Scientist Amgen South San Francisco, California, United States
Background: Recently, an increasing number of protein degraders (PDs) designed for targeted protein degradation via induced protein proximity, have begun entering clinic trials (e.g., ARV-110 & ARV-471, which are both orally bioavailable). However, various groups have reported challenges with the development of oral PDs using traditional assays & parameters. This reveals the gap in knowledge regarding optimal pre-clinical in-vitro assays for predicting PD’s oral bioavailability (F). We selected over 24 chemically diverse PDs to generate preclinical pharmacokinetic (PK) data for, and to test the performance of a battery of ADME assays, including in-vitro partitioning coefficient (Kpuu), Pgp Efflux ratio (ER), and permeability (Papp). Here, we focused on the correlative performance of in-vitro assays traditionally used to screen for and predict oral absorption (Papp, Pgp ER) and systemic distribution (Kpuu).
Methods: MDCK-mdr1 Trans-well assays were used to determine Papp and Pgp ERs. HEK293 cells were used to determine Kpuu. In-vivo PK study was conducted using CD1 mice; PK parameters were estimated using NCA or 2-compartment model.
Results: Most PDs had low Papp (i.e., < 1). Despite most PDs exceeding the Pgp ER threshold (ER > 3), only about 1/3 of PDs were confirmed as substrates of Pgp. A few PDs had Kpuu values ≤ 1. Papp and F were positively correlated (r=0.91, p-value < 0.0001), whereas Pgp ER and F were not significantly correlated (r=0.35, p-value=0.08). Kpuu and volume of distribution in the tissues (Vt) was positively correlated (r=0.95, p-value=0.003).
Conclusion: Papp associates positively with F, but ER and F correlation is not significant. Kpuu positively associates with oral Vt and may reflect a PD’s disposition in tissues in-vivo. To date, this will be the largest preclinical dataset of chemically diverse PDs published.
