Quizartinib (AC220)

Quizartinib (AC220) is a 2nd-generation FLT3 inhibitor for Flt3(ITD/WT) with IC50 value of 1.1 nM/4.2 nM, and it is ten-fold more selective for Flt3 than PDGFRα, PDGFRβ, KIT, RET and CSF-1R [1].

Quizartinib inhibits FLT3 with low nanomolar potency in cellular assays and shows high selectivity when screened against most of the human protein kinome. In addition, the combination of high potency and selectivity exhibited by quizartinib is unique compared with CEP-701, PKC-412, MLN-518, sunitinib, and sorafenib.

Quizartinib (AC220) was identified to be the most potent and selective FLT3 inhibitor with good pharmaceutical properties and superior efficacy in tumor xenograft models. A single dose of 10 mg/kg was administered to mice by oral gavage and plasma levels were measured over a 24-hour period. Quizartinib was well absorbed, achieving a maximum plasma level (Cmax) of 3.8 μM (2100 ng/mL) within 2 hours of dosing. To determine the effect of FLT3-ITD inhibition on cell growth,. These results establish that AC220 has strong activity against FLT3 in biochemical and cellular assays in MV4-11 cell proliferation in the presence of 1.1nM quizartinib [1].

As a FLT3 inhibitor for the treatment of acute myeloid leukemia (AML), when at doses as low as 1 mg/kg orally once a day, quizartinib inhibits FLT3 activity in vivo extending survival significantly. And this eradicates tumors in a FLT3-dependent mouse xenograft model, and potently inhibits FLT3 activity in primary patient cells at a dose of 10 mg/kg. In addition, quizartinib has been demonstrated a desirable safety and PK profile in humans. The emergence of resistant mutations is a common mechanism of resistance to FLT3 inhibitors used clinically, with a mutation emerging in at least 20% of the patients. This shows that the survival of AML blasts depends to a great extent on FLT3 signaling in these cases [2, 3].

References:
[1].  Zarrinkar PP, Gunawardane RN, Cramer MD, et al. AC220 is a uniquely potent and selective inhibitor of FLT3 for the treatment of acute myeloid leukemia (AML). Blood, 2009, 114(14): 2984-2992.
[2]. Chao Q, Sprankle KG, Grotzfeld RM, et al. Identification of N-(5-tert-Butyl-isoxazol-3-yl)-N'-{4-[7-(2-morpholin-4-yl-ethoxy)imidazo[2,1-b][1,3]benzothiazol-2-yl]phenyl}urea Dihydrochloride (AC220), a Uniquely Potent, Selective, and Efficacious FMS-Like Tyrosine Kinase-3 (FLT3) Inhibitor. Journal of Medicinal Chemistry, 2009, 52(23): 7808-7816.
[3].  Alvarado Y , Kantarjian HM, Luthra R, et al. Treatment With FLT3 Inhibitor in Patients With FLT3-Mutated Acute Myeloid Leukemia Is Associated With Development of Secondary FLT3-Tyrosine Kinase Domain Mutations. Cancer, 2014, 120(14): 2142-2149.