Optimization of a Series of RIPK2 PROTACs

Receptor-interacting serine/threonine protein kinase 2 (RIPK2) is an important kinase of the innate immune system. Herein, we describe the optimization of a series of RIPK2 PROTACs which recruit members of the inhibitor of apoptosis (IAP) family of E3 ligases. Our PROTAC optimization strategy focused on reducing the lipophilicity of the early lead which resulted in the identification of analogues with improved solubility and increased human and rat microsomal stability. We identified a range of IAP binders that were successfully incorporated into potent RIPK2 PROTACs with attractive pharmacokinetic profiles. Compound 20 possessed the best overall profile with good solubility, potent degradation of RIPK2, and associated inhibition of TNFα release. A proof-of-concept study utilizing a slow release matrix demonstrated the feasibility of a long-acting parenteral formulation with >1 month duration. This represents an attractive alternative dosing paradigm to oral delivery, especially for chronic diseases where compliance can be challenging.

Extended pharmacodynamic responses observed upon PROTAC-mediated degradation of RIPK2

Proteolysis-Targeting Chimeras (PROTACs) are heterobifunctional small-molecules that can promote the rapid and selective proteasome-mediated degradation of intracellular proteins through the recruitment of E3 ligase complexes to non-native protein substrates. The catalytic mechanism of action of PROTACs represents an exciting new modality in drug discovery that offers several potential advantages over traditional small-molecule inhibitors, including the potential to deliver pharmacodynamic (PD) efficacy which extends beyond the detectable pharmacokinetic (PK) presence of the PROTAC, driven by the synthesis rate of the protein. Herein we report the identification and development of PROTACs that selectively degrade Receptor-Interacting Serine/Threonine Protein Kinase 2 (RIPK2) and demonstrate in vivo degradation of endogenous RIPK2 in rats at low doses and extended PD that persists in the absence of detectable compound. This disconnect between PK and PD, when coupled with low nanomolar potency, offers the potential for low human doses and infrequent dosing regimens with PROTAC medicines.

Mares et al. develop Proteolysis-Targeting Chimeras (PROTACs) that degrade its target RIPK2 in vivo at low doses for a prolonged period of time. This study suggests that PROTAC has a therapeutic potential that is superior to traditional RIPK2 small-molecule inhibitors.

Occupational hygiene measurement strategy in the pharmaceutical industry

In an industry which handles materials which are biologically active it is necessary to limit the exposure of workers engaged in both research and production to these materials. Part of the control procedure is to be able to demonstrate that whatever system is put in place is effective and remains so. This may require a programme of environmental monitoring. To be effective any monitoring programme must be properly planned and executed. This paper sets out the philosophy and practice of one multinational pharmaceutical company which may stimulate debate in the industry.

Estimation of airborne rat-derived antigens by ELISA

Double antibody sandwich ELISA procedures have been devised to estimate the concentrations of airborne rat urinary and epidermal antigens. Both assays were capable of detecting at least 3 ng/ml of antigen protein. Unknown concentrations were estimated in terms of the standard, laboratory-prepared material, as calculated from the linear relationship between absorbance and log concentration. The coefficient of variation of a single assay was 12%, the methods have been applied to extracts of the filter material from static and personal samplers in an animal room.