Introduction
Diabetic kidney disease (DKD), defined as a persistently increased urine albumin-creatinine ratio (UACR) ≥30 mg/g and/or sustained reduction in eGFR <60 ml/min per 1.73 m2 (1–3), is a major cause of CKD, and afflicts approximately 40% of people with type 2 diabetes (3–5). Standard pharmacotherapy for DKD with hypertension has been traditionally the administration of renin-angiotensin-aldosterone system (RAAS) blockers, such as angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) (6). Recently, sodium-glucose cotransporter 2 (SGLT2) inhibitors were approved for the treatment of DKD (6–8). However, an effective treatment option with a different mechanism of action for patients with DKD in addition to available therapies is desired.
Xanthine oxidoreductase inhibitors (XORIs), such as allopurinol, febuxostat, and topiroxostat, have been widely used for the treatment of hyperuricemia and gout due to their uric acid–lowering effect (9–11); however, whether XORIs have a renoprotective effect has been controversial (12–14). In addition to reducing circulating uric acid levels, XORIs may ameliorate renal damage through various mechanisms at the kidney level, including the reduction of inflammation and oxidative stress and the prevention of glomerular hypertension, afferent arteriolar thickening, and ischemic renal histologic changes (14–18). Recently reported large-scale randomized controlled trials (RCTs) of XORIs failed to demonstrate the clinical benefit compared with placebo in slowing the progression of CKD after 2 − 3 years (19–21). Due to the varied background characteristics of patients with CKD, the evaluation of treatment effect of XORIs should target a specific patient population (19,22,23). Several RCTs have evaluated the XORIs in patients with DKD in type 2 diabetes (24–29); however, these studies were relatively small, and the results were not conclusive. Well-designed RCTs to evaluate the renoprotective effect of XORIs in patients with DKD in type 2 diabetes are thus awaited.
TMX-049 is a newly developed XORI with a nonpurine structure (30–33). In preclinical studies, TMX-049 reduced urine albumin excretion and attenuated renal damage without affecting any metabolic parameter in an experimental rodent model of type 2 diabetes (30–32). In Zucker diabetic fatty rats, an experimental rodent model of type 2 diabetes, 1 mg/kg of TMX-049 showed a 66% inhibition in renal XOR activity compared with vehicle, whereas 3 mg/kg of febuxostat did not (renal xanthine oxidase activity in rats treated with vehicle, TMX-049, and febuxostat were 6.5, 2.2, and 6.3 mU/mg protein, respectively) (30). In addition, 12 weeks’ administration of TMX-049 significantly ameliorated the urine albumin excretion compared with vehicle-treated rats, and the effect was more potent than that with febuxostat (urine albumin excretion in rats treated with vehicle, TMX-049, and febuxostat were 103.0, 60.0, and 82.3 mg/day, respectively) (30). Therefore, TMX-049 is expected to have a more potent inhibitory effect on renal XOR activity and the therapeutic potential to the DKD than other XORIs. The safety and pharmacokinetics of TMX-049 had been evaluated in phase 1 studies; multiple doses of up to 380 mg were well tolerated in healthy male adults (33). On the basis of these findings, we hypothesized that TMX-049 would have renoprotective effects in patients with DKD in type 2 diabetes. Therefore, we conducted a proof-of-concept study to investigate the renal effects of TMX-049 in patients with type 2 diabetes and DKD. The safety and tolerability of TMX-049 were also assessed.
Materials and Methods
Study Design
This study was a 12-week, randomized, double-blind, placebo-controlled, phase 2a trial (Figure 1), conducted at 49 centers across the United States, between April 2018 and June 2019. This study was conducted in accordance with the Declaration of Helsinki and the International Conference on Harmonization Good Clinical Practice guidelines. The study protocol was approved by Copernicus Group Institutional Review Board, Ochsner Clinic Foundation Institutional Review Board, and Western Institutional Review Board. Written informed consent was obtained from all patients before screening. The study was registered as “Phase 2 Study of TMX-049 in Subjects with Type 2 Diabetes and Albuminuria” at ClinicalTrials.gov (NCT03449199; registration date February 28, 2018).
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Figure 1.: Study design. The study visits after enrollment were as follows: randomization (baseline), weeks 2, 6, and 12 (or early termination), and follow-up visit (4 weeks after treatment completion). q.d., once daily.
Participants
Key inclusion criteria were age ≥18 years old; type 2 diabetes treated with at least one glucose-lowering medication for ≥12 months and at least a minimal recommended dose of either an ACEI or ARB, but not both, for ≥3 months; UACR 200 − 3000 mg/g at screening (with spot urine) and enrollment (with first-morning void urine); eGFR ≥30 ml/min per 1.73 m2 (using the CKD Epidemiology Collaboration Equation [34]); and serum uric acid (sUA) 4 − 10 mg/dl. Key exclusion criteria were type 1 diabetes, treatment with uric acid–lowering therapy <2 weeks, and glycated hemoglobin >11%.
Intervention and Randomization
Eligible patients were enrolled in a single-blind, run-in phase to receive placebo once daily for 2 weeks. Patients with ≥80% compliance to placebo during the run-in phase moved to a double-blind treatment phase, and were randomized in a 1:1:1 ratio to receive TMX-049 200 mg, 40 mg, or placebo once daily for 12 weeks. The dose levels were selected on the basis of the dose dependency of the effects and predicted human therapeutic dose of TMX-049 (200 mg for DKD and 40 mg for lowering uric acid) (30,33). The duration of the treatment period was determined to assess the safety and effects on the UACR of TMX-049.
Randomization was stratified by UACR (<300 and ≥300 mg/g) and sUA level (<6.0 and ≥6.0 mg/dl), and performed through an interactive voice/web response system using a randomization plan generated by an independent statistician. All investigators, patients, and staff remained blinded to treatment allocation during the study. The double-dummy technique was used to ensure the blinding; on each dosing occasion, all patients took one tablet (TMX-049 40 mg or placebo) orally and two capsules (TMX-049 80 mg or placebo), in accordance with the assigned treatment. To maintain the blind status, the results of UACR and sUA were not reported to investigators, patients, or staff after enrollment, unless an abnormally high level of sUA was noted.
During the study, the regimens of glucose-lowering medications and RAAS blockers (either ACEI or ARB) were continued; diuretics (thiazide, nonthiazide, and loop drugs), antituberculous drugs (pyrazinamide and ethambutol), antihypertensive drugs, antilipemic drugs, contraceptives, and hormone-replacement therapy were permitted; and starting or stopping diet remedies and exercise regimes was prohibited.
Outcomes
The primary efficacy end point was the change in log-transformed UACR at week 12 from baseline. The UACR at enrollment and all subsequent study visits was on the basis of the average of the two consecutive day mid-stream, first-morning void urine samples. Secondary efficacy end points included the proportion with a >30% reduction in UACR from baseline to week 12, and the change from baseline in the UACR, eGFR, and sUA levels at weeks 2, 6, and 12 (or early termination), and follow-up visit (4 weeks after treatment completion). The UACR, eGFR, and sUA were centrally measured. The baseline was defined as the measurement at randomization. Urinary biomarkers (kidney injury molecule-1, liver fatty acid-binding protein, 8 hydroxy-2'-deoxyguanosine, and N-acetyl-β-D-glucosaminidase) and blood biomarkers (soluble TNF receptor 1 and high-sensitivity C-reactive protein) were measured as exploratory biomarkers during the study.
Safety was assessed by adverse events (AEs) after randomization identified by investigators on the basis of the clinical evaluations including vital signs (systolic and diastolic blood pressure, pulse rate, and body temperature), 12-lead electrocardiograms, and laboratory tests. The seriousness, severity (mild, moderate, and severe), and causality of AEs were recorded. AEs were coded using the terms of the Medical Dictionary for Regulatory Activities, version 20.1.
Statistical Analysis
On the basis of data from a previous study (35), we estimated that 40 participants per group would provide the trial with 80% power to detect a 35% reduction (−0.43 for log-transformed value) on the primary end point of UACR, assuming an SD of 0.67 (log-scale) using a two-group t test with a 0.05 two-sided significance level. Taking into account that 10% of patients would be excluded from the analysis, we planned to enroll 132 patients (44 per group).
Efficacy analyses were performed on a modified intention-to-treat (mITT) population, which consisted of all randomized patients who had at least one measurement of the UACR after randomization. For the primary analysis of the primary end point, an analysis of covariance (ANCOVA) model was used, with randomized treatment and randomization strata of the UACR and sUA as independent variables. The last-observation carried-forward imputation algorithm was used for missing data. The least squares mean, P value, and corresponding 95% confidence intervals (95% CIs) for the change in log-transformed UACR from baseline in each treatment group and for the difference of the change between each TMX-049 group and placebo group were presented. The adjusted geometric mean of week 12 to baseline ratio with 95% CIs in UACR for each treatment group and the relative ratio between each TMX-049 group and placebo group with its 95% CIs were presented. Because UACR is not normally distributed, log-transformation was used to calculate the means for changes from baseline.
For the secondary analysis, the primary end point was analyzed by an ANCOVA using observed cases (without imputation of missing data) and by a mixed model for repeated measures, which included randomized treatment, randomization strata of the UACR and sUA, timepoint (week), and a treatment-by-timepoint interaction as fixed effects and patient as a random effect. The restricted maximum likelihood method for estimation was used. Within-patient errors were modeled using an unstructured (co)variance structure. The Kenward–Roger approximation was used to approximate the denominator degrees of freedom. The adjusted mean change in log-transformed UACR from baseline to week 12 for each treatment group and the 95% CIs were estimated in the framework of this model, and the between-group difference and the 95% CIs for the difference. A sensitivity analysis was performed on a per-protocol population, which consisted of all patients in the mITT population who did not experience any important protocol deviations leading to exclusion.
Prespecified subgroup analyses of the primary end point were performed using the ANCOVA model, which included randomized treatment and randomization strata of the UACR and sUA as independent variables. The last-observation carried-forward imputation algorithm was used for missing data. As a post hoc analysis, the P value for interaction was evaluated by the ANCOVA model, which included randomized treatment, randomization strata of the UACR and sUA, the relevant subgroup, and the interaction between the treatment and subgroup as independent variables.
For the secondary efficacy end points, the ANCOVA model was fit for the change from baseline to each timepoint for UACR, eGFR, and sUA. The proportion of patients with a >30% reduction from baseline to week 12 in UACR was presented by treatment group. The changes in the UACR and sUA from baseline at week 12 in each treatment group were plotted to describe their correlation. Safety analyses were performed on the safety population, which included all randomized patients who received at least one dose of the study drug. Demographic and safety data were summarized using descriptive statistics. As a post hoc analysis, the changes in the UACR and the systolic blood pressure from baseline at week 12 in each treatment group were plotted. Statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC, USA), and all statistical tests used a two-sided significance level of 5%, with no adjustments for multiplicity for this explanatory proof-of-concept study.
Results
Patient Disposition and Characteristics
Between April and December 2018, 344 patients were screened for eligibility, and 177 were enrolled in the run-in phase. In total, 130 patients were randomized and received the study treatment at 33 study sites, thus being included in the safety population: TMX-049 200 mg (n=44), 40 mg (n=44), and placebo (n=42). The distribution of randomized patients by study site is presented in the Supplemental Table 1. After excluding one patient with TMX-049 40 mg who was lost to follow-up, 129 patients were included in the mITT population: TMX-049 200 mg (n=44), 40 mg (n=43), and placebo (n=42). Overall, 126 patients completed the study (Figure 2).
Figure 2.: Patient disposition. All randomized patients were included in the safety population (n=130): TMX-049 200 mg (n=44), TMX-049 40 mg (n=44), and placebo (n=42). With the exception of one patient administered TMX-049 40 mg who was lost to follow-up after randomization, all patients were included in the modified intention-to-treat population (n=129): TMX-049 200 mg (n=44), TMX-049 40 mg (n=43), and placebo (n=42).
Baseline characteristics of the patients in the mITT population were similar among the three groups (Table 1). The majority of patients were >65 years old, male, and White. The median UACR was 474.0 (interquartile range, 256.0–915.0) mg/g. The mean of eGFR and sUA was 59 (SD, 21) ml/min per 1.73 m2 and 6.3 (SD, 1.5) mg/dl, respectively. The mean duration of study treatment for the safety population was 82.3 days; all patients had a compliance of ≥80% with the exception of one patient in the TMX-049 40 mg group. All patients received concomitant therapy with RAAS blockers; ACEIs 49% and ARBs 51%. SGLT2 inhibitors and insulin therapy were administered to 7% and 61% of patients, respectively.
Table 1. -
Baseline patient characteristics
| Characteristics |
TMX-049 200 mg |
TMX-049 40 mg |
Placebo |
| (n=44) |
(n=43) |
(n=42) |
| Age, yrs |
68±10 |
66±11 |
65±10 |
| Male sex |
26 (59%) |
26 (61%) |
24 (57%) |
|
Race/ethnicity
|
|
|
|
| White |
35 (80%) |
38 (88%) |
32 (76%) |
| Black |
8 (18%) |
2 (5%) |
5 (12%) |
| Asian |
1 (2%) |
2 (5%) |
4 (10%) |
| Other |
0 |
1 (2%) |
1 (2%) |
| Weight, kg |
98.8±23.6 |
95.9±20.6 |
90.1±19.8 |
| BMI, kg/m2
|
34.3±7.3 |
33.6±6.6 |
31.6±6.0 |
| Cardiac disorders |
14 (35%) |
21 (49%) |
10 (24%) |
| Smoker |
7 (16%) |
4 (9%) |
5 (12%) |
| HbA1C, % |
7.4±1.1 |
7.7±1.7 |
7.9±1.5 |
| eGFR, ml/min per 1.73 m2
|
59±22 |
59±23 |
60±19 |
| sUA, mg/dL |
6.2±1.4 |
6.5±1.6 |
6.2±1.4 |
| UACR, median, mg/g |
523.8 |
420.0 |
514.3 |
| (243.3, 1104.8) |
(252.5, 863.0) |
(316.0, 966.5) |
| SBP, mmHg |
139±13 |
138±13 |
137±12 |
| DBP, mmHg |
77±8 |
73±11 |
74±10 |
|
Concomitant therapy
|
|
|
|
| ACEI |
23 (52%) |
16 (37%) |
24 (57%) |
| ARB |
21 (48%) |
27 (63%) |
18 (43%) |
| SGLT2 inhibitor |
4 (9%) |
3 (7%) |
2 (5%) |
| Insulin therapy |
23 (52%) |
31 (72%) |
25 (60%) |
| Spironolactone |
0 |
1 (2%) |
1 (2%) |
| GLP-1RA |
6 (14%) |
7 (16%) |
11 (26%) |
Values are given as mean±SD, number (percent), or median (interquartile range). Data are presented for the modified intention-to-treat population (n=129). BMI, body mass index; HbA1C, glycated hemoglobin; sUA, serum uric acid; UACR, urine albumin-creatinine ratio; SBP, systolic blood pressure; DBP, diastolic blood pressure; ACEI, angiotensin-converting-enzyme inhibitor; ARB, angiotensin II receptor blocker; SGLT2, sodium-glucose cotransporter 2; GLP-1RA, glucagon-like peptide-1 receptor agonist.
Efficacy
Primary End Point
The least squares mean for changes in log-transformed UACR from baseline to week 12 were −0.53 (95% CI, −0.83 to −0.23) for TMX-049 200 mg (P<0.001), −0.15 (95% CI, −0.45 to 0.15) for 40 mg (P=0.32), and −0.10 (95% CI, −0.40 to 0.21) for placebo (P=0.52, Figure 3A). The least squares mean difference for changes in log-transformed UACR from baseline to week 12 compared with placebo were −0.43 (95% CI, −0.82 to −0.04) for TMX-049 200 mg (P=0.03) and −0.05 (95% CI, −0.44 to 0.34) for 40 mg (P=0.80). For TMX-049 200 mg, 40 mg, and placebo, the adjusted geometric mean of week 12 to baseline ratios in UACR were 0.59 (95% CI, 0.44 to 0.79), 0.86 (95% CI, 0.64 to 1.16), and 0.91 (95% CI, 0.67 to 1.23), respectively (Figure 3B). Compared with placebo, the relative ratio of adjusted geometric means of week 12 to baseline ratio in UACR for TMX-049 200 mg and 40 mg were 0.65 (95% CI, 0.44 to 0.96) and 0.95 (95% CI, 0.64 to 1.41), respectively; thus, a 35% reduction in UACR relative to the placebo group was achieved in the TMX-049 200 mg group but not in the 40 mg group. The secondary and sensitivity analyses showed similar results (Supplemental Table 2). For both TMX-049 200 mg and 40 mg, the results were consistent across the prespecified subgroups including baseline sUA, systolic blood pressure, and glycohemoglobin levels (Supplemental Figure 1).
Figure 3.: Mean change in the log-transformed UACR from baseline to each study visit and adjusted geometric mean of week 12 to baseline ratio in UACR. Data are presented for the modified intention-to-treat population (n=129): TMX-049 200 mg (n=44), TMX-049 40 mg (n=43), and placebo (n=42). (A) Data are shown as mean±SEM. (B) The analysis used a covariance model with treatment group and randomization strata of the UACR and sUA as independent variables. The last-observation carried-forward method was used for missing data. At week 12, the UACR was reduced by 35% relative to placebo in the TMX-049 200 mg group (relative ratio, 0.65; 95% CI, 0.44 to 0.96; P=0.03), whereas no reduction was observed in the TMX-049 40 mg group (relative ratio, 0.95; 95% CI, 0.64 to 1.41; P=0.80). UACR, urine albumin-creatinine ratio; sUA, serum uric acid; 95% CI, 95% confidence interval.
Secondary End Points
There were no reductions in UACR at weeks 2 or 6 with either dose (Figure 3A). The proportion of patients with a >30% reduction in UACR from baseline to week 12 in the TMX-049 200 mg, 40 mg, and placebo groups was 43% (19 out of 44 patients), 33% (14 out of 43 patients), and 24% (10 out of 42 patients), respectively. No changes in eGFR were observed with either TMX-049 dose at any timepoint; a declining trend in eGFR was observed in the placebo group (Figure 4). In both TMX-049 groups, sUA levels sharply decreased at week 2, remained stable until week 12, and returned to baseline levels at the follow-up visit, whereas no changes were observed in the placebo group (Figure 5). No correlation was apparent between the changes in UACR and sUA in any group (Figure 6). Regarding the exploratory biomarkers, there were no relevant findings for the urinary biomarkers (kidney injury molecule-1, liver fatty acid-binding protein, 8 hydroxy-2'-deoxyguanosine, and N-acetyl-β-D-glucosaminidase) or blood biomarkers (soluble TNF receptor 1 and high-sensitivity C-reactive protein) in either treatment group.
Figure 4.: Mean change in the eGFR from baseline to each study visit. Data are shown as mean±SEM. Data are presented for the modified intention-to-treat population (n=129): TMX-049 200 mg (n=44), TMX-049 40 mg (n=43), and placebo (n=42).
Figure 5.: Mean change in the sUA level from baseline to each study visit. Data are shown as mean±SEM. In the table, mean [SEM] is presented, and changes from baseline are shown in parentheses. Data are presented for the modified intention-to-treat population (n=129): TMX-049 200 mg (n=44), TMX-049 40 mg (n=43), and placebo (n=42).
Figure 6.: Scatter plot of change in the UACR versus change in the sUA from baseline at week 12. Data are presented for the modified intention-to-treat population (n=129): TMX-049 200 mg (n=44), TMX-049 40 mg (n=43), and placebo (n=42).
Safety
During the treatment, 17 out of 44 (39%), 19 out of 44 (43%), and 19 out of 42 (45%) patients receiving TMX-049 200 mg, 40 mg, and placebo, respectively, reported AEs (Table 2), of which the majority were either mild or moderate, and not drug related. The most common AEs (observed in three patients per group) were nausea and diarrhea in the TMX-049 200 mg group, nausea and peripheral edema in the TMX-049 40 mg group, and urinary tract infection and nasopharyngitis in the placebo group. Drug-related AEs occurred more frequently with TMX-049 200 mg (six patients) and 40 mg (five patients) than placebo (two patients), and were most likely due to gout attack or low uric acid levels. Gout was reported in two patients in the TMX-049 200 mg group within 30 days after treatment initiation.
Table 2. -
Patients with adverse events
| Adverse events |
TMX-049 |
TMX-049 |
|
| 200 mg |
40 mg |
Placebo |
| (n=44), n (%) |
(n=44), n (%) |
(n=42), n (%) |
| Total adverse events |
17 (39) |
19 (43) |
19 (45) |
| Drug-related adverse events |
6 (14) |
5 (11) |
2 (5) |
| Adverse events leading to study drug discontinuation |
0 |
1 (2) |
0 |
| Serious adverse events |
2 (5) |
4 (9) |
4 (10) |
| Drug-related serious adverse events |
0 |
1 (2) |
1 (2) |
|
Adverse events occurred in ≥2 patients in any group
|
|
|
|
| Nausea |
3 (7) |
3 (7) |
0 |
| Diarrhea |
3 (7) |
0 |
2 (5) |
| Hypoglycemia |
1 (2) |
2 (5) |
1 (2) |
| Edema peripheral |
0 |
3 (7) |
1 (2) |
| Arthralgia |
2 (5) |
0 |
0 |
| Blood uric acid decreased |
2 (5) |
0 |
0 |
| Dizziness |
2 (5) |
0 |
0 |
| Gout |
2 (5) |
0 |
0 |
| Urinary tract infection |
1 (2) |
1 (2) |
3 (7) |
| Edema |
0 |
2 (5) |
1 (2) |
| Hyperkalemia |
0 |
2 (5) |
0 |
| Hypothyroidism |
0 |
2 (5) |
0 |
| Influenza |
0 |
2 (5) |
0 |
| Upper respiratory tract infection |
0 |
2 (5) |
0 |
| Weight increased |
0 |
2 (5) |
0 |
| Nasopharyngitis |
1 (2) |
0 |
3 (7) |
| Headache |
1 (2) |
0 |
2 (5) |
Data are presented for the safety population (n=130).
No deaths were reported during the study. Ten patients experienced serious AEs, of which one was considered to be related to the TMX-049 (myelodysplastic syndrome). This patient with TMX-049 40 mg was anemic before randomization and taking azathioprine (a prohibited medication). Moderate anemia was observed during the study, and the patient was found to have myelodysplastic syndrome and discontinued the TMX-049 and azathioprine; the hemoglobin and hematocrit levels recovered to baseline level after 1 month. No other patient discontinued the study treatment due to AEs. Clinically relevant changes were not found regarding vital signs, 12-lead electrocardiograms, or laboratory tests, except for in one patient with a decreased GFR during the administration of TMX-049 40 mg. No marked differences in blood pressure were observed among the treatment groups throughout the treatment. The mean change in the systolic blood pressure from baseline to each study visit is shown in the Supplemental Figure 2. The post hoc analysis did not show any correlation between the changes in UACR and systolic blood pressure in any group (Supplemental Figure 3).
Discussion
In this study, TMX-049 200 mg reduced the primary end point of the UACR after 3 months by 35% compared with placebo in patients with DKD and type 2 diabetes who had normal or high baseline sUA levels. On the basis of the latest recommendations (23), early changes (e.g., within 6 months) in albuminuria can be a reliable surrogate end point for DKD; the threshold of 30% reduction in the geometric mean UACR can be used for evaluations in phase 2 trials to determine which interventions have the greatest promise for advancing to phase 3 trials. The effect of other XORIs on albuminuria in patients with DKD and type 2 diabetes was investigated in several small RCTs (24–29); however, most of these studies lacked a placebo control (26–28). In an RCT conducted in 80 patients with DKD and hyperuricemia in type 2 diabetes, febuxostat 80 mg/day did not reduce the secondary end point of UACR after 6 months compared with placebo (24). In another RCT conducted in 40 Iranian patients with DKD in type 2 diabetes (25), allopurinol 100 mg/day reduced the urine protein after 4 months compared with placebo (P=0.05), but this study did not report the prespecified primary end point or the effect size between the groups (36). An RCT of topiroxostat (up to 160 mg/day) in 65 Japanese patients with DKD, hyperuricemia, and type 2 diabetes (>95% of participants) did not show any difference in the primary end point of the UACR change after 7 months compared with placebo (29). Due to a lack of evidence from well-designed RCTs, it is premature to conclude the treatment effect of other XORIs in patients with DKD in type 2 diabetes.
Several findings in this study raise the possibility that the observed effects of the 200 mg TMX-049 dose on albuminuria were not entirely due to by the reduction in sUA per se. TMX-049 200 mg, the predicted therapeutic dose for DKD, was much higher than the dose predicted to reduce uric acid levels (40 mg) (30,33), and thus was expected to inhibit XOR strongly. In fact, although marked reductions in sUA levels were observed with both doses of TMX-049, the UACR was reduced only with the dose of 200 mg; no apparent relationship between the changes in UACR and sUA with TMX-049 200 mg was observed. In addition, the reduction in UACR with TMX-049 200 mg was not accompanied by any change in eGFR or blood pressure, and the reduction at week 12 was similar among subgroups with low/high baseline sUA or blood pressure levels. These findings suggest the observed effects of TMX-049 200 mg may not be hemodynamically mediated. Increased oxidative stress is a major factor influencing the development of diabetic complications, such as DKD (37).
XORIs are hypothesized to exert nephroprotective effects by reducing production of reactive oxygen species at the kidney level, thus alleviating oxidative stress (12). XORIs can also exert renoprotective effects via mechanisms such as suppression of superoxide production, or salvage of high-energy adenine nucleotides by XOR inhibition in the kidney (13,38). TMX-049 may have a more potent inhibitory effect on the renal XOR activity than other XORIs (30), and the extent of XOR inhibition in the kidney may play a pivotal role in the treatment of DKD. Furthermore, it has also been hypothesized that hyperuricemia may accelerate DKD progression via a mechanism linked to the RAAS (39,40). Allopurinol has been reported to lower blood pressure, an effect that may be RAAS mediated (41–43). In patients with TMX-049 treatment, we did not observe changes in blood pressure during the treatment, or an acute decline in eGFR immediately after the treatment initiation, as is typically observed with RAAS blockers (44) or SGLT2 inhibitors (7,8).
The safety data of TMX-049 obtained from this study were consistent with those from previous studies (30–33), or known safety profiles of other XORIs (9–11,45), and no new or unexpected safety concerns were observed. In our study, treatment-related gout was reported early in the treatment in two patients receiving TMX-049 200 mg, but not in those receiving TMX-049 40 mg or placebo. An increase in gout flares is frequently observed during initiation of antihyperuricemic therapy (9–11,45). One patient in the TMX-049 40 mg group experienced worsening anemia and discontinued study treatment due to drug interaction (with azathioprine) and myelodysplastic syndrome, which was reported as a serious and drug-related AE. The deterioration of anemia was likely due to a drug-drug interaction that led to increased azathioprine levels. Similar to other XORIs (9–11,45), the risk of drug-drug interaction with azathioprine or mercaptopurine has been identified as a potential risk with TMX-049. Although the possible risks of febuxostat, including cardiovascular events and hepatic effects were reported (9,11,45), we did not observe an increase in liver-related or cardiovascular AEs with TMX-049 in our study.
This study has several limitations. First, this study was designed to evaluate early changes (within 3 months) in albuminuria, and thus the study period might be too short to evaluate any improvement in eGFR, which is an end point directly reflecting the renoprotective effect. A long-term study (e.g., at least 2 years) would be required to evaluate the clinical benefit on GFR decline, cardiovascular disease, and mortality and the safety of the intervention (23). Because this study proved the effect of TMX-049 on reducing albuminuria, a larger and longer study to evaluate the clinical benefit and safety of this drug in patients with DKD is warranted. Second, we obtained data that imply the role of TMX-049 in the kidney; however, the mechanism of action underlying the effects of this drug remains unclear. Further clinical and nonclinical research is needed to understand the role of XORIs in kidney diseases. Finally, although the robustness of the results of the primary end point were confirmed by the secondary and sensitivity analyses, we did not plan any multiplicity adjustment analyses for this early-phase study. The possibility of a chance finding cannot be ruled out.
In conclusion, TMX-049 200 mg ameliorated albuminuria at 12 weeks; therefore, this novel XORI showed potential clinical benefit on DKD in type 2 diabetes. Study results suggested that TMX-049 may exert a renoprotective effect that is independent of its effect on lowering uric acid. TMX-049 also exhibited an acceptable safety profile with good tolerability.
Disclosures
A. Nakajima. H. Mikami, and M. Hirata are employees of Teijin and hold Teijin stocks. G.L. Bakris reports receiving fees from Teijin for his consultation of this study and from Alynium, KBP Bioscience, Ionis, Merck, and Relypsa for consultations outside of the submitted work; and reports serving as a member of the steering committee of international outcome trials; and reports his institution received fees from Bayer, Novo Nordisk, and Vascular Dynamics. M.D. Cressman was an employee of Covance when this trial was conducted, and received fees from Teijin for this publication.
Funding
None.
Acknowledgments
We thank the patients and investigators who participated in the study. The results presented in this paper have not been published previously in whole or part, except in the following scientific congress abstracts: Bakris G. et al., Effects of a novel xanthine oxidase inhibitor, TMX-049, on urinary albumin excretion in patients with type 2 diabetes and albuminuria. Presented at the 80th Scientific Sessions organized by American Diabetes Association, June 12–16, 2020. Statcom Co., Ltd., provided medical writing and publication support services funded by Teijin Pharma Limited, Ms. Kae Uetani of Statcom Co., Ltd., assisted in writing the manuscript. The following individuals from Teijin Pharma Limited reviewed a draft of the manuscript before the authors’ approval: Mr. Hideki Horiuchi, Mr. Fuminori Miyagi, Mr. Hiroshi Murano, and Mr. Takashi Shirakura. Implementation
of the study (development of study protocol, monitoring, data management, and statistical analysis) was performed by Covance Inc. on the basis of an outsourcing contract with Teijin America, Inc.
Author Contributions
G. Bakris, M. Cressman, M. Hirata, H. Mikami, and A. Nakajima conceptualized the study; A. Nakajima was responsible for the formal analysis; M. Cressman was responsible for the methodology; M. Hirata and H. Mikami were responsible for the project administration; G. Bakris provided supervision; G. Bakris, H. Mikami, and A. Nakajima reviewed and edited the manuscript; M. Cressman and M. Hirata wrote the original draft; and each author contributed important intellectual content during manuscript drafting or revision, read and approved the final manuscript, and accepts personal accountability for the overall work.
Data Sharing Statement
The data underlying this article are available in the article and in its online supplemental material, no additional data are available.
Supplemental Material
This article contains the following supplemental material online at http://kidney360.asnjournals.org/lookup/suppl/doi:10.34067/KID.0001672021/-/DCSupplemental.
Supplemental Table 1. Distribution of randomized patients by 33 study sites (n=130).
Supplemental Table 2. Change in log-transformed UACR from baseline to week 12 with analyses using an ANCOVA (LOCF), ANCOVA (OC), and MMRM.
Supplemental Figure 1. Results of a subgroup analysis according to the baseline characteristics. The relative ratio (95% CI) of adjusted geometric means of week 12 to baseline ratio in UACR between TMX-049 200 mg/40 mg group and placebo group for subgroups.
Supplemental Figure 2. Mean change (±SD) in the supine systolic blood pressure from baseline to each study visit.
Supplemental Figure 3. Scatter plot of changes in the UACR versus changes in the supine systolic blood pressure from baseline to week 12.
References
1. National Kidney Foundation: KDOQI Clinical Practice Guideline for Diabetes and CKD: 2012 Update. Available at:
https://www.kidney.org/sites/default/files/docs/diabetes-ckd-update-2012.pdf. Accessed August 4, 2021
2. Tuttle KR, Bakris GL, Bilous RW, Chiang JL, de Boer IH, Goldstein-Fuchs J, Hirsch IB, Kalantar-Zadeh K, Narva AS, Navaneethan SD, Neumiller JJ, Patel UD, Ratner RE, Whaley-Connell AT, Molitch ME: Diabetic kidney disease: A report from an ADA Consensus Conference. Am J Kidney Dis 64: 510–533, 2014
https://doi.org/10.1053/j.ajkd.2014.08.001
3. Alicic RZ, Rooney MT, Tuttle KR: Diabetic kidney disease: Challenges, progress, and possibilities. Clin J Am Soc Nephrol 12: 2032–2045, 2017
https://doi.org/10.2215/CJN.11491116
4. United States Renal Data System: 2018 USRDS Annual Data Report: Epidemiology of kidney disease in the United States, 2018. Available at:
https://www.usrds.org/annual-data-report/previous-adrs/. Accessed August 4, 2021
5. Reutens AT: Epidemiology of diabetic kidney disease. Med Clin North Am 97: 1–18, 2013
https://doi.org/10.1016/j.mcna.2012.10.001
6. Kidney Disease: Improving Global Outcomes (KDIGO) Diabetes Work Group: KDIGO 2020 Clinical Practice Guideline for Diabetes Management in Chronic Kidney Disease. Accessed November 19, 2020. Available at:
https://kdigo.org/wp-content/uploads/2020/10/KDIGO-2020-Diabetes-in-CKD-GL.pdf. Accessed August 4, 2021
7. Perkovic V, Jardine MJ, Neal B, Bompoint S, Heerspink HJL, Charytan DM, Edwards R, Agarwal R, Bakris G, Bull S, Cannon CP, Capuano G, Chu PL, de Zeeuw D, Greene T, Levin A, Pollock C, Wheeler DC, Yavin Y, Zhang H, Zinman B, Meininger G, Brenner BM, Mahaffey KW; CREDENCE Trial Investigators: Canagliflozin and renal outcomes in type 2 diabetes and nephropathy. N Engl J Med 380: 2295–2306, 2019
https://doi.org/10.1056/NEJMoa1811744
8. Zinman B, Wanner C, Lachin JM, Fitchett D, Bluhmki E, Hantel S, Mattheus M, Devins T, Johansen OE, Woerle HJ, Broedl UC, Inzucchi SE; EMPA-REG OUTCOME Investigators: Empagliflozin, cardiovascular outcomes, and mortality in type 2 diabetes. N Engl J Med 373: 2117–2128, 2015
https://doi.org/10.1056/NEJMoa1504720
9. Cicero AFG, Fogacci F, Cincione RI, Tocci G, Borghi C: Clinical effects of xanthine oxidase inhibitors in hyperuricemic patients. Med Princ Pract 30: 122–130, 2020
https://doi.org/10.1159/000512178
10. ZYLOPRIM: (allopurinol) [package insert]. East Brunswick, NJ: Casper Pharma LLC, 2018
11. ULORIC: (febuxostat) [package insert]. Deerfield, IL: Takeda Pharmaceuticals America, Inc., 2019
12. Jalal DI, Chonchol M, Chen W, Targher G: Uric acid as a target of therapy in CKD. Am J Kidney Dis 61: 134–146, 2013
https://doi.org/10.1053/j.ajkd.2012.07.021
13. Johnson RJ, Bakris GL, Borghi C, Chonchol MB, Feldman D, Lanaspa MA, Merriman TR, Moe OW, Mount DB, Sanchez Lozada LG, Stahl E, Weiner DE, Chertow GM: Hyperuricemia, acute and chronic kidney disease, hypertension, and cardiovascular disease: Report of a scientific workshop organized by the National Kidney Foundation. Am J Kidney Dis 71: 851–865, 2018
https://doi.org/10.1053/j.ajkd.2017.12.009
14. Pisano A, Cernaro V, Gembillo G, D’Arrigo G, Buemi M, Bolignano D: Xanthine oxidase inhibitors for improving renal function in chronic kidney disease patients: An updated systematic review and meta-analysis. Int J Mol Sci 18: 2283, 2017
https://doi.org/10.3390/ijms18112283
15. Kabul S, Shepler B: A review investigating the effect of allopurinol on the progression of kidney disease in hyperuricemic patients with chronic kidney disease. Clin Ther 34: 2293–2296, 2012
https://doi.org/10.1016/j.clinthera.2012.10.008
16. Kang DH, Nakagawa T, Feng L, Watanabe S, Han L, Mazzali M, Truong L, Harris R, Johnson RJ: A role for uric acid in the progression of renal disease. J Am Soc Nephrol 13: 2888–2897, 2002
https://doi.org/10.1097/01.ASN.0000034910.58454.FD
17. Mazzali M, Hughes J, Kim YG, Jefferson JA, Kang DH, Gordon KL, Lan HY, Kivlighn S, Johnson RJ: Elevated uric acid increases blood pressure in the rat by a novel crystal-independent mechanism. Hypertension 38: 1101–1106, 2001
https://doi.org/10.1161/hy1101.092839
18. Sánchez-Lozada LG, Tapia E, Soto V, Avila-Casado C, Franco M, Wessale JL, Zhao L, Johnson RJ: Effect of febuxostat on the progression of renal disease in 5/6 nephrectomy rats with and without hyperuricemia. Nephron, Physiol 108: p69–78, 2008
https://doi.org/10.1159/000127837
19. Doria A, Galecki AT, Spino C, Pop-Busui R, Cherney DZ, Lingvay I, Parsa A, Rossing P, Sigal RJ, Afkarian M, Aronson R, Caramori ML, Crandall JP, de Boer IH, Elliott TG, Goldfine AB, Haw JS, Hirsch IB, Karger AB, Maahs DM, McGill JB, Molitch ME, Perkins BA, Polsky S, Pragnell M, Robiner WN, Rosas SE, Senior P, Tuttle KR, Umpierrez GE, Wallia A, Weinstock RS, Wu C, Mauer M; PERL Study Group: Serum urate lowering with allopurinol and kidney function in type 1 diabetes. N Engl J Med 382: 2493–2503, 2020
https://doi.org/10.1056/NEJMoa1916624
20. Badve SV, Pascoe EM, Tiku A, Boudville N, Brown FG, Cass A, Clarke P, Dalbeth N, Day RO, de Zoysa JR, Douglas B, Faull R, Harris DC, Hawley CM, Jones GRD, Kanellis J, Palmer SC, Perkovic V, Rangan GK, Reidlinger D, Robison L, Walker RJ, Walters G, Johnson DW; CKD-FIX Study Investigators: Effects of allopurinol on the progression of chronic kidney disease. N Engl J Med 382: 2504–2513, 2020
https://doi.org/10.1056/NEJMoa1915833
21. Kimura K, Hosoya T, Uchida S, Inaba M, Makino H, Maruyama S, Ito S, Yamamoto T, Tomino Y, Ohno I, Shibagaki Y, Iimuro S, Imai N, Kuwabara M, Hayakawa H, Ohtsu H, Ohashi Y; FEATHER Study Investigators: Febuxostat therapy for patients with stage 3 CKD and asymptomatic hyperuricemia: A randomized trial. Am J Kidney Dis 72: 798–810, 2018
https://doi.org/10.1053/j.ajkd.2018.06.028
22. Alem MM: Allopurinol and endothelial function: A systematic review with meta-analysis of randomized controlled trials. Cardiovasc Ther 36: e12432, 2018
https://doi.org/10.1111/1755-5922.12432
23. Levey AS, Gansevoort RT, Coresh J, Inker LA, Heerspink HL, Grams ME, Greene T, Tighiouart H, Matsushita K, Ballew SH, Sang Y, Vonesh E, Ying J, Manley T, de Zeeuw D, Eckardt KU, Levin A, Perkovic V, Zhang L, Willis K: Change in albuminuria and GFR as end points for clinical trials in early stages of CKD: A scientific workshop sponsored by the National Kidney Foundation in collaboration with the US Food and Drug Administration and European Medicines Agency. Am J Kidney Dis 75: 84–104, 2020
https://doi.org/10.1053/j.ajkd.2019.06.009
24. Beddhu S, Filipowicz R, Wang B, Wei G, Chen X, Roy AC, DuVall SL, Farrukh H, Habib AN, Bjordahl T, Simmons DL, Munger M, Stoddard G, Kohan DE, Greene T, Huang Y: A randomized controlled trial of the effects of febuxostat therapy on adipokines and markers of kidney fibrosis in asymptomatic hyperuricemic patients with diabetic nephropathy. Can J Kidney Health Dis 3: 2054358116675343, 2016
https://doi.org/10.1177/2054358116675343
25. Momeni A, Shahidi S, Seirafian S, Taheri S, Kheiri S: Effect of allopurinol in decreasing proteinuria in type 2 diabetic patients. Iran J Kidney Dis 4: 128–132, 2010
26. Liu P, Chen Y, Wang B, Zhang F, Wang D, Wang Y: Allopurinol treatment improves renal function in patients with type 2 diabetes and asymptomatic hyperuricemia: 3-year randomized parallel-controlled study. Clin Endocrinol (Oxf) 83: 475–482, 2015
https://doi.org/10.1111/cen.12673
27. Mukri MNA, Kong WY, Mustafar R, Shaharir SS, Shah SA, Abdul Gafor AH, Mohd R, Abdul Cader R, Kamaruzaman L: Role of febuxostat in retarding progression of diabetic kidney disease with asymptomatic hyperuricemia: A 6-months open-label, randomized controlled trial. EXCLI J 17: 563–575, 2018
28. Mizukoshi T, Kato S, Ando M, Sobajima H, Ohashi N, Naruse T, Saka Y, Shimizu H, Nagata T, Maruyama S: Renoprotective effects of topiroxostat for Hyperuricaemic patients with overt diabetic nephropathy study (ETUDE study): A prospective, randomized, multicentre clinical trial. Nephrology (Carlton) 23: 1023–1030, 2018
https://doi.org/10.1111/nep.13177
29. Wada T, Hosoya T, Honda D, Sakamoto R, Narita K, Sasaki T, Okui D, Kimura K: Uric acid-lowering and renoprotective effects of topiroxostat, a selective
xanthine oxidoreductase inhibitor, in patients with diabetic nephropathy and hyperuricemia: A randomized, double-blind, placebo-controlled, parallel-group study (UPWARD study). Clin Exp Nephrol 22: 860–870, 2018
https://doi.org/10.1007/s10157-018-1530-1
30. Tsubosaka Y, Shirakura T, Tsujimoto S, Aizawa R, Matsui C, Sakamoto Y, Hase N, Kobayashi T: TMX-049, a novel xanthine oxidase inhibitor, attenuates renal injury in an experimental model of diabetic kidney disease [abstract FR-PO597]. Abstract presented at: American Society of Nephrology Kidney Week October 31−November 5, 2017; New Orleans, LA, 2017
31. Shirakura T, Tsujimoto S, Tsubosaka Y, Aizawa R, Matsui C, Hase N, Kobayashi T: Novel xanthine oxidase inhibitor TEI-B ameliorates urinary albumin excretion in normouricemic diabetic kidney disease models. [abstract MP493] Nephrol Dial Transplant 32[suppl 3]: iii609, 2017
https://doi.org/10.1093/ndt/gfx174.MP493
32. Shirakura T, Tsubosaka Y, Matsui-Watanabe C, Sakamoto Y, Hase N, Kobayashi T: A novel
xanthine oxidoreductase inhibitor TMX-049 attenuates renal injury in albumin overload induced-nephropathy. [abstract FP422] Nephrol Dial Transplant 33[suppl 1]: i177, 2018
https://doi.org/10.1093/ndt/gfy104.FP422
33. Japan Pharmaceutical Information Center: Clinical Trials Information: JapicCTI-163466, 2018. Available at:
https://www.clinicaltrials.jp/cti-user/trial/ShowDirect.jsp?japicId=JapicCTI-163466. Accessed August 4, 2021
34. Levey AS, Stevens LA, Schmid CH, Zhang YL, Castro AF 3rd, Feldman HI, Kusek JW, Eggers P, Van Lente F, Greene T, Coresh J; CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration): A new equation to estimate glomerular filtration rate. [published correction appears in
Ann Intern Med. 2011; 155: 408] Ann Intern Med 150: 604–612, 2009
https://doi.org/10.7326/0003-4819-150-9-200905050-00006
35. Kohan DE, Pritchett Y, Molitch M, Wen S, Garimella T, Audhya P, Andress DL: Addition of atrasentan to renin-angiotensin system blockade reduces albuminuria in diabetic nephropathy. J Am Soc Nephrol 22: 763–772, 2011
https://doi.org/10.1681/ASN.2010080869
36. Schulz KF, Altman DG, Moher D; CONSORT Group: CONSORT 2010 statement: Updated guidelines for reporting parallel group randomized trials. Ann Intern Med 152: 726–732, 2010
https://doi.org/10.7326/0003-4819-152-11-201006010-00232
37. Giacco F, Brownlee M: Oxidative stress and diabetic complications. Circ Res 107: 1058–1070, 2010
https://doi.org/10.1161/CIRCRESAHA.110.223545
38. Fujii K, Kubo A, Miyashita K, Sato M, Hagiwara A, Inoue H, Ryuzaki M, Tamaki M, Hishiki T, Hayakawa N, Kabe Y, Itoh H, Suematsu M: Xanthine oxidase inhibitor ameliorates postischemic renal injury in mice by promoting resynthesis of adenine nucleotides. JCI Insight 4: e124816, 2019
https://doi.org/10.1172/jci.insight.124816
39. Mazzali M, Kanellis J, Han L, Feng L, Xia YY, Chen Q, Kang DH, Gordon KL, Watanabe S, Nakagawa T, Lan HY, Johnson RJ: Hyperuricemia induces a primary renal arteriolopathy in rats by a blood pressure-independent mechanism. Am J Physiol Renal Physiol 282: F991–F997, 2002
https://doi.org/10.1152/ajprenal.00283.2001
40. Perlstein TS, Gumieniak O, Hopkins PN, Murphey LJ, Brown NJ, Williams GH, Hollenberg NK, Fisher ND: Uric acid and the state of the intrarenal renin-angiotensin system in humans. Kidney Int 66: 1465–1470, 2004
https://doi.org/10.1111/j.1523-1755.2004.00909.x
41. Beattie CJ, Fulton RL, Higgins P, Padmanabhan S, McCallum L, Walters MR, Dominiczak AF, Touyz RM, Dawson J: Allopurinol initiation and change in blood pressure in older adults with hypertension. Hypertension 64: 1102–1107, 2014
https://doi.org/10.1161/HYPERTENSIONAHA.114.03953
42. Feig DI, Soletsky B, Johnson RJ: Effect of allopurinol on blood pressure of adolescents with newly diagnosed essential hypertension: A randomized trial. JAMA 300: 924–932, 2008
https://doi.org/10.1001/jama.300.8.924
43. Agarwal V, Hans N, Messerli FH: Effect of allopurinol on blood pressure: A systematic review and meta-analysis. J Clin Hypertens (Greenwich) 15: 435–442, 2013
https://doi.org/10.1111/j.1751-7176.2012.00701.x
44. McCallum W, Tighiouart H, Ku E, Salem D, Sarnak MJ: Acute declines in estimated glomerular filtration rate on enalapril and mortality and cardiovascular outcomes in patients with heart failure with reduced ejection fraction. Kidney Int 96: 1185–1194, 2019
https://doi.org/10.1016/j.kint.2019.05.019
45. Strilchuk L, Fogacci F, Cicero AF: Safety and tolerability of available urate-lowering drugs: A critical review. Expert Opin Drug Saf 18: 261–271, 2019
https://doi.org/10.1080/14740338.2019.1594771
