Dolutegravir Developmental Toxicity is Mitigated by Magnesium and Folate in Zebrafish Embryos.

Integrase-strand-transfer inhibitors have transformed HIV therapy, yet the widely prescribed drug dolutegravir (DTG) has been linked to developmental toxicity and its teratogenic mechanism remains uncertain. Here we use zebrafish to dissect DTG toxicity during early vertebrate development. DTG exposure from 2-4 h post-fertilization (hpf) to 24 hpf produced high mortality and abnormal morphology; co-treatment with folic acid or 5-methyltetrahydrofolate partially restored normal morphology, whereas calcium had no effect. Strikingly, supplementation with magnesium (Mg) rescued DTG-exposed embryos almost as effectively as folate, implicating magnesium availability in protection. In competitive binding assays, Mg increased binding of folate to purified folate receptor (FOLR1) by 30% in the presence of DTG. Maternal-zygotic zebrafish mutant embryos contained significantly less endogenous folate than wild-type embryos yet displayed marked hypersensitivity to DTG that could not be mitigated by folate supplementation. Together, these findings reveal a dual mechanism in which DTG antagonizes FOLR1 while concurrently sequestering Mg. Excess Mg converts DTG into a Mg-bound DTG complex that can no longer antagonize FOLR1, thereby restoring normal development. Our work identifies magnesium status as a modifiable determinant of DTG teratogenicity and provides a proof-of-concept zebrafish model that could be adapted for rapid screening of integrase inhibitors for developmental phenotypes.