Sulbactam-Durlobactam Plus Ceftriaxone Dosing and Novel Treatment Regimens for <i>Mycobacterium abscessus</i> Lung Disease

ABSTRACT Background IDSA guideline-based therapy achieves sputum culture conversion rates in 20-34% of patients with Mycobacterium abscessus (MAB) lung disease (LD). Double-β-lactam combinations have been proposed to improve cure, based on time-kill curves. Methods We performed minimum inhibitory concentrations (MICs) experiments followed by hollow fiber system model of MAB-LD (HFS-MAB) exposure-effect studies with sulbactam-durlobactam administered every 8h (q8h), q12h, and q24h, to identify target exposures. Next, the sulbactam-durlobactam target exposure plus ceftriaxone was administered in the HFS-MAB inoculated with three different MAB isolates, as was the sulbactam-durlobactam-ceftriaxone combination with epetraborole and omadacycline (SDCEO). γ -slopes (kill-speed) were calculated for all regimens. The minimal sulbactam-durlobactam clinical doses that achieved target exposure were identified using Monte Carlo experiments. Results Ceftriaxone reduced sulbactam-durlobactam MICs by 8-tube dilutions. In the HFS-MAB, sulbactam-durlobactam microbial kill and antimicrobial resistance were linked to % time concentration persists above MIC (%T MIC ), with target exposure of 50%. Sulbactam-durlobactam killed 3.85 log 10 CFU/mL below day 0 burden ( B 0 ) with regrowth. Sulbactam-durlobactam plus ceftriaxone killed without regrowth and demonstrated Bliss’ additivity. γ of bacterial population in &gt;95% of virtual subjects were 2.28 (0.97-4.80) log 10 CFU/mL/day for sulbactam-durlobactam-ceftriaxone and 2.91 (1.65-4.93) log 10 CFU/mL/day for SDCEO. The optimal sulbactam-durlobactam dose co-administered with ceftriaxone was 2G q8h for creatinine clearance &gt;90 mL/min, 2G q12h for 60-90 mL/min, 1G q12h for ≥30 to &lt;60 mL/min, and 1G q24h for &lt;30 mL/min. Conclusion Sulbactam-durlobactam-ceftriaxone achieved the highest microbial kill encountered so far in the HFS-MAB. Sulbactam-durlobactam-ceftriaxone should be tested as the backbone for novel treatment shortening regimens.