End Points for Clinical Trials in Primary Hyperoxaluria

Nedosiran Safety and Efficacy in PH1: Interim Analysis of PHYOX3

Introduction

Primary hyperoxaluria (PH) is a rare genetic disorder of hepatic glyoxylate metabolism. Nedosiran is an RNA interference (RNAi) therapeutic that the US Food and Drug Administration has approved for treatment of PH1. PHYOX3 is a trial evaluating monthly nedosiran in patients with PH.

Methods

In this PHYOX3 interim analysis, participants with PH1 who continued from a single-dose nedosiran trial (PHYOX1), with no previous kidney or liver transplantation, dialysis, or evidence of systemic oxalosis were eligible. The safety and efficacy of once-monthly nedosiran was assessed over 30 months.

Results

Thirteen participants completed PHYOX1 and continued into PHYOX3. At baseline, the mean (SD) and median (range) age was 24.2 (6.6) years and 23.0 (14-39) years, respectively; 53.8% were female and 61.5% were White. Mean estimated glomerular filtration rate (eGFR) remained stable (62-84.2 mL/min per 1.73 m2) to month 30. Mean 24-hour urinary oxalate (Uox) excretion showed a sustained reduction from baseline of ≥60% at every visit (months 2-30). From month 2, at least 10 of 13 (76.9%) participants achieved normal (<0.46 mmol/24h; upper limit of assay-normal [ULN]) or near-normal (≥0.46 to <0.60 mmol/24h; ≥ULN to <1.3 × ULN) 24-hour Uox excretion. All participants experienced ≥1 adverse event (AE), mostly mild or moderate in severity (primarily, injection site events). Three serious, not treatment-related AEs were reported; there were no deaths or study discontinuations due to AEs.

Conclusion

Nedosiran was well-tolerated in patients with PH1, and treatment resulted in a sustained, substantial reduction in Uox excretion for at least 30 months in this long-term study. No safety signals have been identified to date. The PHYOX3 study is ongoing.

Lumasiran: A Review in Primary Hyperoxaluria Type 1

Lumasiran (Oxlumo®), a first-in-class synthetic, double-stranded, ribonucleic acid (RNA) interference molecule targeting glycolate oxidase through silencing HAO1 mRNA, is approved in several countries for patients of any age and stage of kidney function with primary hyperoxaluria type 1 (PH1). Approval was based on results from the phase III ILLUMINATE trials. In the double-blind, placebo-controlled, ILLUMINATE-A trial, subcutaneous lumasiran was significantly more effective than placebo in reducing 24-h urinary oxalate excretion in patients aged ≥ 6 years with PH1; this effect was sustained for ≥ 36 months in ongoing longer-term analyses. In the single-arm ILLUMINATE-B trial, lumasiran reduced urinary oxalate:creatinine ratios and plasma oxalate levels in patients aged < 6 years with PH1. In the single-arm ILLUMINATE-C trial, lumasiran reduced plasma oxalate levels in patients with PH1 receiving dialysis as well as those not receiving dialysis. In secondary and exploratory analyses of these trials, nephrocalcinosis grade, kidney stone event rates and estimated glomerular filtration rates were either stable or improved with lumasiran. Lumasiran had an acceptable tolerability profile that remained consistent in longer-term analyses; the most common adverse events were mild and transient injection-site reactions. Thus, lumasiran is an effective treatment option, with an acceptable tolerability profile, in patients with PH1.

Natural history of urine and plasma oxalate in children with primary hyperoxaluria type 1

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is a rare, severe genetic disease causing increased hepatic oxalate production resulting in urinary stone disease, nephrocalcinosis, and often progressive chronic kidney disease. Little is known about the natural history of urine and plasma oxalate values over time in children with PH1.

METHODS

For this retrospective observational study, we analyzed data from genetically confirmed PH1 patients enrolled in the Rare Kidney Stone Consortium PH Registry between 2003 and 2018 who had at least 2 measurements before age 18 years of urine oxalate-to-creatinine ratio (Uox:cr), 24-h urine oxalate excretion normalized to body surface area (24-h Uox), or plasma oxalate concentration (Pox). We compared values among 3 groups: homozygous G170R, heterozygous G170R, and non-G170R AGXT variants both before and after initiating pyridoxine (B6).

RESULTS

Of 403 patients with PH1 in the registry, 83 met the inclusion criteria. Uox:cr decreased rapidly over the first 5 years of life. Both before and after B6 initiation, patients with non-G170R had the highest Uox:cr, 24-h Uox, and Pox. Patients with heterozygous G170R had similar Uox:cr to homozygous G170R prior to B6. Patients with homozygous G170R had the lowest 24-h Uox and Uox:cr after B6. Urinary oxalate excretion and Pox tend to decrease over time during childhood. eGFR over time was not different among groups.

CONCLUSIONS

Children with PH1 under 5 years old have relatively higher urinary oxalate excretion which may put them at greater risk for nephrocalcinosis and kidney failure than older PH1 patients. Those with homozygous G170R variants may have milder disease. A higher resolution version of the Graphical abstract is available as Supplementary information.

End Point Considerations for Clinical Trials in Enteric Hyperoxaluria

Enteric hyperoxaluria is a medical condition characterized by elevated urinary oxalate excretion due to increased gastrointestinal oxalate absorption. Causative features include fat malabsorption and/or increased intestinal permeability to oxalate. Enteric hyperoxaluria has long been known to cause nephrolithiasis and nephrocalcinosis, and, more recently, an association with CKD and kidney failure has been shown. Currently, there are no US Food and Drug Administration-approved therapies for enteric hyperoxaluria, and it is unclear what end points should be used to evaluate the efficacy of new drugs and biologics for this condition. This study represents work of a multidisciplinary group convened by the Kidney Health Initiative to review the evidence supporting potential end points for clinical trials in enteric hyperoxaluria. A potential clinical outcome is symptomatic kidney stone events. Potential surrogate end points include ( 1 ) an irreversible loss of kidney function as a surrogate for progression to kidney failure, ( 2 ) asymptomatic kidney stone growth/new stone formation observed on imaging as a surrogate for symptomatic kidney stone events, ( 3 ) urinary oxalate and urinary calcium oxalate supersaturation as surrogates for the development of symptomatic kidney stone events, and ( 4) plasma oxalate as a surrogate for the development of the clinical manifestations of systemic oxalosis. Unfortunately, because of gaps in the data, this Kidney Health Initiative workgroup was unable to provide definitive recommendations. Work is underway to obtain robust information that can be used to inform trial design and medical product development in this space.

Safety, Pharmacokinetics, and Exposure-Response Modeling of Nedosiran in Participants With Severe Chronic Kidney Disease

Nedosiran is an investigational RNA-interference therapeutic in development for primary hyperoxaluria (PH). Because nedosiran undergoes renal clearance, we assessed its pharmacokinetic profile in non-PH participants with normal kidney function and Stages 4/5 chronic kidney disease (CKD), the latter with/without dialysis. Nedosiran exposure-response modeling in patients with PH Subtype 1 (PH1) with different renal function level was performed to recommend a nedosiran dose for this subpatient population. In this open-label, single-dose, Phase 1 study, 24 participants with estimated glomerular filtration rate <30 mL/min/1.73 m2 (CKD Stages 4/5; on hemodialysis [Groups 1a, 1b] and not on hemodialysis [Group 2]) and 10 participants with normal kidney function (estimated glomerular filtration rate ≥90 mL/min/1.73 m2 ; Group 3) received a single dose of subcutaneous nedosiran sodium 170 mg. Group 1a received nedosiran 8 hours before beginning hemodialysis, Group 1b received nedosiran 2 hours after completing hemodialysis; Group 2 was not on hemodialysis. Nedosiran population pharmacokinetic-pharmacodynamic analyses were conducted using pooled data from this study and 4 others. Nedosiran pharmacokinetic exposure in non-PH participants with CKD Stages 4/5 was approximately 2-fold higher versus participants with normal kidney function. Hemodialysis timing relative to nedosiran administration had no clinically significant impact on pharmacokinetics (Group 1a vs 1b). Nedosiran was well tolerated. Modeling indicated that in patients with PH1 with CKD Stages 4/5, lower nedosiran doses provide similar exposure and potential reduction in 24-hour urinary oxalate to standard nedosiran doses in patients with PH1 with normal kidney function or CKD Stages 2/3. Nedosiran dosage reductions are recommended in patients with PH1 with CKD Stages 4/5; further adjustments are unnecessary if dialysis is started.

Qualitative assessment of the patient experience of primary hyperoxaluria type 1: an observational study

BACKGROUND

Without effective intervention, primary hyperoxaluria type 1 (PH1) causes oxalate-induced kidney damage, leading to end-stage kidney disease and serious complications throughout the body. Although PH1 carries a heavy burden that impacts quality of life, literature on the experiences of those living with PH1 and caring for patients with PH1 is limited. This study aimed to describe the diagnostic journey in PH1 and characterize patients' and caregivers' self-reported experiences throughout the disease course.

METHODS

This was an observational study involving in-depth, semi-structured telephone interviews. Dominant trends were assessed using constant comparative analysis to identify themes in interviewees' descriptions of their experiences. Individuals aged ≥ 12 years and caregivers of children aged 6-17 years with genetically confirmed PH1 were eligible. Informed consent/assent and ability to read and speak English were required.

RESULTS

Interviewees (16 patients, 12 caregivers) reported a prolonged diagnostic journey due to low disease awareness, among other factors. Upon diagnosis, PH1 was frequently symptomatic, typically involving kidney stone-related symptoms but also potentially symptoms arising beyond the kidneys. PH1 most commonly led to worry and social impairment in adolescents, impaired physical function in adults, and a range of impacts on caregivers. In late-stage disease, dialysis was the most burdensome aspect of living with PH1 (due to time requirements, limitations from living with a catheter, etc.), and this burden was exacerbated by the COVID-19 pandemic. Benefits desired from PH1 management included reductions in laboratory measures of oxalate burden, kidney stone and urination frequency, and oxalate-related skin ulcers.

CONCLUSIONS

PH1 greatly impacts patients' and caregivers' lives, primarily due to burdensome disease manifestations and associated emotional, physical, and practical impacts, as well as disease management challenges - particularly those related to dialysis in late-stage disease.

Determinants of Kidney Failure in Primary Hyperoxaluria Type 1: Findings of the European Hyperoxaluria Consortium

Introduction

Primary hyperoxaluria type 1 (PH1) has a highly heterogeneous disease course. Apart from the c.508G>A (p.Gly170Arg) AGXT variant, which imparts a relatively favorable outcome, little is known about determinants of kidney failure. Identifying these is crucial for disease management, especially in this era of new therapies.

Methods

In this retrospective study of 932 patients with PH1 included in the OxalEurope registry, we analyzed genotype-phenotype correlations as well as the impact of nephrocalcinosis, urolithiasis, and urinary oxalate and glycolate excretion on the development of kidney failure, using survival and mixed model analyses.

Results

The risk of developing kidney failure was the highest for 175 vitamin-B6 unresponsive ("null") homozygotes and lowest for 155 patients with c.508G>A and c.454T>A (p.Phe152Ile) variants, with a median age of onset of kidney failure of 7.8 and 31.8 years, respectively. Fifty patients with c.731T>C (p.Ile244Thr) homozygote variants had better kidney survival than null homozygotes (P = 0.003). Poor outcomes were found in patients with other potentially vitamin B6-responsive variants. Nephrocalcinosis increased the risk of kidney failure significantly (hazard ratio [HR] 3.17 [2.03-4.94], P < 0.001). Urinary oxalate and glycolate measurements were available in 620 and 579 twenty-four-hour urine collections from 117 and 87 patients, respectively. Urinary oxalate excretion, unlike glycolate, was higher in patients who subsequently developed kidney failure (P = 0.034). However, the 41% intraindividual variation of urinary oxalate resulted in wide confidence intervals.

Conclusion

In conclusion, homozygosity for AGXT null variants and nephrocalcinosis were the strongest determinants for kidney failure in PH1.

Stiripentol and Lumasiran as a Rescue Therapy for Oxalate Nephropathy Recurrence After Kidney Transplantation in an Adult Patient With Primary Hyperoxaluria Type 1

Primary hyperoxaluria type 1 is a rare cause of kidney failure. Stiripentol, an inhibitor of lactate dehydrogenase A, and lumasiran, a small interfering RNA targeting glycolate oxidase, have been proposed as therapeutic options, but clinical data are scarce, especially in adults and transplanted patients. We describe the case of a 51-year-old patient with a biopsy-proven recurrence of oxalate nephropathy after a kidney-only transplantation. He received stiripentol and lumasiran without adverse events. Fourteen months after transplantation, graft function, serum, and urinary oxalate levels have remained stable, and kidney biopsy showed a complete regression of oxalate crystals. Further studies are needed to assess whether this strategy is effective and could replace liver-kidney transplantation.

Nedosiran in primary hyperoxaluria subtype 3: results from a phase I, single-dose study (PHYOX4)

Nedosiran is an N-acetyl-D-galactosamine (GalNAc)-conjugated RNA interference agent targeting hepatic lactate dehydrogenase (encoded by the LDHA gene), the putative enzyme mediating the final step of oxalate production in all three genetic subtypes of primary hyperoxaluria (PH). This phase I study assessed the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of subcutaneous nedosiran in patients with PH subtype 3 (PH3) and an estimated glomerular filtration rate  ≥ 30 mL/min/1.73 m2. Single-dose nedosiran 3 mg/kg or placebo was administered in a randomized (2:1), double-blinded manner. Safety/tolerability, 24-h urinary oxalate (Uox) concentrations, and plasma nedosiran concentrations were assessed. The main PD endpoint was the proportion of participants achieving a > 30% decrease from baseline in 24-h Uox at two consecutive visits. Six participants enrolled in and completed the study (nedosiran, n = 4; placebo, n = 2). Nedosiran was well-tolerated and lacked safety concerns. Although the PD response was not met, 24-h Uox excretion declined 24.5% in the nedosiran group and increased 10.5% in the placebo group at Day 85. Three of four nedosiran recipients had a > 30% reduction in 24-h Uox excretion during at least one visit, and one attained near-normal (i.e., ≥ 0.46 to < 0.60 mmol/24 h; ≥ 1.0 to < 1.3 × upper limit of the normal reference range) 24-h Uox excretion from Day 29 to Day 85. Nedosiran displayed predictable plasma PK. The acceptable safety and trend toward Uox-lowering after single-dose nedosiran treatment enables further clinical development of nedosiran in patients with PH3 who currently have no viable therapeutic options. A plain language summary is available in the supplementary information.

Healthcare utilization, quality of life, and work productivity associated with primary hyperoxaluria: a cross-sectional web-based US survey

Primary hyperoxaluria (PH) is a family of ultra-rare, autosomal recessive, metabolic disorders associated with frequent kidney stones, chronic kidney disease and kidney failure, and serious complications due to systemic oxalosis, resulting in significant morbidity. We investigated the burden of PH among affected patients and caregivers. This cross-sectional, web-based survey was used to quantify the burden of PH, in terms of healthcare resource utilization, health-related quality of life, and work productivity and activity impairment among adults (≥ 18 years) with PH and caregivers of children (≤ 17 years) with PH in the US. Among the 20 respondents, there were 7 adults with PH and 13 caregivers of children with PH. Adherence to hyperhydration was noted as the most, or one of the most, difficult aspects of PH by 56% of respondents. Most patients (95%) had experienced painful kidney stone events, one-third had visited the emergency room, and 29% were hospitalized for complications due to PH. Of the 24% of patients on dialysis, all found the procedure burdensome. Adult patients' quality of life was negatively affected across several domains. Most respondents (81%) reported that PH had a negative effect on their finances. Employed adult patients and caregivers, and children with PH, had moderate impairment in work productivity, school attendance, and activity. Anxiety about future PH-related sequelae was moderate to high. These findings highlight the need for improvements in PH medical management. A plain language summary is available in the supplementary information.

Obtaining the best igRNAs for bystander-less correction of all ABE-reversible pathogenic SNVs using high-throughput screening

Imperfect -gRNA (igRNA) provides a simple strategy for single-base editing of a base editor. However, a significant number of igRNAs need to be generated and tested for each target locus to achieve efficient single-base reversion of pathogenic single nucleotide variations (SNVs), which hinders the direct application of this technology. To provide ready-to-use igRNAs for single-base and bystander-less correction of all the adenine base editor (ABE)-reversible pathogenic SNVs, we employed a high-throughput method to edit all 5,253 known ABE-reversible pathogenic SNVs, each with multiple systematically designed igRNAs, and two libraries of 96,000 igRNAs were tested. A total of 1,988 SNV loci could be single-base reversed by igRNA with a >30% efficiency. Among these 1,988 loci, 378 SNV loci exhibited an efficiency of more than 90%. At the same time, the bystander editing efficiency of 76.62% of the SNV loci was reduced to 0%, while remaining below 1% for another 18.93% of the loci. These ready-to-use igRNAs provided the best solutions for a substantial portion of the 4,657 pathogenic/likely pathogenic SNVs. In this work, we overcame one of the most significant obstacles of base editors and provide a ready-to-use platform for the genetic treatment of diseases caused by ABE-reversible SNVs.

Prospective Assessment of the Prevalence of Enter Hyperoxalosis in Kidney Transplant Candidates

Enteric hyperoxalosis (EH) is an emerging cause of kidney transplantation (KT) dysfunction. We sought to determine the prevalence of EH and factors that affect plasma oxalate (POx) among at-risk KT candidates.

Methods

We prospectively measured POx among KT candidates evaluated at our center from 2017 to 2020 with risk factors for EH namely bariatric surgery, inflammatory bowel disease, or cystic fibrosis. EH was defined by a POx ≥10 μmol/L. Period-prevalence of EH was calculated. We compared mean POx across 5 factors: underlying condition, chronic kidney disease (CKD) stage, dialysis modality, phosphate binder type, and body mass index.

Results

Of 40 KT candidates screened, 23 had EH for a 4-y period prevalence of 58%. Mean POx was 21.6 ± 23.5 μmol/L ranging from 0 to 109.6 μmol/L. 40% of screened had POx >20 μmol/L. Sleeve gastrectomy was the most common underlying condition associated with EH. Mean POx did not differ by underlying condition (P = 0.27), CKD stage (P = 0.17), dialysis modality (P = 0.68), phosphate binder (P = 0.58), and body mass index (P = 0.56).

Conclusions

Bariatric surgery and inflammatory bowel disease were associated with a high prevalence of EH among KT candidates. Contrary to prior studies, sleeve gastrectomy was also associated with hyperoxalosis in advanced CKD. POx concentrations observed in EH reached levels associated with tissue and potentially allograft deposition. Concentrations can be as high as that seen in primary hyperoxaluria. More studies are needed to assess if POx is indeed a modifiable factor affecting allograft function in patients with EH.

Application of multivariate joint modeling of longitudinal biomarkers and time-to-event data to a rare kidney stone cohort

Background

Time-dependent Cox proportional hazards regression is a popular statistical method used in kidney disease research to evaluate associations between biomarkers collected serially over time with progression to kidney failure. Typically, biomarkers of interest are considered time-dependent covariates being updated at each new measurement using last observation carried forward (LOCF). Recently, joint modeling has emerged as a flexible alternative for multivariate longitudinal and time-to-event data. This study describes and demonstrates multivariate joint modeling using as an example the association of serial biomarkers (plasma oxalate [POX] and urinary oxalate [UOX]) and kidney function among patients with primary hyperoxaluria in the Rare Kidney Stone Consortium Registry.

Methods

Time-to-kidney failure was regressed on serially measured biomarkers in two ways: time-dependent LOCF Cox proportional hazards regression and multivariate joint models.

Results

In time-dependent LOCF Cox regression, higher POX was associated with increased risk of kidney failure (HR = 2.20 per doubling, 95% CI = [1.38-3.51], p < 0.001) whereas UOX was not (HR = 1.08 per doubling, [0.66-1.77], p = 0.77). In multivariate joint models, estimates suggest higher UOX may be associated with lower risk of kidney failure (HR = 0.42 per doubling [0.15-1.04], p = 0.066), though not statistically significant, since impaired urinary excretion of oxalate may reflect worsening kidney function.

Conclusions

Multivariate joint modeling is more flexible than LOCF and may better reflect biological plausibility since biomarkers are not steady-state values between measurements. While LOCF is preferred to naïve methods not accounting for changes in biomarkers over time, results may not accurately reflect flexible relationships that can be captured with multivariate joint modeling.

Lumasiran for Advanced Primary Hyperoxaluria Type 1: Phase 3 ILLUMINATE-C Trial

RATIONALE & OBJECTIVE

Lumasiran reduces urinary and plasma oxalate (POx) in patients with primary hyperoxaluria type 1 (PH1) and relatively preserved kidney function. ILLUMINATE-C evaluates the efficacy, safety, pharmacokinetics, and pharmacodynamics of lumasiran in patients with PH1 and advanced kidney disease.

STUDY DESIGN

Phase 3, open-label, single-arm trial.

SETTING & PARTICIPANTS

Multinational study; enrolled patients with PH1 of all ages, estimated glomerular filtration rate ≤45 mL/min/1.73 m² (if age ≥12 months) or increased serum creatinine level (if age <12 months), and POx ≥20 μmol/L at screening, including patients with or without systemic oxalosis.

INTERVENTION

Lumasiran administered subcutaneously; 3 monthly doses followed by monthly or quarterly weight-based dosing.

OUTCOME

Primary end point: percent change in POx from baseline to month 6 (cohort A; not receiving hemodialysis at enrollment) and percent change in predialysis POx from baseline to month 6 (cohort B; receiving hemodialysis at enrollment). Pharmacodynamic secondary end points: percent change in POx area under the curve between dialysis sessions (cohort B only); absolute change in POx; percent and absolute change in spot urinary oxalate-creatinine ratio; and 24-hour urinary oxalate adjusted for body surface area.

RESULTS

All patients (N = 21; 43% female; 76% White) completed the 6-month primary analysis period. Median age at consent was 8 (range, 0-59) years. For the primary end point, least-squares mean reductions in POx were 33.3% (95% CI, -15.2% to 81.8%) in cohort A (n = 6) and 42.4% (95% CI, 34.2%-50.7%) in cohort B (n = 15). Improvements were also observed in all pharmacodynamic secondary end points. Most adverse events were mild or moderate. No patient discontinued treatment or withdrew from the study. The most commonly reported lumasiran-related adverse events were injection-site reactions, all of which were mild and transient.

LIMITATIONS

Single-arm study without placebo control.

CONCLUSIONS

Lumasiran resulted in substantial reductions in POx with acceptable safety in patients with PH1 who have advanced kidney disease, supporting its efficacy and safety in this patient population.

FUNDING

Alnylam Pharmaceuticals.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT04152200 and at EudraCT with study number 2019-001346-17.

PLAIN-LANGUAGE SUMMARY

Primary hyperoxaluria type 1 (PH1) is a rare genetic disease characterized by excessive hepatic oxalate production that frequently causes kidney failure. Lumasiran is an RNA interference therapeutic that is administered subcutaneously for the treatment of PH1. Lumasiran has been shown to reduce oxalate levels in the urine and plasma of patients with PH1 who have relatively preserved kidney function. In the ILLUMINATE-C study, the efficacy and safety of lumasiran were evaluated in patients with PH1 and advanced kidney disease, including a cohort of patients undergoing hemodialysis. During the 6-month primary analysis period, lumasiran resulted in substantial reductions in plasma oxalate with acceptable safety in patients with PH1 complicated by advanced kidney disease.

Efficacy and safety of lumasiran for infants and young children with primary hyperoxaluria type 1: 12-month analysis of the phase 3 ILLUMINATE-B trial

BACKGROUND

Primary hyperoxaluria type 1 (PH1) is a rare genetic disease that causes progressive kidney damage and systemic oxalosis due to hepatic overproduction of oxalate. Lumasiran demonstrated efficacy and safety in the 6-month primary analysis period of the phase 3, multinational, open-label, single-arm ILLUMINATE-B study of infants and children < 6 years old with PH1 (ClinicalTrials.gov: NCT03905694 (4/1/2019); EudraCT: 2018-004,014-17 (10/12/2018)). Outcomes in the ILLUMINATE-B extension period (EP) for patients who completed ≥ 12 months on study are reported here.

METHODS

Of the 18 patients enrolled in the 6-month primary analysis period, all entered the EP and completed ≥ 6 additional months of lumasiran treatment (median (range) duration of total exposure, 17.8 (12.7-20.5) months).

RESULTS

Lumasiran treatment was previously reported to reduce spot urinary oxalate:creatinine ratio by 72% at month 6, which was maintained at 72% at month 12; mean month 12 reductions in prespecified weight subgroups were 89%, 68%, and 71% for patients weighing < 10 kg, 10 to < 20 kg, and ≥ 20 kg, respectively. The mean reduction from baseline in plasma oxalate level was reported to be 32% at month 6, and this improved to 47% at month 12. Additional improvements were also seen in nephrocalcinosis grade, and kidney stone event rates remained low. The most common lumasiran-related adverse events were mild, transient injection-site reactions (3 patients (17%)).

CONCLUSIONS

Lumasiran treatment provided sustained reductions in urinary and plasma oxalate through month 12 across all weight subgroups, with an acceptable safety profile, in infants and young children with PH1. A higher resolution version of the Graphical abstract is available as Supplementary information.

PHYOX2: a pivotal randomized study of nedosiran in primary hyperoxaluria type 1 or 2

Nedosiran is an investigational RNA interference agent designed to inhibit expression of hepatic lactate dehydrogenase, the enzyme thought responsible for the terminal step of oxalate synthesis. Oxalate overproduction is the hallmark of all genetic subtypes of primary hyperoxaluria (PH). In this double-blind, placebo-controlled study, we randomly assigned (2:1) 35 participants with PH1 (n = 29) or PH2 (n = 6) with eGFR ≥30 mL/min/1.73 m² to subcutaneous nedosiran or placebo once monthly for 6 months. The area under the curve (AUC) of percent reduction from baseline in 24-hour urinary oxalate (Uox) excretion (primary endpoint), between day 90-180, was significantly greater with nedosiran vs placebo (least squares mean [SE], +3507 [788] vs -1664 [1190], respectively; difference, 5172; 95% CI 2929-7414; P < 0.001). A greater proportion of participants receiving nedosiran vs placebo achieved normal or near-normal (<0.60 mmol/24 hours; <1.3 × ULN) Uox excretion on ≥2 consecutive visits starting at day 90 (50% vs 0; P = 0.002); this effect was mirrored in the nedosiran-treated PH1 subgroup (64.7% vs 0; P < 0.001). The PH1 subgroup maintained a sustained Uox reduction while on nedosiran, whereas no consistent effect was seen in the PH2 subgroup. Nedosiran-treated participants with PH1 also showed a significant reduction in plasma oxalate versus placebo (P = 0.017). Nedosiran was generally safe and well tolerated. In the nedosiran arm, the incidence of injection-site reactions was 9% (all mild and self-limiting). In conclusion, participants with PH1 receiving nedosiran had clinically meaningful reductions in Uox, the mediator of kidney damage in PH.

Estimating health state utilities in primary hyperoxaluria type 1: a valuation study

AIMS

Quantitative data on health state utilities in primary hyperoxaluria type 1 (PH1) are lacking. This study was conducted to estimate utility values in PH1 using 3 standard valuation techniques.

MATERIALS AND METHODS

Health state vignettes were developed with input from expert clinicians to describe different stages of chronic kidney disease (CKD) within the setting of PH1, along with a post-combined liver and kidney transplant (CLKT) health state ≥12 months following transplantation. The utility associated with living in each PH1 health state, as described by the vignettes, was evaluated by members of the UK general public using standard utility assessment techniques, including EQ-5D-5L, Visual Analog Scale, and Time Trade-Off.

RESULTS

A similar pattern across the three valuation methods was observed. Utility values were roughly constant from CKD stage 1-3b and then dropped sharply from these states to CKD stage 4. Decreases in utility in the later stages of CKD (stages 4-5) were followed by a recovery in quality of life in the post-CLKT health state.

LIMITATIONS

Vignettes may not fully capture the burden of living with PH1.

CONCLUSIONS

This study serves as an informative source of data on how the burden of PH1 varies across disease stages of CKD and post-CLKT in patients with PH1. The study findings highlight the unique clinical features of PH1 compared with non-PH1-related CKD, such as the need for earlier and more intensive hemodialysis, the risk of systemic oxalosis, and the potential need for CLKT (as opposed to kidney-only transplant). The impact of PH1 on health-related quality of life, which worsens once hemodialysis is required and systemic disease manifestations occur, is captured in this study using quantitative health state utilities. These data provide an understanding of the impact of PH1 on health-related quality of life and will facilitate health economic evaluation of future treatments.

Estimated GFR Slope Across CKD Stages in Primary Hyperoxaluria Type 1

RATIONALE & OBJECTIVE

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disorder of glyoxylate metabolism that results in early-onset kidney stone disease, nephrocalcinosis, and kidney failure. There is an unmet need for reliable markers of disease progression to test effectiveness of new treatments for patients with PH. In this study, we assessed the rate of estimated glomerular filtration rate (eGFR) decline across chronic kidney disease (CKD) glomerular filtration rate (GFR) categories (CKD G2-G5) in a cohort of patients with PH1.

STUDY DESIGN

Retrospective observational study.

SETTING & PARTICIPANTS

Patients with PH1 enrolled in the Rare Kidney Stone Consortium (RKSC) registry who did not have kidney failure at diagnosis and who had at least 2 eGFR values recorded from within 1 month of diagnosis until their last contact date or incident kidney failure event.

PREDICTORS

CKD GFR category, baseline patient and laboratory characteristics.

OUTCOME

Annualized rate of eGFR decline.

ANALYTICAL APPROACH

Generalized estimating equations and linear regression were used to evaluate the associations between CKD GFR category, baseline patient and laboratory characteristics, and annual change in eGFR during follow-up.

RESULTS

Compared with the slope in CKD G2 (-2.3 mL/min/1.73 m2 per year), the mean annual eGFR decline was nominally steeper in CKD G3a (-5.3 mL/min/1.73 m2 per year) and statistically significantly more rapid in CKD G3b and G4 (-14.7 and -16.6 mL/min/1.73 m2 per year, respectively). In CKD G2, older age was associated with a more rapid rate of eGFR decline (P = 0.01). A common PH1-causing variant of alanine glyoxylate aminotransferase, a glycine to arginine substitution at amino acid 170 (G170R), appeared to be associated with less severe annual decline in eGFR.

LIMITATIONS

Data at regular time points were not available for all patients due to reliance on voluntary reporting in a retrospective rare disease registry.

CONCLUSIONS

The eGFR decline was not uniform across CKD GFR categories in this PH1 population, with a higher rate of eGFR decline in CKD G3b and G4. Thus, CKD GFR category needs to be accounted for when analyzing eGFR change in the setting of PH1.

New therapeutics for primary hyperoxaluria type 1

PURPOSE OF REVIEW

Primary hyperoxaluria type 1 (PH1) is a rare genetic disorder that causes hepatic overproduction of oxalate and, often, nephrocalcinosis, nephrolithiasis, chronic kidney disease, and kidney failure. The purpose of the review is to provide an update on current emerging therapies for the treatment of PH1.

RECENT FINDINGS

Use of ribonucleic acid interference (RNAi) therapeutics that target the liver to block production of key enzymes along pathways that generate oxalate is a promising approach. Available evidence supports the efficacy of both Lumasiran (targeting glycolate oxidase) and Nedosiran (targeting hepatic lactate dehydrogenase (LDHa)) to reduce urinary oxalate excretion in PH1. The efficacy of alternative approaches including stiripentol (an anticonvulsant drug that also targets LDHa), lanthanum (a potential gastrointestinal oxalate binder), and Oxalobacter formigenes (a bacterium that can degrade oxalate within the gastrointestinal tract and may also increase its secretion from blood) are all also under study. Genetic editing tools including clustered regularly interspaced short palindromic repeats/Cas9 are also in preclinical study as a potential PH1 therapeutic.

SUMMARY

Novel treatments can reduce the plasma oxalate concentration and urinary oxalate excretion in PH1 patients. Thus, it is possible these approaches will reduce the need for combined kidney and liver transplantation to significantly decrease the morbidity and mortality of affected patients.

Lumasiran in the Management of Patients with Primary Hyperoxaluria Type 1: From Bench to Bedside

Primary hyperoxaluria (PH) is a rare genetic disease caused by excessive hepatic production and elevated urinary excretion of oxalate that leads to recurrent nephrolithiasis, nephrocalcinosis and, eventually, kidney failure. As glomerular filtration rate declines, oxalate accumulates leading to systemic oxalosis, a debilitating condition with high morbidity and mortality. Although PH is usually diagnosed during infancy, it can present at any age with different phenotypes, ranging from mild symptoms to extremely debilitating manifestations. PH is an autosomal recessive disorder and, to date, three types have been identified: PH1, PH2 and PH3. PH1 is the most common and most aggressive type, accounting for almost 80% of primary hyperoxaluria diagnoses. Until 2020, general treatment for PH1 consisted mainly in high fluid intake, urine alkalization, surgical management of recurrent nephrolithiasis and eventually, if and when kidney failure occurred, intensive dialysis regimens and transplantation strategies (simultaneous or sequential liver-kidney transplant or isolated liver/kidney transplant in carefully selected patients). Specific treatment did and still consists in administration of pyridoxine hydrochloride, although it is only effective in a subset of PH1 patients. Lumasiran, a novel biological drug based on mRNA interference that has been recently approved in the US and European Union, showed promising results and is set to be a turning point in the management of PH1. This literature review aims to summarize the available evidence on PH1 treatment with lumasiran, in order to provide both pediatric and adult nephrologists and clinicians with the knowledge for the identification and management of PH1 patients suitable for treatment.

Patient-centred clinical trial design

Patient involvement in clinical trial design can facilitate the recruitment and retention of participants as well as potentially increase the uptake of the tested intervention and the impact of the findings on patient outcomes. Despite these benefits, patients still have very limited involvement in designing and conducting trials in nephrology. Many trials do not address research questions and outcomes that are important to patients, including patient-reported outcomes that reflect how patients feel and function. This limitation can undermine the relevance, reliability and value of trial-based evidence for decision-making in clinical practice and health policy. However, efforts to involve patients with kidney disease are increasing across all stages of the trial process from priority setting, to study design (including selection of outcomes and approaches to improve participant recruitment and retention) and dissemination and implementation of the findings. Harnessing the patient voice in designing trials can ensure that efforts and resources are directed towards patient-centred trials that address the needs, concerns and priorities of patients living with kidney disease with the aim of achieving transformative improvements in care and outcomes.

Treatment of primary hyperoxaluria type 1

Supportive treatment for primary hyperoxaluria type 1 (PH1) focuses on high fluid intake and crystallization inhibitors. A subset of patients with specific PH1 genotypes (c.508G>A and c.454T>A) will respond to pyridoxine, defined as a >30% reduction in urinary oxalate excretion. Response to pyridoxine is variable and in some patients, urinary oxalate may normalize. The first focused treatment for PH1 using an RNA interference agent to reduce urinary oxalate was approved in 2020, and such therapies may significantly alter treatment approaches and long-term outcomes in PH1. Currently PH1 often presents with kidney function impairment and frequently results in end-stage kidney disease (ESKD). With kidney dysfunction, urinary oxalate clearance decreases and multisystem deposition of oxalate (oxalosis) occurs, commonly in bones, eyes, heart and skin. Once plasma oxalate levels exceed 30 µmol/L, aggressive haemodialysis is indicated to prevent oxalosis, even if the glomerular filtration rate (GFR) remains better than for typical dialysis initiation. Peritoneal dialysis alone does not achieve the needed oxalate clearance. Dialysis is a bridge to future transplantation. Liver transplantation restores hepatic alanine-glyoxylate transaminase enzyme activity, allowing glyoxylate detoxification and preventing further oxalosis. The native liver must be removed as part of this process to avoid ongoing pathologic oxalate production. The timing and type of liver transplantation are dependent on pyridoxine sensitivity, age, weight, residual GFR and evidence of systemic oxalate deposition in extrarenal organs. Liver transplant can be isolated or combined with kidney transplantation in a sequential or simultaneous fashion. Isolated kidney transplantation is generally reserved for pyridoxine-sensitive patients only. Although liver transplantation is curative for PH1 and kidney transplantation treats ESKD, ensuing necessary immunosuppression and potential allograft dysfunction impart significant long-term risks.

Primary hyperoxaluria type 1: pathophysiology and genetics

Primary hyperoxaluria type 1 (PH1) is a rare genetic form of calcium oxalate kidney stone disease. It is caused by a deficiency in the liver-specific enzyme, alanine:glyoxylate aminotransferase (AGT), a pyridoxal-5'-phosphate (PLP)-dependent enzyme involved in the metabolism of glyoxylate. The excessive endogenous synthesis of oxalate that ensues leads to hyperoxaluria, and the crystallization of the poorly soluble calcium salt of oxalate is responsible for a severe kidney stone disease, which can progress to end-stage renal disease, systemic deposition of oxalate and death. Knowledge about metabolic precursors of glyoxylate and oxalate, molecular pathology of AGT and analytical methods for diagnosis and clinical assessment have allowed a better understanding of the mechanisms underlying PH1 and opened the door to new therapeutic strategies.

Oxalobacter formigenes treatment confers protective effects in a rat model of primary hyperoxaluria by preventing renal calcium oxalate deposition

In primary hyperoxaluria, increased hepatic oxalate production sometimes leads to severe nephrocalcinosis and early end-stage kidney disease. Oral administration of Oxalobacter formigenes (O. formigenes), an oxalate-degrading bacterium, is thought to derive oxalate from systemic sources by inducing net enteric oxalate secretion. Here, the impact of O. formigenes on nephrocalcinosis was investigated in an ethylene glycol rat model mimicking hepatic oxalate overproduction in primary hyperoxaluria. Eighteen rats were administered ethylene glycol (0.75% in drinking water) for 6 weeks, of which 9 were treated by oral gavage with O. formigenes and 9 received vehicle. Five control rats did not receive ethylene glycol or O. formigenes. Plasma and urinary oxalate levels, calcium oxalate crystalluria, urinary volume, fluid intake, and serum creatinine were monitored during the study. On killing, nephrocalcinosis was quantified. Ethylene glycol intake induced pronounced hyperoxalemia, hyperoxaluria, calcium oxalate crystalluria and nephrocalcinosis. Concomitant O. formigenes treatment partially prevented the ethylene glycol-induced increase in plasma oxalate and completely prevented nephrocalcinosis. Urinary oxalate excretion was not reduced by O. formigenes treatment. Nevertheless, absence of crystals in renal tissue of O. formigenes-treated ethylene glycol animals indicates that the propensity for oxalate to crystallize in the kidneys was reduced compared to non-treated animals. This is supported by the lower plasma oxalate concentrations in O. formigenes-treated animals. This study shows a beneficial effect of O. formigenes treatment on ethylene glycol-induced hyperoxalemia and nephrocalcinosis, and thus supports a possible beneficial effect of O. formigenes in primary hyperoxaluria.

Posttransplant recurrence of calcium oxalate crystals in patients with primary hyperoxaluria: Incidence, risk factors, and effect on renal allograft function

Primary hyperoxaluria (PH) is a metabolic defect that results in oxalate overproduction by the liver and leads to kidney failure due to oxalate nephropathy. As oxalate tissue stores are mobilized after transplantation, the transplanted kidney is at risk of recurrent disease. We evaluated surveillance kidney transplant biopsies for recurrent calcium oxalate (CaOx) deposits in 37 kidney transplants (29 simultaneous kidney and liver [K/L] transplants and eight kidney alone [K]) in 36 PH patients and 62 comparison transplants. Median follow-up posttransplant was 9.2 years (IQR: [5.3, 15.1]). The recurrence of CaOx crystals in surveillance biopsies in PH at any time posttransplant was 46% overall (41% in K/L, 62% in K). Higher CaOx crystal index (which accounted for biopsy sample size) was associated with higher plasma and urine oxalate following transplant (p < .01 and p < .02, respectively). There was a trend toward higher graft failure among PH patients with CaOx crystals on surveillance biopsies compared with those without (HR 4.43 [0.88, 22.35], p = .07). CaOx crystal deposition is frequent in kidney transplants in PH patients. The avoidance of high plasma oxalate and reduction of CaOx crystallization may decrease the risk of recurrent oxalate nephropathy following kidney transplantation in patients with PH. This study was approved by the IRB at Mayo Clinic.

Detection and localization of calcium oxalate in kidney using synchrotron deep ultraviolet fluorescence microscopy

Renal oxalosis is a rare cause of renal failure whose diagnosis can be challenging. Synchrotron deep ultraviolet (UV) fluorescence was assayed to improve oxalosis detection on kidney biopsies spatial resolution and sensitivity compared with the Fourier transform infrared microspectroscopy gold standard. The fluorescence spectrum of synthetic mono-, di- and tri-hydrated calcium oxalate was investigated using a microspectrometer coupled to the synchrotron UV beamline DISCO, Synchrotron SOLEIL, France. The obtained spectra were used to detect oxalocalcic crystals in a case control study of 42 human kidney biopsies including 19 renal oxalosis due to primary (PHO, n = 11) and secondary hyperoxaluria (SHO, n = 8), seven samples from PHO patients who received combined kidney and liver transplants, and 16 controls. For all oxalocalcic hydrates samples, a fluorescence signal is detected at 420 nm. These spectra were used to identify standard oxalocalcic crystals in patients with PHO or SHO. They also revealed micrometric crystallites as well as non-aggregated oxalate accumulation in tubular cells. A nine-points histological score was established for the diagnosis of renal oxalosis with 100% specificity (76-100) and a 73% sensitivity (43-90). Oxalate tubular accumulation and higher histological score were correlated to lower estimated glomerular filtration rate and higher urinary oxalate over creatinine ratio.

Phase 3 trial of lumasiran for primary hyperoxaluria type 1: A new RNAi therapeutic in infants and young children

PURPOSE

Primary hyperoxaluria type 1 (PH1) is a rare, progressive, genetic disease with limited treatment options. We report the efficacy and safety of lumasiran, an RNA interference therapeutic, in infants and young children with PH1.

METHODS

This single-arm, open-label, phase 3 study evaluated lumasiran in patients aged <6 years with PH1 and an estimated glomerular filtration rate >45 mL/min/1.73 m², if aged ≥12 months, or normal serum creatinine, if aged <12 months. The primary end point was percent change in spot urinary oxalate to creatinine ratio (UOx:Cr) from baseline to month 6. Secondary end points included proportion of patients with urinary oxalate ≤1.5× upper limit of normal and change in plasma oxalate.

RESULTS

All patients (N = 18) completed the 6-month primary analysis period. Median age at consent was 50.1 months. Least-squares mean percent reduction in spot UOx:Cr was 72.0%. At month 6, 50% of patients (9/18) achieved spot UOx:Cr ≤1.5× upper limit of normal. Least-squares mean percent reduction in plasma oxalate was 31.7%. The most common treatment-related adverse events were transient, mild, injection-site reactions.

CONCLUSION

Lumasiran showed rapid, sustained reduction in spot UOx:Cr and plasma oxalate and acceptable safety in patients aged <6 years with PH1, establishing RNA interference therapies as safe, effective treatment options for infants and young children.

Randomized Clinical Trial on the Long-Term Efficacy and Safety of Lumasiran in Patients With Primary Hyperoxaluria Type 1

Introduction

Primary hyperoxaluria type 1 (PH1) is a rare genetic disease caused by hepatic overproduction of oxalate, leading to kidney stones, nephrocalcinosis, kidney failure, and systemic oxalosis. In the 6-month double-blind period (DBP) of ILLUMINATE-A, a phase 3, randomized, placebo-controlled trial in patients with PH1 ≥6 years old, treatment with lumasiran, an RNA interference therapeutic, led to substantial reductions in urinary oxalate (UOx) levels.

Methods

We report data to month 12 in the extension period (EP) of ILLUMINATE-A, including patients who continued lumasiran (lumasiran/lumasiran) or crossed over from placebo to lumasiran (placebo/lumasiran).

Results

In the lumasiran/lumasiran group (n = 24), the reduction in 24-hour UOx level was sustained to month 12 (mean reduction from baseline, 66.9% at month 6; 64.1% at month 12). The placebo/lumasiran group (n = 13) had a similar time course and magnitude of 24-hour UOx reduction (mean reduction, 57.3%) after 6 months of lumasiran. Kidney stone event rates seemed to be lower after 6 months of lumasiran in both groups compared with the 12 months before consent, and this reduction was maintained at month 12 in the lumasiran/lumasiran group. At study start, 71% of patients in the lumasiran/lumasiran group and 92% in the placebo/lumasiran group had nephrocalcinosis. Nephrocalcinosis grade improved after 6 months of lumasiran in the lumasiran/lumasiran and placebo/lumasiran groups (13% and 8% of patients, respectively). After an additional 6 months of lumasiran, 46% of patients had improvement in nephrocalcinosis grade within the lumasiran/lumasiran group. Estimated glomerular filtration rate (eGFR) remained stable during the course of lumasiran treatment. The most common adverse events (AEs) related to lumasiran were mild, transient injection-site reactions (ISRs).

Conclusion

Long-term lumasiran treatment enabled sustained lowering of UOx levels with acceptable safety and encouraging results on clinical outcomes.

Primary hyperoxaluria diagnosed after kidney transplantation: a case report and literature review

Background

Primary hyperoxaluria (PH) is a rare inherited autosomal recessive disease caused by disturbed glyoxylate metabolism. The disease is characterized by calcium oxalate crystal deposition in various organs, especially in the kidney. Due to the lack of current understanding of PH, nearly all patients are only initially diagnosed with PH when recurrent lithiasis and progressive end-stage renal disease occur. Many cases are not diagnosed in patients until renal allograft insufficiency occurs after renal transplantation. This case report and literature review aim to emphasize the need for careful pre-transplant PH screening of patients with bilateral nephrocalcinosis or nephrolithiasis.

Case presentation

Renal allograft insufficiency was diagnosed as PH after kidney transplantation. Here, we detail the complete clinical course, including computed tomography images of the original kidney and renal graft, histopathological images of a biopsy of the transplanted kidney, the results of laboratory and molecular genetic tests, and the treatment. In addition, we reviewed the literature from 2000 to 2021 and analyzed 19 reported cases of PH diagnosed after kidney transplantation, and provide a summary of the characteristics, complications, treatment, and prognosis of these cases.

Conclusions

By reviewing and analyzing these cases, we concluded that patients with a history of nephrocalcinosis or nephrolithiasis in both kidneys need preoperative screening for PH and appropriate treatment before kidney transplantation. Delayed graft function caused by PH is easily misdiagnosed as acute rejection, and needle biopsy should be performed at an early stage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02546-0.

Long-Term Transplantation Outcomes in Patients With Primary Hyperoxaluria Type 1 Included in the European Hyperoxaluria Consortium (OxalEurope) Registry

Introduction

In primary hyperoxaluria type 1 (PH1), oxalate overproduction frequently causes kidney stones, nephrocalcinosis, and kidney failure. As PH1 is caused by a congenital liver enzyme defect, combined liver–kidney transplantation (CLKT) has been recommended in patients with kidney failure. Nevertheless, systematic analyses on long-term transplantation outcomes are scarce. The merits of a sequential over combined procedure regarding kidney graft survival remain unclear as is the place of isolated kidney transplantation (KT) for patients with vitamin B6-responsive genotypes.

Methods

We used the OxalEurope registry for retrospective analyses of patients with PH1 who underwent transplantation. Analyses of crude Kaplan–Meier survival curves and adjusted relative hazards from the Cox proportional hazards model were performed.

Results

A total of 267 patients with PH1 underwent transplantation between 1978 and 2019. Data of 244 patients (159 CLKTs, 48 isolated KTs, 37 sequential liver–KTs [SLKTs]) were eligible for comparative analyses. Comparing CLKTs with isolated KTs, adjusted mortality was similar in patients with B6-unresponsive genotypes but lower after isolated KT in patients with B6-responsive genotypes (adjusted hazard ratio 0.07, 95% CI: 0.01–0.75, P = 0.028). CLKT yielded higher adjusted event-free survival and death-censored kidney graft survival in patients with B6-unresponsive genotypes (P = 0.025, P < 0.001) but not in patients with B6-responsive genotypes (P = 0.145, P = 0.421). Outcomes for 159 combined procedures versus 37 sequential procedures were comparable. There were 12 patients who underwent pre-emptive liver transplantation (PLT) with poor outcomes.

Conclusion

The CLKT or SLKT remains the preferred transplantation modality in patients with PH1 with B6-unresponsive genotypes, but isolated KT could be an alternative approach in patients with B6-responsive genotypes.

Safety, pharmacodynamics, and exposure-response modeling results from a first-in-human phase 1 study of nedosiran (PHYOX1) in primary hyperoxaluria

Primary hyperoxaluria (PH) is a family of ultra-rare autosomal recessive inherited disorders of hepatic glyoxylate metabolism characterized by oxalate overproduction. Nedosiran is an RNA interference agent that inhibits hepatic lactate dehydrogenase, the enzyme responsible for the common, final step of oxalate production in all three genetic subtypes of PH. Here, we assessed in a two-part, randomized, single-ascending-dose, phase 1 study (PHYOX1) the safety, pharmacokinetics, pharmacodynamics, and exposure-response of subcutaneous nedosiran in 25 healthy participants (Group A) and 18 patients with PH1 or PH2 (Group B). Group A received nedosiran (0.3, 1.5, 3.0, 6.0, then 12.0 mg/kg) or placebo, and Group B received open-label nedosiran (1.5, 3.0, or 6.0 mg/kg). No significant safety concerns were identified. Injection site reactions (four or more hours post dose) occurred in 13.3% of participants in Group A and 27.8% of participants in Group B. Mean maximum reduction in 24-hour urinary oxalate excretion from baseline to day 57 (end of study) across Group B dose cohorts was 55% (range: 22%-100%) after single-dose nedosiran, with 33% participants reaching normal 24-hour urinary oxalate excretion. Based on the available modeling and simulation data, a fixed monthly dose of nedosiran 160 mg (free acid; equivalent to 170 mg sodium salt) in adults was associated with the highest proportion of simulated individuals achieving normal or near-normal 24-hour urinary oxalate excretion and fewest fluctuations in urinary oxalate response. Thus, single-dose nedosiran demonstrated acceptable safety and evidence of a pharmacodynamic effect in both PH1 and PH2 subpopulations consistent with its mechanism of action.

Genomics Integration Into Nephrology Practice

RATIONALE & OBJECTIVE

The etiology of kidney disease remains unknown in many individuals with chronic kidney disease (CKD). We created the Mayo Clinic Nephrology Genomics Clinic to improve our ability to integrate genomic and clinical data to identify the etiology of unexplained CKD.

STUDY DESIGN

Retrospective study.

SETTING & PARTICIPANTS

An essential component of our program is the Nephrology Genomics Board which consists of nephrologists, geneticists, pathologists, translational omics scientists, and trainees who interpret the patient's clinical and genetic data. Since September 2016, the Board has reviewed 163 cases (15 cystic, 100 glomerular, 6 congenital anomalies of kidney and urinary tract (CAKUT), 20 stones, 15 tubulointerstitial, and 13 other).

ANALYTICAL APPROACH

Testing was performed with targeted panels, single gene analysis, or analysis of kidney-related genes from exome sequencing. Variant classification was obtained based on the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology guidelines.

RESULTS

A definitive genetic diagnosis was achieved for 50 families (30.7%). The highest diagnostic yield was obtained in individuals with tubulointerstitial diseases (53.3%), followed by congenital anomalies of the kidney and urological tract (33.3%), glomerular (31%), cysts (26.7%), stones (25%), and others (15.4%). A further 20 (12.3%) patients had variants of interest, and variant segregation, and research activities (exome, genome, or transcriptome sequencing) are ongoing for 44 (40%) unresolved families.

LIMITATIONS

Possible overestimation of diagnostic rate due to inclusion of individuals with variants with evidence of pathogenicity but classified as of uncertain significance by the clinical laboratory.

CONCLUSIONS

Integration of genomic and research testing and multidisciplinary evaluation in a nephrology cohort with CKD of unknown etiology or suspected monogenic disease provided a diagnosis in a third of families. These diagnoses had prognostic implications, and often changes in management were implemented.

Dual Glycolate Oxidase/Lactate Dehydrogenase A Inhibitors for Primary Hyperoxaluria

Both glycolate oxidase (GO) and lactate dehydrogenase A (LDHA) influence the endogenous synthesis of oxalate and are clinically validated targets for treatment of primary hyperoxaluria (PH). We investigated whether dual inhibition of GO and LDHA may provide advantage over single agents in treating PH. Utilizing a structure-based drug design (SBDD) approach, we developed a series of novel, potent, dual GO/LDHA inhibitors. X-ray crystal structures of compound 15 bound to individual GO and LDHA proteins validated our SBDD strategy. Dual inhibitor 7 demonstrated an IC₅₀ of 88 nM for oxalate reduction in an Agxt-knockdown mouse hepatocyte assay. Limited by poor liver exposure, this series of dual inhibitors failed to demonstrate significant PD modulation in an in vivo mouse model. This work highlights the challenges in optimizing in vivo liver exposures for diacid containing compounds and limited benefit seen with dual GO/LDHA inhibitors over single agents alone in an in vitro setting.

Phase 1/2 Study of Lumasiran for Treatment of Primary Hyperoxaluria Type 1: A Placebo-Controlled Randomized Clinical Trial

BACKGROUND AND OBJECTIVES

In the rare disease primary hyperoxaluria type 1, overproduction of oxalate by the liver causes kidney stones, nephrocalcinosis, kidney failure, and systemic oxalosis. Lumasiran, an RNA interference therapeutic, suppresses glycolate oxidase, reducing hepatic oxalate production. The objective of this first-in-human, randomized, placebo-controlled trial was to evaluate the safety, pharmacokinetic, and pharmacodynamic profiles of lumasiran in healthy participants and patients with primary hyperoxaluria type 1.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This phase 1/2 study was conducted in two parts. In part A, healthy adults randomized 3:1 received a single subcutaneous dose of lumasiran or placebo in ascending dose groups (0.3-6 mg/kg). In part B, patients with primary hyperoxaluria type 1 randomized 3:1 received up to three doses of lumasiran or placebo in cohorts of 1 or 3 mg/kg monthly or 3 mg/kg quarterly. Patients initially assigned to placebo crossed over to lumasiran on day 85. The primary outcome was incidence of adverse events. Secondary outcomes included pharmacokinetic and pharmacodynamic parameters, including measures of oxalate in patients with primary hyperoxaluria type 1. Data were analyzed using descriptive statistics.

RESULTS

Thirty-two healthy participants and 20 adult and pediatric patients with primary hyperoxaluria type 1 were enrolled. Lumasiran had an acceptable safety profile, with no serious adverse events or study discontinuations attributed to treatment. In part A, increases in mean plasma glycolate concentration, a measure of target engagement, were observed in healthy participants. In part B, patients with primary hyperoxaluria type 1 had a mean maximal reduction from baseline of 75% across dosing cohorts in 24-hour urinary oxalate excretion. All patients achieved urinary oxalate levels ≤1.5 times the upper limit of normal.

CONCLUSIONS

Lumasiran had an acceptable safety profile and reduced urinary oxalate excretion in all patients with primary hyperoxaluria type 1 to near-normal levels.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Study of Lumasiran in Healthy Adults and Patients with Primary Hyperoxaluria Type 1, NCT02706886.

Combined liver kidney transplantation for primary hyperoxaluria type 1: Will there still be a future? Current transplantation strategies and monocentric experience

Combined liver-kidney transplantation is a therapeutic option for children affected by type 1 primary hyperoxaluria. Persistently high plasma oxalate levels may lead to kidney graft failure. It is debated whether pre-emptive liver transplantation, followed by kidney transplantation, might be a better strategy to reduce kidney graft loss. Our experience of 6 pediatric combined liver-kidney transplants for primary hyperoxaluria type 1 in pediatric recipients was retrospectively analyzed. Plasma oxalate levels were monitored before and after transplantation. All the recipients were on hemodialysis at transplantation. Median [IQR] recipient's age at transplantation was 11 [1-14] years; in all cases, a compatible graft from a pediatric brain-dead donor aged 8 [2-16] years was used. In a median follow-up of 7 [2-19] years after combined liver-kidney transplantation, no child died and no liver graft failure was observed; three kidney grafts were lost, due to chronic rejection, primary non-function, and early renal oxalate accumulation. Liver and kidney graft survival remained stable at 1, 3, and 5 years, at 100% and 85%, respectively. Kidney graft loss was the major complication in our series. Risk is higher with very young, low-weight donors. The impact of treatment with glyoxalate pathway enzyme inhibitors treatment in children with advanced disease as well as of donor kidney preservation by ex vivo machine perfusion needs to be evaluated. At present, a case-by-case discussion is needed to establish an optimal treatment strategy.

Understanding and Overcoming the Challenges Related to Cardiovascular Trials Involving Patients with Kidney Disease

Cardiovascular disease is a prevalent and prognostically important comorbidity among patients with kidney disease, and individuals with kidney disease make up a sizeable proportion (30%-60%) of patients with cardiovascular disease. However, several systematic reviews of cardiovascular trials have observed that patients with kidney disease, particularly those with advanced kidney disease, are often excluded from trial participation. Thus, currently available trial data for cardiovascular interventions in patients with kidney disease may be insufficient to make recommendations on the optimal approach for many therapies. The Kidney Health Initiative, a public-private partnership between the American Society of Nephrology and the US Food and Drug Administration, convened a multidisciplinary, international work group and hosted a stakeholder workshop intended to understand and develop strategies for overcoming the challenges with involving patients with kidney disease in cardiovascular clinical trials, with a particular focus on those with advanced disease. These efforts considered perspectives from stakeholders, including academia, industry, contract research organizations, regulatory agencies, patients, and care partners. This article outlines the key challenges and potential solutions discussed during the workshop centered on the following areas for improvement: building the business case, re-examining study design and implementation, and changing the clinical trial culture in nephrology. Regulatory and financial incentives could serve to mitigate financial concerns with involving patients with kidney disease in cardiovascular trials. Concerns that their inclusion could affect efficacy or safety results could be addressed through thoughtful approaches to study design and risk mitigation strategies. Finally, there is a need for closer collaboration between nephrologists and cardiologists and systemic change within the nephrology community such that participation of patients with kidney disease in clinical trials is prioritized. Ultimately, greater participation of patients with kidney disease in cardiovascular trials will help build the evidence base to guide optimal management of cardiovascular disease for this population.

Clinical characterization of primary hyperoxaluria type 3 in comparison to types 1 and 2: a retrospective cohort study

BACKGROUND

Primary hyperoxaluria type 3 (PH3) is caused by mutations in the HOGA1 gene. PH3 patients often present with recurrent urinary stone disease (USD) in first decade of life, but prior reports suggested PH3 may have a milder phenotype in adults. The current study characterized clinical manifestations of PH3 across the decades of life in comparison to PH1 and PH2.

METHODS

Clinical information was obtained from the Rare Kidney Stone Consortium Primary Hyperoxaluria Registry (PH1 n = 384; PH2 n = 51; PH3 n = 62).

RESULTS

PH3 patients presented with symptoms at a median 2.7 yrs old compared to PH1 (4.9 yrs) and PH2 (5.7 yrs) (p = 0.14). Nephrocalcinosis was present at diagnosis in 4 (7%) PH3 patients while 55 (89%) had stones. Median urine oxalate excretion was lowest in PH3 patients compared to PH1 and PH2 (1.1 vs 1.6 and 1.5 mmol/day/1.73m2, respectively, p < 0.001) while urine calcium was highest in PH3 (112 vs 51 and 98 mg/day/1.73m2 in PH1 and PH2, respectively, p < 0.001). Stone events per decade of life were similar across the age span and the 3 PH types. At 40 years of age, 97% of PH3 patients had not progressed to ESKD compared to 36% PH1 and 66% PH2 patients.

CONCLUSIONS

Patients with all forms of PH experience lifelong stone events often beginning in childhood. Kidney failure is common in PH1 but rare in PH3. Longer term follow up of larger cohorts will be important for a more complete understanding of the PH3 phenotype.

Hepatic Lactate Dehydrogenase A: An RNA Interference Target for the Treatment of All Known Types of Primary Hyperoxaluria

Introduction

Primary hyperoxaluria (PH) is a family of 3 rare genetic disorders of hepatic glyoxylate metabolism that lead to overproduction and increased renal excretion of oxalate resulting in progressive renal damage. LDHA inhibition of glyoxylate-to-oxalate conversion by RNA interference (RNAi) has emerged as a potential therapeutic option for all types of PH. LDHA is mainly expressed in the liver and muscles.

Methods

Nonclinical data in mice and nonhuman primates show that LDHA inhibition by RNAi reduces urinary oxalate excretion and that its effects are liver-specific without an impact on off-target tissues, such as the muscles. To confirm the lack of unintended effects in humans, we analyzed data from the phase I randomized controlled trial of single-dose nedosiran, an RNAi therapy targeting hepatic LDHA. We conducted a review of the literature on LDHA deficiency in humans, which we used as a baseline to assess the effect of hepatic LDHA inhibition.

Results

Based on a literature review of human LDHA deficiency, we defined the phenotype as mainly muscle-related with no liver manifestations. Healthy volunteers treated with nedosiran experienced no drug-related musculoskeletal adverse events. There were no significant alterations in plasma lactate, pyruvate, or creatine kinase levels in the nedosiran group compared with the placebo group, signaling the uninterrupted interconversion of lactate and pyruvate and normal muscle function.

Conclusion

Phase I clinical data on nedosiran and published nonclinical data together provide substantial evidence that LDHA inhibition is a safe therapeutic mechanism for the treatment of all known types of PH.

Small Molecule-Based Enzyme Inhibitors in the Treatment of Primary Hyperoxalurias

Primary hyperoxalurias (PHs) are a group of inherited alterations of the hepatic glyoxylate metabolism. PHs classification based on gene mutations parallel a variety of enzymatic defects, and all involve the harmful accumulation of calcium oxalate crystals that produce systemic damage. These geographically widespread rare diseases have a deep impact in the life quality of the patients. Until recently, treatments were limited to palliative measures and kidney/liver transplants in the most severe forms. Efforts made to develop pharmacological treatments succeeded with the biotechnological agent lumasiran, a siRNA product against glycolate oxidase, which has become the first effective therapy to treat PH1. However, small molecule drugs have classically been preferred since they benefit from experience and have better pharmacological properties. The development of small molecule inhibitors designed against key enzymes of glyoxylate metabolism is on the focus of research. Enzyme inhibitors are successful and widely used in several diseases and their pharmacokinetic advantages are well known. In PHs, effective enzymatic targets have been determined and characterized for drug design and interesting inhibitory activities have been achieved both in vitro and in vivo. This review describes the most recent advances towards the development of small molecule enzyme inhibitors in the treatment of PHs, introducing the multi-target approach as a more effective and safe therapeutic option.

Opportunities and challenges for antisense oligonucleotide therapies

Antisense oligonucleotide (AON) therapies involve short strands of modified nucleotides that target RNA in a sequence-specific manner, inducing targeted protein knockdown or restoration. Currently, 10 AON therapies have been approved in the United States and Europe. Nucleotides are chemically modified to protect AONs from degradation, enhance bioavailability and increase RNA affinity. Whereas single stranded AONs can efficiently be delivered systemically, delivery of double stranded AONs requires capsulation in lipid nanoparticles or binding to a conjugate as the uptake enhancing backbone is hidden in this conformation. With improved chemistry, delivery vehicles and conjugates, doses can be lowered, thereby reducing the risk and occurrence of side effects. AONs can be used to knockdown or restore levels of protein. Knockdown can be achieved by single stranded or double stranded AONs binding the RNA transcript and activating RNaseH-mediated and RISC-mediated degradation respectively. Transcript binding by AONs can also prevent translation, hence reducing protein levels. For protein restoration, single stranded AONs are used to modulate pre-mRNA splicing and either include or skip an exon to restore protein production. Intervening at a genetic level, AONs provide therapeutic options for inherited metabolic diseases as well. This review provides an overview of the different AON approaches, with a focus on AONs developed for inborn errors of metabolism.

Plasma oxalate and eGFR are correlated in primary hyperoxaluria patients with maintained kidney function-data from three placebo-controlled studies

BACKGROUND

In patients with primary hyperoxaluria (PH), endogenous oxalate overproduction increases urinary oxalate excretion, leading to compromised kidney function and often kidney failure. Highly elevated plasma oxalate (Pox) is associated with systemic oxalate deposition in patients with PH and severe chronic kidney disease (CKD). The relationship between Pox and estimated glomerular filtration rate (eGFR) in patients with preserved kidney function, however, is not well established. Our analysis aimed to investigate a potential correlation between these parameters in PH patients from three randomized, placebo-controlled trials (studies OC3-DB-01, OC3-DB-02, and OC5-DB-01).

METHODS

Baseline data from patients with a PH diagnosis (type 1, 2, or 3) and eGFR > 40 mL/min/1.73 m² were analyzed for a correlation between eGFR and Pox using Spearman's rank and Pearson's correlation coefficients. Data were analyzed by individual study and additionally were pooled for Studies OC3-DB-02 and OC5-DB-01 in which the same Pox assay was used.

RESULTS

A total of 106 patients were analyzed. A statistically significant inverse Spearman's correlation between eGFR and Pox was observed across all analyses; correlation coefficients were - 0.44 in study OC3-DB-01, - 0.55 in study OC3-DB-02, - 0.51 in study OC5-DB-01, and - 0.49 in the pooled studies (p < 0.0064).

CONCLUSIONS

Baseline evaluations showed a moderate and statistically significant inverse correlation between eGFR and Pox in patients with PH already at early stages of CKD (stages 1-3b), demonstrating that a correlation is present before substantial loss in kidney function occurs.

Transplantation for Primary Hyperoxaluria Type 1: Designing New Strategies in the Era of Promising Therapeutic Perspectives

Primary hyperoxaluria type 1 (PH1) is an autosomal recessive disease caused by the functional defect of alanine-glyoxylate aminotransferase that results in the overproduction of oxalate. It can be devastating especially for kidneys, leading to end-stage renal disease (ESRD) during the first 2 to 3 decades of life in most patients. Consequently, many PH1 patients need kidney transplantation. However, because PH1 is caused by a liver enzyme deficiency, the only cure of the metabolic defect is liver transplantation. Thus, current transplant strategies to treat PH1 patients with ESRD include dual liver-kidney transplantation. However, the morbidity and mortality associated with liver transplantation make these strategies far from optimal. Fortunately, a therapeutic revolution is looming. Indeed, innovative drugs are being currently tested in clinical trials, and preliminary data show impressive efficacy to reduce the hepatic overproduction of oxalate. Hopefully, with these therapies, liver transplantation will no longer be necessary. However, some patients with progressing renal disease or those who will be diagnosed with PH1 at an advanced stage of chronic kidney disease will ultimately need kidney transplantation. Here we review the current knowledge on this subject and discuss the future of kidney transplant management in PH1 patients in the era of novel therapies.

Effect of alanine supplementation on oxalate synthesis

The Primary Hyperoxalurias (PH) are rare disorders of metabolism leading to excessive endogenous synthesis of oxalate and recurring calcium oxalate kidney stones. Alanine glyoxylate aminotransferase (AGT), deficient in PH type 1, is a key enzyme in limiting glyoxylate oxidation to oxalate. The affinity of AGT for its co-substrate, alanine, is low suggesting that its metabolic activity could be sub-optimal in vivo. To test this hypothesis, we examined the effect of L-alanine supplementation on oxalate synthesis in cell culture and in mouse models of Primary Hyperoxaluria Type 1 (Agxt KO), Type 2 (Grhpr KO) and in wild-type mice. Our results demonstrated that increasing L-alanine in cells decreased synthesis of oxalate and increased viability of cells expressing GO and AGT when incubated with glycolate. In both wild type and Grhpr KO male and female mice, supplementation with 10% dietary L-alanine significantly decreased urinary oxalate excretion ~30% compared to baseline levels. This study demonstrates that increasing the availability of L-alanine can increase the metabolic efficiency of AGT and reduce oxalate synthesis.

Effects of Oxalobacter formigenes in subjects with primary hyperoxaluria Type 1 and end-stage renal disease: a Phase II study

BACKGROUND

In primary hyperoxaluria Type 1 (PH1), endogenous oxalate overproduction significantly elevates urinary oxalate excretion, resulting in recurrent urolithiasis and/or progressive nephrocalcinosis and often early end-stage renal disease (ESRD). In ESRD, dialysis cannot sufficiently remove oxalate; plasma oxalate (Pox) increases markedly, inducing systemic oxalate deposition (oxalosis) and often death. Interventions to reduce Pox in PH1 subjects with ESRD could have significant clinical impact. This ongoing Phase II, open-label trial aimed to evaluate whether long-term Oxabact™ (Oxalobacter formigenes, OC5, OxThera Intellectual Property AB, Sweden) lowers Pox in PH1 ESRD subjects, ameliorating clinical outcome.

METHODS

PH1 ESRD subjects on stable dialysis regimens were examined. Subjects were administered one OC5 capsule twice daily for up to 36 months or until transplantation. Total Pox values, cardiac function and safety were evaluated. Free Pox was evaluated in a comparative non-treated PH1 dialysis group using retrospective chart reviews and analyses.

RESULTS

Twelve subjects enrolled in an initial 6-week treatment phase. Following a washout of up to 4 weeks, eight subjects entered a continuation study; outcomes after 24 months of treatment are presented. After 24 months, all subjects had reduced or non-elevated Pox compared with baseline. Cardiac function improved, then stabilized. No treatment-related serious adverse events were reported.

CONCLUSIONS

Compared with an untreated natural control cohort, 24 months OC5 administration was beneficial to PH1 ESRD subjects by substantially decreasing Pox concentrations, and improving or stabilizing cardiac function and clinical status, without increasing dialysis frequency. OC5 was safe and well-tolerated.