Afferent sensory input by orally- administered TRPV1 and TRPA1 ac4vators inhibits electrically- induced muscle cramps in normal healthy volunteers

Transcription

1 Afferent sensory input by orally- administered TRPV1 and TRPA1 ac4vators inhibits electrically- induced muscle cramps in normal healthy volunteers Glenn F. Short III, Brooke W. Hegarty, Bruce P. Bean, Roderick MacKinnon, Christoph H. Westphal and Jennifer M. Cermak Flex Pharma, Boston, MA Disclosure statement: Work supported by Flex Pharma, Inc. Drs. G.F. Short, B.W. Hegarty, C.H. Westphal, and J.M. Cermak are employees of Flex Pharma, Inc. Dr. B.P. Bean and R. MacKinnon hold stock and receive compensanon for service on the ScienNfic Advisory Board of Flex Pharma American Academy of Neurology Washington D.C., April 21, 2015 Novel Treatments for Neuromuscular Condi4ons

2 The causes of muscle cramping are poorly understood Muscle cramping is a common problem with no approved clinical treatment. Recent research has shown that most cramping is not caused by dehydration or electrolyte imbalance. The best current hypothesis is that cramping reflects persistent firing of alpha motor-neurons, not a direct property of the muscle itself. There is no laboratory animal model of cramping. 2

3 The key element in muscle cramping may be the same as in muscle spasms: persistent motor neuron firing Muscle spasms in a rat model of spinal cord injury reflect long-lasting firing of motoneurons. K.C. Murray, M.J. Stephens, E.M. Ballou, C.J. Heckman, D.J. Bennett J. Neurophysiol. 105: , 2010 Self-sustained long-lasting firing produced by Ia synaptic input in the motoneuron of a decerebrate cat. R.H. Lee and C.J. Heckman J. Neurophysiol. 76: ,

4 Muscle cramp can be reproducibly induced by brief repetitive stimulation of motor end-plates at 5-20 Hz Flexor hallucis brevis SNmulated with 180 microsecond biphasic square pulses at 8, 10 or 12 Hz for 5 seconds. 4

5 Drinking pickle juice decreases cramp duration and acts within 90 seconds (Miller et al., 2010) K.C. Miller, G.W. Mack, K.L. Knight, J. Ty Hopkins, D.O. Draper, P.J. Fields, and I. Hunter Med Sci Sports Exerc. 42: , We hypothesized that the acetic acid in pickle juice acts by stimulating sensory nerve endings in the mouth, esophagus or stomach via activation of TRPV1 and/or TRPA1 channels. More potent and efficacious TRPV1 and TRPA1 activators are available in natural products, including capsicum (TRPV1), gingerols (TRPV1 and TRPA1), and cinnamaldehyde (TRPA1). 5

6 Drinking Flex beverage containing natural extracts produces long-lasting inhibition of electrically-induced muscle cramping Subjects drank 50 ml of a beverage containing aqueous extracts of capsicum, cinnamon and ginger. 6

7 Collected data in 37 subjects showed highly significant effect of Flex treatment vs. vehicle control Overall Time- course (aggregate over 3 studies) Overall treatment Effect (aggregate over all time points) ΔEMG-AUC from Baseline (uv sec) Time (h) Flex Treatment Vehicle Control ΔEMG-AUC from Baseline (uv sec) Error bars represent standard deviation Error bars represent standard error of the mean **** Vehicle Control Flex Treatment Flex treatment and vehicle data were compiled across three independent, randomized, blinded crossover studies (n=37, normal healthy volunteers) Flex treatment decreased the mean cramp intensity within 15 min and effect lasted 6-8h Flex treatment significantly reduced cramp intensity by 3-fold (ANOVA, p<0.0001) Flex treatment was well-tolerated with no serious adverse events 7

8 Primary sensory neurons can be activated by TRPV1 and TRPA1 agonists in Flex natural extracts Rat trigeminal ganglion neurons exposed to highly-diluted capsicum, cinnamon, or ginger extracts. Stimulation monitored by intracellular calcium indicator. A : 1/800,000 Capsicum extract B : 1/5,000 Cinnamon extract C : 1/12,000 Ginger extract s A B C Ionomycin A B C A B C Ionomycin A B C s s s Highly synergistic action of combined effects of individual extracts at low dilutions. A : 1/20,000,000 Capsicum extract C : 1/2,000,000 Ginger extract Data by Yong Ho Kim and Seog Bae Oh 8

9 Identification of beverage components Ginger Extract Capsicum Extract Cinnamon Extract 6-Gingerol Capsaicin Cinnamaldehyde 9

10 Tests of purified components of Flex treatment to activate human sensory neurons Potentiation of [Ca] i 2+ by combination of TRPV1 and TRPA1 activators Potentiation of [Ca] i 2+ by single agent that activates both TRPV1 and TRPA1 ΔF/F um Cinnamaldehyde (TRPA1) 50 nm Capsaicin (TRPV1) Cinnamaldehyde- Capsaicin Combination ΔF/F um 6-Gingerol (TRPV1/TRPA1) 100 um Cinnamaldehyde (TRPA1) 50 nm Capsaicin (TRPV1) Time (sec) Time (sec) Naturally-occurring compound components of the Flex treatment activate human DRGs Co-activation of TRPV1 and TRPA1 potentiates and prolongs stimulation 10

11 Molecular structures of TRPV1 and TRPA1 channels are known from Cryo-EM TRPV1 TRPA1 E. Cao, M. Liao, Y. Cheng and D. Julius, Nature, 5 Dec 2013 C.E. Paulsen, J. Armache, Y. Gao, Y. Cheng and D. Julius, Nature, 8 April

12 Muscle cramping occurs in a spectrum of neuromuscular disorders Nocturnal Leg Cramps Sudden painful contraction reducing sleep quality No drug approved in the U.S. U.S. Patient Population 37% prevalence for 50+ yo 1 ~4M over 65 yo suffer daily 2 No evidence that common remedies such as electrolyte replacement, bananas and hydration afford relief No approved drug in US to treat Severe Neuromuscular Conditions Spinal Cord Spasticity, Dystonias, Multiple Sclerosis U.S. Patient Population Cervical dystonia: 90K patients 3 Spinal spasticity: 150K patients 4 MS: 250K 350K patients 5, 84% of whom experience spasticity Exercise Associated Muscle Cramps (EAMCs) Rhona Wise European Pressphoto Agency Impacts both weekend warriors and elite athletes 1 Naylor & Young, A General Population Survey of Rest Cramps, Age and Ageing Estimates based on third party survey results 3 National Spasmodic Torticollis Association 4 Own estimates 5 National Institute of Neurological Disorders and Stroke 12

13 Summary and Clinical Implications TRPV1 and TRPA1 activation demonstrates a significant reduction in muscle cramp intensity compared to vehicle control Results from three independent human studies: o o o Treatment effect observed at 15 minutes lasting up to 6-8 hours Cramp muscle contractions reduced by 3-fold Well-tolerated with no serious adverse events Identification of active components may allow improved formulations 13

14 Acknowledgements Jennifer M. Cermak, PhD Brooke W. Hegarty, MSHS Roderick MacKinnon, MD Glenn F. Short III, PhD Christoph H. Westphal, MD, PhD Rat Trigeminal Ganglion Recording Yong Ho Kim, PhD Seog Bae Oh, DDS, PhD 14

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16 Flex beverage inhibits natural cramping Subject G Spontaneous cramping of flexor hallucis brevis 100 µv RMS EMG 1 sec Voluntary toe flex Voluntary toe flex Control #1 8 sec cramp Control #2 5 sec cramp Voluntary toe flex 10 min after TRP-Stim No cramp Voluntary toe flex 15 min after TRP-Stim No cramp 16

17 Ease of electrically-induced cramping correlates with susceptibility to natural cramping 17

18 Stability of cramping under control conditions Subjects drank 50 ml of a beverage containing aqueous extracts of capsicum (0.075%), cinnamon (1%) and ginger (1.5%) diluted in 1:1 mixture of water and corn syrup. 18

19 Inhibition of calf cramps Subject E Calf muscle Stimulation 28 Hz 2 Hz 20 sec Control 59 sec cramp 100 µv RMS EMG 3 min after TRP-Stim 3 sec cramp 19

20 The causes of muscle cramping are poorly understood There is no laboratory animal model of cramping. Recent research has shown that most cramping is not caused by dehydration or electrolyte imbalance. Significant and serious dehydration does not affect skeletal muscle cramp threshold frequency Braulick KW, Miller KC, Albrecht JM, et al. Br J Sports Med 2013;47: Cramp threshold frequency Euhydrated Dehydrated (4.7±0.5% of body mass) by exercise 15±5 Hz 13±6 Hz (=0.12) Cramp Intensity 94.2±41% 115.9±73% (p=0.2) Cramp Amplitude 0.18±0.06 mv 0.18±0.09 mv [Na + ] plasma 141.9±3.1 mm 149.5±1.8 mm [K + ] plasma 4.9± ±0.4 20

21 The causes of muscle cramping are poorly understood Recent research shows that muscle cramping originates in the motor neurons innervating muscle, not in the muscle itself. Mechanisms of cramp contracnons: peripheral or central generanon? M.A. MineVo, A. Holobar, A. BoVer, R. Ravenni, D. Farina J Physiol 589: ,