Tirasemtiv

Tirasemtiv is an activator of the fast skeletal muscle troponin complex. Tirasemtiv is a click chemistry reagent, itcontains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups. IC50 & Target: Troponin^[1] In Vitro: Tirasemtiv is a fast skeletal troponin activator that sensitizes the sarcomere to calcium; this mechanism of action amplifies the response of muscle to neuromuscular input producing greater force when nerve input is reduced. Tirasemtiv selectively sensitizes fast skeletal muscle troponin to calcium (Ca²⁺), and slows the rate of Ca²⁺ release from the regulatory troponin complex of fast skeletal muscle^[1]. In Vivo: A single dose of Tirasemtiv significantly increases submaximal isometric force, forelimb grip strength, grid hang time, and rotarod performance in a female transgenic mouse model (B6SJL-SOD1^G93A) of ALS with functional deficits. Additionally, diaphragm force and tidal volume are significantly higher in Tirasemtiv-treated female B6SJL-SOD1^G93A mice. At the 25% deficit milestone, vehicle-treated B6SJL-SOD1^G93A mice demonstrated forelimb grip strength of 49.6±4.6 g. Tirasemtiv increases grip strength by 38% to 68.6±8.1g (p<0.05, single tailed t-test). Tirasemtiv doses of 2, 2, 2, and 4 mg/kg given at approximately 20 min intervals to achieve a cumulative dose of 10 mg/kg. Regression analysis of the log dose vs. response relationship indicated that Tirasemtiv significantly increased muscle force in WT and mid-stage B6SJL-SOD1^G93A mice (WT p<0.0001; mid-stage p=0.0028). At later stages of disease, the mice exhibited a trend for increased muscle function in response to Tirasemtivcompared to baseline (p=0.064)^[1].