Secreted virulence factors like bacterial collagenases are conceptually attractive targets for fighting microbial infections. However, previous attempts to develop potent compounds against these metalloproteases failed to achieve selectivity against human matrix metalloproteinases (MMPs). Using a surface plasmon resonance-based screening complemented with enzyme inhibition assays, we discovered an N-aryl mercaptoacetamide-based inhibitor scaffold that showed sub-micromolar affinities toward collagenase H (ColH) from the human pathogen Clostridium histolyticum. Moreover, these inhibitors also efficiently blocked the homologous bacterial collagenases, ColG from C. histolyticum, ColT from C. tetani, and ColQ1 from the Bacillus cereus strain Q1, while showing negligible activity toward human MMPs-1, -2, -3, -7, -8, and -14. The most active compound displayed a more than 1000-fold selectivity over human MMPs. This selectivity can be rationalized by the crystal structure of ColH with this compound, revealing a distinct non-primed binding mode to the active site. The non-primed binding mode presented here paves the way for the development of selective broad-spectrum bacterial collagenase inhibitors with potential therapeutic application in humans.

Microbial infections are a significant threat to public health, and resistance is on the rise, so new antibiotics with novel modes of action are urgently needed. The extracellular zinc metalloprotease collagenase H (ColH) from Clostridium histolyticum is a virulence factor that catalyses tissue damage, leading to improved host invasion and colonisation. Besides the major role of ColH in pathogenicity, its extracellular localisation makes it a highly attractive target for the development of new antivirulence agents. Previously, we had found that a highly selective and potent thiol prodrug (with a hydrolytically cleavable thiocarbamate unit) provided efficient ColH inhibition. We now report the synthesis and biological evaluation of a range of zinc-binding group (ZBG) variants of this thiol-derived inhibitor, with the mercapto unit being replaced by other zinc ligands. Among these, an analogue with a phosphonate motif as ZBG showed promising activity against ColH, an improved selectivity profile, and significantly higher stability than the thiol reference compound, thus making it an attractive candidate for future drug development.

Antimicrobial resistance is currently one of the serious global public health threats. Unlike the conventional antimicrobial drugs, antivirulence agents disarm rather than kill bacterial pathogens and therefore represent an alternative option to skirt the problem of resistance. Pseudomonas aeruginosa elastase (LasB) and Clostridium histolyticum collagenase (ColH) are extracellular bacterial proteases which play a critical role in the establishment and progression of the respective bacterial infection. In this study, we report the modulation of the α-position of the previously reported N aryl mercaptoacetamide class leading to a new type of highly potent LasB and ColH inhibitors (N aryl 2-iso-butylmercaptoacetamides). In addition to their non-toxicity and high selectivity over several human off-targets, selected derivatives may be considered unprecedented dual inhibitors of both LasB and ColH. Among the prepared derivatives, compound 37 showed the most promising properties: it had a favorable safety profile, maintained the viability and integrity of both skin- and lung-cells treated with P. aeruginosa supernatant, demonstrated in vivo efficacy in Galleria mellonella larvae, and revealed a good volume of distribution and moderate in vivo clearance in mice. Taking together, these results demonstrate that compound 37 is a promising candidate for antivirulence drug development.

Despite the progress in surgical techniques and antibiotic prophylaxis, opportunistic wound infections with Bacillus cereus remain a public health problem. Secreted toxins are one of the main factors contributing to B. cereus pathogenicity. A promising strategy to treat such infections is to target these toxins and not the bacteria. Although the exoenzymes produced by B. cereus are thoroughly investigated, little is known about the role of B. cereus collagenases in wound infections. In this report, the collagenolytic activity of secreted collagenases (Col) is characterized in the B. cereus culture supernatant (csn) and its isolated recombinantly produced ColQ1 is characterized. The data reveals that ColQ1 causes damage on dermal collagen (COL). This results in gaps in the tissue, which might facilitate the spread of bacteria. The importance of B. cereus collagenases is also demonstrated in disease promotion using two inhibitors. Compound 2 shows high efficacy in peptidolytic, gelatinolytic, and COL degradation assays. It also preserves the fibrillar COLs in skin tissue challenged with ColQ1, as well as the viability of skin cells treated with B. cereus csn. A Galleria mellonella model highlights the significance of collagenase inhibition in vivo.

Increasing antimicrobial resistance evolves to be one of the major threats to public health. To reduce the selection pressure and thus to avoid a fast development of resistance, novel approaches...

Infections caused by the Gram-negative pathogen Pseudomonas aeruginosa are emerging worldwide as a major threat to human health. Conventional antibiotic monotherapy suffers from rapid resistance development, underlining urgent need for novel treatment concepts. Here, we report on a non-traditional approach to combat P. aeruginosa-derived infections by targeting its main virulence factor, the elastase LasB. We discovered a new chemical class of phosphonates with an outstanding in vitro ADMET and PK profile, auspicious activity both in vitro and in vivo. We established the mode of action through a co-crystal structure of our lead compound with LasB and in several in vitro and ex vivo models. The proof of concept of a combination of our pathoblocker with levofloxacin in a murine neutropenic lung infection model and the reduction of LasB protein levels in blood as a proof of target engagement demonstrate the great potential for use as an adjunctive treatment of lung infections in humans.

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