Abstract
The investigation of interleukin 1beta (IL-1beta) in human inflammatory diseases is hampered by the fact that it is virtually undetectable in human plasma. We demonstrate that by administering the anti-human IL-1beta antibody canakinumab (ACZ885) to humans, the resulting formation of IL-1beta-antibody complexes allowed the detection of in vivo-produced IL-1beta. A two-compartment mathematical model was generated that predicted a constitutive production rate of 6 ng/d IL-1beta in healthy subjects. In contrast, patients with cryopyrin-associated periodic syndromes (CAPS), a rare monogenetic disease driven by uncontrolled caspase-1 activity and IL-1 production, produced a mean of 31 ng/d. Treatment with canakinumab not only induced long-lasting complete clinical response but also reduced the production rate of IL-1beta to normal levels within 8 wk of treatment, suggesting that IL-1beta production in these patients was mainly IL-1beta driven. The model further indicated that IL-1beta is the only cytokine driving disease severity and duration of response to canakinumab. A correction for natural IL-1 antagonists was not required to fit the data. Together, the study allowed new insights into the production and regulation of IL-1beta in man. It also indicated that CAPS is entirely mediated by IL-1beta and that canakinumab treatment restores physiological IL-1beta production.