Durst, G. | Search bioRxiv

bioRxiv2026

Discovery and Structure Activity Relationship Optimization of a Novel Rv1625c Agonist Chemotype with Antitubercular Activity

Rv1625c/Cya has emerged as a promising target for the development of treatment-shortening therapies for tuberculosis. Screening of an Enamine compound library identified sBQQ004 as an initial hit, and rapid hit optimization led to compound 1, which was subsequently confirmed as an Rv1625c/Cya agonist. Structure activity relationship studies identified lead compound 25 with potent activity against Mycobacterium tuberculosis H37Rv under cholesterol-dependent growth conditions (MIC = 0.27 uM) and strong intramacrophage activity (EC50 = 0.079 uM). Compounds 1 and 25 showed oral bioavailabilities of 84.5% and 51.9% in mice, respectively. Repeat BID dosing of compound 1 resulted in a dose- and time-dependent decrease in systemic exposure. Despite this pharmacokinetic limitation, the potency and overall profile of this chemotype encouraged continued optimization.

microbiology↗

bioRxiv2026

Potent reaction hijacking inhibitors of Plasmodium falciparum asparagine tRNA synthetase

Malaria remains one of the major threats to human health. Breakthrough drugs with high potency and low resistance risk are needed to combat the ever-increasing resistance to currently deployed antimalarials. Here, we explore a series of 4-amino-quinazoline-based sulfonamides, with drug-like physicochemical parameters and a synthetically accessible scaffold. Exemplars exhibit nanomolar potency against blood stage Plasmodium cultures, with up to 300-fold selectivity compared with a mammalian cell line. The compounds are also active against transmissible stages of P. falciparum and are refractory to resistance development. Targeted mass spectrometry reveals that the compounds act as reaction hijacking inhibitors targeting P. falciparum aminoacyl tRNA synthetases (aaRSs). Subtle changes to the chemical structure switch the main target from cytoplasmic tRNA threonine synthetase (PfThrRS) to cytoplasmic asparagine synthetase (PfAsnRS), a change that is associated with increased potency and selectivity. The target preference was confirmed by selective knock-down of different P. falciparum aaRSs and by tolerance selection in a mutator line. Consistent with aaRS targets, exemplar compounds activate the amino acid starvation response. Recombinant enzyme inhibition and thermal stabilisation assays confirm the susceptibility of PfAsnRS to reaction hijacking and show that human AsnRS is less susceptible. A molecular model of Asn-tRNA-bound PfAsnRS reveals that a potent hijacker adopts a pose similar to adenosine 5-monophosphate (AMP). An AlphaFold model of the native PfAsnRS dimer helps explain the tolerance-conferring effect of a mutation at the dimer interface.

biochemistry↗