Inhibition of in vivo neutrophil transmigration by a novel humanized anti-CD11/CD18 monoclonal antibody

Giving monoclonal antibodies to healthy volunteers in phase 1 trials: is it safe?

Many monoclonal antibodies (MAbs) have been studied in healthy volunteers in phase 1, but few data have been published on the safety of that practice. We aimed to review the available data, and thereby to estimate the risks of participation in phase 1trials of MAbs. We searched PubMed, the ClinicalTrials.gov database and Google, using the search terms 'monoclonal antibody', 'phase 1' and 'healthy volunteers'. We identified 70 completed trials of MAbs in healthy volunteers, but the published data were too sparse to allow confident assessment of the risks of MAbs in healthy volunteers. Our best estimate of risk of a life-threatening adverse event was between 1: 425 and 1: 1700 volunteer-trials, but all such events occurred in a single trial (of TGN1412). In a phase 1trial of a small molecule, the risk of death or a life-threatening adverse event appears to be 1: 100,000-1,000,000 volunteer-trials, which is similar to the risk of many ordinary daily activities. Most people would consider that level of risk to be 'minimal' or 'negligible' and, therefore, acceptable. On that basis, the safety record of MAbs in healthy volunteers has been ruined by the TGN1412 disaster. However, that experience is unlikely to be repeated, because of improvements in governance and practice of phase 1trials. If the experience of TGN1412 is disregarded, it seems reasonable to continue using healthy volunteers in phase 1trials of MAbs, provided that there are scientific and medical reasons to conclude that the risk is truly minimal.

Prevention of vasospasm by anti-CD11/CD18 monoclonal antibody therapy following subarachnoid hemorrhage in rabbits

OBJECT

Adhesion of leukocytes and their migration into the periadventitial space may be critical in the pathophysiology of vasospasm following subarachnoid hemorrhage (SAH). The cell adhesion molecules involved in this process are lymphocyte function-associated antigen-1 (CD11a/CD18) and macrophage antigen-1 (CD11b/CD18), which are present on neutrophils/macrophages, and intercellular adhesion molecule-1 (CD54), which is present in endothelial cells. A humanized monoclonal antibody (mAb), Hu23F2G, targets CD11/CD18 and prevents leukocyte adhesion to endothelial cells. In this study, systemic administration of Hu23F2G prevented vasospasm in the rabbit model of SAH.

METHODS

Twenty-six New Zealand White rabbits were injected with autologous blood into the cisterna magna to induce SAH, after which they were randomized to receive injections of either Hu23F2G (10 animals) or a placebo at 30 minutes and 24 and 48 hours after SAH (six animals). Control animals underwent sham operations (four animals) or SAH alone (six animals). The animals were killed 72 hours after SAH, their bodies perfused and fixed, and their basilar arteries processed for morphometric analysis. Peripheral white blood cells (WBCs) were counted at 72 hours. The percentages of lumen patency were compared using the Student t-test. The presence of neutrophils and macrophages was confirmed by immunohistochemical analysis in which a rat anti-rabbit anti-CD18 mAb and cresyl violet were used. Treatment with Hu23F2G resulted in the significant prevention of vasospasm. Animals treated with Hu23F2G had 90 +/- 7% lumen patency compared with 65 +/- 7% in the placebo group (p = 0.025). The percentage of lumen patency in the SAH-only group was 59 +/- 10%. The mean WBC count was 16,300 +/- 2710/microl in the treatment group, compared with 7000 +/- 386/microl in the control group (p = 0.02). Administration of Hu23F2G produced increased numbers of WBCs in 70% of the animals treated.

CONCLUSIONS

This study supports the concept that leukocyte-endothelial cell interactions play an important role in the pathophysiology of chronic vasospasm after SAH. Systemic therapy with an anti-CD11/CD18 mAb prevents vasospasm after SAH by inhibiting adhesion of neutrophils and macrophages and their migration into the periadventitial space.

UK-279,276, a neutrophil inhibitory glycoprotein, in acute stroke: tolerability and pharmacokinetics

BACKGROUND AND PURPOSE

UK-279,276, a recombinant glycoprotein, binds selectively to the CD11b/CD18 integrin on neutrophils and has the potential to modulate the neuroinflammation associated with acute stroke. After preclinical evidence of neuroprotection, UK-279,276 has entered clinical development. The purposes of this study were to evaluate the safety and tolerability of UK-279,276 and to examine its pharmacokinetics and pharmacodynamics (binding to neutrophil CD11b) in patients with acute stroke.

METHODS

This was a multicenter, double-blind, dose-escalation study in 176 patients randomized to a single intravenous dose of UK-279,276 (6 cohorts: 0.06, 0.1, 0.2, 0.5, 1.0, 1.5 mg/kg) or placebo (3:1 randomization within each cohort) within 12 hours of stroke onset.

RESULTS

Age and stroke severity were well balanced across groups, with a mean age of 70 years (range, 39 to 92 years) and moderate baseline stroke severity (mean Scandinavian Stroke Scale score, 36.5 to 43.2; mean National Institutes of Health Stroke Scale score, 6.3 to 8.5). UK-279,276 was well tolerated at doses up to 1.5 mg/kg. There was no evidence of a relationship between dose of UK-279,276 and adverse events or clinical chemistry or hematology laboratory tests, or of an increased incidence of infection-related adverse events with the study drug. A dose-dependent UK-279,276-specific IgG antibody response was observed in patients treated with the 1.0- and 1.5-mg/kg doses. UK-279,276 displayed nonlinear pharmacokinetics across the dose range investigated. The duration of CD11b saturation was dose dependent, with >80% saturation achieved for at least 7 days after treatment with UK-279,276 1.0 and 1.5 mg/kg.

CONCLUSIONS

UK-279,276 was well tolerated in acute stroke patients at single doses up to 1.5 mg/kg. Further clinical investigation of UK-279,276 is ongoing.

Therapeutic potential of monoclonal antibodies in myocardial reperfusion injury

While reperfusion therapy in myocardial infarction is associated with better short- and long-term outcomes, it paradoxically results in reperfusion injury mediated by interactions between leukocytes, endothelial cells, platelets, and the myocardium. Several surface receptors, adhesion molecules, and ligands have been shown to be important in the pathogenesis of myocardial reperfusion injury, and therapeutic strategies employing the use of monoclonal antibodies have been attempted against many of them. These have included monoclonal antibodies against activated complement 5 (C5a) to inhibit leukotaxis, monoclonal antibodies against P-selectin, P-selectin glycoprotein ligand (PSGL)-1, L-selectin and E-selectin to inhibit leukocyte rolling, and monoclonal antibodies against the Mac-1 (CD11b/CD18) receptor and intercellular adhesion molecule (ICAM)-1 to block firm adhesion of leukocytes to endothelial cells. In addition, although initially developed as an antiplatelet agent, the glycoprotein IIb/IIIa receptor antagonist abciximab shows significant ability to diminish or prevent reperfusion injury, presumably through its ability to block the Mac-1 receptor on leukocytes. Finally, monoclonal antibodies have also been tested against several cytokines and adhesion molecules implicated in so-called subacute endothelial activation, including interleukin-8 and vascular cell adhesion molecule (VCAM)-1. Studies in animals evaluating the use of monoclonal antibodies in reperfusion injury against various potential targets have largely been successful; however, studies in humans have been disappointing, underscoring the pitfalls of using animal models for the study of complex diseases. Based upon current knowledge, it is becoming clear that a successful strategy against reperfusion injury will require targeting several pathways at once, rather than attempting to block one final common pathway. In addition, inhibition of subacute endothelial activation through inhibition of transcription factors, namely nuclear factor (NF)-kappa B, may be a prerequisite to significantly reducing the extent of myocardial damage in this condition. The future of monoclonal antibodies in the overall strategy remains unclear. Newer small molecule inhibitors are also under development, and the eventual role of gene therapy remains to be elucidated.