Initial experience with FK506 (tacrolimus) in pediatric renal transplant recipients

The efficacy and safety of the new immunosuppressant agent, FK506 (tacrolimus), was assessed in pediatric renal transplant recipients over a mean 12-month follow-up period.

Twenty pediatric renal transplant recipients received oral FK506 therapy (0.3 mg/kg/d) in combination with azathioprine (1 to 2 mg/kg/d) and low-dose prednisone as primary therapy (n = 11) or were converted from cyclosporine-based therapy (n = 9) for complications including cyclosporine toxicity (n = 2), acute refractory rejection (n = 4), and chronic rejection (n = 3). Patients were then followed-up prospectively to evaluate effectiveness of therapy and complications.

In the primary treatment group, 45% of patients had one or more rejection episodes. Two required OKT3 therapy (18%) for persistent rejection, with one (9%) graft loss at 3 months. All other episodes were treated effectively with FK506 dose adjustment and steroid pulses. Patient and graft survival was 100% and 91%, respectively, at 12 months mean follow-up. In the FK506 conversion group, two teenage girls with intractable acne and hirsutism were converted with complete resolution and no change in renal function. Four patients were converted for acute rejection: two who did not respond to steroid pulse and two who did not respond to both steroids and OKT3. All four grafts were salvaged (mean follow-up, 12 months; mean Creatinine [Cr], 1.1). Three patients were converted for biopsy-proven chronic rejection at 3, 10, and 12 years after transplant (mean Cr, 2.4) with two of three of patients stable with functioning grafts at 1 year after conversion. Complications of FK506 therapy included temporary insulin-dependent diabetes mellitus (10%), neurological complications (25%), renal toxicity (15%), and hypertension (85%). There were no cases of gastrointestinal toxicity, hepatic dysfunction, lymphoproliferative disorders, or life threatening viral infection. All symptoms of toxicity responded to dose adjustment. No patient required conversion from FK506 to other agents.

This early experience indicates that FK506 in combination with low-dose steroids and azathioprine appears to provide safe and effective immunosuppression in the pediatric age group as a primary agent and may salvage grafts in patients with refractory steroid and OKT3 resistant rejection. Graft and patient survival is comparable to that seen with conventional cyclosporine-based immunosuppression.