In vitro Screening of drug candidates against cancer and autoimmune diseases for effects on human blood cells

Acerta Pharma develops covalently binding kinase inhibitors for treatment of
human diseases including cancer and autoimmune diseases. We target signalling
pathways in disease-relevant immune cells. Optimising target specificity,
selectivity and reactivity is crucial for successful drug development (Barf T
et al. 2012)

The ideal in vitro method to aid selection for further development is testing
of drug candidate effects on human blood cells in the context of whole blood
(Covey TM et al. 2010). It is important to perform tests in whole blood because
blood components such as plasma proteins might non-specifically bind drug
candidates. Non-specific binding can dramatically reduce potency and efficacy.
In addition, with all cells present in the circulation cell-cell mediated
interactions affected by the drug substance tested will be part of the overall
study outcome. In order to dissect the effect of whole blood components on
efficacy, white blood cells will be purified and tested in parallel.

We have already successfully applied this method in preclinical studies testing
a Bruton*s tyrosine kinase (Btk) inhibitor. Our colleagues in San Carlos
(California) demonstrated that our drug candidate ACP-196 was less susceptible
to potency loss in whole blood testing compared to competitors (Covey TM et al.
2015). Avoiding potency loss through non-specific binding to whole blood
components translates into a lower drug dose required to achieve clinical
effects which reduces the risk of side effects due to off target effects of the
drug. The use of the whole blood assay has been an important selection tool,
significantly lowering the need for in vivo studies. Therefore, we want to
continue optimising the potency of our new drug candidates and implement this
method in Acerta Pharma*s location in Oss, the Netherlands.

The study population used for blood donation will be healthy volunteers because
we aim to test drug candidates under normal conditions of blood composition and
blood cell function.



References:

Barf T and Kaptein A: Irreversible Protein Kinase Inhibitors: Balancing the
Benefits and Risks. 2012 J Med Chem 55:6243-6262.

Covey TM, Putta S, Cesano A: Single cell network profiling (SCNP): mapping drug
and target interactions. 2010 Assay Drug Dev Technol 8(3):321-343

Covey TM, Barf T, Gulrajani M, Krantz F, van Lith B, Bibikova E, van de Kar B,
de Zwart E, Hamdy A, Izumi R, Kaptein A: ACP-196: a novel covalent Bruton*s
tyrosine kinase (Btk) inhibitor with imporved selectivity and in vivo target
coverage in chronic lymphocytic leukemia (CLL) patients. 20 April 2015, Annual
Meeting American Association for Cancer Research (AACR), Abstract 2596

Primary Objective: Test the capacity of drug candidates to specifically inhibit
the signalling pathways they target in human blood cells in vitro in the
setting of human whole blood.

Secondary Objective(s): Test whether drug candidates exert undesired off-target
effects on human blood cells in vitro in the setting of human whole blood.

Up to 50 ml of peripheral blood will be drawn from healthy volunteers. No
further intervention is required. The blood will be transferred to the
laboratory of Acerta Pharma in Oss, the Netherlands and used for in vitro
assays to address the objectives mentioned above.

The frequency with which freshly drawn human whole blood is required will
depend on the number of drug candidates that require testing. Only compounds
that fulfill pre-selection criteria such as binding capacity in biochemical
assays and in relevant cell lines will be tested using these human whole blood
samples. It is anticipated that 10-20 drug candidates per year will be profiled
in human whole blood assays. Therefore, we expect testing, and thus blood
draws, will be required once a month or less frequently.

Compounds will be initially tested in whole blood and purified PBMC from 1
donor. Potent and selective inhibitors that present potential clinical
candidates will be tested up to 4 independent donors in total.

This study is solely carried out in vitro. The only risk for the participants
is the standard risk associated with drawing peripheral blood, which is
minimal.