomes Consortium (PKDOC).

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease. Expansion of multiple cysts throughout both kidneys is thought to lead to progressive loss of kidney function and kidney failure in some patients. In recent years, much has been learned about the pathophysiology of ADPKD. However, to date, only one therapy has been approved in the United States and in other regions for the treatment of ADPKD. Feasible end points and a clear regulatory pathway may stimulate further development in this area and ultimately lead to more treatments for ADPKD successfully reaching the market. In July 2016, the PKD Outcomes Consortium under the auspices of the Critical Path Institute and the PKD Foundation convened a PKD Summit to facilitate a discussion among patients, regulators, pharmaceutical sponsors, and academic clinical trialists regarding trial end points and the regulatory path to approval of new drugs for ADPKD. Following the summit, participants continued the dialogue using regularly scheduled teleconferences. This article addresses key considerations related to the design of clinical trials in ADPKD based on these discussions.

FDA Regulatory Perspectives for Studies on Hemodialysis Vascular Access.

In an effort to foster innovation and new product development, the American Society of Nephrology and the US Food and Drug Administration partnered to form the Kidney Health Initiative in 2012. Part of the Kidney Health Initiative's mission is to foster development of therapies by creating a collaborative environment where the US Food and Drug Administration and the greater nephrology community can interact to optimize product evaluation. This particular Kidney Health Initiative project focused on products related to hemodialysis vascular access, with the goal of clarifying appropriate trial end points that could subsequently inform clinical, regulatory, and coverage decisions. Both the lack of common definitions and the lack of consensus on trial end points have been viewed as barriers to innovation in this area. Toward this end, the Kidney Health Initiative convened teams of expert stakeholders to address these issues for each major vascular access category (arteriovenous grafts, arteriovenous fistulas, and central venous catheters), and each team provided recommendations. This commentary provides an overview of the US Food and Drug Administration centers that regulate hemodialysis vascular access and certain laws and regulations that affect these products as well as our perspectives on some of the issues raised and end points proposed by the Kidney Health Initiative teams. The standardized definitions and clinical trial end points proposed by the teams represent an important step forward to improve innovation in this area.

Glomerular Diseases: Registries and Clinical Trials.

Nephrology has conducted few high-quality clinical trials, and the trials that have been conducted have not resulted in the approval of new treatments for primary or inflammatory glomerular diseases. There are overarching process issues that affect the conduct of all clinical trials, but there are also some specialty-specific issues. Within nephrology, primary glomerular diseases are rare, making adequate recruitment for meaningful trials difficult. Nephrologists need better ways, beyond histopathology, to phenotype patients with glomerular diseases and stratify the risk for progression to ESRD. Rigorous trial design is needed for the testing of new therapies, where most patients with glomerular diseases are offered the opportunity to enroll in a clinical trial if standard therapies have failed or are lacking. Training programs to develop a core group of kidney specialists with expertise in the design and implementation of clinical trials are also needed. Registries of patients with glomerular disease and observational studies can aid in the ability to determine realistic estimates of disease prevalence and inform trial design through a better understanding of the natural history of disease. Some proposed changes to the Common Rule, the federal regulations governing the ethical conduct of research involving humans, and the emerging use of electronic health records may facilitate the efficiency of initiating multicenter clinical trials. Collaborations among academia, government scientific and regulatory agencies, industry, foundations, and patient advocacy groups can accelerate therapeutic development for these complex diseases.

Design of clinical trials in acute kidney injury: report from an NIDDK workshop on trial methodology.

Acute kidney injury (AKI) remains a complex clinical problem associated with significant short-term morbidity and mortality and lacking effective pharmacologic interventions. Patients with AKI experience longer-term risks for progressive chronic ESRD, which diminish patients' health-related quality of life and create a larger burden on the healthcare system. Although experimental models have yielded numerous promising agents, translation into clinical practice has been unsuccessful, possibly because of issues in clinical trial design, such as delayed drug administration, masking of therapeutic benefit by adverse events, and inadequate sample size. To address issues of clinical trial design, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored a workshop titled "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers" in December 2010. Workshop participants included representatives from academia, industry, and government agencies whose areas of expertise spanned basic science, clinical nephrology, critical care medicine, biostatistics, pharmacology, and drug development. This document summarizes the discussions of collaborative workgroups that addressed issues related to patient selection, study endpoints, the role of novel biomarkers, sample size and power calculations, and adverse events and pilot/feasibility studies in prevention and treatment of AKI. Companion articles outline the discussions of workgroups for model trials related to prevention or treatment of established AKI in different clinical settings, such as in patients with sepsis.

Design of clinical trials in AKI: a report from an NIDDK workshop. Trials of patients with sepsis and in selected hospital settings.

AKI remains an important clinical problem, with a high mortality rate, increasing incidence, and no Food and Drug Administration-approved therapeutics. Advances in addressing this clinical need require approaches for rapid diagnosis and stratification of injury, development of therapeutic agents based on precise understanding of key pathophysiological events, and implementation of well designed clinical trials. In the near future, AKI biomarkers may facilitate trial design. To address these issues, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored a meeting, "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers," in December of 2010 that brought together academic investigators, industry partners, and representatives from the National Institutes of Health and the Food and Drug Administration. Important issues in the design of clinical trials for interventions in AKI in patients with sepsis or AKI in the setting of critical illness after surgery or trauma were discussed. The sepsis working group discussed use of severity of illness scores and focus on patients with specific etiologies to enhance homogeneity of trial participants. The group also discussed endpoints congruent with those endpoints used in critical care studies. The second workgroup emphasized difficulties in obtaining consent before admission and collaboration among interdisciplinary healthcare groups. Despite the difficult trial design issues, these clinical situations represent a clinical opportunity because of the high event rates, severity of AKI, and poor outcomes. The groups considered trial design issues and discussed advantages and disadvantages of several short- and long-term primary endpoints in these patients.

Design of clinical trials in acute kidney injury: a report from an NIDDK workshop--prevention trials.

AKI is an important clinical problem that has become increasingly more common. Mortality rates associated with AKI remain high despite advances in supportive care. Patients surviving AKI have increased long-term mortality and appear to be at increased risk of developing CKD and progressing to ESRD. No proven effective pharmacologic therapies are currently available for the prevention or treatment of AKI. Advances in addressing this unmet need will require the development of novel therapeutic agents based on precise understanding of key pathophysiological events and the implementation of well designed clinical trials. To address this need, the National Institute of Diabetes and Digestive and Kidney Diseases sponsored the "Clinical Trials in Acute Kidney Injury: Current Opportunities and Barriers" workshop in December 2010. The event brought together representatives from academia, industry, the National Institutes of Health, and the US Food and Drug Administration. We report the discussions of workgroups that developed outlines of clinical trials for the prevention of AKI in two patient populations: patients undergoing elective surgery who are at risk for or who develop AKI, and patients who are at risk for contrast-induced AKI. In both of these populations, primary prevention or secondary therapy can be delivered at an optimal time relative to kidney injury. The workgroups detailed primary and secondary endpoints for studies in these groups, and explored the use of adaptive clinical trial designs for trials of novel preventive strategies to improve outcomes of patients with AKI.

Endogenous and exogenous vasopressin during hemodialysis.

Intradialytic hypotension likely results from hypovolemia as well as patient and dialysis-specific factors. An impaired vasoconstrictive response to volume loss during hemodialysis has been demonstrated and increasing evidence suggests that deficiency in the hormone arginine vasopressin may be a contributing factor. Although vasopressin is widely recognized for its role in the regulation of serum osmolality, vasopressin is also an important regulator of blood pressure in health and in various disease states. That vasopressin deficiency contributes to the pathogenesis of intradialytic hypotension is suggested by several observations. First, vasopressin levels typically fall during hemodialysis when a rise might be expected as a result of volume loss. Second, therapies that prevent a fall in osmolality during dialysis, including dialysis against a high sodium bath and isolated ultrafiltration, have been shown to improve intradialytic blood pressure stability. Finally, and perhaps most importantly, the administration of low-dose exogenous vasopressin during dialysis has been shown to support blood pressure and improve volume removal. Further research is needed to determine the effect of chronic vasopressin (or selective V1a agonist) administration during dialysis on volume removal, inter- and intradialytic blood pressure control, and, ultimately, clinical outcomes in end-stage renal disease patients on dialysis.

Validation of an oscillometric home blood pressure monitor in an end-stage renal disease population and the effect of arterial stiffness on its accuracy.

OBJECTIVES: Increased arterial stiffness, common in end-stage renal disease patients, has been shown to affect the correspondence between oscillometric and mercury sphygmomanometer blood pressure readings. The purpose of this study was to validate an oscillometric home blood pressure monitor in an end-stage renal disease population and to determine the effect of arterial stiffness on its accuracy. METHODS: Blood pressure measurements were taken with the Microlife 3AC1-1PC (Microlife; Taipei, Taiwan), an oscillometric home blood pressure monitor, and a mercury sphygmomanometer in 33 patients as specified by the European Society of Hypertension Validation Protocol. Radial pulse wave analyses were also performed. RESULTS: On the basis of European Society of Hypertension criteria, the Microlife 3AC1-1PC received a passing score for systolic and diastolic blood pressures. On average, the oscillometric monitor overestimated diastolic blood pressure by 2.4 mmHg (P=0.005, SD=4.5 mmHg) and there was a trend towards overestimation of systolic blood pressure as well (1.3 mmHg, P=0.09, SD=4.4 mmHg). A positive correlation was found between arterial stiffness, as assessed by augmentation index and pulse pressure, and the diastolic blood pressure difference between the device and the mercury sphygmomanometer (r=0.54, P=0.003; and r=0.65, P=0.001, respectively). Diastolic blood pressure was negatively correlated with the diastolic blood pressure difference (r=-0.49, P=0.003). No significant relationship was found between the systolic blood pressure difference and augmentation index, pulse pressure or systolic blood pressure. CONCLUSION: The Microlife 3AC1-1PC was shown to accurately measure blood pressure in patients with end-stage renal disease. As arterial stiffness increased and diastolic blood pressure fell, diastolic blood pressure was increasingly overestimated.