Researchers have corrected a disease-causing gene mutation with a single infusion carrying a treatment that precisely targeted the errant gene.

This was the first time a mutated gene has been restored to normal.

The small study of nine patients announced Monday by the company Beam Therapeutics of Cambridge, Mass., involved fixing a spelling error involving the four base sequences — G, A, C and T — in DNA. The effect was to change an incorrect DNA letter to the right one. The result was a normal gene that functioned as it should, potentially halting liver and lung damage of patients with a rare disorder.

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The small study in patients with a rare disorder that causes liver and lung damage showed the potential for precisely targeted infusions.