Pentoxifylline in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the most frequent cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD) in the U.S. and in U.S. Veterans. Control of blood pressure and reduction in proteinuria, for instance by blockade of the renin-angiotensin-aldosterone system (RAAS) with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin-receptors blockers (ARBs), have led to some improvement in outcomes in recent years. However, many patients continue to progress to ESRD, requiring costly dialysis or transplantation and resulting in high mortality. Patients with ESRD on maintenance dialysis also have markedly impaired quality of life. Thus, novel treatments are needed for this disease.

The non-specific phosphodiesterase inhibitor pentoxifylline (PTX) was approved by the FDA in 1984 for the treatment of peripheral vascular disease. Therefore, this drug has been in clinical use for over 3 decades and has been found to have an excellent safety profile. Recent experimental and clinical data suggest that PTX, when added to usual care in patients with DKD, leads to a reduction in albuminuria and reduced inflammation, as evidenced by lower levels of inflammatory cytokines, and may decrease progression of renal disease. The available evidence thus suggests the possibility of the use of PTX as a valuable repurposing of an old drug in the treatment of DKD. However, a large scale multicenter randomized clinical trial is needed to determine whether this agent can reduce hard endpoints such as ESRD and death in patients with DKD.

The objective of this study is to test the hypothesis that PTX, when added to usual care, leads to a reduction in the incidence of ESRD and mortality in type-2 diabetic patients with DKD when compared to usual care plus placebo.

The primary endpoint will be time to ESRD or death. ESRD will be defined as need for chronic dialysis or renal transplantation.

Secondary efficacy endpoints will be: (1) quality of life as measured by the Kidney Disease Quality of Life Short Form (KDQoL-SF), (2) time until doubling of serum creatinine, (3) hospitalization for congestive heart failure (CHF), (4) a three-point MACE (cardiovascular death, non-fatal myocardial infarction, non-fatal stroke), (5) peripheral vascular disease (PVD), (6) percentage of participants with 50% reduction in UACR from baseline, (7) Rate of change in eGFR per year during the study period. Safety (serious adverse events and adverse events possibly or probably related to study drug, discontinuation of study drug) will also be analyzed as a secondary safety outcome.

The design will be simple with only 2 face-to-face visits (randomization and end of trial visits). The remaining quarterly contacts can be conducted by telephone collecting minimal targeted information. Laboratory testing specifically for the study will be done only at randomization, at 6 months and the end of the study, if needed. However, coordinators will assure that a serum creatinine will have been measured every 6 months as part of routine clinical care or, in rare instances where one has not been done, obtain this measurement. Other than randomization to PTX or matched placebo, patient care will be handled by usual providers according to recommended standards of care.

There will be a one-year ramp-up phase which will include 6 VA hospitals. The purpose of the ramp-up phase will be to optimize procedures prior to widespread implementation, including assessing the recruitment rate to determine whether the expected rate can be achieved and assessing the efficacy of central distribution of study drug/placebo.

In addition, the investigators will refine methods of recruitment, demonstrate that the proposed follow-up methods are working as intended, and address unforeseen problems. This will be followed by the full study at 40 sites (which includes the 6 ramp-up sites) and will involve 3 years of recruitment and 5 years of follow-up.

Sample size calculation, assuming a 26.6% event rate in the control group and 21.6% event rate in PTX group (corresponding to a 19% relative reduction), two-sided alpha = 0.05, 85% power, a 3-year enrollment period, a minimum 5-year follow-up period, and one proposed interim analysis indicates that 2510 participants will need to be randomized.

If this study is successful and PTX is found to reduce the incidence of ESRD and/or death, this will reduce the personal and financial burden of renal replacement therapy (dialysis/transplantation) for Veterans with diabetic kidney disease