Nonclinical safety, pharmacokinetics, and pharmacodynamics of atacicept.

Atacicept, a soluble recombinant fusion protein of the human immunoglobulin (Ig) G(1) Fc and the extracellular domain of the human transmembrane activator and calcium modulator and cyclophylin ligand interactor receptor, acts as an antagonist of both B lymphocyte stimulator and a proliferating-inducing ligand. Here we determined the nonclinical safety, pharmacokinetics and pharmacodynamics of atacicept in mice and cynomolgus monkeys. Subcutaneous atacicept treatment (twice weekly in cynomolgus monkeys, three times weekly in mice) was generally safe and well tolerated safe and well tolerated with dosing up to 10 mg/kg every other day for up to 39 weeks or up to 80 mg/kg when dosed for 4 weeks. At a dose of 1 mg/kg subcutaneous (sc) bioavailability of atacicept in mice and monkeys was 76 and 92%, with a mean serum t(1/2) of 44 and 179 h, respectively. In accord with its anticipated mechanism of action, repeated administration of atacicept decreased serum IgG concentrations up to 50%, IgM concentrations >99%, and circulating mature B-cell concentrations up to 60%. These effects were dose-related but reversible, as determined in a 25-week follow-up period. Microscopically, B cells numbers were reduced in the follicular marginal zone of the spleen and the mantle surrounding germinal centers of the lymph nodes. These data confirm the preclinical safety and the pharmacological activity of atacicept and support its clinical development.

Carcinogenicity study of 217 Hz pulsed 900 MHz electromagnetic fields in Pim1 transgenic mice.

In an 18-month carcinogenicity study, Pim1 transgenic mice were exposed to pulsed 900 MHz (pulse width: 0.577 ms; pulse repetition rate: 217 Hz) radiofrequency (RF) radiation at a whole-body specific absorption rate (SAR) of 0.5, 1.4 or 4.0 W/kg [uncertainty (k = 2): 2.6 dB; lifetime variation (k = 1): 1.2 dB]. A total of 500 mice, 50 per sex per group, were exposed, sham-exposed or used as cage controls. The experiment was an extension of a previously published study in female Pim1 transgenic mice conducted by Repacholi et al. (Radiat. Res. 147, 631-640, 1997) that reported a significant increase in lymphomas after exposure to the same 900 MHz RF signal. Animals were exposed for 1 h/day, 7 days/week in plastic tubes similar to those used in inhalation studies to obtain well-defined uniform exposure. The study was conducted blind. The highest exposure level (4 W/kg) used in this study resulted in organ-averaged SARs that are above the peak spatial SAR limits allowed by the ICNIRP (International Commission on Non-ionizing Radiation Protection) standard for environmental exposures. The whole-body average was about three times greater than the highest average SAR reported in the earlier study by Repacholi et al. The results of this study do not suggest any effect of 217 Hz-pulsed RF-radiation exposure (pulse width: 0.577 ms) on the incidence of tumors at any site, and thus the findings of Repacholi et al. were not confirmed. Overall, the study shows no effect of RF radiation under the conditions used on the incidence of any neoplastic or non-neoplastic lesion, and thus the study does not provide evidence that RF radiation possesses carcinogenic potential.

Interference with heparin binding and oligomerization creates a novel anti-inflammatory strategy targeting the chemokine system.

A hallmark of autoimmunity and other chronic diseases is the overexpression of chemokines resulting in a detrimental local accumulation of proinflammatory immune cells. Chemokines play a pivotal role in cellular recruitment through interactions with both cell surface receptors and glycosaminoglycans (GAGs). Anti-inflammatory strategies aimed at neutralizing the chemokine system have to-date targeted inhibition of the receptor-ligand interaction with receptor antagonists. In this study, we describe a novel strategy to modulate the inflammatory process in vivo through mutation of the essential heparin-binding site of a proinflammatory chemokine, which abrogates the ability of the protein to form higher-order oligomers, but retains receptor activation. Using well-established protocols to induce inflammatory cell recruitment into the peritoneal cavity, bronchoalveolar air spaces, and CNS in mice, this non-GAG binding variant of RANTES/CCL5 designated [44AANA47]-RANTES demonstrated potent inhibitory capacity. Through a combination of techniques in vitro and in vivo, [44AANA47]-RANTES appears to act as a dominant-negative inhibitor for endogenous RANTES, thereby impairing cellular recruitment, not through a mechanism of desensitization. [44AANA47]-RANTES is unable to form higher-order oligomers (necessary for the biological activity of RANTES in vivo) and importantly forms nonfunctional heterodimers with the parent chemokine, RANTES. Therefore, although retaining receptor-binding capacity, altering the GAG-associated interactive site of a proinflammatory chemokine renders it a dominant-negative inhibitor, suggesting a powerful novel approach to generate disease-modifying anti-inflammatory reagents.