The rate of antibiotic resistance continues to grow, outpacing small-molecule-drug development efforts. Novel therapies are needed to combat this growing threat, particularly for the treatment of urinary tract infections (UTIs), which are one of the largest contributors to antibiotic use and associated antibiotic resistance. LBP-EC01 is a novel, genetically enhanced, six-bacteriophage cocktail developed by Locus Biosciences (Morrisville, NC, USA) to address UTIs caused by Escherichia coli, regardless of antibiotic resistance status. In this first part of the two-part phase 2 ELIMINATE trial, we aimed to define a dosing regimen of LBP-EC01 for the treatment of uncomplicated UTIs that could advance to the second, randomised, controlled, double-blinded portion of the study.

This first part of ELIMINATE is a randomised, uncontrolled, open-label, phase 2 trial that took place in six private clinical sites in the USA. Eligible participants were female by self-identification, aged between 18 years and 70 years, and had an uncomplicated UTI at the time of enrolment, as well as a history of at least one drug-resistant UTI caused by E coli within the 12 months before enrolment. Participants were initially randomised in a 1:1:1 ratio into three treatment groups, but this part of the trial was terminated on the recommendation of the safety review committee after a non-serious tolerability signal was observed based on systemic drug exposure. A protocol update was then implemented, comprised of three new treatment groups. Groups A to C were dosed with intraurethral 2 × 10¹² plaque-forming units (PFU) of LBP-EC01 on days 1 and 2 by catheter, plus one of three intravenous doses daily on days 1–3 of LBP-EC01 (1 mL of 1 × 10¹⁰ PFU intravenous bolus in group A, 1 mL of 1 × 10⁹ PFU intravenous bolus in group B, and a 2 h 1 × 10¹¹ PFU intravenous infusion in 100 mL of sodium lactate solution in group C). In all groups, oral trimethoprim–sulfamethoxazole (TMP–SMX; 160 mg and 800 mg) was given twice daily on days 1–3. The primary outcome was the level of LBP-EC01 in urine and blood across the treatment period and over 48 h after the last dose and was assessed in patients in the intention-to-treat (ITT) population who received at least one dose of LBP-EC01 and had concentration–time data available throughout the days 1–3 dosing period (pharmacokinetic population). Safety, a secondary endpoint, was assessed in enrolled patients who received at least one dose of study drug (safety population). As exploratory pharmacodynamic endpoints, we assessed E coli levels in urine and clinical symptoms of UTI in patients with at least 1·0 × 10⁵ colony-forming units per mL E coli in urine at baseline who took at least one dose of study drug and completed their day 10 test-of-cure assessment (pharmacodynamic-evaluable population). This trial is registered with ClinicalTrials.gov, NCT05488340, and is ongoing.

Between Aug 22, 2022, and Aug 28, 2023, 44 patients were screened for eligibility, and 39 were randomly assigned (ITT population). Initially, eight participants were assigned to the first three groups. After the protocol was updated, 31 participants were allocated into groups A (11 patients), B (ten patients), and C (ten patients). One patient in group C withdrew consent on day 2 for personal reasons, but as she had received the first dose of the study drug was included in the modified ITT population. Maximum urine drug concentrations were consistent across intraurethral dosing, with a maximum mean concentration of 6·3 × 10⁸ PFU per mL (geometric mean 8·8 log₁₀ PFU per mL and geometric SD [gSD] 0·3). Blood plasma level of bacteriophages was intravenous dose-dependent, with maximum mean concentrations of 4·0 × 10³ (geometric mean 3·6 log₁₀ PFU per mL [gSD 1·5]) in group A, 2·5 × 10³ (3·4 log₁₀ PFU per mL [1·7]) in group B, and 8·0 × 10⁵ (5·9 log₁₀ PFU per mL [1·4]) in group C. No serious adverse events were observed. 44 adverse events were reported across 18 (46%) of the 39 participants in the safety population, with more adverse events seen with higher intravenous doses. Three patients in groups 1 to 3 and one patient in group C, all of whom received 1 × 10¹¹ LBP-EC01 intravenously, had non-serious tachycardia and afebrile chills after the second intravenous dose. A rapid reduction of E coli in urine was observed by 4 h after the first treatment and maintained at day 10 in all 16 evaluable patients; these individuals had complete resolution of UTI symptoms by day 10.

A regimen consisting of 2 days of intraurethral LBP-EC01 and 3 days of concurrent intravenous LBP-EC01 (1 × 10¹⁰ PFU) and oral TMP–SMX twice a day was well tolerated, with consistent pharmacokinetic profiles in urine and blood. LBP-EC01 and TMP–SMX dosing resulted in a rapid and durable reduction of E coli, with corresponding elimination of clinical symptoms in evaluable patients. LBP-EC01 holds promise in providing an alternative therapy for uncomplicated UTIs, with further testing of the group A dosing regimen planned in the controlled, double-blind, second part of ELIMINATE.

Federal funds from the US Department of Health and Human Services, Administration for Strategic Preparedness and Response, and Biomedical Advanced Research and Development Authority (BARDA).