Altiratinib blocks Toxoplasma gondii and Plasmodium falciparum development by selectively targeting a spliceosome kinase

Abstract

The Apicomplexa comprise a large phylum of single-celled, obligate intracellular protozoa that include Toxoplasma gondii , Plasmodium , and Cryptosporidium spp., which infect humans and animals and cause severe parasitic diseases. Available therapeutics against these diseases are limited by suboptimal efficacy and frequent side effects, as well as the emergence and spread of resistance. We use a drug repurposing strategy and identify altiratinib, a compound originally developed to treat glioblastoma, as a promising drug candidate with broad spectrum activity against apicomplexans. Altiratinib is parasiticidal and blocks the development of intracellular zoites in the nanomolar range and with a high selectivity index when used against T. gondii . We have identified Tg PRP4K of T. gondii as the primary target of altiratinib using genetic target deconvolution, which highlighted key residues within the kinase catalytic site that conferred drug resistance when mutated. We have further elucidated the molecular basis of the inhibitory mechanism and species selectivity of altiratinib for Tg PRP4K and for its Plasmodium falciparum counterpart, Pf CLK3. Our data identified structural features critical for binding of the other Pf CLK3 inhibitor, TCMDC-135051. Consistent with the splicing control activity of this kinase family, we have shown that altiratinib can cause global disruption of splicing, primarily through intron retention in both T. gondii and P. falciparum . Thus, our data establish parasitic PRP4K/CLK3 as a potential pan-apicomplexan target whose repertoire of inhibitors can be expanded by the addition of altiratinib.

In vitroproduction of cat-restrictedToxoplasmapre-sexual stages by epigenetic reprogramming

“…Immunoblot analysis of protein was performed as described in Swale et al (2022) 45 . Briefly, ∼10 7 cells were lysed and sonicated in 50 μl lysis buffer (10 mM Tris-HCl, pH6.8, 0.5% SDS [v/v], 10% glycerol [v/v], 1 mM EDTA, and protease inhibitor cocktail).…”

3′‐end mRNA processing within apicomplexan parasites, a patchwork of classic, and unexpected players

“…Part of the reason for this may lie in the fact that these eukaryotic cells have much higher replication rates and overall pervasive mRNA transcription. The recent discovery of PRP4K kinase inhibitors in P. falciparum and T. gondii (Alam et al, 2019; Swale et al, 2022) also suggests that inhibition of splicing activity, another component of the mRNA maturation process, is also a critical vulnerability in these organisms, leading to an irreversible inhibition process in cellulo.…”

Roles of alternative splicing in infectious diseases: from hosts, pathogens to their interactions

“…Reported anti-IAV agents mainly target specific splicing events [62,63] . Besides, drugs against other viruses, parasites, and fungi infections are also documented [64–71] . Of note, drugs targeting bacterial infection have not been reported.…”

“…Altiratinib Altiratinib induces the intron retention in both T. gondii and P. falciparum by inhibiting PRP4K/CLK3. [69] Plasmodium falciparum Fungal infection…”

“…[62,63] Besides, drugs against other viruses, parasites, and fungi infections are also documented. [64][65][66][67][68][69][70][71] Of note, drugs targeting bacterial infection have not been reported. Similar splicing regulatory patterns in different infections lead us to hold the view that these developed drugs may have certain applicability for bacterial infections.…”