Lomeguatrib

Lomeguatrib is an O6-methylguanine-DNA-methyl-transferase (MGMT) inhibitor [1], with an IC50 value of about 6 nM to inactivate MGMT in MCF-7 cells, effectively [2].

MGMT activity is closely related to MTIC (a metabolite of dacarbazine)-mediated DNA damage [1].

Lomeguatrib sensitized MGMT-activity-bearing A375P cells to temozolomide (TMZ), but it failed to affect the effect of dacarbazine (DTIC). In other mutBRAF cells and several mutNRAS cell lines such as WM1361, similar results were obtained [1].

With one exception, patients treated with lomeguatrib showed no active or very low MGMT in PBMCs. Lomeguatrib at a dose of 20 mg resulted in 16.7 fmol/μg DNA active MGMT in a CNS-tumor-bearing patient. This patient showed a percentage of 25% for inactive tumor MGMT. This percentage was lower than that in the other two CNS patients with lomeguatrib at the same dose. Different tumor types showed remarkable differences in total tumor MGMT. Prostate cancers had the highest (554 ± 404 fmol/mg protein), CNS tumors had the lowest (89.9 ± 44.5 fmol/mg protein), and colorectal tumors had intermediate levels of total protein (244 ± 181 fmol/mg protein). In the colorectal cancer, the primary CNS tumor, and the prostate cancer of patients, increasing lomeguatrib doses resulted in increasing inactive MGMT proportions [3].

References:
[1].  Imanol Arozarena, Ibai Goicoechea, Oihane Erice, et al. Differential chemosensitivity to antifolate drugs between RAS and BRAF melanoma cells. Molecular Cancer, 2014, 13:154.
[2].  M Clemons, J Kelly, AJ Watson, et al. O6-(4-bromothenyl)guanine reverses temozolomide resistance in human breast tumour MCF-7 cells and xenografts. British Journal of Cancer, 2005, 93:1152-1156.
[3].  Amanda J. Watson, Ami Sabharwal, Mary Thorncroft, et al. Tumor O6-methylguanine-DNA Methyltransferase Inactivation by Oral Lomeguatrib. Clinical Cancer Research, 2010, 16(2):743-9.