Sulbactam/Durlobactam: First Approval

A comprehensive review of small molecule drugs approved by the FDA in 2023: Advances and prospects

In 2023, the U.S. Food and Drug Administration has approved 55 novel medications, consisting of 17 biologics license applications and 38 new molecular entities. Although the biologics license applications including antibody and enzyme replacement therapy set a historical record, the new molecular entities comprising small molecule drugs, diagnostic agent, RNA interference therapy and biomacromolecular peptide still account for over 50 % of the newly approved medications. The novel and privileged scaffolds derived from drugs, active molecules and natural products are consistently associated with the discovery of new mechanisms, the expansion of clinical indications and the reduction of side effects. Moreover, the structural modifications based on the promising scaffolds can provide the clinical candidates with the improved biological activities, bypass the patent protection and greatly shorten the period of new drug discovery. Therefore, conducting an appraisal of drug approval experience and related information will expedite the identification of more potent drug molecules. In this review, we comprehensively summarized the pertinent information encompassing the clinical application, mechanism, elegant design and development processes of 28 small molecule drugs, and expected to provide the promising structural basis and design inspiration for pharmaceutical chemists.

Lacticaseibacillus rhamnosus CRL 2244 secreted metabolites display killing and antibiotic synergistic activity against multi-drug resistant pathogens

A growing increase in the number of serious infections caused by multidrug resistant bacteria (MDR) is challenging our society. Despite efforts to discover novel therapeutic options, few antibiotics targeting MDR have been approved by the Food and Drug Administration (FDA). Lactic acid bacteria have emerged as a promising therapeutic alternative due to their demonstrated ability to combat MDR pathogens in vitro. Our previous co-culture studies showed Lacticaseibacillus rhamnosus CRL 2244 as having a potent killing effect against carbapenem-resistant Acinetobacter baumannii (CRAB) strains. Here we report that cell-free conditioned media (CFCM) samples obtained from Lcb. rhamnosus CRL 2244 cultures incubated at different times display antimicrobial activity against 43 different pathogens, including CRAB, methicillin-resistant Staphylococcus aureus (MRSA) and carbapenemase Klebsiella pneumoniae (KPC)-positive strains. Furthermore, transwell and ultrafiltration analyses together with physical and chemical/biochemical tests showed that Lcb. rhamnosus CRL 2244 secretes a <3 kDa metabolite(s) whose antimicrobial activity is not significantly impaired by mild changes in pH, temperature and various enzymatic treatments. Furthermore, sensitivity and time-kill assays showed that the bactericidal activity of the Lcb. rhamnosus CRL 2244 metabolite(s) enhances the activity of some current FDA approved antibiotics. We hypothesize that this observation could be due to the effects of Lcb. rhamnosus CRL 2244 metabolite(s) on cell morphology and the enhanced transcriptional expression of genes coding for the phenylacetate (PAA) and histidine catabolic Hut pathways, metal acquisition and biofilm formation, all of which are associated with bacterial virulence. Interestingly, the extracellular presence of Lcb. rhamnosus CRL 2244 induced the transcription of the gene coding for the CidA/LgrA protein, which is involved in programmed cell death in some bacteria. Overall, the findings presented in this report underscore the promising potential of the compound(s) released by Lcb. rhamnosus CRL2244 as an alternative and/or complementary option to treat infections caused by A. baumannii as well as other MDR bacterial pathogens.

Friends or foes? Novel antimicrobials tackling MDR/XDR Gram-negative bacteria: a systematic review

Gram-negative bacteria have been one of the most studied classes in the field of microbiology, especially in the context of globally alarming antimicrobial resistance levels to these pathogens over the course of the past decades. With high numbers of these microorganisms being described as multidrug-resistant (MDR), or even extended-drug-resistant (XDR) bacteria, specialists in the field have been struggling to keep up with higher prevalence of difficult-to-treat infections caused by such superbugs. The FDA approval of novel antimicrobials, such as cefiderocol (FDC), ceftolozane/tazobactam (C/T), ceftazidime/avibactam (CZA), imipenem/relebactam (IMR), sulbactam/durlobactam (SUL-DUR) and phase 3 clinical trials' results of aztreonam/avibactam (ATM-AVI) has proven that, while all these substances provide encouraging efficacy rates, antibiotic resistance keeps up with the pace of drug development. Microorganisms have developed more extensive mechanisms of resistance in order to target the threat posed by these novel antimicrobials, thus equiring researchers to be on a constant lookout for other potential drug candidates and molecule development. However, these strategies require a proper understanding of bacterial resistance mechanisms to gain a comprehensive outlook on the issue. The present review aims to highlight these six antibiotic agents, which have brought hope to clinicians during the past decade, discussing general properties of these substances, as well as mechanisms and patterns of resistance, while also providing a short overview on further directions in the field.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#searchadvanced, Identifier CRD42024505832.

Balancing the scales: achieving the optimal beta-lactam to beta-lactamase inhibitor ratio with continuous infusion piperacillin/tazobactam against extended spectrum beta-lactamase producing Enterobacterales

Piperacillin/tazobactam (TZP) is administered intravenously in a fixed ratio (8:1) with the potential for inadequate tazobactam exposure to ensure piperacillin activity against Enterobacterales. Adult patients receiving continuous infusion (CI) of TZP and therapeutic drug monitoring (TDM) of both agents were evaluated. Demographic variables and other pertinent laboratory data were collected retrospectively. A population pharmacokinetic approach was used to select the best kidney function model predictive of TZP clearance (CL). The probability of target attainment (PTA), cumulative fraction of response (CFR) and the ratio between piperacillin and tazobactam were computed to identify optimal dosage regimens by continuous infusion across kidney function. This study included 257 critically ill patients (79.3% male) with intra-abdominal, bloodstream, and hospital-acquired pneumonia infections in 89.5% as the primary indication. The median (min-max range) age, body weight, and estimated glomerular filtration rate (eGFR) were 66 (23-93) years, 75 (39-310) kg, and 79.2 (6.4-234) mL/min, respectively. Doses of up to 22.5 g/day were used to optimize TZP based on TDM. The 2021 chronic kidney disease epidemiology equation in mL/min best modeled TZP CL. The ratio of piperacillin:tazobactam increased from 6:1 to 10:1 between an eGFR of <20 mL/min and >120 mL/min. At conventional doses, the PTA is below 90% when eGFR is ≥100 mL/min. Daily doses of 18 g/day and 22.5 g/day by CI are expected to achieve a >80% CFR when eGFR is 100-120 mL/min and >120-160 mL/min, respectively. Inadequate piperacillin and tazobactam exposure is likely in patients with eGFR ≥ 100 mL/min. Dose regimen adjustments informed by TDM should be evaluated in this specific population.

Current treatment options for pneumonia caused by carbapenem-resistant Acinetobacter baumannii

PURPOSE OF REVIEW

The purpose of this review is to briefly summarize the challenges associated with the treatment of pneumonia caused by carbapenem-resistant Acinetobacter baumannii (CRAB), discuss its carbapenem-resistance, and review the literature supporting the current treatment paradigm and therapeutic options.

RECENT FINDINGS

In a multicenter, randomized, and controlled trial the novel β-lactam-β-lactamase inhibitor sulbactam-durlobactam was compared to colistin, both in addition to imipenem-cilastatin. The drug met the prespecified criteria for noninferiority for 28-day all-cause mortality while demonstrating higher clinical cure rates in the treatment of CRAB pneumonia. In an international, randomized, double-blind, placebo controlled trial colistin monotherapy was compared to colistin combined with meropenem. In this trial, combination therapy was not superior to monotherapy in the treatment of drug-resistant gram-negative organisms including CRAB pneumonia.

SUMMARY

CRAB pneumonia is a preeminent public health threat without an agreed upon first line treatment strategy. Historically, there have been drawbacks to available treatment modalities without a clear consensus on the first-line treatment regimen. CRAB pneumonia is a top priority for the continued development of antimicrobials, adjuvant therapies and refinement of current treatment strategies.

Synthesis and clinical application of new drugs approved by FDA in 2023

In 2023, the U.S. Food and Drug Administration (FDA) granted approval to a total of 55 new drugs, comprising 29 new chemical entities (NCEs) and 25 new biological entities (NBEs). These drugs primarily focus on oncology, the central nervous system, anti-infection, hematology, cardiovascular, ophthalmology, immunomodulatory and other therapeutic areas. Out of the 55 drugs, 33 (60 %) underwent an accelerated review process and received approval, while 25 (45 %) were specifically approved for the treatment of rare diseases. The purpose of this review is to provide an overview of the clinical uses and production techniques of 29 newly FDA-approved NCEs in 2023. Our intention is to offer a comprehensive understanding of the synthetic approaches employed in the creation of these drug molecules, with the aim of inspiring the development of novel, efficient, and applicable synthetic methodologies.

Guiding the Way: Traditional Medicinal Chemistry Inspiration for Rational Gram-Negative Drug Design

The discovery and development of small-molecule therapeutics effective against Gram-negative pathogens are highly challenging tasks. Most compounds that are active in biochemical settings fail to exhibit whole-cell activity. The major reason for this lack of activity is the effectiveness of bacterial cell envelopes as permeability barriers. These barriers originate from the nutrient-selective outer membranes, which act synergistically with polyspecific efflux pumps. Guiding principles to enable rational optimization of small molecules for efficient penetration and intracellular accumulation in Gram-negative bacteria would have a transformative impact on the discovery and design of chemical probes and therapeutics. In this Perspective, we draw on inspiration from traditional medicinal chemistry approaches for eukaryotic drug design to present a broader call for action in developing comparable approaches for Gram-negative bacteria.

Cefiderocol and Sulbactam-Durlobactam against Carbapenem-Resistant Acinetobacter baumannii

Infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) remain a clinical challenge due to limited treatment options. Recently, cefiderocol, a novel siderophore cephalosporin, and sulbactam-durlobactam, a bactericidal β-lactam-β-lactamase inhibitor combination, have been approved by the Food and Drug Administration for the treatment of A. baumannii infections. In this review, we discuss the mechanisms of action of and resistance to cefiderocol and sulbactam-durlobactam, the antimicrobial susceptibility of A. baumannii isolates to these drugs, as well as the clinical effectiveness of cefiderocol and sulbactam/durlobactam-based regimens against CRAB. Overall, cefiderocol and sulbactam-durlobactam show an excellent antimicrobial activity against CRAB. The review of clinical studies evaluating the efficacy of cefiderocol therapy against CRAB indicates it is non-inferior to colistin/other treatments for CRAB infections, with a better safety profile. Combination treatment is not associated with improved outcomes compared to monotherapy. Higher mortality rates are often associated with prior patient comorbidities and the severity of the underlying infection. Regarding sulbactam-durlobactam, current data from the pivotal clinical trial and case reports suggest this antibiotic combination could be a valuable option in critically ill patients affected by CRAB infections, in particular where no other antibiotic appears to be effective.

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.