Highlights
- Sulopenem, an oral thiopenem antibiotic, demonstrated noninferiority to amoxicillin/clavulanate for uncomplicated urinary tract infections (UTIs) in adult women by combined clinical and microbiologic cure.
- Among Enterobacterales uropathogens, sulopenem showed favorable efficacy across antibiotic-resistant strains, addressing growing resistance challenges in uUTIs.
- Adverse events such as diarrhea, nausea, and headache were more frequent but mild with sulopenem compared to amoxicillin/clavulanate.
- Comparative trials with ciprofloxacin and ertapenem reinforce sulopenem’s potential role in both uncomplicated and complicated UTI management, highlighting nuances in asymptomatic bacteriuria rates and resistance profiles.
Background
Urinary tract infections (UTIs), particularly uncomplicated cystitis in women, are among the most frequent outpatient bacterial infections. The therapeutic landscape is increasingly challenged by escalating antimicrobial resistance, notably among Enterobacterales such as Escherichia coli and Klebsiella species. Common first-line agents include trimethoprim-sulfamethoxazole, nitrofurantoin, fosfomycin, with beta-lactams like amoxicillin/clavulanate considered second-line due to lower efficacy and emerging resistance. The need for effective oral agents against multidrug-resistant pathogens has driven research into sulopenem, an oral thiopenem with broad-spectrum activity including against resistant uropathogens.
Key Content
1. Clinical Trials Comparing Sulopenem with Established Agents
Sulopenem vs Amoxicillin/Clavulanate (Puttagunta et al., 2025) conducted a double-blind randomized controlled noninferiority trial enrolling 2222 adult women with uncomplicated UTI. The primary endpoint was a composite of clinical cure and microbiological eradication at day 12 in the microbiologic-modified intent-to-treat (mMITT) population. Results demonstrated overall success rates of 60.9% for sulopenem and 55.6% for amoxicillin/clavulanate (difference 5.4%, 95% CI -0.8 to 11.5), thereby establishing sulopenem’s noninferiority. Notably, sulopenem showed improved efficacy in strains susceptible to amoxicillin/clavulanate but mixed results in resistant strains. Adverse events were more frequent with sulopenem, predominantly mild gastrointestinal symptoms.
Sulopenem vs Ciprofloxacin (DeAnda et al., 2023) compared 5 days sulopenem with 3 days ciprofloxacin in women with uncomplicated UTI, including patients harboring ciprofloxacin-nonsusceptible pathogens. Sulopenem was superior in ciprofloxacin-resistant infections but not noninferior in susceptible infections, largely driven by higher post-treatment asymptomatic bacteriuria with sulopenem. Diarrhea was more frequent with sulopenem (12.4% vs 2.5%). This trial highlighted sulopenem’s utility against resistant strains but raised questions about clinical significance of asymptomatic bacteriuria in treatment efficacy definitions.
Sulopenem for Complicated UTIs (Motsch et al., 2023) evaluated intravenous sulopenem followed by oral sulopenem etzadroxil/probenecid against ertapenem followed by step-down oral ciprofloxacin or amoxicillin/clavulanate in hospitalized adults with complicated UTIs. Sulopenem did not meet noninferiority criteria, driven by reduced asymptomatic bacteriuria rates following ciprofloxacin use. However, sulopenem’s tolerability was favorable and supports its role as an oral option in complicated UTIs requiring broader-spectrum intravenous coverage initially.
2. Mechanistic and Translational Insights
Sulopenem, as a thiopenem β-lactam antibiotic, inhibits bacterial cell wall synthesis and exhibits stability against many β-lactamases, including ESBLs frequently found in resistant Enterobacterales. Its oral bioavailability and broad spectrum position it as a promising agent amidst dwindling oral antibiotic choices for resistant uropathogens. The inclusion of probenecid delays renal clearance, enhancing pharmacokinetics for sustained urinary concentrations.
3. Established Therapies and Resistance Patterns in Uncomplicated UTI
The 2014 JAMA review highlights that first-line agents trimethoprim-sulfamethoxazole, nitrofurantoin, and fosfomycin remain preferred empiric treatments where resistance rates remain low. Beta-lactams, including amoxicillin/clavulanate, have historically shown lower clinical cure rates and are associated with increased resistance and adverse events. The dynamic resistance landscape necessitates new oral agents with better coverage, as demonstrated by the sulopenem clinical trials.
4. Safety and Tolerability Profile
Across clinical studies, sulopenem’s adverse events are primarily mild, gastrointestinal complaints such as diarrhea (up to 12.4%), nausea, and headache, occurring more frequently than comparators but seldom leading to discontinuation. These tolerability considerations are critical for outpatient UTI management.
Expert Commentary
Sulopenem represents a significant advance by offering an oral β-lactam option with broad coverage against MDR uropathogens, addressing a major unmet need in outpatient UTI therapy. The REASSURE trial’s noninferiority to amoxicillin/clavulanate provides reassurance on clinical utility, although the relatively modest efficacy rates (around 60%) reflect the complexity of UTI treatment in a population with diverse resistance patterns.
The increased adverse event frequency, mostly mild, should be weighed against the benefit of potentially improved coverage. Clinical decision-making should incorporate local resistance data and patient tolerability. The variable outcomes in ciprofloxacin-nonsusceptible infections underscore the need for susceptibility-informed therapy and reinforce the role of sulopenem in resistant infections as supported by ciprofloxacin comparator studies.
Notably, increased rates of post-treatment asymptomatic bacteriuria seen with sulopenem in some trials merit further evaluation regarding long-term outcomes and impact on recurrence. Additionally, expanded studies including men, diabetic women, and complicated UTI populations will refine clinical positioning.
Conclusion
Sulopenem emerges as a valuable oral agent for uncomplicated urinary tract infections with demonstrated noninferiority to amoxicillin/clavulanate and superiority over ciprofloxacin in resistant cases. Its efficacy against multidrug-resistant Enterobacterales offers a promising solution amid rising antimicrobial resistance. Mildly increased adverse events are manageable in routine care. Future research should focus on comparative effectiveness in broader populations, strategies to mitigate asymptomatic bacteriuria, and real-world effectiveness to optimize its clinical integration.
References
- Puttagunta S, Aronin SI, Gupta J, Das AF, Gupta K, Dunne MW. Sulopenem versus Amoxicillin/Clavulanate for the Treatment of Uncomplicated Urinary Tract Infection. NEJM Evid. 2025 Jul;4(7):EVIDoa2400414. doi: 10.1056/EVIDoa2400414. PMID: 40552968.
- DeAnda C, Winokur P, Das AF, et al. Sulopenem or Ciprofloxacin for the Treatment of Uncomplicated Urinary Tract Infections in Women: A Phase 3, Randomized Trial. Clin Infect Dis. 2023 Jan 6;76(1):66-77. doi:10.1093/cid/ciac738. PMID: 36069202.
- Motsch J, Wagenlehner FM, Broadhurst H, et al. Sulopenem for the Treatment of Complicated Urinary Tract Infections Including Pyelonephritis: A Phase 3, Randomized Trial. Clin Infect Dis. 2023 Jan 6;76(1):78-88. doi:10.1093/cid/ciac704. PMID: 36068705.
- Gupta K, Hooton TM, Naber KG, et al. Diagnosis and management of urinary tract infections in the outpatient setting: a review. JAMA. 2014 Oct 22;312(16):1677-84. doi:10.1001/jama.2014.12842. PMID: 25335150.
- Scholes D, Hooton TM, Roberts PL, et al. Comparison of single-dose administration and three-day course of amoxicillin with those of clavulanic acid for treatment of uncomplicated urinary tract infection in women. Antimicrob Agents Chemother. 1991 Aug;35(8):1688-90. doi:10.1128/AAC.35.8.1688. PMID: 1929343.
