Complement C3d/C4d Deposition on Platelets Correlates with 2'-O-Methoxyethyl Antisense Oligonucleotide-Induced Thrombocytopenia in Monkeys.

2'-O-Methoxyethyl antisense oligonucleotide (2'-MOE ASO)-induced severe thrombocytopenia (TCP) [platelet (PLT) count <50 K/µL] was observed in the Asian-sourced cynomolgus monkeys with low incidence (2%-4% at doses >5 mg/kg/week). The potential mechanisms for TCP were studied using the Mauritian-sourced cynomolgus monkeys, which were shown to be more susceptible to ASO-induced TCP, along with the Asian-sourced animals. ISIS 405879, a 2'-MOE ASO, induced severe TCP (PLT <50 K/µL) in seven of nine Mauritian-sourced monkeys but not in the Asian-sourced monkeys after 16 weeks of treatment at 40 mg/kg/week. Marked increases in PLT-bound C3d/C4d were detected in all thrombocytopenic Mauritian-sourced monkeys but not in the unaffected Mauritian- or Asian-sourced monkeys, suggesting increased PLT clearance due to complement deposition on the PLTs. However, this effect was independent of the ASO-mediated fluid-phase alternative complement activation. A correlation was also observed between serum antiglycoprotein (GP) IIb/IIIa immunoglobulin G (IgG) and PLT reduction. In addition, increases in total serum IgM, anti-PLT IgM, and anti-PLT factor 4 IgM levels were observed in monkeys from both sources but were more evident in the Mauritian-sourced monkeys. These data suggest an enhanced innate immune cell activation to ISIS 405879, leading to increased PLT destruction through complement fixation on the PLTs or PLT crossreacting polyclonal antibody production.

Tau reduction prevents neuronal loss and reverses pathological tau deposition and seeding in mice with tauopathy.

Accumulation of hyperphosphorylated tau directly correlates with cognitive decline in Alzheimer's disease and other primary tauopathies. One therapeutic strategy may be to reduce total tau expression. We identified antisense oligonucleotides (ASOs) that selectively decreased human tau mRNA and protein in mice expressing mutant P301S human tau. After reduction of human tau in this mouse model of tauopathy, fewer tau inclusions developed, and preexisting phosphorylated tau and Thioflavin S pathology were reversed. The resolution of tau pathology was accompanied by the prevention of hippocampal volume loss, neuronal death, and nesting deficits. In addition, mouse survival was extended, and pathological tau seeding was reversed. In nonhuman primates, tau ASOs distributed throughout the brain and spinal cord and reduced tau mRNA and protein in the brain, spinal cord, and cerebrospinal fluid. These data support investigation of a tau-lowering therapy in human patients who have tau-positive inclusions even after pathological tau deposition has begun.

Distinct domains in the adenovirus E3 RIDalpha protein are required for degradation of Fas and the epidermal growth factor receptor.

Adenovirus (Ad) types 2 and 5 encode at least five proteins within the E3 transcription unit that help the virus evade the immune system. Two such proteins, RIDalpha (formerly E3-10.4K) and RIDbeta (formerly E3-14.5K), form the RID (receptor internalization and degradation) complex (formerly E3-10.4K/14.5K). RID mediates clearance from the cell surface and lysosomal degradation of a number of important members in the tumor necrosis factor receptor (TNFR) superfamily and the receptor tyrosine kinase receptor family. Affected receptors include Fas, TRAIL (TNF-related apoptosis-inducing ligand) receptor 1 (TR1), TR2, and epidermal growth factor receptor (EGFR). Degradation of Fas and TRAIL receptors protects Ad-infected cells from apoptosis. To investigate the mechanism of action of RIDalpha, 14 mutant RIDalpha proteins, each containing a three- to five-amino-acid deletion, were constructed and then expressed from the E3 region of a replication-competent recombinant Ad in the same context as wild-type RIDalpha. Each mutant protein was characterized with regard to five physical properties associated with wild-type RIDalpha, namely, protein stability, proteolytic cleavage, insertion into the membrane, complex formation with RIDbeta, and transport to the cell surface. Additionally, the mutant proteins were tested for their ability to mediate internalization and degradation of EGFR and Fas and to protect cells from Fas-mediated apoptosis. The majority of mutant RIDalpha proteins (8 out of 14) were physically similar to wild-type RIDalpha. With regard to functional characteristics, the cytoplasmic domain of RIDalpha is largely unimportant for receptor internalization and degradation and the extracellular domain of RIDalpha is important for down-regulation of EGFR but not Fas.