On May 8, 2017 Aptose Biosciences Inc. (NASDAQ:APTO) (TSX:APS) reported the presentation of preclinical data demonstrating that CG’806, a highly potent pan-FLT3/BTK inhibitor, exerts compelling activity against acute myeloid leukemia (AML) cells harboring mutant forms of FLT3 and eradicates AML tumors in a murine xenograft model (Press release, Aptose Biosciences, MAY 8, 2017, View Source;p=RssLanding&cat=news&id=2270752 [SID1234518895]). The data were presented in a poster on Sunday, May 7, 2017 at the 2017 American Association for Cancer Research (AACR) (Free AACR Whitepaper) Conference Hematologic Malignancies: Translating Discoveries to Novel Therapies, held May 6-9 in Boston, MA.
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The poster, entitled CG’806, a first-in-class FLT3/BTK inhibitor, exerts superior potency against AML cells harboring ITD, TKD and gatekeeper mutated FLT3 or wild-type FLT3, demonstrated the superior potency of CG’806, relative to competitive agents, against hematologic malignancy cell lines driven by various WT or mutant forms of FLT3. In addition, once daily oral dosing of CG’806 in a murine model achieved sustained micromolar plasma concentration over a 24hr period, and was accompanied by complete elimination of AML FLT3-ITD tumors in the absence of toxicity.
Results were presented by Weiguo Zhang, M.D., Ph.D., Assistant Professor of Leukemia at The University of Texas MD Anderson Cancer Center, for a research team led by Michael Andreeff, M.D., Ph.D., Professor of Leukemia.
"Given the potency of CG’806 against all of the mutant forms of FLT3 AML and the ability to eradicate AML tumors in murine xenograft models, CG’806 has demonstrated the potential to be superior to other FLT3 inhibitors and is beginning to differentiate itself as a targeted treatment for AML," commented William G. Rice, Ph.D., Chairman and Chief Executive Officer of Aptose. "We believe CG’806 has the potential to become the best-in-class FLT3 inhibitor, and our internal efforts now are focused on delivering CG’806 to AML patients as soon as practicable."
CG’806 and competitor FLT3 inhibitors were tested for potency to kill a series of isogenic cells, in which a specific form (WT or mutant) of FLT3 drove survival and proliferation of cells. Compared to second-generation FLT3 inhibitors (quizartinib, gilteritinib, or crenolanib), CG’806 showed more pronounced anti-proliferative effects in leukemia cells with the ITD mutation, D835 mutations, the ITD plus F691I/Y842D/D835 mutations, or in FLT3 wild-type cells. The IC50s were 0.17, 0.82, 9.49, 0.30, 8.26, 9.72, and 0.43 nM for human FLT3-ITD mutated AML cells MV4-11 (FLT3-ITD) and MOLM13 (FLT3-ITD), murine leukemia Ba/F3 (FLT3-WT), Ba/F3 (FLT3-ITD), Ba/F3 (FLT3-D835Y), Ba/F3 (FLT3-ITD+D835Y), and Ba/F3 (FLT3-ITD+F691L) cells, respectively. CG’806 triggered profound apoptosis in cell lines harboring FLT3-ITD mutations and suppressed FLT3 and its downstream MAPK/AKT signaling. Moreover, CG’806 demonstrated in vivo tumor eradication without toxicity when administered orally, once daily for 14 days as a single agent in the MV4-11 AML murine xenograft model, and demonstrated sustained micromolar plasma drug levels in mice after a single oral administration.
The presentation will be published in the AACR (Free AACR Whitepaper) Hematologic Malignancies Conference Proceedings. The poster can also be accessed here or at the Publications & Presentations section of the Aptose website, www.aptose.com.
About CG’806
CG ‘806 is a once daily, oral, first-in-class pan-FLT3/BTK inhibitor. This small molecule demonstrates potent inhibition of mutant forms of FLT3 (including internal tandem duplication, or ITD, and mutations of the receptor tyrosine kinase domain and gatekeeper region), eliminates AML tumors in the absence of toxicity in murine xenograft models, and represents a potential best-in-class therapeutic for patients with FLT3-driven AML. Likewise, CG’806 demonstrates potent, non-covalent inhibition of the Cys481Ser mutant of the BTK enzyme, as well as other oncogenic kinases operative in B cell malignancies, suggesting CG’806 may be developed for CLL and MCL patients that are resistant/refractory/intolerant to covalent BTK inhibitors.