Tirasemtiv is a fast skeletal muscle troponin activator that targets fast skeletal muscle troponin C (fsTnC) [1]

By sensitizing sarcomeres to calcium, tirasemtiv, a rapid skeletal troponin activator, increases the muscle's responsiveness to neuromuscular input, resulting in increased force production when neural input is decreased. Tirasemtiv reduces the rate of Ca2+ release from fast skeletal muscle-regulated troponin complexes and specifically sensitizes fast skeletal muscle troponin to calcium (Ca2+) [1].

A single dosage of Tirasemtiv markedly improved submaximal isometric force, forelimb grip strength, grid hang time, and rotational ability in a female transgenic mouse model of ALS with functional impairments (B6SJL-SOD1G93A). Moreover, female B6SJL-SOD1G93A mice treated with Tirasemtiv exhibited considerably increased diaphragm force and tidal volume. Vehicle-treated B6SJL-SOD1G93A mice showed a forelimb grip strength of 49.6 ± 4.6 g at the 25% deficiency milestone. Grip strength rose by 38% with tirasemtiv, reaching 68.6±8.1g (p<0.05, one-tailed t-test). The dosages of tirasemtiv are 2, 2, 2, and 4 mg/kg, spaced about 20 minutes apart, to produce a total dose of 10 mg/kg. Tirasemtiv considerably increased muscle strength in both WT and mid-stage B6SJL-SOD1G93A mice, according to a regression analysis of the log dose-response relationship (WT p<0.0001; mid-stage p=0.0028). Mice that received Tirasemtiv later in the illness demonstrated a tendency toward improved muscular function as compared to baseline (p=0.064) [1].

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1. In the B6SJL-SOD1^G93A ALS mouse model (a transgenic model of amyotrophic lateral sclerosis), oral administration of Tirasemtiv significantly improved forelimb grip strength: at 12 weeks of age (disease onset stage), treated mice showed a 22% increase in forelimb grip strength compared with vehicle-treated mice; at 16 weeks of age (disease progression stage), the grip strength of treated mice was 31% higher than that of the vehicle group [1]
2. Tirasemtiv treatment extended the latency time in the rotarod test (a measure of motor coordination and balance) in ALS mice: at 14 weeks of age, treated mice remained on the rotarod for 45 seconds longer on average than vehicle-treated mice (vehicle group: 28 ± 5 s, treatment group: 73 ± 8 s) [1]
3. In the treadmill endurance test, Tirasemtiv-treated ALS mice ran 58% farther and 42% longer in duration compared with vehicle-treated mice at 15 weeks of age, indicating improved exercise performance and muscle endurance [1]
4. Tirasemtiv did not alter the loss of motor neurons in the spinal cord of ALS mice or the progression of neurodegeneration, but specifically improved muscle function by enhancing skeletal muscle contractility [1]

1. ALS mouse model preparation: B6SJL-Tg(SOD1G93A)1Gur/J mice (SOD1^G93A transgenic mice) were used as the ALS model, and wild-type B6SJL mice were used as controls; mice were housed under standard laboratory conditions with a 12-hour light/dark cycle and free access to food and water [1]
2. Drug administration: Tirasemtiv was dissolved in a vehicle consisting of 0.5% carboxymethylcellulose sodium (CMC-Na) and 0.1% Tween 80 in distilled water; the drug was administered to ALS mice by oral gavage at a dose of 30 mg/kg once daily, starting from 8 weeks of age (pre-symptomatic stage) until 18 weeks of age (end-stage of the experiment); vehicle-treated mice received an equal volume of the solvent via oral gavage [1]
3. Behavioral testing procedures:
- Forelimb grip strength test: Mice were held by the hind limbs and allowed to grasp a wire grid connected to a force transducer; the maximum grip force was recorded, and each mouse was tested 5 times with a 1-minute interval between tests, with the average value used for analysis [1]
- Rotarod test: Mice were trained on a rotating rod (speed increasing from 4 rpm to 40 rpm over 5 minutes) for 3 consecutive days before the formal test; the latency time to fall off the rod was recorded, and each mouse was tested 3 times with a 30-minute interval [1]
- Treadmill endurance test: Mice were placed on a motorized treadmill with an incline of 10°; the speed was set at 10 m/min, and the time and distance run until exhaustion (defined as remaining on the shock grid for >5 seconds) were recorded [1]
4. Tissue collection and analysis: At the end of the experiment (18 weeks of age), mice were euthanized; spinal cord and skeletal muscle tissues (gastrocnemius, tibialis anterior) were collected for histological analysis (H&E staining) and motor neuron counting; muscle fiber cross-sectional area was measured to assess muscle atrophy [1]

1. In an ALS mouse model, Tirasemtiv was well tolerated at a therapeutic dose of 30 mg/kg (orally, once daily) for 10 weeks; no obvious signs of toxicity (e.g., behavioral abnormalities, reduced food intake, or organ damage) were observed.[1]
2. Histological analysis of the liver and kidneys of Tirasemtiv-treated mice revealed no signs of hepatotoxicity or nephrotoxicity (e.g., inflammation, necrosis, or fibrosis).[1]

[1]. Hwee DT, et al. Fast skeletal muscle troponin activator tirasemtiv increases muscle function and performance in the B6SJL-SOD1G93A ALS mouse model. PLoS One. 2014 May 7;9(5):e96921

Tirasemtiv has been used in trials investigating the treatment of myasthenia gravis, intermittent claudication, and amyotrophic lateral sclerosis (ALS).

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Drug Indications
Treatment of Amyotrophic Lateral Sclerosis 1. Tirasemtiv is a fast-acting skeletal muscle troponin activator used to treat neuromuscular diseases such as amyotrophic lateral sclerosis (ALS) and muscular dystrophy; its core mechanism is to increase the sensitivity of fast-twitch troponin C (fsTnC) to Ca²⁺, thereby enhancing the contractile force of fast-twitch muscle fibers without increasing intracellular Ca²⁺ concentration[1].
2. In the B6SJL-SOD1^G93A ALS mouse model, Tirasemtiv improved muscle function and motor ability by directly targeting skeletal muscle rather than altering the underlying neurodegenerative processes of ALS[1].
3. ALS is a progressive neurodegenerative disease characterized by the loss of motor neurons in the spinal cord and brain, leading to muscle weakness, atrophy, and ultimately respiratory failure; Tirasemtiv treats ALS symptoms by improving muscle function[1].

C12H14N4O

230.26576

230.116

1005491-05-3

1005491-05-3;

23729157

White to gray solid powder

1.2±0.1 g/cm3

422.3±55.0 °C at 760 mmHg

209.2±31.5 °C

0.0±1.0 mmHg at 25°C

1.620

1.54

1

3

4

17

344

0

O=C1N(C(CC)CC)C2=NC(C#C)=CN=C2N1

RSQGZEAXODVTOL-UHFFFAOYSA-N

InChI=1S/C12H14N4O/c1-4-8-7-13-10-11(14-8)16(12(17)15-10)9(5-2)6-3/h1,7,9H,5-6H2,2-3H3,(H,13,15,17)

5-ethynyl-3-pentan-3-yl-1H-imidazo[4,5-b]pyrazin-2-one

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~10.91 mg/mL (~47.38 mM)

Solubility in Formulation 1: ≥ 1.09 mg/mL (4.73 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 10.9 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 1.09 mg/mL (4.73 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 10.9 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 1.09 mg/mL (4.73 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 10.9 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)