NOVEL THERAPEUTICS FOR MIXED LINEAGE LEUKAEMIA IN INFANTS — ASN Events

NOVEL THERAPEUTICS FOR MIXED LINEAGE LEUKAEMIA IN INFANTS (#133)

Shiloh MC Middlemiss 1 , O Chernova 2 , Li Korotchkina 2 , Richard B Lock 1 , A V Gudkov 3 , Michelle Haber 1 , Murray D Norris 1 , Michelle J Henderson 1
  1. Children's Cancer Institute, Randwick, NSW, Australia
  2. OncoTartis Inc., Buffalo, New York, USA
  3. Roswell Park Cancer Institute, Buffalo, New York, USA

Mixed Lineage Leukaemia (MLL) gene rearrangement is detected in 80% of acute lymphoblastic leukaemias (ALL) diagnosed in infancy (<12 months). A biologically distinct disease, infant MLL-rearranged leukaemia is highly aggressive and often refractory to treatment, with less than 50 % of patients surviving their disease. Hence there is an urgent need for targeted therapies to improve survival in MLL patients.

High Throughput Screening identified a novel small molecule inhibitor, OT-82, with selectivity against haematopoietic cancers.  Cytotoxicity assays showed OT-82 to be particularly effective against cell lines harbouring MLL gene rearrangement, causing reduced cell viability at concentrations in the low nanomolar (nM) range (IC50 0.31-1.8 nM). Affinity chromatography identified nicotinamide adenine phosphoribosyltransferase (NAMPT) as the likely target of OT-82. This was further confirmed in cytotoxicity assays where nicotinic acid addition had a protective affect against OT-82 in haematopoietic cells.

A significant reduction in leukaemia burden was also observed in relevant preclinical animal models of MLL-rearranged ALL. Severe combined immunodeficient (SCID) mice subcutaneously xenografted with the leukaemia cell line MV4;11 (MLL-AF4) were treated with single agent OT-82 which resulted in an 80 day event free survival (EFS), representing a 60 day leukaemia growth delay (LGD) compared to mice receiving vehicle control. In systemic leukaemia models where primary infant MLL-ALL samples, derived from either MLL-AF4 or MLL-ENL patients, were engrafted  in non-obese diabetic/SCID (NOD/SCID) mice, OT-82 significantly  increased EFS and LGD for both xenografts (MLL-AF4: 45.6 day EFS, 41.4 day LGD; MLL-ENL: 67.8 day EFS, 57.6 day LGD, p < 0.0001 in each case).

 

In summary, we have identified a novel small molecule compound, OT-82, as a promising inhibitor of the NAD+ pathway that may ultimately be clinically useful for the treatment of infant leukaemia and other MLL-translocated cancers. Further preclinical studies are underway to determine the utility of OT-82 in combination with currently used standard and high-risk treatment regimens.