Preliminary results of [99mTc]OKT3 scintigraphy to evaluate acute rejection in renal transplants

Allograft rejection can be classified as humoral or cellular mechanisms. Accurate diagnosis of acute rejection remains a formidable challenge in renal transplantation. The need to avoid unnecessary immunosuppressive therapy to treat this complication has led to a continued search for improved diagnostic methods to evaluate and identify postoperative episodes. Here we evaluated the use of [(99m)Tc]OKT3 scintigraphy to diagnose acute rejection in renal transplants. Among 22 patients undergoing renal transplant, we observed an increased [(99m)Tc]OKT3 kidney uptake with the passage of time in patients with rejecting allografts. These findings agreed with those of biopsies. We suggest the [(99m)Tc]OKT3 scans may be useful for the monitoring of renal transplants to detect acute rejection.

[The preparation and study on hepatic targeting tendency of galactosyl-anti-CD3-McAb in mice]

OBJECTIVE

This study sought to reduce the recurrence rate of primary liver cacer (PLC) after hepatectomy by increasing the concentration of infiltrating lymphocytes(TILs) at the target organ.

METHODS

It has been reported that galactosyl-anti-CD3-McAb has an obvious hepatic targeting tendency in vitro. On the basis of that work, the present authors conducted a study in mice. Galactosyl-anti-CD3-McAb was prepared and its carbohydrate density was measured with the phenol-sulphyric acid method, and then anti-CD3-McAb (labeled with 125I) and galactosyl-anti-CD3-McAb (labeled with 131I) were infused respectively via the peripheral vein and the radioactivity in each organ was measured.

RESULTS

The carbohydrate density of galactosyl-anti-CD3-McAb in this experiment was 58.12, which effectively guaranteed the specific binding between galactosyl-anti-CD3-McAb and hepatic binding protein(HBP). It was also noticed that anti-CD3-McAb tended to aggregate in the lungs while being infused via the peripheral vein, and that galactosyl-anti-CD3-McAb had an obvious hepatic targeting tendency in vivo and it stayed in liver for quite a long period.

CONCLUSIONS

Galactosyl-anti-CD3-McAb has an obvious hepatic targeting tendency in vivo while being infused through peripheral vein; this may be due to the specific binding between galactose and HBP.

Tacrolimus: a superior agent to OKT3 for treating cases of persistent rejection after intrathoracic transplantation

Acute myocardial rejection refractory to treatment still contributes significantly to patient death after intrathoracic transplantation. A historical series of 25 patients who received OKT3 (5 mg/day for 10 days) was compared with our current experience with 14 patients treated with tacrolimus (0.1 mg/kg/day targeting whole blood concentrations of 13 to 18 ng/ml): all 39 patients having persistent rejection unresponsive to treatment at the time of conversion. Mean periods of follow-up were 842.9 days and 342.6 days, respectively. Actuarial 1-year patient survival rates were 64.0% and 76.2% for the OKT3 and tacrolimus treatment groups, with most of the deaths in the OKT3 group occurring early (p = 0.064). Causes of death for patients receiving OKT3 included acute rejection (n = 5), infection (n = 3), carcinoma (n = 2), multiorgan failure (n = 1) and graft vessel disease (n = 1). The two deaths in the tacrolimus treatment group were the result of infections. Eighty percent of patients treated with OKT3 subsequently experienced further rejection episodes, in many cases necessitating methotrexate therapy. In contrast, only one patient (7.1%) from the tacrolimus group was diagnosed with rejection after conversion (p < 0.001). In conclusion, when compared with OKT3 therapy, a switch in baseline immunosuppression from cyclosporine to tacrolimus seems to be markedly more effective, as well as being safe for the treatment of persistent acute rejection.

Muromonab CD3: a reappraisal of its pharmacology and use as prophylaxis of solid organ transplant rejection

The murine monoclonal antibody muromonab CD3 (OKT3) is directed against the CD3 antigen on peripheral human T cells and effectively blocks all T cell function. Prophylaxis with muromonab CD3 (5mg intravenously once daily for 10 to 14 days) as induction therapy together with corticosteroids, azathioprine and delayed cyclosporin (sequential therapy) optimises early graft function by delaying the potentially nephrotoxic and hepatotoxic effects of cyclosporin until graft function is established. Although clinical data are limited (by inconsistencies in trial design and trial size), prophylactic muromonab CD3-based sequential therapy is significantly more effective than standard triple therapy in the prophylaxis of allograft rejection in renal and hepatic, but not cardiac, transplant recipients. Benefits are particularly notable in patients with delayed graft function. No significant between-treatment differences in patient survival have been observed. The overall efficacy of muromonab CD3- and polyclonal-based prophylactic regimens appears to be similar, although results vary between investigators and confirmation is needed. An anti-interleukin-2 monoclonal antibody-based prophylactic regimen improved graft and patient survival compared with muromonab CD3-based prophylaxis in hepatic transplant recipients. Antimuromonab CD3 antibodies may develop; however, muromonab CD3 may be successfully reused in patients with low titres. Preliminary pharmacoeconomic data suggest that mean drug costs are greater with quadruple immunosuppressive regimens containing muromonab CD3, antithymocyte globulin (ATG) or antilymphocyte globulin (ALG) than with triple therapy. Drug costs with prophylactic muromonab CD3-based regimens were similar or greater than those with polyclonal-based protocols. The first doses of muromonab CD3 are associated with the 'cytokine-release syndrome'. More severe first-dose events include aseptic meningitis, intragraft thromboses, seizures and potentially fatal pulmonary oedema. The incidence and/or severity of cytomegalovirus infection with prophylactic muromonab CD3 based immunosuppression is similar to or greater than that with triple therapy and ATG- or ALG-based regimens. However, the risk of infection and also the observed increase in lymphoproliferative disorders appears to be related to the degree of immunosuppression rather than to the drug itself Thus, sequential muromonab CD3-based therapy is more effective than standard triple therapy (in renal and hepatic transplant recipients) and appears to be similar to that of polyclonal-based regimens in the prophylaxis of transplant rejection. Although the routine use of prophylactic muromonab CD3 in low-risk patients with primary graft function does not appear to be justified, prophylactic muromonab CD3-based therapy has a role in patients at high risk of rejection.

Clinical and immunological effects of treatment with murine anti-CD3 monoclonal antibody along with interleukin 2 in patients with cancer

Anti-CD3 mAb and interleukin 2 (IL-2) were used in a Phase I study to treat 29 patients with cancer. The anti-CD3 was given as an i.v. bolus infusion over 10 min followed by two i.v. 96-h continuous infusions of IL-2 at 3 x 10(6) units/m2/day with a 3-day rest between the IL-2 infusions. Four patients were treated with 6, 18, 60, and 300 microgram/m2 anti-CD3. One patient received 3000 microgram/m2 anti-CD3. This patient developed profound hypotension and the IL-2 infusions were delayed for 2 weeks. Two patients were treated at an intermediate dose of 600 microgram/m2. These patients developed dose-limiting toxicities including hypotension, dyspnea and increased blood urea nitrogen, creatinine, and bilirubin. They were unable to complete their first course of therapy. In an effort to achieve a dose of anti-CD3 which would activate T cells in vivo, pentoxifylline was given to blunt the toxicities seen with anti-CD3 thought to be due predominantly to the cytokine syndrome and tumor necrosis factor release. Four patients received p.o. pentoxifylline to cover an anti-CD3 dose of 600 microgram/m2. The IL-2 infusion was initiated 1 week after the mAb. While there was an anti-CD3 dose-dependent increase in serum tumor necrosis factor level 1 h after mAb infusion, pentoxifylline did not reduce the serum tumor necrosis factor level. There was also an anti-CD3 dose-dependent increase in the serum soluble IL-2 receptor levels. Other immune parameters monitored, including in vitro cytotoxic and proliferative responses and lymphocyte count, were similar to treatment courses with IL-2 alone. Fourteen of 26 patients examined developed human anti-murine antibodies following a single dose of anti-CD3. There were no objective antitumor responses. We conclude that in vivo treatment with anti-CD3 did not enhance T cell activity or expansion with subsequent IL-2 infusion and that the combination of anti-CD3 followed by IL-2 did not improve upon the antitumor activity previously seen with IL-2 alone.

Tumor localization and therapeutic potential of an antitumor-anti-CD3 heteroconjugate antibody in human renal cell carcinoma xenograft models

A heteroconjugate (HC) antibody, constructed with the monoclonal antibody (MoAB) Dal K29 to human renal cell carcinoma (RCC) and an anti-CD3 MoAb, could induce a very high level of lysis of human RCC cells when incubated with human peripheral blood lymphocytes (PBL) in vitro (Kerr et al., 1990, J. Immunol., 144, 4060-4067). We now report that this HC antibody selectively localizes in RCC xenografts in nude mice and could inhibit RCC in an ascites tumor xenograft model when administered intraperitoneally together with PBL.