Alsterpaullone is a small molecule cyclin-dependent kinase (CDK) inhibitor [1,2].

Cyclin-dependent kinases (CDKs) are protein kinases that play important roles in the control of cell division and modulate transcription in response to several extra- and intracellular cues. Deregulation of CDKs is a hallmark of several diseases, including cancer, and drug-targeted inhibition of specific members has generated very encouraging results in clinical trials [3].

Alsterpaullone (Alp) induced apoptosis and promoted loss in clonogenicity in the Jurkat cell line. Alp activated both caspase-8 and -9, leading to cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP). Alp disrupted the activation of caspase-9 followed mitochondrial perturbation. Alp activated caspase-9 via mitochondrial perturbation [1]. Alsterpaullone regulated the cell cycle progression. Alsterpaullone inhibited HeLa cells in a time-dependent (0–72 h) and dose-dependent (0–30 μM) manner. Alsterpaullone arrested HeLa cells in G2/M prior to undergoing apoptosis via a mechanism that is involved in the regulation of various antiapoptotic genes, DNA-repair, transcription, and cell cycle progression. Alsterpaullone effectively prevented HeLa cells from entering S-phase [2].

References:
[1] Lahusen T, De Siervi A, Kunick C, et al.  Alsterpaullone, a novel cyclin‐dependent kinase inhibitor, induces apoptosis by activation of caspase‐9 due to perturbation in mitochondrial membrane potential[J]. Molecular carcinogenesis, 2003, 36(4): 183-194.
[2] Cui C, Wang Y, Wang Y, et al.  Alsterpaullone, a cyclin-dependent kinase inhibitor, mediated toxicity in HeLa cells through apoptosis-inducing effect[J]. Journal of analytical methods in chemistry, 2013, 2013.
[3] Malumbres M.  Cyclin-dependent kinases[J]. Genome biology, 2014, 15(6): 122.