Biomedical Imaging, Genentech, Inc., South San Francisco, CA, USA.
Biostatistics, Genentech, Inc., South San Francisco, CA, USA.
Br J Clin Pharmacol. 2021 Jan;87(1):129-139. doi: 10.1111/bcp.14370. Epub 2020 Jun 2.
Develop a translational assay of Transient Receptor Potential Ankyrin 1 (TRPA1) activity for use as a preclinical and clinical biomarker.
Allyl isothiocyanate (AITC), capsaicin or citric acid were applied to ears of wildtype and Trpa1-knock out (Trpa1 KO) rats, and changes in dermal blood flow (DBF) were measured by laser speckle contrast imaging. In humans, the DBF, pain and itch responses to 5-20% AITC applied to the forearm were measured and safety was evaluated. Reproducibility of the DBF, pain and itch responses to topically applied 10% and 15% AITC were assessed at two visits separated by 13-15 days. DBF changes were summarized at 5-minute intervals as areas under the curve (AUC) and maxima. Intraclass correlation coefficient (ICC) was calculated to assess arm-arm and period-period reproducibility.
AITC- and citric acid-induced DBF were significantly reduced in Trpa1 KO rats compared to wildtype (90 ± 2% and 65 ± 11% reduction, respectively), whereas capsaicin response did not differ. In humans, each AITC concentration significantly increased DBF compared to vehicle with the maximal increase occurring 5 minutes post application. Ten percent and 15% AITC were selected as safe and effective stimuli. AUC from 0 to 5 minutes was the most reproducible metric of AITC-induced DBF across arms (ICC = 0.92) and periods (ICC = 0.85). Subject-reported pain was more reproducible than itch across visits (ICC = 0.76 vs 0.17, respectively).
AITC-induced DBF is a suitable target engagement biomarker of TRPA1 activity for preclinical and clinical studies of TRPA1 antagonists.
开发瞬时受体电位锚蛋白 1（TRPA1）活性的转化测定法，用作临床前和临床生物标志物。
异硫氰酸烯丙酯（AITC）、辣椒素或柠檬酸应用于野生型和 Trpa1 敲除（Trpa1 KO）大鼠的耳朵，通过激光散斑对比成像测量皮肤血流（DBF）的变化。在人类中，测量前臂应用 5-20% AITC 引起的 DBF、疼痛和瘙痒反应，并评估安全性。在两次就诊之间间隔 13-15 天，评估了 10%和 15% AITC 局部应用时 DBF、疼痛和瘙痒反应的重现性。DBF 变化在 5 分钟间隔内总结为曲线下面积（AUC）和最大值。计算组内相关系数（ICC）以评估手臂间和周期间的重现性。
与野生型相比，AITC 和柠檬酸诱导的 DBF 在 Trpa1 KO 大鼠中显著降低（分别为 90±2%和 65±11%降低），而辣椒素反应没有差异。在人类中，与载体相比，每种 AITC 浓度均显著增加 DBF，最大增加发生在应用后 5 分钟。10%和 15% AITC 被选为安全有效的刺激物。0 到 5 分钟的 AUC 是 AITC 诱导的 DBF 在手臂之间最具重现性的指标（ICC=0.92）和周期之间（ICC=0.85）。与瘙痒相比，受试者报告的疼痛在就诊时更具重现性（ICC=0.76 对 0.17）。
AITC 诱导的 DBF 是 TRPA1 拮抗剂的临床前和临床研究中 TRPA1 活性的合适靶标参与生物标志物。
