Human genetic phenotypes associated with loss or gain of function implicate the Na_v1.7 channel as a promising target for novel analgesics.^1,2 However, the expression of Na_V1.7 on autonomic afferent c-type fibers, on sympathetic efferent fibers, and cardiovascular–related autonomic adverse effects reported in gain-of-function mutation phenotypes^2,3 create concern for potential Na_v1.7 antagonists. Recent clinical assessment of a Na_v1.7 antagonist suggested that cardiovascular adverse events could be related to on-target activity.⁴ The clinical pharmacodynamic relationship between efficacy and cardiovascular adverse events or the predictive value of nonclinical models has not been fully explored. As such, the effects of MK-2075,⁵ a small-molecule selective Na_v1.7 inhibitor (human and rhesus half-maximal inhibitory concentration [IC₅₀]=85 and 161 nmol/L, respectively), were assessed in rhesus monkey (non-human primate [NHP]) and in phase I clinical studies to understand the pharmacodynamics and cardiovascular safety of Na_v1.7 blockade.

MK-2075 was highly selective against peripheral Na_v channels (Na_v1.4 and Na_v1.6 IC₅₀ >300 µmol/L), cardiac ion channels (hERG, IKs, and Na_v1.5 IC₅₀ >30 µmol/L), a broad panel of 114 potential off-targets (IC₅₀ >10 µmol/L). Moreover, NHP whole-body autoradiography demonstrated no brain penetrance. The Figure shows the concentration-dependent decrease in heart rate variability (HRV, Figure B) and spontaneous baroreceptor sensitivity (Figure C) with physiologically meaningful trends occurring at unbound plasma concentrations as low as 0.18 µmol/L (0.3 mg/kg) and statistically significant decreases at 2.3 µmol/L (6 mg/kg). Frequency domain HRV analysis (Figure D) showed concomitant decreases in both high- and low-frequency domains, suggestive of an MK-2075–dependent effect on sympathetic and parasympathetic tone. Supratherapeutic exposures of MK-2075 (50 mg/kg; maximum plasma concentration after rest article administration=169 µmol/L or 16 µmol/L unbound; 100-fold over the rhesus in vitro Na_v1.7 IC₅₀) demonstrated complete loss of all HRV indices, paradoxical decreases in heart rate and blood pressure on animal handling (Figure E and F), and one animal exhibited a brief loss of consciousness on postural change; all are indicative of compromised cardiovascular reflexes. Consistent with these being on-target effects, a Na_v1.7 inhibitory peptide analogue of JzTx-V with greater NaV1.7 specificity elicited similar effects on HRV in NHPs. In situ hybridization (RNAscope, Figure G–L) on NHP or commercially sourced human tissue demonstrated Na_v1.7 colocalized with markers for cardiac and stellate ganglia but not sinoatrial node (NHP) and cardiac/sympathetic ganglia and sinoatrial node/right atrium (human). Clinical testing of MK-2075 was conducted on healthy adult male participants in 2 protocol number (PN) studies: PN001 where participants were given up to 30 mg IV over 8 hours and PN005 where participants were given up to 8 mg IV over 2 hours. Overall, adverse events were generally mild, with the most frequently reported being paresthesia, and there was a low incidence of cardiovascular-related observations. One PN001 participant experienced orthostatic hypotension 5 hours into the 30 mg/8 h IV infusion. Maximum plasma concentration after rest article administration exposures (0.36 µmol/L unbound) was ≈4-fold the in vitro Na_V1.7 IC₅₀ at that time. The orthostatic hypotension resolved after the completion of drug administration. Five other reports of self-limited, presyncope symptoms at lower doses were reported but were often associated with study procedures and without concomitant changes in vital signs. One PN005 participant lost consciousness during protocol-driven orthostatic hypotension testing 1 hour after the start of the 8 mg/2 h IV infusion (≈126 nmol/L unbound). The participant spontaneously regained consciousness after ≈20 seconds. Review of the temporal telemetry ECG showed a period of severe bradycardia with two episodes of sinus arrest of ≈4 to 5 seconds each, followed by a brief junctional escape rhythm and then return to normal sinus rhythm. The MK-2075 infusion was stopped immediately, and the participant remained asymptomatic thereafter. One additional participant receiving 8 mg MK-2075 exhibited a ≈70% reduction in spontaneous baroreceptor sensitivity slope at the 2-hour measurement point that was unaccompanied by clinical signs and resolved 2 hours later. In PN005, there were no mean changes in HRV or spontaneous baroreceptor sensitivity nor were there any effects on afferent sensory function to cold (cold water bath)- or heat (Peltior thermode)-induced painful stimuli, or olfactory sensory function assessed by Sniffin’ Sticks.

Figure. Effects of MK-2075 on cardiac autonomic nervous system balance and reflex control through the assessment of HRV and sBRS in telemetered rhesus monkey at 2 to 6 hours postdose (A–D). Adult male rhesus monkeys (n=4) were given increasing subcutaneous doses of MK-2075 and continuous ECG was evaluated for changes in heart rate (HR, A), the time domain HRV parameter, standard deviation of N-N intervals (SDNN, B), baroreceptor effectiveness index (sBRS, C), and both high-frequency (HF) and low-frequency (LF) domain heart rate variability (HRV, D). To further clarify persistent effects during the diurnal phase, continuous data extracted as 15-minute means were aggregated into a 4-hour time period (2–6 hours postdose). A dose-dependent trend in SDNN, sBRS, and HRV decreases can be observed with a statistically significant (P<0.05) difference in all parameters at the 6 mg/kg SC dose. Statistical significance from vehicle was determined for change from baseline data using a linear mixed-effects model (Y=Group×Time+ID+error) where Group×Time capture the fixed group and time effects and their interactions; ID characterizes the between-subject random effects. E and F, Effect of supratherapeutic doses of MK-2075 on heart rate and diastolic blood pressure. Adult male rhesus monkeys (n=5) were given a continuous 8-hour intravenous infusion through jacketed infusion pumps to determine the effect of MK-2075 on HR (E) and diastolic blood pressure (F) parameters at supratherapeutic exposures (50 mg/kg over 8 hours). Increased HR and no change in diastolic pressure were observed during the infusion. Note that postinfusion handling procedures (noted as “room entry” on the graphs) caused an expected increase in HR and diastolic blood pressure in vehicle-treated animals (VEH), but the HR increase was attenuated and the diastolic blood pressure paradoxically decreased after administration of MK-2075 suggestive of compromised cardiovascular autonomic regulation. G through L, In situ hybridization Nav1.7 mRNA expression in rhesus and human tissues. G, H, and I represent Nav1.7 staining in formalin-fixed paraffin-embedded rhesus sinoatrial node, cardiac ganglia, and dorsal root ganglia, and J, K, and L represent Nav1.7 staining in human sinoatrial node, cardiac ganglia, and dorsal root ganglia, respectively. Nav1.7 is not detected in rhesus sinoatrial node, but mildly expressed in human sinoatrial node (40×). It highly expressed in cardiac ganglia and dorsal root ganglia of both rhesus and human subjects (20×).

This study reports for the first time that acute Na_v1.7 inhibition could lead to autonomic effects in NHP and human subjects, and that these may be observed with no therapeutic margin to analgesic pharmacology on the basis of quantitative sensory testing. Dose-dependent decreases in HRV and spontaneous baroreceptor sensitivity occurred in NHPs, and clinical events of syncope were observed that were suggestive of Na_v1.7-dependent cardiac autonomic dysfunction.

It is tempting to speculate that these results and those of others,⁴ which contrast the lack of effects in NaV1.7 null individuals, serve as a reminder of the potential phenotypic differences between acute pharmacological block versus genetic deficiency and the important role developmental compensation may play in the latter.

Animal studies were conducted in accordance with the Guide for the Care and Use of Laboratory Animals (2011) and received facility approval. Clinical studies were approved by an institutional ethics review committee and subjects gave informed consent. Nonclinical data may be available on reasonable request and completion of required agreements.

The authors thank A. Houghton, D. Henze, R. Briscoe, and C. Burgey for their helpful scientific dialog and perspective, H. Regan, T. Detwiler, S. Gruver, B. Rockafellow, and M. Syrylo for the conduct of the telemetered non-human primate experiments, P. Fanelli for help with data analysis, S. Wang for the conduct of the statistical analysis, and D. Gilberto and A. Bone for veterinarian surgical support and care.

Conceptualization, Drs Regan, Morissette, and A. Struyk; Investigation, Drs Regan and Kraus, M. Vavrek, Drs Wang and A. Struyk; Supervision, Dr A. Stoch; Writing – original draft, Drs Regan, Morissette, and A. Struyk; Writing – review and editing, Drs Regan, Morissette, and Kraus, M. Vavrek, Drs Wang, de Hoon, Depre, T. Lodeweyck, Demeyer, Laethem, A. Stoch, and A. Struyk.

None.

Nonstandard Abbreviations and Acronyms

hERG	human ether-a-go-go ion channel
HRV	heart rate variability
IC50	half-maximal inhibitory concentration
NHP	non-human primate

human ether-a-go-go ion channel

heart rate variability

half-maximal inhibitory concentration

non-human primate

Disclosures Drs Regan, Morissette, and Kraus, M. Vavrek, and Drs Wang, T. Laethem, A. Stoch, and A. Struyk are employed by Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ. L. Arrington is employed by Amgen Inc. but was employed by Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, at the time of the study. Drs de Hoon, Dupre, and T. Lodeweyck are employed by the University of Leuven, Belgium. Dr Demeyer is employed by the Military Hospital Queen Astrid, Belgium.

*C.P. Regan and P. Morisette contributed equally.

For Sources of Funding and Disclosures, see page 1396.

Circulation is available at www.ahajournals.org/journal/circ

中文翻译：

---

自主神经功能障碍与 Nav1.7 钠通道抑制有关

与功能丧失或获得相关的人类遗传表型表明 Na _v 1.7 通道是新型镇痛药的有希望的靶点。^{1,2然而，Na} _V 1.7 在自主神经传入 c 型纤维、交感传出纤维上的表达以及功能获得突变表型^2,3中报告的心血管相关自主神经不良反应引起了对潜在 Na _v 1.7的担忧对手。最近对 Na _v 1.7 拮抗剂的临床评估表明，心血管不良事件可能与目标活动有关。⁴疗效与心血管不良事件之间的临床药效关系或非临床模型的预测价值尚未得到充分探索。因此，在恒河猴中评估了 MK-2075，5 一种小分子选择性 Na v 1.7 抑制剂（人类和恒河猴半最大抑制浓度 [IC 50 ] = 85 和 161 nmol ^/ L _）的_作用（非人类灵长类动物 [NHP]）和 I 期临床研究，以了解 Na _v 1.7 阻断的药效学和心血管安全性。

MK-2075 对外周 Na _v通道（Na _v 1.4 和 Na _v 1.6 IC ₅₀ >300 µmol/L）、心脏离子通道（hERG、IKs 和 Na _v 1.5 IC ₅₀ >30 µmol/L）具有高度选择性，广泛的 114 个潜在脱靶点 (IC ₅₀ >10 µmol/L)。此外，NHP 全身放射自显影显示没有脑渗透性。该图显示了心率变异性（HRV，图 B）和自发压力感受器敏感性（图 C）的浓度依赖性下降，在未结合血浆浓度低至 0.18 µmol/L (0.3 mg/kg) 时出现具有生理意义的趋势，并且具有统计学意义显着降低至 2.3 µmol/L (6 mg/kg)。频域 HRV 分析（图 D）显示高频域和低频域同时下降，表明 MK-2075 对交感神经和副交感神经张力有依赖性影响。 MK-2075 的超治疗暴露（50 mg/kg；剩余物品给药后的最大血浆浓度=169 µmol/L 或未结合的 16 µmol/L；体外 Na _v 1.7 IC ₅₀是恒河猴的 100 倍）证明所有活性完全丧失HRV 指数、动物处理时心率和血压的反常下降（图 E 和 F），一只动物在姿势改变时表现出短暂的意识丧失；所有这些都表明心血管反射受损。与这些中靶效应一致，具有更高 NaV1.7 特异性的 JzTx-V 的 Na _v 1.7 抑制肽类似物对 NHP 中的 HRV 产生了类似的影响。对 NHP 或商业来源的人体组织进行原位杂交（RNAscope，图 G-L）证明 Na _v 1.7 与心脏和星状神经节标记物共定位，但不与窦房结 (NHP) 和心脏/交感神经节和窦房结/右心房（人）共定位。 ）。 MK-2075 的临床测试是在 2 个方案号 (PN) 研究中对健康成年男性参与者进行的：PN001，参与者在 8 小时内静脉注射 30 mg；PN005，参与者在 2 小时内静脉注射 8 mg。总体而言，不良事件一般较轻微，最常报告的是感觉异常，并且与心血管相关的观察结果发生率较低。一名 PN001 参与者在 30 mg/8 h IV 输注后 5 小时出现体位性低血压。剩余物品给药暴露后的最大血浆浓度（0.36 µmol/L 未结合）约为体外 Na _V 1.7 IC _{50 的4 倍}当时。给药完成后，体位性低血压消失。另外五份报告也报告了低剂量时的自限性晕厥前症状，但通常与研究程序有关，并且没有伴随生命体征的变化。一名 PN005 参与者在开始 8 mg/2 h IV 输注（约 126 nmol/L 未结合）后 1 小时在方案驱动的直立性低血压测试中失去意识。约 20 秒后，参与者自发恢复意识。回顾颞部遥测心电图显示一段严重心动过缓期，伴有两次窦性停搏，每次约 4 至 5 秒，随后出现短暂的交界性逸搏节律，然后恢复正常窦性节律。 MK-2075 输注立即停止，此后参与者一直保持无症状。另一位接受 8 mg MK-2075 治疗的参与者在 2 小时测量点表现出自发压力感受器敏感性斜率降低约 70%，但没有伴随临床症状，并在 2 小时后消失。在 PN005 中，HRV 或自发压力感受器敏感性没有平均变化，对冷（冷水浴）或热（珀尔蒂奥热电极）引起的疼痛刺激的传入感觉功能或通过 Sniffin' 评估的嗅觉感觉功能也没有任何影响棍子。

数字。 通过在给药后 2 至 6 小时（A-D）评估遥测恒河猴的 HRV 和 sBRS，MK-2075 对心脏自主神经系统平衡和反射控制的影响。成年雄性恒河猴 (n=4) 皮下注射剂量不断增加的 MK-2075，并评估连续心电图的心率变化 (HR, A )、时域 HRV 参数、NN 间隔的标准差 (SDNN, B ) 、压力感受器有效性指数 (sBRS, C ) 以及高频 (HF) 和低频 (LF) 域心率变异性 (HRV, D )。为了进一步阐明昼夜阶段的持续影响，以 15 分钟平均值提取的连续数据被汇总到 4 小时时间段（给药后 2-6 小时）。在 6 mg/kg SC 剂量下，可以观察到 SDNN、sBRS 和 HRV 降低的剂量依赖性趋势，所有参数均具有统计学显着性 ( P <0.05) 差异。使用线性混合效应模型（ Y=组×时间+ID+误差）确定车辆相对于基线数据变化的统计显着性，其中组×时间捕获固定组和时间效应及其相互作用；ID表征了受试者之间的随机效应。E和F，超治疗剂量的 MK-2075 对心率和舒张压的影响。通过夹套输液泵对成年雄性恒河猴 (n=5) 进行连续 8 小时静脉输注，以确定 MK-2075 在超治疗暴露（50 mg/公斤超过8小时）。输注期间观察到心率增加且舒张压没有变化。请注意，输注后处理程序（在图表中标记为“进入房间”）导致媒介物治疗动物 (VEH) 的 HR 和舒张压出现预期增加，但给药后 HR 增加减弱，舒张压反而下降MK-2075 表明心血管自主调节受损。G至L，原位杂交 Nav1.7 mRNA 在恒河猴和人体组织中的表达。G、H和I代表福尔马林固定石蜡包埋的恒河猴窦房结、心神经节和背根神经节中的 Nav1.7 染色，J、K和L分别代表人窦房结、心脏神经节和背根神经节的 Nav1.7 染色。 Nav1.7 在恒河猴窦房结中未检测到，但在人窦房结中轻度表达（40×）。它在恒河猴和人类受试者的心脏神经节和背根神经节中高表达（20×）。

这项研究首次报告，急性 Na _v 1.7 抑制可能会导致 NHP 和人类受试者的自主神经效应，并且基于定量感觉测试，可能会在镇痛药理学没有治疗裕度的情况下观察到这些效应。 NHP 中 HRV 和自发压力感受器敏感性出现剂量依赖性下降，观察到晕厥临床事件，提示 Na _v 1.7 依赖性心脏自主神经功能障碍。

人们很容易推测，这些结果和其他结果⁴对比了 NaV1.7 无效个体中缺乏作用，提醒人们急性药理学阻断与遗传缺陷之间的潜在表型差异，以及发育补偿可能的重要作用。玩后者。

动物研究是根据《实验动物护理和使用指南》（2011 年）进行的，并获得了机构批准。临床研究得到了机构伦理审查委员会的批准，并且受试者给予了知情同意。非临床数据可根据合理请求并完成所需协议提供。

作者感谢 A. Houghton、D. Henze、R. Briscoe 和 C. Burgey 提供的有益的科学对话和观点，感谢 H. Regan、T. Detwiler、S. Gruver、B. Rockafellow 和 M. Syrylo 的指导遥测非人类灵长类动物实验中，P. Fanelli 帮助进行数据分析，S. Wang 进行统计分析，D. Gilberto 和 A. Bone 提供兽医手术支持和护理。

概念化，Regan 博士、Morissette 博士和 A. Struyk 博士；调查，Regan 博士和 Kraus 博士、M. Vavrek、Wang 博士和 A. Struyk 博士；监督，A. Stoch 博士；写作——原稿，由 Regan 博士、Morissette 博士和 A. Struyk 博士撰写；写作 – 审查和编辑，Regan 博士、Morissette 博士和 Kraus 博士、M. Vavrek 博士、Wang 博士、de Hoon、Depre、T. Lodeweyck、Demeyer、Laethem、A. Stoch 和 A. Struyk。

没有任何。

非标准缩写词和首字母缩略词

ERG	人以太-a-go-go离子通道
心率变异性	心率变异性
IC50	半数抑制浓度
NHP	非人类灵长类动物

人以太-a-go-go离子通道

心率变异性

半数抑制浓度

非人类灵长类动物

Regan、Morissette、Kraus、M. Vavrek 博士以及 Wang、T. Laethem、A. Stoch 和 A. Struyk博士受雇于 Merck Sharp & Dohme LLC（Rahway 的 Merck & Co, Inc. 的子公司） ，新泽西州。 L. Arrington 受雇于 Amgen Inc.，但在研究进行时受雇于 Merck Sharp & Dohme LLC，该公司是位于新泽西州拉威的 Merck & Co., Inc. 的子公司。 de Hoon、Dupre 和 T. Lodeweyck 博士受聘于比利时鲁汶大学。 Demeyer 医生受雇于比利时阿斯特丽德王后军事医院。

*CP Regan 和 P. Morisette 的贡献相等。

有关资金来源和披露信息，请参阅第 1396 页。

流通量可在 www.ahajournals.org/journal/circ 上获取