Cryptococcosis is a devastating opportunistic infection caused primarily by Cryptococcus neoformans. Cryptococcosis most often spreads to the brain, causing cryptococcal meningitis (CM), and is fatal if left untreated. CM is the AIDS-defining central nervous system (CNS) illness and occurs in 60-70% of HIV positive individuals worldwide. In sub-Saharan Africa, CM causes more than 500,000 annual deaths among HIV positive patients compared with 350,000 annual fatalities for tuberculosis in the overall population. CM presents with symptoms including severe nausea, headache due to inflammation of the meninges, altered mental status, and fever. Lack of access to the recommended first-line therapeutic combination of amphotericin B/flucytosine (AmB/flucytosine) is a key component of the high mortality rate in the developing world. Access in this setting is hindered by the need for hospital-based i.v. administration of these drugs which lack an oral formulation. Moreover, the mortality rate for HIV-infected acute CM patients is over 20% within 3 months after infection in North America, despite patient access to AmB/flucytosine. Fluconazole, an oral, fungistatic drug, is used after the initial treatment with AmB/flucytosine, and is often used for months after induction therapy. Sales of Gilead's liposomal Ambisome B alone (not counting generic AmB) were $330 million in 2011 while sales of fluconazole exceeded $1 billion annually, prior to 2003. By employing a novel screen for fungicidal compounds, we identified several molecules that target C. neoformans Pkh2-02 kinase. Encouraged by preliminary data demonstrating that orally available Pkh2-02 kinase inhibitors combined with fluconazole have fungicidal activity, we plan to create a novel and efficacious treatment for CM.
Aim 1. Employ initial library screening results and SAR to design a small library of Pkh2-02 inhibitors Aim 2. Screen and select compounds for antifungal activity against strains of C. neoformans as monotherapy and combined with fluconazole (FL) or posaconazole (POS), evaluate initial pk properties and cytotoxicity, and iterate library based on observed SAR.
Aim 3. Iterate library as needed to generate an additional 40 compounds based on the Aim 2 results to refocus library and perform more detailed pk and pd screens.
Cryptococcal meningitis (CM) is the AIDS-defining illness for 60-70% of HIV positive individuals with an estimated worldwide occurrence of 1 million cases annually. CM is invariably fatal if left untreated and even with access to preferred therapeutics, the mortality rate is over 20%. There is a clear need for new, readily-available therapeutics to improve the treatment of this deadly disease.