Identification of a series of substituted 2-piperazinyl-5-pyrimidylhydroxamic acids as potent histone deacetylase inhibitors.

Pursuing our efforts in designing 5-pyrimidylhydroxamic acid anti-cancer agents, we have identified a new series of potent histone deacetylase (HDAC) inhibitors. These compounds exhibit enzymatic HDAC inhibiting properties with IC(50) values in the nanomolar range and inhibit tumor cell proliferation at similar levels. Good solubility, moderate bioavailability, and promising in vivo activity in xenograft model made this series of compounds interesting starting points to design new potent HDAC inhibitors.

Translation of a tumor microenvironment mimicking 3D tumor growth co-culture assay platform to high-content screening.

For drug discovery, cell-based assays are becoming increasingly complex to mimic more realistically the nature of biological processes and their diversifications in diseases. Multicellular co-cultures embedded in a three-dimensional (3D) matrix have been explored in oncology to more closely approximate the physiology of the human tumor microenvironment. High-content analysis is the ideal technology to characterize these complex biological systems, although running such complex assays at higher throughput is a major endeavor. Here, we report on adapting a 3D tumor co-culture growth assay to automated microscopy, and we compare various imaging platforms (confocal vs. nonconfocal) with correlating automated image analysis solutions to identify optimal conditions and settings for future larger scaled screening campaigns. The optimized protocol has been validated in repeated runs where established anticancer drugs have been evaluated for performance in this innovative assay.

JNJ-26481585, a novel "second-generation" oral histone deacetylase inhibitor, shows broad-spectrum preclinical antitumoral activity.

PURPOSE: Histone deacetylase (HDAC) inhibitors have shown promising clinical activity in the treatment of hematologic malignancies, but their activity in solid tumor indications has been limited. Most HDAC inhibitors in clinical development only transiently induce histone acetylation in tumor tissue. Here, we sought to identify a "second-generation" class I HDAC inhibitor with prolonged pharmacodynamic response in vivo, to assess whether this results in superior antitumoral efficacy. EXPERIMENTAL DESIGN: To identify novel HDAC inhibitors with superior pharmacodynamic properties, we developed a preclinical in vivo tumor model, in which tumor cells have been engineered to express fluorescent protein dependent on HDAC1 inhibition, thereby allowing noninvasive real-time evaluation of the tumor response to HDAC inhibitors. RESULTS: In vivo pharmacodynamic analysis of 140 potent pyrimidyl-hydroxamic acid analogues resulted in the identification of JNJ-26481585. Once daily oral administration of JNJ-26481585 induced continuous histone H3 acetylation. The prolonged pharmacodynamic response translated into complete tumor growth inhibition in Ras mutant HCT116 colon carcinoma xenografts, whereas 5-fluorouracil was less active. JNJ-26481585 also fully inhibited the growth of C170HM2 colorectal liver metastases, whereas again 5-fluorouracil/Leucovorin showed modest activity. Further characterization revealed that JNJ-26481585 is a pan-HDAC inhibitor with marked potency toward HDAC1 (IC(50), 0.16 nmol/L). CONCLUSIONS: The potent antitumor activity as a single agent in preclinical models combined with its favorable pharmacodynamic profile makes JNJ-26481585 a promising "second-generation" HDAC inhibitor. The compound is currently in clinical studies, to evaluate its potential applicability in a broad spectrum of both solid and hematologic malignancies.