MDL 28170 is a selective inhibitor, which inhibites calpain with Ki values of 10nM and cathepsin B with Ki values of 25 nM while does not inhibit trypsin-like serine proteases. And it can penetrate the blood–brain barrier rapidly and show the activity in inhibiting brain cysteine protease activity following systemic administration [1,2].

Calpain could affect reperfusion function directly through limited proteolysis of the sarcomeres.And function improvement of MDL-28170 during reperfusion were supported byexperimets. It is thought to act by blocking the sites of catalysis ofcalpains. The experiments also showed skinned muscle fibers which was isolated from the tropical of stunned ferret hearts reveal decreased sensitivity to Ca2+, and the decrease in sensitivity could be reversed if MDL-28170 is treated prior to ischemia and during early reperfusion [1].

When peritoneal mouse macrophages were pre-infected with trypomastigotes for 3 h , MDL28170 was able to reduce the viability of bloodstream trypomastigotes significantly with an IC50/24h value of 20.4 mM. Also, asparasitespre-treated with MDL28170 concentration rose from 6.25 to 50 mM, presenting a clear dose-dependent inhibition profile prior to of macrophage, where the corresponding inhibition from 20% increased to 50%. In addition, macrophages experimentally infected with T. cruzi which were treated with MDL 28170 presented a reduction in the percentage of infection even at the lowest concentrations of 6.25 mM [3].

Upon Ca2+ repletion in the isolated heart of rats, the hearts deteriorated immediately, revealing a marked depression in cardiac function and an enlarged myocardial injury area. This was accompanied by significant increases in lactate dehydrogenase, mitochondrial release of cytochrome c, the apoptotic index and degraded TnI. MDL 28170 significantly inhibited these changes, with the exception of TnI degradation [4].

References:
[1].  Urthaler F, Wolkowicz PE, Digerness SB, et al. MDL-28170, a membrane-permeantcalpain inhibitor, attenuates stunning and PKC epsilon proteolysis in reperfused ferret hearts. Cardiovasc Res, 1997, 35 (1): 60-7.
[2].  Li P, Wendy H, He Q, et al. Postischemic treatment withcalpain inhibitor MDL 28170ameliorates brain damage in a gerbil model of global ischemia, Neuroscience Letters, 1998, 247 :17–20.
[3].  V?′tor EV, Rubem F, Andre′ L, Effects of the calpain inhibitor MDL28170 on the clinically relevant forms of Trypanosomacruzi in vitro. J AntimicrobChemother , 2010, 65: 1395–1398.
[4].  Bi S H, Jin Z X, Zhang J Y, et al. Calpaininhibi tor MDL 28170 protectsagainst the Ca2+paradox in rat hearts.Clinical and Experimental Pharmacology and Physiology , 2012, 39:385–392 .