• Median age of AML diagnosis is 67 years, and incidence

increases with age

• Five-year survival rate is dismal at 24% and less than 5%

for patients over the age of 60 years

• A high proportion of patients relapse, and one-third of

patients exhibit primary refractory disease

• New treatments are urgently required

Investigating PARP inhibitors for the treatment of

acute myeloid leukaemiaCheenie Nieva1, Lisa Lincz1,2,3, Kathryn Skelding1

1 School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308

2 Hunter Medical Research Institute, New Lambton NSW 2305

3 Hunter Haematology Research Group, Calvary Mater Newcastle Hospital, Waratah NSW 2298

ABBREVIATIONS

AML Acute myeloid leukaemia

PARPi Poly (adenosine diphosphate [ADP]-ribose polymerase

Acute myeloid leukaemia (AML) is the

most common and aggressive acute

leukaemia in adults

Inhibition of PARP is a potential new for

AML

• AML cells with perturbations in DNA repair pathways

exhibit alterations in sensitivity to a range of anti-cancer

agents [1]

• Cells with defective homologous recombination (HR)

repair are very sensitive to a class of drugs called PARP

inhibitors (PARPi) [2]

• PARPi have shown significant clinical efficacy among a

range of solid tumours, including breast, ovarian, lung and

prostate cancers

• Therapeutic potential of PARPi in AML remains relatively

unexplored

• The PARPi olaparib has been demonstrated to induce cell

death as a monotherapy in a panel of AML cell lines and

primary AML patient blasts in vitro [3]

AIM:

To examine the pharmacological efficacy of PARPi in

AML cells, singly and in combination with existing

chemotherapeutics in vitro.

• Treatment with each of the PARPi led to a reduction in cell

viability in a dose-dependent manner in all AML cell lines

examined (THP-1, MV4-11, KG-1, Kasumi-1, BDCM and

AML-193)

• AML cell lines exhibited differing sensitivities to each

PARPi

Figure 1. Cell viability of AML cells 96 h post-treatment with PARPi as single

agents. A panel of AML cells were treated with increasing concentrations (0.002,

0.02, 0.2, 2 and 20 mM) of PARPi (A) veliparib, (B) olaparib, (C) rucaparib and (D)

pamiparib for 96 h and cell viability was determined by resazurin assay. Mean ±

SEM. n=3 in triplicate.

Table 1. The IC50 values for PARPi (mM) as single agents. Mean ± SEM. n=3 in

triplicate.

• This highlights that different AML subtypes may be more

sensitive to treatment with different PARPi

CONCLUSIONS:

• PARPi demonstrate efficacy against AML cell lines as

single agents in vitro

• PARPi potentiates the cytotoxic activity of cytarabine in

vitro, suggesting that administration of PARPi in

combination with cytarabine may provide benefits to

improving AML patient outcomes.

• Further examination of PARPi may be useful

therapeutically as a new strategy for the treatment of

AML.

• Treatment of AML cells with increasing doses of PARPi led

to a reduction in colony formation with the highest dose

• AML cells exhibited varying sensitivities to each PARPi

treatments

METHODS:

CELL VIABILITY ASSAY:

• A panel of 6 AML cell lines were treated with varying

concentrations of the PARPi veliparib, olaparib, rucaparib

and pamiparib, alone or in combination with daunorubin or

cytarabine, for 96 h and cell viability was assessed by

resazurin assay

CLONOGENIC ASSAY:

• A panel of 6 AML cell lines were treated with increasing

concentrations of PARPi and were growth in soft agar for

7 days before staining with 0.5% crystal violet/10%

methanol/PBS for 30 mins to visualise colonies.

CALCULATION OF COMBINATION INDICES:

• Data was quantitatively analysed to ascertain the degree

of drug interaction using the CompuSyn software

(ComboSyn, Inc, Paramus, NJ) which is based on the

combination index (CI) and isobologram equation

methods derived from the median-effect theorem of Chou

and Talalay [4]

AML cells are sensitive to PARPi in vitro

Long-term treatment with PARPi reduce

clonogenicity of AML cells

Table 2. Combination index (CI) values for AML cells treated with a combination

of PARP inhibitors and chemotherapeutics. Combination indices were calculated

using CompuSyn and the values were defined as synergistic if less than 0.9,

additive if between 0.9 and 1.1, and antagonistic if greater than 1.1. Mean ± SEM.

n=3 in duplicate.

Figure 2. Clonogenic assay of AML cell lines treated with increasing doses of

veliparib. Cells were treated with increasing doses (0.002, 0.02, 0.2, 2 and 20 mM)

of PARPi and were grown for 7 days in soft agar. Bar graphs depict the average

number of colonies grown for AML cell lines treated with (A) veliparib, (B) olaparib,

(C) rucaparib and (D) pamiparib. Statistical significance * (p<0.05); ** (p <0.01);

****(p<0.0001). Mean ± SEM. n=3 in triplicate.

• PARPi synergistically or at least additively enhanced the

sensitivity of THP-1, MV4-11, KG-1, and BDCM cells to

cytarabine as evidenced by combination indices of less

than 0.9 or in between 0.9 and 1.1, but mostly antagonised

the effects of cytarabine in Kasumi-1 and AML-193 cells

with combination indices of greater than 1.1 being

observed

AML cells are sensitive to treatment with

PARPi in combination with daunorubicin

and cytarabine in vitro

REFERENCES[1] Pearsall E. A., et al 2018, Curr Drug Targets In press.

[2] McCabe N., et al., 2006, Cancer Research 66: 16

[3] Faraoni I. et al., 2015, Biochim Biophys Acta 1852: 3

[4] T. C., Talalay P., 1984, Adv Enzyme Regul 22

• In the majority of cases (THP-1, KG-1, Kasumi-1 and

BDCM cells) PARPi exerted antagonistic effects with

daunorubicin as evidenced by combination indices of less

than 0.9 being observed, but were mostly synergistic in

MV4-11 and AML-193 cells with combination indices

greater than 1.1

• Concurrent administration of PARPi and daunorubicin or

cytarabine led to a greater reduction in cell viability

compared to treatment with either agents alone