Monoclonal antibodies in organ transplantation

Ten Years of Orthoclone OKT3 (Muromonab-CD3): A Review

Many important advances in transplantation have been made during the last decade. The introduction of Orthoclone OKT3 into clinical trials and its subsequent approval by the Food and Drug Administration in 1985 for use as an antirejection agent for renal transplantation were landmarks in the field of clinical transplantation of solid organs. In the decade since the approval of OKT3 for clinical use, much has been learned and written about OKT3. OKT3 now is considered a safe and effective agent for prophylaxis and first-line treatment of acute rejection of solid organ allografts. In this article, the development and use of OKT3 over the last 10 years, as well as the present status and future implications of immune therapy with OKT3, are reviewed.

Risk factors for steroid-resistant T-cell-mediated acute cellular rejection and their effect on kidney graft and patient outcome

OBJECTIVES

Acute rejection in renal transplant is considered a risk factor for short-term and long-term allograft survival. The expected reversal rate for the first acute cellular rejection, by steroid pulse, ranges between 60% and 100%, and lack of improvement within 1 week of treatment is defined as steroid-resistant rejection. This work sought to evaluate factors that lead to steroid-resistant acute cellular rejection among patients with first live-donor renal allotransplant and its effect on graft and patient survival.

MATERIALS AND METHODS

Patients with an improvement in serum creatinine levels were considered controls (group 1; n=100); while the others were considered an early steroid-resistant group (group 2; n=99). Both groups were matched demographically.

RESULTS

Patients with a target cyclosporine level below accepted therapeutic levels were significantly higher in group 2 (P = .02). We found no significant differences between the groups regarding posttransplant complications (P > .05). Mean hospital stay was longer in group 2 (P = .021). Living patients with functioning graft were more prevalent in group 1, while those alive on dialysis were more prevalent in group 2. The groups were comparable regarding long-term patient and graft survival despite significantly lower creatinine values in patients of group 1 at 6 months' follow-up (P ≤ .001).

CONCLUSIONS

Prebiopsy low cyclosporine trough levels and associated chronic changes among patients who were maintained on calcineurin inhibitor-based regimens represented the most-important risk factors for the early steroid-resistant group. Rescue therapies improve short-term graft outcome; however, they did not affect either patient or long-term graft survival after 5 years' follow-up.

Individualized T cell monitored administration of ATG versus OKT3 in steroid-resistant kidney graft rejection

Acute steroid-resistant rejection episodes are recommended to be treated with set doses of anti-thymocyte globulin (ATG) or anti-CD3 monoclonal antibody (OKT3). Individualized T cell monitoring has been proposed as a tool for dose finding. A randomized study comparing the efficacy and safety of ATG (n = 27) with OKT3 (n = 28) in the treatment of biopsy verified acute steroid-resistant rejection (ASRR) when both drugs were administered on the basis of daily individualized T cell measurements. A drop to below 50 cells/mm3 CD2+ T cells was considered adequate and used to guide the dose of ATG/OKT3. Demographic, clinical and histopathological severities of rejections were equal in the two groups. During the 10 days of T cell monitoring and antibody treatment, 13 patients were in need of dialysis (ATG = 7/OKT3 = 6). Two grafts did not respond to antibody treatment and were lost due to rejection (ATG = 1/OKT3 = 1). There were 26 biopsy verified re-rejections (ATG = 12/OKT3 = 14) within the first 3 months following antibody treatment. Mean serum creatinine (micromol/L) was similar in the two groups (ATG/OKT3: before rejection 157 +/- 72/151 +/- 88, at start of antibody treatment 308 +/- 125/330 +/- 94, end of antibody treatment 254 +/- 122/246 +/- 144 and at follow-up after a mean of 32 months 166 +/- 55 (n = 24)/164 +/- 57(n = 23)). To keep the T cell count below 50 cells/mm3, average dose ATG given was 354 +/- 151 mg (2.3 administrations, range 1-4) and average OKT3 was 32.5 +/- 6.8 mg in 10 doses. In conclusion, individualized T cell monitored administration of ATG and OKT3 is safe and seems as effective as a standard set dose in treatment of ASRR. Tailoring the dose for each individual patient lowers the cost.

Immunosuppression in older renal transplant patients

Renal transplantation procedures in patients older than 60 years of age have clearly improved in recent years. In the cyclosporin era, graft and patient survival are good. However, older patients exhibit a higher mortality, especially from infectious and cardiovascular causes, than young patients. In this article we review the immunosuppressive treatment in older patients, analyse what drugs can be used and finally propose several immunosuppressive combinations to treat this group of patients. Currently, new immunosuppressive drugs enable more flexible immunosuppressive protocols. Nevertheless, to avoid overimmunosuppression, elderly patients should be treated with lower doses and fewer immunosuppressive drugs.

Gastrointestinal complications of immunosuppression

The gastrointestinal manifestations of drug-induced immunosuppression may result from direct drug effects, from infectious complications, or both. Graft-versus-host disease (GVHD) is a third mechanism whereby immunosuppressive agents are linked with gastrointestinal injury. This article reviews individual immuno-suppressive medications, first concentrating on their reported gastrointestinal side effects, then reviewing other gastrointestinal phenomena, which may represent side effects of immunosuppressive agents but have not been reported yet.

Clinical application of immunosuppressive agents in renal transplantation

The availability of a number of new immunosuppressive drugs has resulted in significant improvements in the outcome of kidney transplantation. Currently 1-year graft survival rate for cadaver kidney transplants is approximately 85%. A number of new agents are presently in clinical studies. This article reviews the currently available agents and examines various aspects of induction and maintenance immunosuppressive therapy, and the treatment of acute rejection episodes. In addition, the agents currently in clinical trials and future directions in immunosuppressive therapy are discussed.

An update on new immunosuppressive drugs undergoing preclinical and clinical trials: potential applications in organ transplantation

Recent advances in immunobiology and immunopharmacology have led to a better understanding of the actions of immunosuppressive drugs. Over the past 2 years, a number of new agents have been approved for use in solid organ transplant recipients. In addition, new immunosuppressive agents are being tested in preclinical and clinical trials, leading to the promise of an exciting future in organ transplantation. This report reviews the mechanisms of action and the potential future role of these agents in clinical transplantation.

Pharmacology of immunosuppressive medications used in renal diseases and transplantation

As understanding of the molecular basis for the immune response has expanded rapidly, so have the possibilities for designing therapeutic interventions that are more effective, more specific, and safer than current treatment options. The promise of therapeutic advances in the future is based on the rapidly expanding insights into the pathogenesis of abnormal immunologic reactions. Nowhere is the understanding of molecular mechanisms, pathophysiology, and targeted therapy more relevant than in the field of renal transplantation, which makes up much of the clinical database for the use of immunosuppressive therapy for renal disease. Despite the recent advances in basic immunology, clinical validation of new agents and approaches is lacking for most drugs at present. This review will focus in the pharmacology of agents used in the therapy of immunologic renal disease and in renal transplantation. It should be recognized that clinical pharmacology and experience with newer agents is limited, and potential utility is based largely on experimental data.

Ten years of Orthoclone OKT3 (muromonab-CD3): a review

Many important advances in transplantation have been made during the last decade. The introduction of Orthoclone OKT3 into clinical trials and its subsequent approval by the Food and Drug Administration in 1985 for use as an antirejection agent for renal transplantation were landmarks in the field of clinical transplantation of solid organs. In the decade since the approval of OKT3 for clinical use, much has been learned and written about OKT3. OKT3 now is considered a safe and effective agent for prophylaxis and first-line treatment of acute rejection of solid organ allografts. In this article, the development and use of OKT3 over the last 10 years, as well as the present status and future implications of immune therapy with OKT3, are reviewed.

The IgE humoral response in OKT3-treated patients. Incidence and fine specificity

We recently described a case of anaphylaxis occurring at the time of retreatment with OKT3 of a renal allograft recipient in whom, for the first time, high anti-OKT3 IgE levels were documented. This led us to examine a large series of sera from 181 OKT3-treated patients to better define the frequency of IgE sensitization, its fine specificity (anti-isotypic and/or anti-idiotypic) and its relation to the appearance of IgG anti-OKT3 antibodies (Abs). Six patients out of the 181 assayed have developed anti-OKT3 IgE Abs as detected by ELISA. The earliest time of appearance of IgE anti-OKT3 Abs was 10 days after starting OKT3 (range, 10-25). The IgE response peaked by day 18 (range, 11-35) and had usually disappeared at 3 months after treatment. A more careful dissection of the fine specificity of the IgE response revealed that three of the four patients tested had developed an exclusive anti-idiotypic response. In the last patient, an anti-isotypic component was present since anti-OKT3 IgE Abs also reacted with control IgG2a, IgG2b, and IgG3 monoclonal antibodies. Importantly, anti-OKT3 IgE Abs were only detected in heavily sensitized patients also showing high titers of IgG specific Abs by ELISA (> or = 1/1000) as well as "blocking" anti-OKT3 antibodies, as assessed by immunofluorescence. We conclude that (1) exposure to OKT3 may lead to specific IgE sensitization that, however, only appears in about 38% of the patients; (2) IgE Abs mostly appear in patients also showing high levels of conventional IgG anti-OKT3 Abs including the presence of "blocking" anti-idiotypic Abs, and (3) IgE Abs may be directed to both idiotypic and isotypic determinants of the monoclonal antibody.

High-dose glucocorticosteroids increase the procoagulant effects of OKT3

The use of OKT3 as prophylaxis in renal transplantation carries an increased risk of intragraft thrombosis, which is related to the systemic activation of the coagulation system that consistently occurs after the first dose of OKT3. As only a few patients develop thrombosis after OKT3 therapy, we searched for possible additional risk factor by comparing the demographic and clinical parameters of the 13 patients who developed thrombosis in our institution to those of 218 patients who did not. Multivariate analysis showed a relationship between the dose of methylprednisolone (mPDS) given before the first OKT3 injection and the risk of thrombosis: 6 out of 42 patients (14%) who received high (30 mg/kg) mPDS experienced a thrombotic event, as compared to 7 out of the 189 patients (3.7%) who received < or = 8 mg/kg of mPDS (P < 0.01). This led us to study the effects of mPDS on the procoagulant activity induced by OKT3 on peripheral blood mononuclear cells (PBMC) in vitro. The procoagulant activity of unstimulated PBMC (mean +/- SEM: 0.6 +/- 0.1 mU/ml) reached 3.0 +/- 0.7 mU/ml after OKT3 stimulation (P = 0.0062) and further increased to 7.4 +/- 2.0 mU/ml when PBMC were first preincubated overnight with mPDS before OKT3 stimulation (P = 0.018 as compared to OKT3 alone). This process involved the tissue factor/factor VII pathway, as shown by increased membrane expression of tissue factor on monocytes as well as by a marked reduction of the induced procoagulant activity when the clotting assay was performed with factor VII-deficient plasma.(ABSTRACT TRUNCATED AT 250 WORDS)