PF-489791

Diabetic nephropathy (DN) is the leading cause of ESRD worldwide. Reduced bioavailability or uncoupling of nitric oxide in the kidney, leading to decreased intracellular levels of the nitric oxide pathway effector molecule cyclic guanosine monophosphate (cGMP), has been implicated in the progression of DN. Preclinical studies suggest that elevating the cGMP intracellular pool through inhibition of the cGMP-hydrolyzing enzyme phosphodiesterase type 5 (PDE5) might exert renoprotective effects in DN. To test this hypothesis, the novel, highly specific, and long-acting PDE5 inhibitor, PF-00489791, was assessed in a multinational, multicenter, randomized, double-blind, placebo-controlled, parallel group trial of subjects with type 2 diabetes mellitus and overt nephropathy receiving angiotensin converting enzyme inhibitor or angiotensin receptor blocker background therapy. In total, 256 subjects with an eGFR between 25 and 60 ml/min per 1.73 m2 and macroalbuminuria defined by a urinary albumin-to-creatinine ratio >300 mg/g, were randomly assigned 3:1, respectively, to receive PF-00489791 (20 mg) or placebo orally, once daily for 12 weeks. Using the predefined primary assessment of efficacy (Bayesian analysis with informative prior), we observed a significant reduction in urinary albumin-to-creatinine ratio of 15.7% (ratio 0.843; 95% credible interval 0.73 to 0.98) in response to the 12-week treatment with PF-00489791 compared with placebo. PF-00489791 was safe and generally well tolerated in this patient population. Most common adverse events were mild in severity and included headache and upper gastrointestinal events. In conclusion, the safety and efficacy profile of PDE5 inhibitor PF-00489791 supports further investigation as a novel therapy to improve renal outcomes in DN.

Chronic kidney disease (CKD) represents a worldwide health problem. Traditionally, the nephroprotective treatment for CKD aims to slow progression to end-stage renal disease and includes dietary protein restriction, correction of metabolic acidosis, and renin-angiotensin system blockers. However, current standard therapeutic options may not be enough for preventing CKD progression in a subset of patients making necessary to develop novel therapeutic options to further slow renal function loss. Phosphodiesterase type 5 (PDE5) inhibitors represent a class of drugs traditionally used to treat erectile dysfunction and pulmonary hypertension. However, recent evidence suggests that PDE5 inhibitors may have additional therapeutic effects, such as cardioprotection and cerebrovascular protection. In the current review, we summarize PDE5 inhibitors' utility in disease states and clinical conditions related to kidney disease such as systemic hypertension and acute and chronic kidney injury and discuss the mechanisms explaining possible kidney protective roles of PDE5 inhibitors. A recently completed phase 2 trials demonstrated that the long-acting PDE5 inhibitor PF-00489791 decreased albuminuria in patients with overt diabetic nephropathy when added on top of renin-angiotensin system blockade.