Layer‐Specific BTX‐A Delivery to the Gastric Muscularis Achieves Effective Weight Control and Metabolic Improvement

The rising incidence of health‐endangering obesity constantly calls for more effective treatments. Gastric intramural injection of botulinum neurotoxin A (BTX‐A) as a new modality carries great promise yet inconsistent therapeutic efficacy. A layer‐specific delivery strategy enabled by dissolving microneedles is hence pioneered to investigate the working site of BTX‐A and the resulting therapeutic effects. The drug‐loaded tips of the layer‐specific gastric paralysis microneedles (LGP‐MN) rapidly release and achieve uniform distribution of BTX‐A within the designated gastric wall layers. In an obesity rat model, the LGP‐MNs not only prove safer than conventional injection, but also demonstrate consistently better therapeutic effects with muscular layer delivery, including 16.23% weight loss (3.06‐fold enhancement from conventional injection), 55.20% slower gastric emptying rate, improved liver steatosis, lowered blood lipids, and healthier gut microbiota. Further hormonal study reveals that the elevated production of stomach‐derived glucagon‐like peptide‐1 due to the muscularis‐targeting LGP‐MN treatment is an important contributor to its unique glucose tolerance‐improving effect. This study provides clear indication of the gastric muscularis as the most favorable working site of BTX‐A for weight loss and metabolic improvement purposes, and meanwhile suggests that the LGP‐MNs could serve as a novel clinical approach to treat obesity and metabolic syndromes.