(T1530-09-59) Effects of Permeation Enhancers on the Epithelial Transport and Bioavailability of the Proteolysis Targeting Chimera (PROTAC) ARV-471 in Rats

Purpose: PROTACs exhibit a unique and promising pharmacology. However, this comes with molecular properties exceeding the ‘drug-like’ Ro5 chemical space, which often limits oral bioavailability and intestinal absorption. This study aimed to investigate the potential of permeation enhancers as a drug delivery strategy to improve intestinal absorption and bioavailability of the poorly soluble and permeable model PROTAC, ARV-471 (724 Da, LogP 5.9, Peff 0.23 × 10^ (- 4) cm/s, BCS class IV). We present novel mechanistic insights into how permeation enhancers can help overcome absorption barriers associated with complex small molecules, a delivery approach that has not yet been explored in literature for PROTACs.

Methods: Structurally diverse permeation enhancers with good safety profiles – sodium caprate (C10), salcaprozate sodium (SNAC), and lauroyl-L-carnitine (LLC) - were investigated for their potential for intestinal absorption enhancement. Intestinal absorption and bioavailability were determined based on plasma drug exposure over 4 hours following intraduodenal administration of ARV-471 (2.5 mg/kg), either alone or co-administered with a permeation enhancer (22 mg/kg) in rats. To isolate the effect on epithelial transport, single-pass intestinal perfusions (SPIP) were conducted in rats to evaluate changes in effective intestinal permeability (P_eff) in the presence of permeation enhancers, as well as membrane integrity and recovery post-treatment. Additionally, an ultracentrifugation assay was employed to distinguish the contribution of enhanced drug solubilization from that of true permeability enhancement.

Results: All permeation enhancers increased both the bioavailability and P<sub>eff of the PROTAC ARV-471. Sodium caprate demonstrated only modest effects on absorption and permeability. In contrast, SNAC increased plasma AUC_0-4h by 70% and enhanced P<sub>eff by 2.5-fold with minimal contribution from solubilization. Lauroyl-L-carnitine led to a 150% increase in plasma AUC_0-4h, a 2.2-fold enhancement in P<sub>eff, and a 20-fold increase in micellar ARV-471 concentrations in rat simulated intestinal fluid, indicating a combined effect of permeability enhancement and solubilization. Membrane recovery was indicated by the return of P<sub>eff values to baseline within 20 minutes post-perfusion for all tested permeation enhancers.

Conclusion: This study demonstrates that permeation enhancers offer a promising strategy to improve the oral bioavailability of PROTACs and other BCS Class IV compounds. Depending on the enhancer type, bioavailability and intestinal absorption gains can result from enhanced drug solubilization, transient modulation of the epithelial permeability, or both. SNAC improved ARV-471 plasma exposure primarily through membrane interaction, while lauroyl-L-carnitine enhanced exposure through a combined effect, increasing both permeability and solubilization in intestinal fluids. These novel findings in rats support the potential of permeation enhancer-based formulations to enable the oral delivery of PROTACs and translate their pharmacological promise into effective therapeutics.

Acknowledgements: Ethical Approval and Animal Welfare. The animal study was approved by the local ethics committee for animal research (5.8.18–00250/2022) in Uppsala, Sweden. The animal studies were carried out in compliance with the EU regulations for animal welfare

Funding: This work was funded by AbbVie.

Plasma concentration-time curves after intraduodenal administration of ARV-471 with and without permeation enhancers. (n=6) (mean ± SEM)

Mean ± SEM effective intestinal permeability over time after single-pass intestinal perfusion of ARV-471 alone (section 1), with permeation enhancer (section 2, light red), and ARV-471 alone (section 3). (n=5)

Mean ± SD of micellar concentrations of ARV-471 in the vehicle with and without permeation enhancers and after dilution of the vehicle in rat simulated intestinal fluids (ratSIF) (2:1). (n=3)