A team at UCLA has discovered that a single dose of rapamycin — a decades-old immunosuppressant drug — can rapidly reverse autism-like brain dysfunction and behaviors in adult mice, a finding that challenges the long-held assumption that such neural patterns are permanently fixed after early development.

The study, published July 24 in the journal Science, found that rapamycin normalized abnormally overactive neurons, reduced seizure susceptibility, eased sensory hypersensitivity, and decreased repetitive behaviors in mice exposed to prenatal valproic acid — a common model for autism spectrum disorder.

Critically, the improvements occurred within hours of administration and were observed in adult mice, not just during early developmental windows. The drug works by inhibiting the mTOR signaling pathway, a cellular growth regulator that is overactive in many autism models.

The researchers noted that rapamycin appeared to change brain function by recalibrating neural circuit activity rather than physically rebuilding brain structures. This suggests that some neural circuits in autism may retain unexpected plasticity well into adulthood.

Rapamycin is already FDA-approved for preventing organ transplant rejection and is used in low doses as an anti-aging intervention in clinical trials. However, the researchers cautioned that human trials for autism would need to carefully evaluate dosing and long-term effects.

The findings were widely covered by ScienceDaily, UCLA Health, NewsNation, and the Mirror.

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