In vitro activity: ML329 is a potent small molecule inhibitor of MITF (Micropthalmia-associated transcription factor) which inhibits TRPM-1 (melastatin, a MITF target gene) promoter activity with an IC50 of 1.2 μM. MITF is a lineage restricted basic helix-loop-helix leucine zipper transcription factor that is essential for melanocyte development, function and survival. 15% of human melanomas have MITF gene amplification. In addition, a vast majority of melanomas are dependent upon MITF for survival. ML329 was discovered by a high throughput screening (HTS) of 331,578 compounds from the NIH MLPCN compound library. ML329 was tested in two MITF-dependent melanoma cell viability assays, SK-MEL-5 and MALME-3M plus a MITF-independent cell line, A375. ML329 showed specific activity against the MITF-dependent cells, primary melanocytes but no effect on the viability in A375 cells. ML329 reduced the expression of multiple MITF target genes, including pigment-related genes and the cell cycle regulator CDK2. As a tool compound, ML329 will be useful in elucidating the role of MITF in melanocyte lineage development and in melanoma disease progression.

Cell Assay: ML329 suppreses the expression of a variety of micropthalmia-associated transcription factor (MITF) target genes and blocks the proliferation of many cell lines that require MITF for proliferation. ML329 could directly or indirectly interact with MITF or components of the MITF regulatory network. As a transcription factor that regulates cell cycle and pigmentation, interference of MITF with ML329 will be useful in characterizing the specific roles of MITF in melanoma and validate blockade of MITF function as a potential treatment of melanoma. ML329 shows specific activity against the MITF-dependent cells, primary melanocytes but no effect on the viability in A375 cells. ML329 reduces the expression of multiple MITF target genes, including pigment-related genes and the cell cycle regulator CDK2. As a tool compound, ML329 will be useful in elucidating the role of MITF in melanocyte lineage development and in melanoma disease progression.