Targeting translation initiation yields fast-killing therapeutics against the zoonotic parasite Cryptosporidium parvum.

Cryptosporidium parvum is a zoonotic apicomplexan that causes moderate-to-severe watery diarrhea in children, immunocompromised patients, and neonatal ruminants, yet no fully effective drug is available. We show that the parasite's eukaryotic initiation factor 4A (CpeIF4A; a DEAD-box RNA helicase in the eIF4F translation-initiation complex) can be exploited as a fast-killing therapeutic target. Rocaglamide A (Roc-A), a plant-derived rocaglate, binds the CpeIF4A-RNA-ATP complex with high affinity (Kd = 33.7 nM) and blocks protein synthesis in excysting sporozoites (IC50 ≈ 3.7 µM). In host-cell culture, Roc-A suppresses intracellular growth with nanomolar potency (EC50 = 1.77 nM) and a selectivity index exceeding 56,000 in HCT-8 cells and 1,400 in HepG2 cells. A five-day oral regimen (0.5 mg/kg/d) reduced oocyst shedding by >90% within 48 h in interferon-γ-knockout mice and by 70-90% from day 2 onward without rebound during a 15-day follow-up in NCG mice. Two amino-acid differences at the Roc-A binding surface (D165 and V192 in CpeIF4A vs. N167 and D194 in the human ortholog) offer a foothold for medicinal optimization toward greater parasite selectivity. These findings establish translation initiation as an unexplored but tractable pathway for anti-cryptosporidial drug discovery and position Roc-A as a promising lead compound.