# The cyclin dependent kinase (CDK)7 inhibitor BS-181 inhibits pathogenic Cryptococcus species, causing G2/M arrest and a splicing defect

## TL;DR

A CDK7 inhibitor called BS-181 stops the growth of Cryptococcus fungi, causes cell cycle arrest, and works well with existing antifungals.

## Contribution

BS-181 is shown to inhibit Cryptococcus species by targeting CDK7, with potential for antifungal repurposing.

## Key findings

- BS-181 inhibits Cryptococcus growth by causing G2/M arrest and splicing defects.
- BS-181 synergizes with amphotericin B to reduce its effective concentration.
- BS-181 combination therapy improves survival in a mouse model of Cryptococcus infection.

## Abstract

The fungal priority pathogen and basidiomycete, Cryptococcus neoformans (Cn), causes lung and brain infection in predominantly immuno-compromised individuals and there is an urgent need for new treatment options. The pyrazolopyrimidine-based cyclin dependent kinase (CDK)7 inhibitor, BS-181, has anticancer properties, but its antifungal activity has not been investigated. We show that cryptococcal CDK7 more closely resembles the human enzyme than that of ascomycetes, and that BS-181 inhibits its activity. BS-181 inhibited growth of both Cn and Cryptococcus gattii (Cg), but not ascomycete fungi and delayed progression through the G2/M phase of the cell cycle. Transcriptomic analysis revealed that BS-181 induces splicing defects leading to elevated intron retention within the transcriptome and also suppresses translational processes. BS-181 displayed additive or synergistic activity with licensed antifungals against laboratory and clinical Cn and Cg strains, most notably with amphotericin B where synergy (2–4-fold reduction in the amphotericin B MIC) was achieved using low-sub micromolar concentrations of BS-181. Compared with either drug alone, BS-181-AmB combination therapy provided greater protection against Cn infection in a wax moth model (p ≤ 0.032) and extended survival of Cn-infected mice. These findings demonstrate that CDK7 inhibitors, already of interest as anticancer agents, could be repurposed to prevent or treat opportunistic fungal infections in cancer patients when combined with licensed antifungals limited by either toxicity or resistance.