Peripheral T-cell lymphomas (PTCL) are a clinically aggressive disease with poor responses to current modes of therapy and a dismal survival rate. In an abstract presented before the 56th annual American Society of Hematology conference we sought to identify an active new drug for PTCL patients.
We began by performing a cell-based progressive screen from a library of 105 anti-neoplastic drugs in clinical use. Initially within the clinical-range limit we identified 3 active drugs groups HDAC inhibitors (HDI, romidepsin), proteasome inhibitors (bortezomib, carfilozimib), and transcription inhibitors (dactinomycin). Secondary screenings were conducted for the active drug groups with six drug concentrations, in an extended panel of 9 TCL cell lines. To expand the scope of our drug groups we added vorinostat, panobinostat and valproic acid for HDI and SNS032 (CDK9>2>>7 inhibitor) and THZ1 (CDK7>12 inhibitor) for transcription inhibitors.
We found that the most active drugs were bortezomib, carfilzomib, romidepsin, dactinomycin, and THZ1, focusing on the transcriptional inhibitors, using THZ1 to investigate the functional relevance of CDK7/12 targeting in PTCL. THZ1 was found to decrease mRNA and protein levels of MCL1, JAK1, and MYC as early as 3 hours into treatment. The levels of anti-apoptotic proteins BCL2, BCL-XL, JUND, and NFkB also decreased, while proteins like the pro-apoptotic BAX increased.
In conclusion we found a mechanism by which CDK7/12 inhibition with the compound THZ1 simultaneously inhibits prominent PTCL survival pathways, causing apoptosis and re-sensitization to BCL2-family inhibitors. These findings led us to identify a mechanism by which CDK7/12 inhibition and presents a potential new paradigm in treating patients with PTCL.