Toxicity of OKT3 increases with dosage: a controlled study in renal transplant recipients

Concordance of preclinical and clinical pharmacology and toxicology of therapeutic monoclonal antibodies and fusion proteins: cell surface targets

Monoclonal antibodies (mAbs) and fusion proteins directed towards cell surface targets make an important contribution to the treatment of disease. The purpose of this review was to correlate the clinical and preclinical data on the 15 currently approved mAbs and fusion proteins targeted to the cell surface. The principal sources used to gather data were: the peer reviewed Literature; European Medicines Agency 'Scientific Discussions'; and the US Food and Drug Administration 'Pharmacology/Toxicology Reviews' and package inserts (United States Prescribing Information). Data on the 15 approved biopharmaceuticals were included: abatacept; abciximab; alefacept; alemtuzumab; basiliximab; cetuximab; daclizumab; efalizumab; ipilimumab; muromonab; natalizumab; panitumumab; rituximab; tocilizumab; and trastuzumab. For statistical analysis of concordance, data from these 15 were combined with data on the approved mAbs and fusion proteins directed towards soluble targets. Good concordance with human pharmacodynamics was found for mice receiving surrogates or non-human primates (NHPs) receiving the human pharmaceutical. In contrast, there was poor concordance for human pharmacodynamics in genetically deficient mice and for human adverse effects in all three test systems. No evidence that NHPs have superior predictive value was found.

Treatment of acute kidney allograft rejection with a non-mitogenic CD3 antibody

T3/4.A is a non-mitogenic murine IgA mAb to human CD3 that was selected for clinical studies to provide an alternative for the mitogenic, T cell-activating, therapeutic mAb OKT3. Previously, we reported that T3/4.A is better tolerated in humans than the IgG2a-CD3 mAb T3/4.2a. Here we report the results of a phase II clinical trial to assess the immunosuppressive potential of T3/4.A. Eighteen first kidney transplant recipients with a first rejection episode were included. Baseline immunosuppression consisted of cyclosporin and prednisolone. Rejection treatment consisted of 5 mg mAb per day during 10 days. Fourteen patients responded, of whom four experienced a second rejection within 2 weeks, one experienced chronic rejection after 2.5 years, whereas the others remained rejection-free after treatment (median duration of follow-up 42 months). Four patients did not respond and eventually lost their graft. These results are similar to treatment results with OKT3, as reported in the literature. Following the first dose of T3/4.A, side effects were limited, and reduced compared to OKT3-treated controls. On the second day, 15 patients developed transient vomiting and/or diarrhoea, which coincided with elevated serum levels of proinflammatory cytokines. Minimal or even no side effects occurred during the remaining days, which is in sharp contrast to that seen generally during OKT3 treatment. Both T cell numbers and TCR expression were reduced during the therapy. We conclude that T3/4.A is a good alternative for OKT3 to treat rejection episodes in renal transplant recipients.

OKT3 and IL-2 treatment for purging of the latent HIV-1 reservoir in vivo results in selective long-lasting CD4+ T cell depletion

Activation of resting T cells has been proposed to purge the reservoir of HIV-1-infected resting CD4+ T cells. We therefore treated three HIV-1-infected patients on antiretroviral therapy with OKT3, a CD3 monoclonal antibody, and recombinant human IL-2. Here we report the profound and partially long-lasting host responses induced by the OKT3 and IL-2 treatment. OKT3/IL-2 induced a strong but transient release of plasma cytokines and chemokines. The percentage CD4+ and CD8+ cells in the blood expressing the activation marker CD38 transiently increased to almost 100%, and in lymph nodes we "observed" a 10-fold increase in the number of dividing Ki67+ cells and increased numbers of apoptotic cells. Following OKT3/IL-2 treatment, a long-lasting depletion of CD4+ cells in the peripheral blood and lymph nodes occurred, suggesting the physical deletion of these cells. Increases in CD4+T cell numbers during the two year followup period were due mainly to increased memory cell numbers. CD8+ cells were also depleted in the blood, but less severely in lymph nodes, and returned to baseline levels within several weeks.