Dual-drug codelivery gelatin-based hydrogel of ARV-471 and Palbociclib enhances synergistic effect in breast cancer treatment.

Current therapeutic strategies for breast cancer increasingly focus on combination regimens. While targeting estrogen receptors (ER) has demonstrated clinical benefit, strategies to enhance ER inhibition and degradation are still needed. PROTAC technology enables the selective degradation of ER and other oncogenic proteins, but its clinical application may be limited by toxicity. In parallel, advanced drug delivery systems such as hydrogels are gaining attention for their ability to improve drug stability, reduce systemic toxicity, and enhance therapeutic performance. This study aims to co-encapsulate a CDK4/6 inhibitor, Palbociclib, and an ER-targeting PROTAC, ARV-471, within a hydrogel matrix as a proof-of-concept to demonstrate the feasibility and potential synergistic efficacy of this co-delivery strategy. Hydrogels were prepared using passive loading and tested for encapsulation efficiency and release in PBS (pH 7.4). Biological evaluation included MCF7, T47D, MCF10A, and HaCaT cell lines. Antiproliferative effects were assessed by MTT assay, together with 3D Matrigel growth, clonogenic survival, and flow cytometry for cell cycle and cell death. Drug synergism was determined by calculating the combination index (CI) at different molar ratios. Hydrogels achieved 100% encapsulation efficiency and preserved cytotoxicity against breast cancer cells. Notably, co-encapsulation of ARV-471 and Palbociclib produced a stronger synergistic effect than the free-drug combination. This study provides a proof-of-concept that hydrogel-based delivery can preserve the activity of individual drugs while amplifying their combinatorial effectiveness, paving the way for advanced in vivo validation.