Apoptozole is an inhibitor of ATPase activity of HSP70 [1].

The heat shock protein 70 (HSP70) protein family plays diverse roles in biological processes and has multiple functions involved in suppression of apoptotic pathways through multiple anti-apoptotic processes. The two major members, constitutive Hsc70 and inducible Hsp70, are composed of an N-terminal ATPase domain and a C-terminal substrate binding domain [1][2].

Apoptozole (Az) is an inhibitor of ATPase activity of HSP70. Apoptozole inhibited the ATPase activity of HSP70 by binding to its ATPase domain. In the presence of 200 μM ATP, Apoptozole inhibited the ATPase activity of HSP70 by 32% and 65% at 100 μM and 200 μM, respectively. Apoptozole bound HSP70 but not HSP40, HSP60, and HSP90. In several cancer cell lines, Apoptozole induced apoptosis in a dose-dependent way with IC50 values ranged from 5 to 7 μM. In HeLa cells, Apoptozole decreased the amount of APAF-1 associated with HSP70 without affecting the expression level of APAF-1, and produced cleaved procaspase-9, suggesting that Apoptozole blocked association of HSP70 with APAF-1 and induced caspase-dependent apoptosis.

In the nude mice xenografted with A549, RKO (colorectal carcinoma), and HeLa cells, i.p injection of Apoptozole reduced tumor volumes by 61%, 65%, and 68%, respectively [1]. In mice administered with both protein antigen and Az, Az increased immune responses to administered antigens and produced more antibodies [2].

References:
[1].  Ko SK, Kim J, Na DC, et al. A small molecule inhibitor of ATPase activity of HSP70 induces apoptosis and has antitumor activities. Chem Biol. 2015 Mar 19;22(3):391-403.
[2].  Baek KH, Zhang H, Lee BR, et al. A small molecule inhibitor for ATPase activity of Hsp70 and Hsc70 enhances the immune response to protein antigens. Sci Rep. 2015 Dec 3;5:17642.