Drug Target Strategies
Advances in Cellular Target Engagement
Mono(ADP-ribosylation) (MARylation) and poly(ADP-ribosylation) (PARylation) are post-translational modifications deposited on multiple amino acids, and emerging evidence suggests they are also deposited onto nucleic acids. There are 12 mono(ADP-ribose) polymerase (monoPARP) enzymes and 4 poly(ADP-ribose) polymerase (polyPARP) enzymes that use nicotinamide adenine dinucleotide (NAD+) as the ADP-ribose donating substrate to generate these modifications. While there are approved drugs and clinical trials on-going for inhibitors of the enzymes that deposit PARylation (specifically PARP1 and PARP2 inhibitors), MARylation is gaining recognition for its role in immune function, inflammation and cancer, however there is a lack of chemical probes to study the function of monoPARPs in cells and in vivo. An important first step to generating chemical probes for monoPARPs is to develop screening assays to enable determination of potency and selectivity of inhibitors during the hit finding and lead optimization phases. Complicating the development of enzyme assays is that the substrates for the majority of the monoPARPs are unknown, and even for the ones with identified substrates, it is uncertain how they engage their substrates. Here we describe the development of multiple family-wide approaches to developing robust high-throughput monoPARP assays that overcome this lack of knowledge around their substrates.