Targeting the hepcidin-ferroportin pathway in anaemia of chronic kidney disease.

AIMS: Erythropoiesis-stimulating agents used to treat anaemia in patients with chronic kidney disease (CKD) have been associated with cardiovascular adverse events. Hepcidin production, controlled by bone morphogenic protein 6 (BMP6), regulates iron homeostasis via interactions with the iron transporter, ferroportin. High hepcidin levels are thought to contribute to increased iron sequestration and subsequent anaemia in CKD patients. To investigate alternative therapies to erythropoiesis-stimulating agents for CKD patients, monoclonal antibodies, LY3113593 and LY2928057, targeting BMP6 and ferroportin respectively, were tested in CKD patients. METHODS: Preclinical in vitro/vivo data and clinical data in healthy subjects and CKD patients were used to illustrate the translation of pharmacological properties of LY3113593 and LY2928057, highlighting the novelty of targeting these nodes within the hepcidin-ferroportin pathway. RESULTS: LY2928057 bound ferroportin and blocked interactions with hepcidin, allowing iron efflux, leading to increased serum iron and transferrin saturation levels and increased hepcidin in monkeys and humans. In CKD patients, LY2928057 led to slower haemoglobin decline and reduction in ferritin (compared to placebo). Serum iron increase was (mean [90% confidence interval]) 1.98 [1.46-2.68] and 1.36 [1.22-1.51] fold-relative to baseline following LY2928057 600 mg and LY311593 150 mg respectively in CKD patients. LY3113593 specifically blocked BMP6 binding to its receptor and produced increases in iron and transferrin saturation and decreases in hepcidin preclinically and clinically. In CKD patients, LY3113593 produced an increase in haemoglobin and reduction in ferritin (compared to placebo). CONCLUSION: LY3113593 and LY2928057 pharmacological effects (serum iron and ferritin) were translated from preclinical-to-clinical development. Such interventions may lead to new CKD anaemia treatments.

Anti-TGF-ß1 Antibody Therapy in Patients with Diabetic Nephropathy.

TGF-ß has been implicated as a major pathogenic factor in diabetic nephropathy. This randomized, double-blind, phase 2 study assessed whether modulating TGF-ß1 activity with a TGF-ß1-specific, humanized, neutralizing monoclonal antibody (TGF-ß1 mAb) is safe and more effective than placebo in slowing renal function loss in patients with diabetic nephropathy on chronic stable renin-angiotensin system inhibitor treatment. We randomized 416 patients aged ≥25 years with type 1 or type 2 diabetes, a serum creatinine (SCr) level of 1.3-3.3 mg/dl for women and 1.5-3.5 mg/dl for men (or eGFR of 20-60 ml/min per 1.73 m2), and a 24-hour urine protein-to-creatinine ratio ≥800 mg/g to TGF-ß1 mAb (2-, 10-, or 50-mg monthly subcutaneous dosing for 12 months) or placebo. We assessed a change in SCr from baseline to 12 months as the primary efficacy variable. Although the Data Monitoring Committee did not identify safety issues, we terminated the trial 4 months early for futility on the basis of their recommendation. The placebo group had a mean±SD change in SCr from baseline to end of treatment of 0.33±0.67 mg/dl. Least squares mean percentage change in SCr from baseline to end of treatment did not differ between placebo (14%; 95% confidence interval [95% CI], 9.7% to 18.2%) and TGF-ß1 mAb treatments (20% [95% CI, 15.3% to 24.3%], 19% [95% CI, 14.2% to 23.0%], and 19% [95% CI, 14.0% to 23.3%] for 2-, 10-, and 50-mg doses, respectively). Thus, TGF-ß1 mAb added to renin-angiotensin system inhibitors did not slow progression of diabetic nephropathy.

Effect of ruboxistaurin (RBX) On visual acuity decline over a 6-year period with cessation and reinstitution of therapy: results of an open-label extension of the Protein Kinase C Diabetic Retinopathy Study 2 (PKC-DRS2).

PURPOSE: The PKC-DRS2 was a Phase 3, randomized, double-masked, placebo (PBO)-controlled, 3-year study of the effect of 32 mg/day of ruboxistaurin (RBX), an orally administered protein kinase C inhibitor, on vision loss in patients with moderate to severe nonproliferative diabetic retinopathy. Ruboxistaurin reduced the occurrence of sustained moderate visual loss (SMVL; ≥15-letter decline in visual acuity sustained for the last 6 months of study participation) from 9.1% in the PBO group (N = 340) to 5.5% in the RBX group (N = 345, P = 0.034). This study evaluates the primary end point of SMVL in a 2-year open-label extension (OLE) of the PKC-DRS2, which began a median of 466 days (range, 263-1,296 days) after the conclusion of PKC-DRS2. METHODS: Visual acuity was measured by certified examiners using the Early Treatment Diabetic Retinopathy Study chart. RESULTS: Of the 514 patients who completed PKC-DRS2, 366 did so in the 32 study centers participating in the OLE, and of these, 203 (55%) enrolled in the OLE for treatment with 32 mg/day of RBX for 2 years. Of the 203 enrolled in the OLE, 100 had previously been treated with PBO (prior PBO subgroup) and 103 had been treated with RBX (prior RBX subgroup). PKC-DRS2 baseline patient and ocular characteristics were well matched between these two subgroups and were similar to the PKC-DRS2 patient population as a whole. Using the PKC-DRS2 baseline as the starting point, SMVL occurred in 6% of the prior PBO subgroup during the PKC-DRS2, increasing to 26% by the end of the OLE. However, in the prior RBX subgroup, SMVL occurred in only 4% and 8% during the PKC-DRS2 and by the end of the OLE, respectively (P < 0.001 for difference at the end of the OLE). In the prior PBO subgroup, mean visual acuity declined from 79.6 letters at PKC-DRS2 baseline to 73.1 letters at OLE end point (-6.5 letters). In the prior RBX subgroup, this loss was 2.7 letters (79.8 to 77.1) over the same period (P = 0.02). CONCLUSION: Over a 6-year study period incorporating 3 years of a rigorously placebo-controlled trial, approximately 1 year off treatment and 2-year OLE where all groups received therapy, those patients with greatest RBX exposure (∼5 years) experienced less SMVL compared with those in the original PBO group (∼2-year RBX exposure).

Oral protein kinase c ß inhibition using ruboxistaurin: efficacy, safety, and causes of vision loss among 813 patients (1,392 eyes) with diabetic retinopathy in the Protein Kinase C ß Inhibitor-Diabetic Retinopathy Study and the Protein Kinase C ß Inhibitor-Diabetic Retinopathy Study 2.

PURPOSE: To evaluate efficacy, safety, and causes of vision loss among 813 patients (1,392 eyes) with moderately severe to very severe nonproliferative diabetic retinopathy from the Protein Kinase C ß Inhibitor-Diabetic Retinopathy Study and Protein Kinase C ß Inhibitor-Diabetic Retinopathy Study 2 ruboxistaurin (RBX) protein kinase C ß inhibitor trials. METHODS: Patients in these 3-year, randomized, placebo-controlled, double-masked, Phase 3 trials had best-corrected Early Treatment Diabetic Retinopathy Study visual acuity ≥45 letters (∼20/125 Snellen), Early Treatment Diabetic Retinopathy Study retinopathy level 47A/B-53E, and no previous panretinal photocoagulation in ≥1 eye. Patients received placebo (N = 401) or RBX 32 mg/day (N = 412). Data from the 2 studies were combined and masked evaluation of retinal photographs was performed for cause of visual decline in all patients experiencing sustained moderate visual loss (≥15-letter loss sustained for the last 6 months of study). RESULTS: In the studies combined, sustained moderate visual loss occurred in 10.2% of placebo-treated patients versus 6.1% of RBX-treated patients (P = 0.011). A ≥15-letter gain occurred in 2.4% of placebo versus 4.7% of RBX eyes (P = 0.021) and a ≥15-letter loss occurred in 11.4% versus 7.4%, respectively (P = 0.012). Diabetic macular edema was the probable primary cause of vision loss. Among eyes without focal/grid photocoagulation at baseline, fewer RBX group eyes (26.7%) required initial focal/grid photocoagulation versus placebo (35.6%; P = 0.008). No safety concerns were identified. CONCLUSION: Analysis of data combined from two similar studies adds further statistical significance to RBX's beneficial effects on visual loss, need for focal laser, and vision gain, most likely through effects on macular edema.

Selective PKC beta inhibition with ruboxistaurin and endothelial function in type-2 diabetes mellitus.

PURPOSE: Type-2 diabetes mellitus increases risk of atherosclerotic cardiovascular disease. However, the mechanisms linking hyperglycemia and atherosclerosis remain poorly understood. One proposed mechanism involves endothelial dysfunction via activation of protein kinase C beta (PKC beta). Prior studies demonstrate beneficial effects of PKC beta inhibition on microvascular parameters, but, to date, no study has examined the effect on macrovascular atherosclerotic readouts. METHODS: The goal of this double-masked, placebo-controlled trial in type-2 diabetes was to assess the effect of the PKC beta-specific inhibitor, ruboxistaurin (32 mg/day for 6 weeks) on ultrasound assessed brachial artery flow mediated dilatation (FMD), a surrogate of macro vascular endothelial function, and urinary isoprostanes, indices of oxidant stress. RESULTS: Compared to placebo, ruboxistaurin tended to improve FMD (difference in 6-week change in FMD, mean +/- SD millimeter) at one (0.13 +/- 0.26 mm, p = 0.08) and 5 min (0.12 +/- 0.21 mm, p = 0.02) after cuff deflation, but had no effect on nitroglycerin-mediated dilatation or urinary isoprostanes. CONCLUSIONS: This proof of concept trial is the first to suggest that specific inhibition of PKC beta may improve macro vascular endothelial function in type-2 diabetes. Larger trials including clinical endpoints are warranted to determine the potential efficacy of PKC beta inhibition in reducing atherosclerotic cardiovascular complications in diabetes mellitus.

Inhibition of PKC beta by oral administration of ruboxistaurin is well tolerated and ameliorates diabetes-induced retinal hemodynamic abnormalities in patients.

PURPOSE: To assess ocular and systemic safety and pharmacodynamic effects of the oral PKC beta selective inhibitor ruboxistaurin (RBX; LY333531) mesylate in patients with diabetes. METHODS: This was a double-masked, placebo-controlled, parallel, randomized, single-center clinical study evaluating the effect of oral administration of RBX (8 mg twice a day, 16 mg per day, or 16 mg twice a day) or placebo for 28 days in patients with no or very mild diabetic retinopathy on mean retinal circulation time (RCT), retinal blood flow (RBF), treatment-emergent adverse events, and other safety parameters. RESULTS: Twenty-nine persons aged 18 to 65 years with type 1 or 2 diabetes were evaluated. The only treatment-emergent adverse event with a statistically significant difference among treatment groups was abdominal pain, which was more common in placebo-treated subjects (P = 0.049). Statistically significant effects of RBX were observed on several hematologic and laboratory parameters, but values were within the normal reference range and none of the changes was deemed clinically meaningful. In patients receiving 16 mg RBX twice daily, the diabetes-induced increase in RCT was ameliorated, with a baseline-to-endpoint difference of -0.84 seconds (P = 0.046) relative to placebo. Increasing RBX dose was linearly associated with greater effect on RCT (P = 0.03). Similar results were observed with RBF. CONCLUSIONS: RBX was well tolerated at doses up to 16 mg twice daily for 28 days in patients with diabetes. It ameliorated diabetes-induced RCT abnormalities. No serious safety problems were identified in this patient population. Compared with prior published data, these findings represent the first direct human evidence of both bioavailability of RBX to retinal vessels and amelioration of diabetes-induced retinal hemodynamic abnormalities by an oral PKC beta inhibitor.

Effect of ruboxistaurin on visual loss in patients with diabetic retinopathy.

OBJECTIVE: To evaluate the effect of ruboxistaurin, an orally administered protein kinase C beta (PKC beta) isozyme-selective inhibitor, on vision loss in patients with diabetes. DESIGN: Thirty-six-month, randomized, double-masked, placebo-controlled, parallel, multicenter trial. PARTICIPANTS: Six hundred eighty-five patients randomized at 70 clinical sites. METHODS: Ophthalmologic examination was performed at screening and at each 3-month visit. Retinopathy status was assessed every 6 months with Early Treatment Diabetic Retinopathy Study (ETDRS) standard 7-field 30 degrees color stereoscopic fundus photography. Levels of diabetic retinopathy and diabetic macular edema were determined by 2 independent graders masked to site and treatment assignment, with additional independent adjudication as required. Eligible patients had a best-corrected visual acuity (VA) score of > or =45 letters, retinopathy level > or = 47A and < or = 53E, and no prior panretinal photocoagulation in at least one eye. MAIN OUTCOME MEASURE: Effect of oral ruboxistaurin (32 mg/day) on reduction of sustained moderate visual loss (> or =15-letter decrease in ETDRS VA score maintained > or = 6 months) in patients with moderately severe to very severe nonproliferative diabetic retinopathy. RESULTS: Sustained moderate visual loss occurred in 9.1% of placebo-treated patients versus 5.5% of ruboxistaurin-treated patients (40% risk reduction, P = 0.034). Mean VA was better in the ruboxistaurin-treated patients after 12 months. Baseline-to-end point visual improvement of > or =15 letters was more frequent (4.9% vs. 2.4%) and > or =15-letter worsening was less frequent (6.7% vs. 9.9%) in ruboxistaurin-treated patients relative to placebo (P = 0.005). When clinically significant macular edema was >100 microm from the center of the macula at baseline, ruboxistaurin treatment was associated with less frequent progression of edema to within 100 microm (68% vs. 50%, P = 0.003). Initial laser treatment for macular edema was 26% less frequent in eyes of ruboxistaurin-treated patients (P = 0.008). CONCLUSION: Oral ruboxistaurin treatment reduced vision loss, need for laser treatment, and macular edema progression, while increasing occurrence of visual improvement in patients with nonproliferative retinopathy.

The effect of the oral PKC ß inhibitor ruboxistaurin on vision loss in two phase 3 studies.

PURPOSE: To assess the effect of ruboxistaurin (RBX) on vision loss through a prospectively defined combined analysis of two phase 3 trials (MBDL and MBCU). METHODS: Patients in both of these 3-year randomized, placebo-controlled, double-masked trials had best-corrected Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) ≥ 75 letters (∼20/32 Snellen), ETDRS retinopathy level 20 to 47D (MBDL) or 35B to 53E (MBCU), and no prior panretinal or focal photocoagulation in at least one eye at baseline. Patients received oral placebo (N = 508 total from both studies) or RBX 32 mg/d (N = 520 total). Best-corrected ETDRS VA was measured at 6-month intervals for 3 years (MBDL) or for 18 to 48 months (MBCU). Sustained moderate visual loss (SMVL) was defined as a 15-letter or more reduction from baseline in VA sustained for a patient's last 6 months of study participation. RESULTS: In the combined studies (N = 1028 total), SMVL occurred in 4.4% of placebo- versus 2.3% of RBX-treated patients (P = 0.069). In patients with a minimum of 2 years of follow-up (N = 825 total), there was less SMVL in the RBX group (4.4% placebo versus 2.1% RBX, P = 0.045). Other VA-related measures (mean VA, contrast sensitivity, Visual Functioning Questionnaire 25 [VFQ-25]) either trended toward a benefit for RBX or were also statistically significant in favor of RBX. In contrast, diabetic macular edema (DME) morphology-related measures (occurrence of significant center of macula involvement, optical coherence tomography [OCT]-determined center of macula thickness, application of focal photocoagulation) did not show a consistent trend in favor of or against RBX. CONCLUSIONS: SMVL data in a prospectively defined combined analysis from these two phase 3 trials suggest a magnitude of effect of RBX on vision loss similar to that seen in two prior studies (approximately 50% reduction above standard care). However, event rates were low and statistical significance was not achieved. (ClinicalTrials.gov numbers, NCT00133952, NCT00090519.).

Ruboxistaurin: PKC-beta inhibition for complications of diabetes.

Diabetes mellitus is the most common cause of blindness among working-age adults, with a prevalence of 7 - 8% of adults in the USA, and is one of the most common causes of renal failure requiring kidney transplant and the most common cause of non-traumatic lower limb amputation in developed nations [1] . The role of the intracellular signaling enzyme protein kinase C (PKC) in the development of diabetic complications has become a field of intense research interest. An inhibitor of the PKC-beta isoform ruboxistaurin (RBX) has in vitro and in vivo benefits in ameliorating disturbances of cell regulation and blood flow related to hyperglycemia. The benefit of RBX for peripheral neuropathy has not been successfully demonstrated in Phase III trials. Although there was a beneficial effect of RBX on nephropathy in a pilot study, there has been no further clinical development for this indication. The major cause of visual disability - diabetic macular edema - seems to respond to RBX treatment with both anatomic and functional benefits. The manufacturer, Eli Lilly Co., has received an approvable letter from the FDA for the prevention of vision loss in patients with diabetic retinopathy with RBX, pending results of additional clinical trials for this indication.

Effect of ruboxistaurin on the visual acuity decline associated with long-standing diabetic macular edema.

PURPOSE: To compare relationships between severity and duration of diabetic macular edema (DME) and visual acuity (VA) observed in the PKC-DRS2 with those from the Early Treatment Diabetic Retinopathy Study (ETDRS) and to assess the effect of the orally administered PKC beta inhibitor ruboxistaurin (RBX) on these parameters. METHODS: In the PKC-DRS2, patients with moderately severe to very severe nonproliferative diabetic retinopathy (n = 685) were randomly assigned to 32 mg/d RBX or placebo and followed up for 36 months with ETDRS VA measurements and fundus photographs (FP) every 3 to 6 months. Mean VA was calculated across all FP visits for eyes in each level of the ETDRS DME severity scale at those visits. For eyes with baseline VA > or = 20/40, relationships between change in VA from baseline to last visit and duration of severe DME were analyzed with linear regression. RESULTS: Mean VA decreased by approximately 22 letters between the mildest and most severe levels of the DME scale in the PKC-DRS2, compared with 27 letters in the ETDRS. In the placebo group, the rate of decrease in VA over time associated with duration of severe DME was 0.67 letters per month (24 letters over 36 months, compared with 20 letters over 28-36 months in the ETDRS). This rate was 30% less in the RBX group (0.47 letter per month, P = 0.022). CONCLUSIONS: The VA decrease in the PKC-DRS2 associated with long-standing DME agrees well with estimates from the ETDRS. RBX appears to ameliorate this decrease, an effect that could be important clinically. (ClinicalTrials.gov number, NCT00604383.).

Molecular understanding of hyperglycemia's adverse effects for diabetic complications.

Diabetic complications are the major cause of morbidity and mortality in persons with diabetes. Chronic hyperglycemia is a major initiator of diabetic microvascular complications (eg, retinopathy, neuropathy, nephropathy). Glucose processing uses a variety of diverse metabolic pathways; hence, chronic hyperglycemia can induce multiple cellular changes leading to complications. Several predominant well-researched theories have been proposed to explain how hyperglycemia can produce the neural and vascular derangements that are hallmarks of diabetes. These theories can be separated into those that emphasize the toxic effects of hyperglycemia and its pathophysiological derivatives (such as oxidants, hyperosmolarity, or glycation products) on tissues directly and those that ascribe pathophysiological importance to a sustained alteration in cell signaling pathways (such as changes in phospholipids or kinases) induced by the products of glucose metabolism. This article summarizes these theories and the potential therapeutic interventions that may prevent diabetic complications in the presence of hyperglycemia, control of which is often difficult with current therapeutic options.