Venatorx Pharmaceuticals (Venatorx) and Melinta Therapeutics (Melinta) announced that the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter (CRL) regarding the New Drug Application (NDA) for cefepime-taniborbactam, a beta-lactam/beta-lactamase inhibitor (BL/BLI) combination antibiotic under review as a potential treatment for adult patients with complicated urinary tract infections (cUTI), including acute pyelonephritis caused by susceptible gram-negative microorganisms. The CRL did not identify clinical safety or efficacy issues in the NDA, and the FDA did not request any new clinical trials to support the approval of cefepime- Taniborbactam. The FDA requested additional chemistry, manufacturing, and controls (CMC) and related data about the drug, testing methods, and manufacturing process. Taniborbactam is a beta-lactamase inhibitor ("BLI") that, in combination with cefepime, is being studied as a potential treatment option for patients with serious bacterial infections caused by antibiotic resistant gram-negative bacteria, most notably Extended Spectrum Beta-lactamase (ESBL)-expressing Enterobacterales, carbapenem-resistant Enterobacterales (CRE), and multidrug-resistant (MDR) Pseudomonas aeruginosa (MDR-PA), which can include carbapenem-resistant P. aeruginosa (CRPA).

Cefepime-tanibiborbactam has been granted Qualified Infectious Disease Product (QIDP) and Fast Track designations by the U.S. food and Drug Administration (FDA). Fast Track designation is designed to facilitate the development, and to expedite the review of drugs to treat serious conditions that do not have sufficient treatment options. QIDP designation provides certain incentives for the development of new antibiotics, including priority review, as well as a five-year regulatory exclusivity extension.

QIDP was authorized under the Generating Antibiotic Incentives Now (GAIN) Act of 2012, as part of the FDA Safety and Innovation Act, to underscore the urgency in development of new antibiotics. In a recent report on AMR, the U.S. Centers for Disease Control and Prevention (CDC) reported rates of resistance have increased significantly in the U.S. among bacterial pathogens including those commonly causing cUTI, pyelonephritis, and bacteremia. The CDC also cited that there are more than 2.8 million AMR infections annually in the U.S., which are directly related to more than 35,000 deaths.

Between 2014 and 2019, an analysis of U.S. UTI patients determined that 4.4% of cases were carbapenem resistant (CR) and 24.5% of U.S. UTI patients were bacteremic with 1.7% of cases caused by a CR pathogen. Patients with CR infections had a significantly longer hospital length of stay (LOS), were less likely to be discharged home, had a higher readmission rate, and had greater LOS-associated charges than patients with carbapenem-susceptible infections. Additionally, patients with bacteremia (urosepsis) due to CR pathogens had a significantly higher rate of mortality than those with carbapenem susceptible pathogens.

Gram-negative bacteria have multiple AMR mechanisms that continue to adapt in response to increases in antibiotic usage. Carbapenems are broad-spectrum antibiotics that have been widely used to treat infections caused by multidrug-resistant gram-negative bacteria, including Enterobacterales. With the increased global use of carbapenems, CRE have emerged, which have limited treatment options and are associated with increased morbidity and mortality.

Resistance to carbapenems among Enterobacterales is primarily achieved by production of carbapenemases, which are enzymes capable of hydrolyzing carbapenem antibiotics and most other beta-lactams and fall into two distinct families: serine beta-lactamases and metallo-beta-lactamases (MBLs). Klebsiella pneumoniae carbapenemase (KPC), a class-A serine beta-lactamase, is one of the most prevalent carbapenemases, and New Delhi MBL (NDM) and Verona Integron-encoded MBL (VIM) are common variants of MBLs identified in gram-negative infections due to Enterobacterales and P. aeruginosa. According to an IHMA surveillance study in 2018-2019 and a JMI U.S. Surveillance study from 2021, MBLs were the most commonly identified carbapenem resistance mechanism globally among Enterobacterales isolates, with ~16 to 18% of U.S. CRE isolates carrying MBLs.

While CRPA is also increasing in some geographies due to emergence of MBLs, MDR-PA, which may exhibit resistance to carbapenems, represents an increasing challenge for clinicians and their patients in the U.S. and globally due to the paucity of treatment options for this primarily hospital-associated pathogen. Especially outside the U.S., CRPA may carry carbapenemases including MBLs (i.e., VIM); however, non-carbapenemase resistance mechanisms (i.e., efflux pumps, porins) also contribute to the growing global resistance of MDR-PA and CRPA. If AMR infections continue on this trajectory, it has been projected that an estimated 10 million people will die per year of resistant infections by 2050?a number that surpasses the projected annual number of deaths (8.2 million) caused by cancer?and the cumulative cost to the global economy could be as high as $100 trillion.

In the U.S., estimates have reached as high as $20 billion in excess direct healthcare costs, with an additional$35 billion associated with lost productivity.[7] By 2050, the world is at risk of losing up to 3.8% of its annual gross domestic product with an annual shortfall of up to $3.4 trillion by 2030, a figure on par with losses attributable to the 2008 global financial crisis. For those patients who do not respond to current treatment, new antibiotic therapies are needed to combat AMR. Complicated UTIs, which include pyelonephritis, are defined as urinary tract infections ascending from the bladder accompanied by local and systemic signs and symptoms, including fever, chills, malaise, flank pain, back pain, and/or costovertebral angle pain or tenderness, that usually occur in the presence of a functional or anatomical abnormality of the urinary tract or in the presence of catheterization. Bacteremia can arise secondary to infections like cUTI and can result in substantial morbidity and mortality.

[1] Annually in U.S., it is estimated that more than 3 million cUTI patients will be diagnosed and require antibiotic therapy leading to over $6 billion in annualized 30-day costs.