Field researchers in West Africa today released the first long-running data set from a CRISPR-based gene drive trial in Anopheles gambiae mosquitoes, the species responsible for the bulk of malaria transmission on the continent. The drive — designed to bias inheritance of a female-sterility allele — was released into a contained 1.2-hectare enclosure in 2024. After 30 generations and a year of monitoring, the drive remains effective at near-theoretical levels and shows no signs of the resistance mutations that earlier laboratory work had predicted would emerge by the tenth generation.
Resistance has been the field's biggest worry. In small cage trials, mosquitoes typically evolve target-site mutations that disable the CRISPR cut within a few dozen generations, neutralising the drive. The new data show a different picture in larger, more realistic populations: the wild population carries a much wider range of starting alleles, but none of them appears to rescue fertility once the drive is present.
The authors caution that 30 generations is still short by ecological standards and that the enclosure-vs-wild distinction matters — predator pressure, geographic structure, and seasonal bottlenecks could all shift the picture in a true release. A second-phase trial expanding to a 25-hectare site is now under review with the host country's biosafety authority.