Invasive fungal diseases cause more than 1.5 million deaths per year, with an estimated 181,000 attributable to meningitis caused by the fungal priority pathogen, Cryptococcus neoformans (WHO, 2023). Despite the high death rate, treatment options are limited. In contrast to humans, fungal cells maintain phosphate homeostasis via a CDK signalling complex, providing new drug-targeting opportunities. To identify candidate CDK component targets for new therapy, we created strains with a constitutively active (pho80Δ) and an activation-defective (pho81Δ) phosphate (PHO) signalling pathway, leading to phosphate overload and phosphate deficiency, respectively. We showed that phosphate overload coincided with elevated metal ions, metal stress sensitivity, and a muted calcineurin response, all of which were ameliorated by phosphate depletion. However, blocking, as opposed to permanently activating the PHO pathway, reduced fungal virulence to a greater extent in a mouse infection model, with virulence attenuation most likely attributable to depleted phosphate and ATP stores, and compromised cellular bioenergetics, irrespective of external phosphate availability. Our studies suggest that inhibiting Pho81, which has no human homologue, would therefore have the most detrimental impact on fungal growth in the host.