Long acting injectable of pan-RAF-MEK molecular-glue: Metronomic exposure for the treatment of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies, with 5-year survival rates below 12%. KRAS mutations (95% of cases) driving aberrant MAPK signaling-yet MEK inhibitors have failed due to rapid resistance, off target inhibition, and poor pharmacokinetics. There is an urgent need of paradigm-shifting approach that blocks MAPK pathway beyond conventional inhibitors. NST-628 (NST) is a potent pan-RAF-MEK molecular glue that provide dual blockade by preventing the activation of MEK and by blocking the RAF proteins, thus enabling prolonged inhibition of MAPK oncogenic signaling pathway. NST's physicochemical properties make oral delivery suboptimal, limiting clinical translation, prompting for a sustained-release injectable formulation of NST to ensure therapeutic efficacy. We developed a self-injectable, biodegradable, sustained-release depot formulation of NST (DepNeST). This represents the first extended-release formulation of a molecular glue for cancer therapy. We aim to a) To evaluate anticancer efficacy in 2D and 3D PDAC models; b) To optimize and characterize DepNeST for sustained NST release kinetics. NST demonstrated potent in-vitro cytotoxicity with an IC 50 of 183.8 nM in MIA PaCa-2 and showed concentration dependent increase in cell size. NST treatment induced concentration-dependent cytoskeletal disruption in MIA PaCa-2, characterized by actin filament accumulation and aberrant lamellipodia/filopodia formation. Acridine orange and Giemsa staining confirmed chromatin condensation and marked morphological remodeling, reflecting NST-driven antitumoral activity. NST triggered 2-fold G0/G1 arrest in MIA PaCa-2 and inducing 1.8- to 2.2-fold increases in apoptosis (acute vs. chronic), effectively blocking proliferation and driving cell death. Multicellular 3D spheroid models demonstrate superior cytotoxicity with ~50% reduction in spheroid area with NST compared to control. Live/Dead assays revealed extensive apoptosis in both regimens, with marked red fluorescence confirming cell death and validating NST's potency in clinically relevant 3D models. DepNeST was fabricated by dissolving biodegradable polymers in different concentrations in a biocompatible solvent, N-methyl pyrrolidone (NMP). Subsequently, NST was dissolved into a polymer-NMP solution. DepNeST formulation with constant PLGA and increasing Poloxamer 338 concentrations enhanced depot dissolution profile. The in-vitro release study demonstrated an initial burst release followed by a sustained release of NST from DepNeST over a period of 6 days. This first-ever investigation of NST-628 molecular glue in pancreatic cancer establishes DepNeST as a paradigm-shifting depot platform that delivers sustained MAPK suppression at reduced doses-potentially transforming therapeutic landscape for RAS/RAF-driven malignancies.