NCT06938867

Inclusion Criteria: 1. Male or female ≥18 years of age at the time of consent. 2. Patient is able and willing to provide written informed consent prior to any study-related procedure. 3. Confirmed diagnosis of any hematologic malignancy. 4. Planned to undergo an allogeneic hematopoietic stem cell transplant. 5. Patient is scheduled to receive fluoroquinolone (levofloxacin) prophylaxis. 6. Colonized with Fluoroquinolone resistant E. coli (patients will be pre-screened for the presence of at least 1 Fluoroquinolone resistant E. coli colony \[cultured from a perianal swab\] performed at the local hospital lab, qualitative assessment +/-). 7. Female patients must be of non-childbearing potential (surgically sterile or menopausal for at least 1 year) or agree to use a highly effective contraception method, per local standard, while receiving treatment with SNIPR001 and for 28 days after the last dose of SNIPR001. Male patients must utilize highly effective contraceptive precautions for the duration of SNIPR001 dosing and for 28 days after the last dose of SNIPR001. 8. Female patients of childbearing potential must have a negative serum pregnancy test at Screening and a negative serum or urine test on Day -2 prior to SNIPR001 dosing. 9. Are willing to comply with all scheduled visits, laboratory tests, and other study procedures, including drinking the study medications, in the opinion of the Investigator. Exclusion Criteria: 1. Use of any treatment (approved or investigational product) considered to interact with the study drug, or which might impact the outcome of the study within 14 days (or 5 half-lives of the approved or investigational product, whichever is greater) prior to the first administration of study drug, as judged by the Investigator. 2. Use or planned use of any antibiotics with intrinsic activity against E. coli in the gut (e.g., beta-lactam antibiotics) between Pre-Screening and until the end of the SNIPR001/placebo treatment period, with the exception of TMP-SMX and levofloxacin. 3. Have known hypersensitivity or allergy to any component of SNIPR001, levofloxacin and/or Alka-Seltzer treatment. 4. Unwilling or unable to comply with the requirements of this Protocol, including providing stool samples. 5. Female patients who are pregnant or lactating. 6. Have abnormal liver enzymes (alanine aminotransferase \[ALT\] or aspartate aminotransferase \[AST\] \>2 × upper limit of normal \[ULN\] or total bilirubin \>1.5 × ULN). 7. Have hepatic disease associated with impaired liver function. 8. Have a history of Achilles tendinopathy or tendon rupture.

• Registry updated October 8, 2026: Part 1 completed and Part 2 initiated; estimated enrollment 66; estimated completion October 2027. Eight listed sites recruiting; Dana-Farber and Memorial Sloan Kettering not yet recruiting. Study-specific eligibility applies.