The complete amino acid sequence of ecarin is deduced from the nucleotide sequence of a cDNA clone isolated by screening a venomous gland cDNA library of Kenyan Echis carinatus. The cDNA sequence with 2379 base pairs encodes an open reading frame of 616 amino acids with a remarkable sequence homology to the putative precursor protein of trigramin from Trimeresurus gramineus venom (61% identity) and a large hemorrhagin, jararhagin, from the pit viper Bothrops jararaca venom (62% identity). Thus, ecarin, as well as jararhagin and trigramin, is translated as a precursor protein, which may be processed posttranslationally. The ecarin proprotein has a "cysteine switch" motif (-Pro-Lys-Met-Cys-Gly-Val-) similar to that involved in the activation of matrix metalloproteinase zymogens. The processed mature protein consists of 426 amino acid residues (residues 191-616), showing the strongest sequence similarity with that of Russell's viper venom factor X activator (RVV-X) heavy chain (64% identity). Like RVV-X heavy chain, ecarin contains metalloproteinase, disintegrin, and cysteine-rich domains. The metalloproteinase domain has a typical zinc-chelating sequence (-His-Glu-Xaa-Xaa-His-Xaa-Xaa-Gly-Xaa-Xaa-His-), as found in crayfish astacin. In the disintegrin domain of ecarin, the Arg-Gly-Asp sequence is replaced by Arg-Asp-Asp, as found in the disintegrin domains of RVV-X heavy chain (Arg-Asp-Glu) and a guinea pig sperm fusion protein, PH-30 beta (Thr-Asp-Glu). These findings show that while there are structural and evolutionary relationships among these proteins, each has a unique functional activity.
Background Tisagenlecleucel demonstrated a high rate of durable response in adult patients with relapsed/refractory (r/r) diffuse large B-cell lymphoma (DLBCL) in the pivotal global phase 2 JULIET study. Here, we report the efficacy and safety of tisagenlecleucel in the Japanese subgroup. Methods JULIET (NCT02445248) is a single-arm, open-label, multicenter, phase 2 study involving adult patients with r/r DLBCL who either relapsed after or were ineligible for autologous stem cell transplant. Primary endpoint was best overall response rate (ORR; complete response [CR] + partial response [PR]) as judged by an independent review committee. Results In Japan, of 17 patients enrolled, 9 were infused with tisagenlecleucel and completed ≥ 3 months of follow-up. Best ORR was 77.8% (7/9; 95% confidence interval, 40.0-97.2), with 5 patients (55.6%) in CR and 2 (22.2%) in PR. Cytokine release syndrome (CRS) occurred in 6 patients (66.7%), with grade 3 CRS in 2 patients (Penn grading scale). Two patients received tocilizumab. Two deaths (22.2%) occurred more than 30 days after tisagenlecleucel infusion due to disease progression, neither of which were related to tisagenlecleucel. Conclusion Tisagenlecleucel showed a high best ORR with a manageable safety profile, thus offering a new treatment option in selected Japanese patients with r/r DLBCL.
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