Safety, recovery, and pharmacodynamics of CRISPR–Cas therapeutic SNIPR001: a phase 1, randomised, double-blind, first-in-human, dose-escalation study

SummaryBackground Patients with haematological cancer who receive stem-cell transplantation are at risk of bloodstream infections, often caused by multidrug resistant gut pathogens such as Escherichia coli. SNIPR001 is a cocktail of four CRISPR–Cas-armed bacteriophages that reduce colonisation of E coli in the gastrointestinal tract in animal models and is designed to not affect other members of the commensal microbiota. We aimed to investigate the safety and tolerability of SNIPR001 in healthy participants. Methods In this randomised, placebo-controlled, double-blind, first-in-human, dose-escalation trial conducted at a single centre (Medpace Clinical Pharmacology Unit; Cincinnati, OH, USA), we sequentially enrolled healthy participants (aged 18–65 years) with more than 107 E coli colony-forming units per gram of stool into cohorts 1, 2, and 3, pending a safety review of the previous enrolment group where applicable. Participants in each cohort were randomly assigned to treatment or placebo using a unique three-digit participant identification number. Participants were orally administered 108 plaque-forming units (PFU) per dose (cohort 1), 1010 PFU per dose (cohort 2), and 1012 PFU per dose (cohort 3) of SNIPR001 or placebo (phosphate-buffered saline buffer), twice daily for 7 days. All personnel, except for a pharmacy staff member who prepared both SNIPR001 and placebo vials, were masked to the administered dose and assignment; masking was ensured by fully covering the surface of each vial. Participants were followed up to day 187. The primary outcome was the incidence and severity of adverse events and medically attended adverse events from the first administration of the study drug until 4 weeks after the last dose administration on day 35 of the study. Recovery and biodistribution of SNIPR001 in faeces, blood, and urine; pharmacodynamics, including the ability of SNIPR001 to reduce E coli levels in stool (assessed using a linear mixed-effects model); and microbiome composition (using Bray–Curtis dissimilarity) were secondary outcomes. Primary safety analyses were assessed per-protocol (ie, all enrolled participants who received at least one administration of the study drug). This trial was conducted under an Investigational New Drug application from the US Food and Drug Administration, is registered with ClinicalTrials.gov (NCT05277350), and is closed to new participants. Findings The trial was carried out between March 24, 2022, and Nov 30, 2022. 36 eligible participants were randomly assigned to receive SNIPR001 or placebo in cohorts 1 (six assigned to 108 PFU per dose and two assigned to placebo), 2 (six to 1010 PFU per dose and two to placebo), and 3 (12 to 1012 PFU per dose and eight to placebo). The mean age of participants was 42·1 years (SD 13·8), with 14 (39%) female participants and 22 (61%) male participants. During the trial and 4-week follow-up period, only mild and moderate adverse events were observed, with most adverse events occurring in the placebo group (13, six, one, and nine for participants receiving either placebo or SNIPR001 at 108, 1010, and 1012 PFU twice a day, respectively). The number of participants who had adverse events was not significantly higher in treatment groups than in the placebo group (p=0·94, one-sided Fisher's exact test). The most frequently reported adverse events were headaches and diarrhoea. No grade 3–4 adverse events were reported and no serious adverse events were reported in the SNIPR001 dose groups. During and after the dosing period, the gut microbiota composition did not significantly differ between the treatment and placebo groups (p>0·05, two-sided Mann–Whitney U test of Bray–Curtis distances, false discovery rate FDR-corrected). Functional SNIPR001 was recovered from stool samples in concentrations proportional to the administered dose but was not meaningfully detected in plasma (only one sample) or urine (only one sample). SNIPR001 was undetected in all samples 6 months after the last dosing, which is a favourable pharmacokinetic property and meets regulatory expectations. We observed the largest reduction in E coli levels compared with placebo 2 weeks after treatment initiation at day 14 (78%; −0·65 log10 SE 0·64 for 1012 PFU SNIPR001 twice-daily group), according to a linear mixed-effects model for the highest dose population; however, this change was not statistically significant (p=0·811, linear mixed-effects model, FDR-corrected). Interpretation This first-in-human study of SNIPR001 supported its safety, tolerability, and restriction to the gastrointestinal tract, while not systemically disrupting the gut microbiome. These results justify further clinical development of SNIPR001 in an ongoing phase 1b/2a trial. Funding Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator (CARB-X) and SNIPR Biome.