<p>Amyotrophic lateral sclerosis (ALS) is a multifactorial neurodegenerative disorder that complicates the identification of effective therapeutic targets. The potential of stem cells and neurotrophins as promising candidates has become increasingly evident, owing to their neuroprotective and anti-inflammatory properties. In this study, a preclinical evaluation of the safety and biodistribution of mesenchymal stromal/stem cells (MSCs) combined with neurotrophin-releasing polyelectrolyte nanoparticles (NTs) was conducted in a porcine intrathecal delivery model relevant to ALS therapy development. Four groups of male pigs were administered saline with NTs, adipose-derived stem cells (ASCs) with NTs, Wharton’s jelly-derived MSCs (WJ-MSCs) with NTs, or spinal puncture only. The safety of the treatment was assessed using magnetic resonance imaging (MRI), haematological and biochemical analyses, cerebrospinal fluid profiling, and histology. No adverse effects or significant systemic alterations were observed. It is noteworthy that C-reactive protein levels diminished following NT and NT–MSC administration, suggesting a systemic anti-inflammatory effect. The migration of MSCs was facilitated by cerebrospinal fluid, leading to their accumulation around the spinal cord and brain parenchyma. The present findings demonstrate short-term safety and biodistribution patterns following intrathecal administration of MSCs combined with neurotrophin-releasing nanoparticles in a large-animal model. These preliminary observations provide a pilot framework for future efficacy studies in disease-specific ALS models. This work establishes a translational platform for the development of future ALS therapies, with subsequent studies focused on efficacy testing in disease-specific models that more accurately reflect the slow, heterogeneous, multisystem nature of human ALS.</p>