Fingolimod for the Abrogation of Interstitial Fibrosis and Tubular Atrophy Following Kidney Transplantation

Prevention of, or slowing the progression of, the development of allograft fibrosis has not been successful in previous efforts. This study will to evaluate the potential of fingolimod (Gilenya®, Novartis Pharmaceuticals, East Hanover, NJ) (1), a sphingosine 1-phosphate receptor modulator and a RhoA inhibitor (2), to abrogate the presence of interstitial fibrosis/tubular atrophy (IF/TA) after kidney transplantation. The study may provide important information for future clinical trials for prevention of IF/TA in kidney transplant recipients.

Interstitial fibrosis and tubular atrophy almost invariably occur together (10) and are present in approximately 45% of kidney allografts by the first year posttransplant (11). Naesens et al (11) demonstrated that any positive chronic interstitial fibrosis score is associated with graft loss after the first year post transplant with a more rapidly declining slope than those without interstitial fibrosis. Furthermore, they demonstrated that a tubular atrophy score of 2-3 was associated with 20% graft loss during the 2nd year posttransplant, >30% graft loss by 5 years and ~60% graft loss by 10 years posttransplant. Combined, IF/TA contributes to renal graft dysfunction or the decline in kidney function after transplantation and may be a factor in the 20.6% of total grafts lost (including death) by 5 years post-transplant (11,12).

Expansion of the interstitial compartment is a major component of IF/TA. Protocol (12,13) and for-cause (10,11) biopsies have provided evidence of the worsening of IF/TA with time in kidney transplant recipients and demonstrated a direct relationship between interstitial expansion and renal allograft functional decline and graft failure (11-14). Assessing the interstitial expansion by quantifying the fraction of renal cortical volume:interstitial compartment changes over time standardizes the assessment of IF/TA (15,16) and will be used in the current protocol (Section 10.2.1).

Fingolimod was originally intended as a prophylaxis against acute rejection in transplant recipients (17). A full development program was produced beginning with pharmacokinetics of single dose (18) and multiple doses (19) in healthy volunteers and evaluations of the effect of FTY720 on T-lymphocytes to better understand the immunosuppressive properties of the sphingosine 1-phosphate receptor modulator (20). Development proceeded with several studies where fingolimod was compared to standard immunosuppression regimens as an adjunct therapy with calcineurin inhibitors for prevention of kidney transplant acute rejection. After two cardiac events occurred in an open-label trial and lack of efficacy for prevention of acute rejection was demonstrated, the development of fingolimod as a therapeutic agent for rejection prophylaxis in transplantation ceased. Whereas the current study is not proposed to prevent acute rejection and will be using a smaller dose than those evaluated in phase 3 trials for acute rejection prophylaxis, a summary of these studies is important to the understanding of the safety of fingolimod in kidney transplant recipients.

Studies of de novo kidney transplant recipients report a reduction in absolute lymphocyte counts of approximately 25-35% in the lower dose groups (0.25mg and 0.5mg FTY720, respectively) that corrects to within approximately 20% of baseline (day of transplant surgery) level (22-28). Additionally, asymptomatic bradycardia or reduced heart rate was reported and responded to treatment when required or resolved on its own (23-26,28). Prudent exclusion criteria of patients who have heart rate <50bpm at baseline is warranted for the current study. Macular edema occurred more often in kidney transplant patients taking ≥2.5mg FTY720 (15/667, 2.2%) compared to mycophenolate mofetil (MMF, 5/373, 1.3%; 25,26,28); thus, the current study will exclude patients with a history of macular degeneration or diabetic retinopathy. Only one report indicated that liver enzymes were elevated in participants taking FTY720 (25) and the increase was mild (<2x upper limit of normal [ULN]).

Controlling hypertension and prevention and treatment of acute rejection are standard approaches to kidney function preservation in kidney transplant recipients. Additionally, the use of calcineurin inhibitor (CNI)-sparing protocols has been reported with various approaches but data are insufficient to equivocally demonstrate consistently lower IF/TA in the approaches reported to date (7). Thus, it is important to examine additional approaches for prevention of IF/TA in this population.

Preliminary data from Chen W et al strongly suggests that fingolimod is able to inhibit chronic rejection of transplanted hearts in a rat and mouse model by inhibiting RhoA and down-regulating mammalian target of rapamycin (mTOR) Complex 2 (mTORC2)/Regulatory Associated Protein Of MTOR Complex 1 Independent Companion Of MTOR Complex 2 (RICTOR; 30,31). Therefore, this study will test the hypothesis that abrogating the fibrogenic effects of both RhoA and mTOR pathways with fingolimod would abrogate IF/TA and that reducing this structural damage in transplanted kidneys would result in improved or preserved kidney function and reduced graft loss.

The purpose of this study is to demonstrate that 0.5mg/day of fingolimod for 3 months administered to de novo kidney transplant recipients will be safe and to examine the course of IF/TA over a 1-year period by testing the ability of 0.5mg/day fingolimod for 3 months to abrogate the development of IF/TA in de novo kidney transplant recipients compared to placebo.