Phase I study of NKT-01

Prolonged treatment of refractory Wegener's granulomatosis with 15-deoxyspergualin: an open study in seven patients

BACKGROUND

A subset of patients with Wegener's granulomatosis does not respond to daily oral cyclophosphamide (CYC) plus corticosteroids or suffers from intolerable side effects. A 6 month course of the immunosuppressant 15-deoxyspergualin (DSG) has previously been employed successfully in these refractory cases. However, there are no reports on long-term treatment with DSG.

METHODS

To document the effects of prolonged DSG treatment, this study reports on seven patients suffering refractory Wegener's granulomatosis, who were successfully treated with DSG over an average of 26.5 months (range: 11-55.5 months).

RESULTS

Before administration of DSG, patients had experienced an average of 6.6 relapses (range: 3-12) under an average of 5.4 (range: 2-11) different therapeutic approaches, which included CYC in all cases. All suffered active disease when DSG was initiated. Four were unresponsive to CYC and three did not tolerate it. DSG (0.5 mg/kg/day subcutaneous) was given for 2-3 weeks until the leukocyte count dropped to 3000/microl, followed by a rest until a leukocyte count of 4000/microl was reached again. No other immunosuppressants besides corticosteroids were given. All patients showed a long-lasting, favourable response to DSG with complete (n = 5) or partial (n = 2) remission. Only one case relapsed while being treated with DSG. Termination/interruption of DSG was followed by relapse in four of five occasions. Resumption of DSG led to complete remission. Currently, five of the seven patients are still treated with DSG and are in remission. Infections, mainly of the respiratory tract, were observed in five cases and resolved after treatment. One case developed a third-degree heart block that required pacing.

CONCLUSIONS

In patients with refractory Wegener's granulomatosis, prolonged treatment with DSG seems safe and successful.

15-Deoxyspergualin in patients with refractory ANCA-associated systemic vasculitis: a six-month open-label trial to evaluate safety and efficacy

The combination of cyclophosphamide (CYC) and oral corticosteroids is effective in the majority of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AASV), but it carries substantial risk of drug-related morbidity and mortality. New regimens are desired, especially in refractory cases. The immunosuppressant 15-deoxyspergualin (DSG) is effective in experimental autoimmune disease and transplantation as well as in acute kidney transplant rejection in humans. To assess the efficacy and safety of DSG, an open label multicenter trial was conducted in patients with AASV who were either unresponsive or had contraindications for standard immunosuppressants. Included were 19 cases of Wegener granulomatosis and one case of microscopic polyangiitis. Nine of them had received CYC shortly before study entry without apparent therapeutic success. DSG (0.5 mg/kg per d) was given for 2 to 3 wk until the WBC count dropped to 3000/ micro l followed by a rest until at least a WBC of 4000/ micro l was reached again. This was repeated up to six cycles. During the study, no other immunosuppressants besides steroids were allowed. Disease improvement during treatment with DSG was achieved in 70% of cases (six cases of complete remission; eight cases of partial remission). Leucopenia occurred in each patient in a regular pattern during the cycles and was transient without exception. No mortality or septicemia was observed. Mild to moderate infections mainly in the respiratory tract were observed but resolved under adequate treatment without sequel. It is concluded that treatment with DSG is successful in patients with refractory Wegener granulomatosis under careful monitoring of WBC count.

Tresperimus: a new agent for transplant tolerance induction

Tresperimus is a novel agent that induces allogeneic transplant tolerance. It is structurally related to deoxyspergualin (DSG) but has been modified to resist rapid hydrolysis in aqueous solution, which simplifies administration. Despite this modification, tresperimus's actions in experimental models seem almost identical to DSG. Initially, DSG was developed as an antitumour agent. Its antitumour efficacy appears limited but DSG and tresperimus have favourable effects on transplant rejection. A short course of tresperimus has been shown to have similar or greater quantitative effects to cyclosporin in bone marrow, cardiac and skin transplant models. However, qualitatively the effects are different. Prevention of rejection is due to induction of donor-specific tolerance without affecting immunity to third party antigens. In addition, CD4+ T-cells from tresperimus-treated animals can transfer donor specific tolerance to naïve animals, an effect not seen with cyclosporin or other traditional immunosuppressive drugs. The mechanism by which tolerance is induced is not clear. Tresperimus (like DSG) binds to Hsc70, which among other effects inhibits nuclear localisation of NF-kappa B. NF-kappa B nuclear localisation is induced by CD40 ligation in antigen-presenting cells, an important early step in T-cell co-stimulation. NF-kappa B is also required for CD28 ligation signalling, important in late co-stimulation. It also is involved in B-cell activation, via CD40 ligation and kappa light chain production. Hsc70 is also required for efficient cytosolic peptide chaperoning to MHC class I molecules. Presumably, it is disruption of T-cell/dendritic cell interaction that leads to induction of T-cell anergy. Tresperimus is well-tolerated. The main dose limiting side effects are orthostatic hypotension and peri-oral numbness. These effects are dependant on blood drug levels and, due to its short half-life, correspond to the rate of infusion. Phase II/III clinical studies are accruing patients and results have not yet been reported. Tresperimus shows promise in the move from immunosuppression to tolerance induction as the way to prevent transplant rejection and graft versus host disease (G v HD). However, its role in tolerance induction and effect in combination with other tolerance inducing agents e.g., CTLA-4-Ig and anti-CD40L antibodies remains unclear.

Pharmacokinetics and pharmacodynamics of 15-deoxyspergualin in a canine renal allograft model of local immunosuppression

Local immunosuppression is based on the rationale that one can simultaneously prevent rejection and reduce systemic side effects by administering appropriately chosen immunosuppressive agents directly into the allograft. We utilized a mongrel canine renal transplant model with a programmable, implantable pump/catheter system to estimate the first-pass extraction of 15-deoxyspergualin (DSG) during renal artery infusion and to compare the efficacy and toxicity of continuous intraarterial (ia) versus intravenous (iv) DSG delivery. Six autotransplanted dogs were given DSG by both iv bolus (1 mg/kg) and ia infusion (1.0 mg/kg/d). DSG was administered to allograft recipients by continuous ia infusion at 0.5 (n = 11) and 0.75 (n = 8) mg/kg/day and by continuous iv infusion at 0.5 (n = 12) and 0.75 (n = 6) mg/kg/day. Mean +/- SD elimination half-life was 0.6 +/- 0.1 hr, and the transplanted kidney removed as much as 55-88% (mean 66%) of locally infused DSG. When compared with untreated controls [mean survival time (MST) = 8 days], low-dose (0. 5 mg/kg/day) DSG produced a significant antirejection effect when given ia (MST = 12 days; P = 0.04) but not iv (MST = 9 days; P = 0. 09), with equivalent overall mean drug levels during normal renal function. However, two of the four longest-surviving animals in the ia group died from severe systemic toxicity, manifested by anorexia, diarrhea, leukopenia, and sepsis. High-dose (0.75 mg/kg/day) DSG significantly prolonged survival via both local (MST = 12 days; P = 0.04) and systemic (MST = 11 days; P = 0.02) routes, but half of the iv-treated dogs died from, and four of the longer-surviving ia-treated animals manifested signs of, systemic toxicity, with significantly higher mean drug levels in the iv group. DSG significantly suppressed vascular rejection at both doses when administered locally and systemically, dose-dependently affected the severity of tubulointerstitial rejection and graft edema, and was not nephrotoxic. Our autotransplant pharmacokinetic data overestimated the allografted kidney's ability to extract DSG during local infusion of slightly lower, but immunosuppressive, doses, so that death from systemic toxicity was not prevented and a direct survival benefit of ia vs iv therapy was not realized. Local DSG administration might be combined with other immunosuppressants to therapeutic advantage.