3-(4-pyridyl)indole (Rockout) is a Rho-kinase inhibitor [1].

Rho-associated protein kinase (ROCK) belongs to a family of serine-threonine kinases mainly involved in regulating the shape and movement of cells by acting on the cytoskeleton [2].

Rockout caused decreased migration and aberrant morphology. Rockout showed no effect on phagocytosis, listeria motility or actin polymerization in permeabilized yeast. In a human melanoma cell line M2 cells that blebs constitutively in a manner that is sensitive to actin cytoskeletal perturbation, Rockout (50 μM) stopped the cell blebbing within 2 min and with washout blebbing returned to normal levels within 3 min. The IC50 of Rockout was 12 μM and it inhibited blebbing in nearly all cells at 50 μM. In B3T3 cells, treatment with 50 μM Rockout resulted in significant morphological change within 10 min [1]. At an ATP concentration of 100 μM, Rockout inhibited ROCK activity with an approximate IC50 of 25 μM. Rockout (25 μM) inhibited ROCK-II and PRK to a similar degree, and MSK-1 and PKA to a lesser extent. Rockout showed no inhibitory effect on PKCα or SAPK2a [1].

References:
[1] Yarrow J C, Totsukawa G, Charras G T, et al.  Screening for cell migration inhibitors via automated microscopy reveals a Rho-kinase inhibitor[J]. Chemistry & biology, 2005, 12(3): 385-395.
[2] Amano M, Fukata Y, Kaibuchi K.  Regulation and functions of Rho-associated kinase[J]. Experimental cell research, 2000, 261(1): 44-51.