[Pharmacological and clinical profiles of avacopan (TAVNEOS® capsule), a selective C5a receptor antagonist].

Avacopan (TAVNEOS® capsules) is an orally available selective C5a receptor (C5aR) antagonist. It has been approved in Japan since 2021 for the treatment of microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA), the two major subtypes of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The current standard therapy combining glucocorticoids (GC) and immunosuppressants has greatly improved the prognosis of AAV, however, issues such as side effects associated with GC use remain to be resolved. Avacopan suppresses priming of neutrophils induced by the complement component C5a, a process deeply involved in the pathogenesis of AAV. In pre-clinical studies, avacopan inhibited chemotaxis and priming of neutrophils induced by C5a-C5aR signaling. It also significantly suppressed nephritis and renal damage in an ANCA-induced glomerulonephritis mouse model. In the global phase 3 study "ADVOCATE", avacopan achieved both primary endpoints being 1) non-inferior to prednisone in inducing remission at week 26 and 2) superior in sustained remission at week 52 for MPA and GPA patients. Additionally, with avacopan, GC toxicity score was significantly lower and fewer adverse events possibly related to GC were observed. Furthermore, avacopan increased estimated glomerular filtration rate (eGFR) more than prednisone indicating improved renal function. Thus, the novel mechanism of avacopan targeting the complement system is a promising new therapeutic option for AAV with fewer GC-related side effects and better improvement of renal function.

Efficacy and safety of avacopan in Japanese patients with antineutrophil cytoplasmic antibody-associated vasculitis: A subanalysis of a randomized Phase 3 study.

OBJECTIVES: This subgroup analysis of the randomized, double-blind, Phase 3 ADVOCATE study evaluated the efficacy and safety of avacopan compared with tapered prednisone in Japanese patients with antineutrophil cytoplasmic antibody-associated vasculitis. METHODS: Patients with microscopic polyangiitis (MPA) or granulomatosis with polyangiitis (GPA) received either avacopan 30 mg twice daily for 52 weeks plus prednisone-matching placebo or tapered prednisone over 20 weeks plus avacopan-matching placebo for 52 weeks. The two primary efficacy endpoints were clinical remission at Week 26 and sustained remission at Week 52. RESULTS: Compared with the overall population (N = 330), Japanese patients (N = 21) were older and had worse renal function, and a higher proportion were female and had MPA. The proportion of Japanese patients with clinical remission at Week 26 was 9/11 (81.8%) with avacopan vs. 7/10 (70.0%) with prednisone (overall population: 72.3% vs. 70.1%) and with sustained remission at Week 52 was 8/11 (72.7%) vs. 4/10 (40.0%), respectively (overall population: 65.7% vs. 54.9%). The safety profile of avacopan was similar in Japanese patients and the overall study population. CONCLUSIONS: The efficacy and safety of avacopan in Japanese patients with MPA or GPA were comparable to that observed in the overall ADVOCATE study population.

Roles of conserved basic amino acid residues and activation mechanism of the hyperthermophilic aspartate racemase at high temperature.

X-ray crystallography has revealed two similar alpha/beta domains of the aspartate racemase from the hyperthermophilic archaeon, Pyrococcus horikoshii OT3. The active site is located in the cleft between the two domains where two cysteine residues face each other. This arrangement allows the substrate to enter the cleft and enables the two cysteine residues to act synergistically. However, the distance between their thiolates was estimated to be 9.6 angstroms, which is beyond the distance for cooperative action of them. We examined the molecular mechanism for the racemization reaction of this hyperthermophilic aspartate racemase by mutational analyses and molecular dynamics simulations. The mutational analyses revealed that Arg48 and Lys164 were essential for catalysis in addition to the putative catalytic cysteine residues. The molecular dynamics simulations revealed that the distance between the two active gamma-sulfur atoms of cysteine residues oscillate to periodically become shorter than the predicted cooperative distance at high temperature. In addition, the conformation of Tyr160, which is located at the entrance of the cleft and inhibits the entry of a substrate, changes periodically to open the entrance at 375 K. The opening of the gate is likely to be induced by the motion of the adjacent amino acid, Lys164. The entrance of an aspartate molecule was observed by molecular dynamics (MD) simulations driven by the force of the electrostatic interaction with Arg48, Lys164, and also Asp47. These results provide insights into the roles of amino acid residues at the catalytic site and also the activation mechanism of a hyperthermophilic aspartate racemase at high temperature.