Authors: Seodhna M. Lynch1, Rachael Wilson2, Tríona Ní Chonghaile3, Alex Thompson4,5, Ken Mills4, Ross Levine6, Kyle B. Matchett1

Affiliations: 1 Personalised Medicine Centre, School of Medicine, Ulster University, C-TRIC, Altnagelvin Hospital Campus, Glenshane Road, Derry/Londonderry, BT47 6SB, UK. 2 Wellcome-MRC Cambridge Stem Cell Institute, Jeffrey Cheah Biomedical Centre, Puddicombe Way, Cambridge Biomedical Campus, Cambridge, CB2 0AW, UK. 3 Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephens Green, Dublin 2, Ireland. 4 Patrick G Johnston Centre for Cancer Research, Queen’s University Belfast, Belfast, BT9 7AE, UK. 5 Centre for Cancer Sciences, The Biodiscovery Institute, Faculty of Medicine & Health Sciences, University Park, Nottingham, NG7 2RD, UK. 6 Department of Medicine, Memorial Sloan Kettering Cancer Centre, 1275 York Avenue, New York, NY 10065, United States

Background/ Introduction: Venetoclax (VEN), a B-cell lymphoma (BCL)-2 inhibitor, is approved for the treatment of acute myeloid leukaemia (AML) in patients >75years. The effects of VEN remain restrictive and little is known about it’s efficacy in paediatric AML. AML is a leading cause of paediatric leukaemia death with ~60% of children diagnosed with AML surviving >5years. These poor outcomes alongside toxic side effects from treatment means there is an urgent clinical need for novel therapies, that will provide efficacy and reduce therapy-associated side effects in paediatric AML.

Material & Methods: The novel anthelmintic agent albendazole (ABZ), identified from a single agent FDA drug library screen (performed in primary murine cells representing MLL-AF9-driven paediatric AML and normal karyotype HOXA9-Meis1 driven AML), was evaluated for anti-leukaemia efficacy in murine/human models of childhood AML (in vitro/vivo). The synergy of the ABZ-VEN combination was also investigated.

Results: Low dose ABZ (IC50<300nM at 72hours) reduced viability in human AML cell lines, with minimal effect on normal cells. ABZ caused G2/M arrest and PARP cleavage (at 4hours following 100nM ABZ treatment), leading to apoptosis (PI/Annexin V-based flow cytometry, Western blot). Luciferase expressing THP-1 childhood AML cells were generated and pre-treated (vehicle/ABZ/untreated). Live tracking of pSLIEW-transduced AML cells in NSG mice showed ABZ decreased leukaemia burden and extended lifespan (Control (30days) vs ABZ (53days)). Results also demonstrated the novel ABZ-VEN drug combination as synergistic in THP-1 (resistant to VEN alone) cells (at 24/48/72 hours with varying concentrations of ABZ/VEN).

Conclusion: The novel drug ABZ has remarkable anti-leukaemia efficacy in paediatric AML (in vitro/vivo). In addition, the ABZ-VEN drug combination is synergistic in AML cells. The effective anti-leukaemic concentrations of ABZ/VEN are clinically achievable and both have excellent toxicity profiles. Current work is focused on evaluating if ABZ alone or in combination with VEN, has potential to progress to clinical trial for paediatric AML.