PF-03882845, a non-steroidal mineralocorticoid receptor antagonist, prevents renal injury with reduced risk of hyperkalemia in an animal model of nephropathy

Abstract

The mineralocorticoid receptor (MR) antagonists PF-03882845 and eplerenone were evaluated for renal protection against aldosterone-mediated renal disease in uninephrectomized Sprague-Dawley (SD) rats maintained on a high salt diet and receiving aldosterone by osmotic mini-pump for 27 days. Serum K(+) and the urinary albumin to creatinine ratio (UACR) were assessed following 14 and 27 days of treatment. Aldosterone induced renal fibrosis as evidenced by increases in UACR, collagen IV staining in kidney cortex, and expression of pro-fibrotic genes relative to sham-operated controls not receiving aldosterone. While both PF-03882845 and eplerenone elevated serum K(+) levels with similar potencies, PF-03882845 was more potent than eplerenone in suppressing the rise in UACR. PF-03882845 prevented the increase in collagen IV staining at 5, 15 and 50 mg/kg BID while eplerenone was effective only at the highest dose tested (450 mg/kg BID). All doses of PF-03882845 suppressed aldosterone-induced increases in collagen IV, transforming growth factor-β 1 (Tgf-β 1), interleukin-6 (Il-6), intermolecular adhesion molecule-1 (Icam-1) and osteopontin gene expression in kidney while eplerenone was only effective at the highest dose. The therapeutic index (TI), calculated as the ratio of the EC50 for increasing serum K(+) to the EC50 for UACR lowering, was 83.8 for PF-03882845 and 1.47 for eplerenone. Thus, the TI of PF-03882845 against hyperkalemia was 57-fold superior to that of eplerenone indicating that PF-03882845 may present significantly less risk for hyperkalemia compared to eplerenone.

Keywords: UACR; albuminuria; hyperkalemia; mineralocorticoid receptor; nephropathy; urinary albumin to creatinine ratio.

Figure 1

Effect of eplerenone on UACR on day 14 (A) and day 26 (B). Data are represented as mean ± standard error of the mean. See Materials and Methods for statistical analysis. ^*Indicates a significant difference from the vehicle sham (Veh Sham) group; ^#Indicates a significant difference from the vehicle + aldosterone (Veh Aldo) group.

Figure 2

Effect of PF-03882845 on UACR on day 14 (A) and day 26 (B). Data are represented as mean ± standard error of the mean. See Materials and Methods for statistical analysis. ^*Indicates a significant difference from the vehicle sham (Veh Sham) group; ^#Indicates a significant difference from the vehicle + aldosterone (Veh Aldo) group.

Figure 3

Effect of eplerenone on serum K⁺ on day 14 (A) and day 26 (B). Data are represented as mean ± standard error of the mean. See Materials and Methods for statistical analysis. ^*Indicates a significant difference from the vehicle sham (Veh Sham) group; ^# Indicates a significant difference from the vehicle + aldosterone (Veh Aldo) group.

Figure 4

Effect of PF-03882845 on serum K⁺ on day 14 (A) and day 26 (B). Data are represented as mean ± standard error of the mean. See Materials and Methods for statistical analysis. ^*Indicates a significant difference from the vehicle sham (Veh Sham) group; ^#Indicates a significant difference from the vehicle + aldosterone (Veh Aldo) group.

Figure 5

PK-PD modeling of UACR and serum potassium. Concentration-effect curves of eplerenone (gray lines) and PF-03882845 (black lines) for UACR (A) and serum K⁺ (B) following 27 days of treatment. Dashed lines indicate the 95% upper and lower confidence intervals. Data were modeled using an indirect response model. A double delta equation was used to express the pharmacodynamic response for serum K⁺.

Figure 6

Representative images of collagen IV immunohistochemical localization in kidney cortex. Study A, vehicle sham (A), vehicle + aldosterone (B), 50 mg/kg BID eplerenone (C), and 450 mg/kg BID eplerenone (D), groups following 27 days of treatment; and Study B, kidney cortex from sham vehicle (E), vehicle + aldosterone (F), 5 mg/kg BID PF-03882845 (G), 15 mg/kg BID PF-03882845 (H), and 50 mg/kg BID PF-03882845 (I) following 27 days of treatment. Data expressed as % collagen IV staining in kidney cortex and represented as mean ± standard error of the mean: Study A (J) and Study B (K). See Materials and Methods for statistical analysis. ^*Indicates a significant difference from the vehicle sham (Veh Sham) group; ^#Indicates a significant difference from the vehicle + aldosterone (Veh Aldo) group.

Figure 7

Effect of eplerenone and PF-03882845 on urinary Na⁺/K⁺ ratio. SD rats received single doses of 0, 5, 30, or 3.0 mg/kg eplerenone or 0, 3, 10, or 30 mg/kg PF-03882845 and urinary Na⁺/K⁺ was assessed at 0–2, 2–4, and 4–7 h post-dose. Both compounds yielded analogous concentration-effect curves for urinary Na⁺/K⁺. Data were expressed as free concentration normalized to in vitro IC50 (0.75 nM for PF-03882845 and 109 nM for eplerenone in a serum free assay). Data were modeled using an indirect response model. Dashed lines indicate the 95% lower and upper confidence boundary limits.