NRx Pharmaceuticals, Inc. announced new data that demonstrate that in a rodent model NRX-101 shows no measurable damage to either intestinal or vaginal flora, compared to the significant negative effect caused by drugs such as ciprofloxacin. Antibiotics commonly used to treat complicated urinary tract infections (cUTI) are associated with pseudomembranous colitis caused by Clostridium difficile (C diff) and vaginal yeast infections, primarily owing to their impact on normal flora. C. diff causes an intractable diarrhea in approximately 500,000 Americans each year and kills 1 in 11 Americans over age 65 who contract the infection.

Costs of C. diff are estimated at $24,000 per patient and are significantly higher when C. diff occurs as part of a hospital admission. Whereas most antibiotics have substantial effect in the large bowel, the key component of NRX-101 (D-cycloserine) is entirely absorbed in the small intestine and excreted unmetabolized in the urine. If the nonclinical data reported are replicated in patients, NRX-101 could represent the first antibiotic for cUTI and pyelonephritis that has essentially no risk of causing C. diff infection or vaginal yeast infection.

There is an extensive literature surrounding the use of D-cycloserine to treat tuberculosis and cases of C. Diff are unknown. D-cycloserine's effect as an antibiotic is based on its propensity to substitute for the amino acid alanine in the formation of the bacterial cell wall.