Biaryl Amides and Hydrazones as Therapeutics for Prion Disease in Transgenic Mice

Abstract

The only small-molecule compound demonstrated to substantially extend survival in prion-infected mice is a biaryl hydrazone termed "Compd B" (4-pyridinecarboxaldehyde,2-[4-(5-oxazolyl)phenyl]hydrazone). However, the hydrazone moiety of Compd B results in toxic metabolites, making it a poor candidate for further drug development. We developed a pharmacophore model based on diverse antiprion compounds identified by high-throughput screening; based on this model, we generated biaryl amide analogs of Compd B. Medicinal chemistry optimization led to multiple compounds with increased potency, increased brain concentrations, and greater metabolic stability, indicating that they could be promising candidates for antiprion therapy. Replacing the pyridyl ring of Compd B with a phenyl group containing an electron-donating substituent increased potency, while adding an aryl group to the oxazole moiety increased metabolic stability. To test the efficacy of Compd B, we applied bioluminescence imaging (BLI), which was previously shown to detect prion disease onset in live mice earlier than clinical signs. In our studies, Compd B showed good efficacy in two lines of transgenic mice infected with the mouse-adapted Rocky Mountain Laboratory (RML) strain of prions, but not in transgenic mice infected with human prions. The BLI system successfully predicted the efficacies in all cases long before extension in survival could be observed. Our studies suggest that this BLI system has good potential to be applied in future antiprion drug efficacy studies.

Drug resistance confounding prion therapeutics

“…Tg(Gfap-luc)/FVB and Tg4053 mice were on the FVB/N genetic background; Tg1014, Tg2669, Tg152, and Tg12584 mice were on the FVB/Prnp 0/0 background. Female mice were used for all experiments, due to problems observed with long-term dosing of male mice (17). Mice were inoculated intracerebrally with 30 μL of 1% brain homogenate containing RML, ME7, sCJD(MM1), sCJD(VV2), or CWD prions, unless otherwise stated, when 30 μL of 0.001% sCJD(MM1) brain homogenate (generated by serial tenfold dilution), was used.…”

“…Unlike quinacrine, treatment with Compound B or anle138b substantially extended the survival of prion-infected mice (15)(16)(17). Prions from the brains of mice treated with Compound B showed different ratios of mono-to diglycosylated PrP Sc compared with the inoculum (15), and had a different conformational stability (17), but it was not determined whether the resulting prions were resistant to further treatment with Compound B.…”

“…Prions from the brains of mice treated with Compound B showed different ratios of mono-to diglycosylated PrP Sc compared with the inoculum (15), and had a different conformational stability (17), but it was not determined whether the resulting prions were resistant to further treatment with Compound B. Importantly, Compound B contains a hydrazone functionality likely under physiologic conditions to produce an aryl hydrazine, a toxic metabolite and carcinogen (18), limiting its utility as a therapeutic (17).…”

Quinacrine promotes replication and conformational mutation of chronic wasting disease prions

“…This article is a PNAS Direct Submission. 1 To whom correspondence should be addressed. E-mail: glenn.telling@colostate.edu.…”

“…Compounds targeting prevention of PrP misfolding have been aggressively pursued as therapeutics. Cells chronically infected with rodent prions are used as a means either to screen compounds inhibiting PrP Sc accumulation (1)(2)(3)(4)(5) or to confirm the proposed antiprion effects of compounds discovered by other means (6,7). Such strategies rest on the assumption that compounds with efficacy against experimentally adapted rodent prions will be effective against naturally occurring prions, in particular those causing human diseases.…”