Discovery of HDAC6-Selective Inhibitor NN-390 with <i>in Vitro</i> Efficacy in Group 3 Medulloblastoma
Nabanita Nawar, Shazreh Bukhari, Ashley Adile, Yujin Suk, Pimyupa Manaswiyoungkul, Krimo Toutah, Olasunkanmi O. Olaoye, Yasir S. Raouf, Abootaleb Sedighi, Harsimran Kaur Garcha, Muhammad Murtaza Hassan, William D. Gwynne, Johan Israelian, Tudor B. Radu, Mulu Geletu, Ayah Abdeldayem, Justyna M. Gawel, Aaron D. Cabral, Chitra Venugopal, Elvin D. de Araujo, Sheila K. Singh, Patrick T. Gunning
Abstract
Histone deacetylase 6 (HDAC6) has been targeted in clinical studies for anticancer effects due to its role in oncogenic transformation and metastasis. Through a second-generation structure–activity relationship (SAR) study, the design, and biological evaluation of the selective HDAC6 inhibitor NN-390 is reported. With nanomolar HDAC6 potency, >200–550-fold selectivity for HDAC6 in analogous HDAC isoform functional assays, potent intracellular target engagement, and robust cellular efficacy in cancer cell lines, NN-390 is the first HDAC6-selective inhibitor to show therapeutic potential in metastatic Group 3 medulloblastoma (MB), an aggressive pediatric brain tumor often associated with leptomeningeal metastases and therapy resistance. MB stem cells contribute to these patients’ poor clinical outcomes. NN-390 selectively targets this cell population with a 44.3-fold therapeutic margin between patient-derived Group 3 MB cells in comparison to healthy neural stem cells. NN-390 demonstrated a 45-fold increased potency over HDAC6-selective clinical candidate citarinostat. In summary, HDAC6-selective molecules demonstrated in vitro therapeutic potential against Group 3 MB.