As a subtype of acute myeloid leukemia (AML), acute promyelocytic leukemia (APL) 
is characterized by a chromosomal translocation, most of which result in the 
production of a PML-RAR alpha fusion protein. Although the overall survival rate 
of APL patients has improved dramatically due to all-trans retinoic acid (ATRA) 
treatment, ATRA-resistance remains a clinical challenge in the management of 
APL. Therefore, alternative agents should be considered for ATRA-resistant APL 
patients. Here, we report that antimalaria drug primaquine phosphate (PRQ) 
exhibits an anti-leukemia effect on both ATRA-sensitive cell line NB4 and 
ATRA-resistant APL cell lines, NB4-LR2, NB4-LR1, and NB4-MR2. Moreover, PRQ 
significantly inhibited primary colony formation of untreated or relapsed APL 
patients. Further study showed that PRQ could induce the apoptosis of APL cells 
by inhibiting NF-κB signaling pathway. The in vivo study showed that PRQ 
significantly inhibited NB4-LR2 xenograft tumors growth. These results suggest 
that PRQ is a potential therapeutic agent for ATRA-resistant APL patients.