> **License: CC0 (public domain).** Fork it, rename it, submit it. Every [ILLUSTRATIVE] figure is a placeholder to replace. # Precision Phage Therapy to Disarm Cytolytic *Enterococcus faecalis* in Severe Alcohol-Associated Hepatitis: A Biomarker-Paired, IND-Enabling Oral Cocktail ## Project Summary / Abstract Severe alcohol-associated hepatitis (AH) is a frequently fatal emergency with short-term mortality commonly cited at roughly 30–50% and only one marginally effective pharmacotherapy (corticosteroids), to which many patients are ineligible or non-responsive. A defined, gut-derived driver of disease has been identified: cytolysin-positive (cytolytic) *Enterococcus faecalis* secretes a two-subunit exotoxin that translocates to the liver and kills hepatocytes, worsening ethanol-induced injury, and fecal cytolysin positivity correlates with disease severity and mortality in patients (Duan et al., *Nature* 2019). Because the hepatotoxin is produced by a discrete bacterial subset rather than the whole microbiome, lytic bacteriophages offer surgical precision—depleting toxin producers while sparing commensals and avoiding the resistance-selection and collateral-dysbiosis liabilities of broad-spectrum antibiotics. Our **central hypothesis** is that an orally delivered, rationally composed phage cocktail will reduce intestinal cytolytic *E. faecalis* burden and hepatic cytolysin, attenuate liver injury, and do so durably because phage escape carries a steep colonization fitness cost. We build on a defined oral 3-phage cocktail—sewage-isolated, covering the majority of tested cytolysin-positive strains, and characterized as safe with a predominantly anti-inflammatory, tissue-restoring immune profile (Garcia Mendes et al., *Viruses* 2022)—and on evidence that resistance arises via IS256-mediated events but impairs gut colonization rather than producing rebound disease (Fujiki et al., *Microbiology Spectrum* 2025). **Aim 1** defines host range against a contemporary, geographically diverse cytolytic *E. faecalis* panel and locks a coverage-maximizing, resistance-suppressing cocktail. **Aim 2** tests efficacy and dissects the phage–host–liver axis (biodistribution, resistance dynamics) in humanized, ethanol-fed mice. **Aim 3** generates the IND-enabling safety, manufacturing (CMC), and companion-diagnostic (stool cytolysin qPCR) package needed to support an FDA investigational-phage submission. The expected outcome is a defined, manufacturable, biomarker-paired phage product positioned for a precision first-in-human trial restricted to cytolysin-positive patients—a treat-the-responder strategy for a high-mortality, therapy-poor indication squarely within the NIAAA mission. ## Specific Aims Severe AH is a frequently fatal emergency with one marginal therapy. Duan et al. (*Nature* 2019) showed that cytolytic *E. faecalis* causally drives ethanol-induced liver injury through a secreted cytolysin that reaches the liver and kills hepatocytes; that fecal cytolysin positivity tracks with disease severity and mortality; that a substantial fraction of AH patients (on the order of ~60% in the index cohort) carry cytolysin-positive *E. faecalis*; and that phage targeting of these bacteria abolished ethanol-induced liver disease in humanized mice. Garcia Mendes et al. (*Viruses* 2022) advanced a defined oral 3-phage cocktail—isolated from sewage, covering the majority of tested cytolysin-positive strains, safe after chronic-binge ethanol, with a predominantly anti-inflammatory immune signature—and judged it suitable for clinical-trial testing. Fujiki et al. (*Microbiology Spectrum* 2025) showed that phage resistance arises through IS256 insertion-sequence events (disrupting *xylA*, mutating *epaR*, and deleting *galE* in the Epa polysaccharide pathway) but at a steep fitness cost: reduced intestinal adherence, increased bile-salt sensitivity, and attenuated gut colonization. **Central hypothesis:** A rationally composed, orally delivered phage cocktail will durably deplete cytolytic *E. faecalis* and lower hepatic cytolysin in cytolysin-positive hosts, attenuating liver injury, with escape variants self-limited by their colonization fitness cost. **Aim 1 — Define and optimize cocktail coverage against contemporary cytolytic *E. faecalis*.** Assemble a diverse clinical-isolate panel and a sewage-derived phage library; quantify host range by efficiency-of-plating and growth-suppression; and rationally lock a 3-phage composition that maximizes coverage of cytolysin-positive strains while suppressing resistance in co-culture. *Outcome:* a coverage map and a justified, locked cocktail. **Aim 2 — Establish efficacy and the phage–host–liver mechanism in humanized ethanol-fed mice.** In fecal-transplanted, chronic-plus-binge ethanol-fed mice, test whether the optimized oral cocktail reduces intestinal cytolytic *E. faecalis*, lowers hepatic cytolysin, and attenuates steatosis, hepatocyte death, and inflammation, while mapping phage biodistribution and IS256-mediated resistance dynamics in vivo. *Outcome:* quantitative efficacy and mechanism data with prespecified effect-size thresholds. **Aim 3 — Generate IND-enabling safety, CMC, and a companion cytolysin diagnostic.** Complete repeat-dose oral safety/toxicology, define manufacturing and release specifications toward clinical-grade material, and validate a stool cytolysin qPCR to identify the cytolysin-positive subset most likely to benefit. *Outcome:* a regulatory package and theranostic suitable for an FDA investigational-phage submission. **Impact.** Success delivers the first precision, biomarker-paired microbiome therapeutic for an often-fatal liver emergency—disarming a hepatotoxin at its bacterial source while sparing the gut, and treating only patients predicted to respond. ## Significance Severe AH is among hepatology's deadliest acute conditions, with short-term mortality commonly reported in the ~30–50% range and only corticosteroids as marginally effective therapy; many patients are steroid-ineligible or steroid-non-responsive. This therapeutic vacuum motivates mechanism-based approaches. Duan et al. (*Nature* 2019) converted a diffuse "dysbiosis" narrative into a discrete molecular target by showing that cytolytic *E. faecalis* is causal rather than a bystander: its secreted two-subunit cytolysin reaches the liver, directly kills hepatocytes, and exacerbates ethanol-induced injury, and fecal cytolysin positivity correlates with severity and mortality. Critically, pathogenic activity is confined to a defined bacterial subset, making precision depletion—rather than global microbiome disruption—both biologically rational and clinically attractive. Broad-spectrum antibiotics cannot achieve this selectivity and risk fueling resistant enterococci; lytic phages remove the toxin producers while leaving surrounding commensals intact. This program is squarely within the NIAAA mission—alcohol-associated organ injury and its gut–liver mechanisms—and directly addresses the Institute's priority of translating mechanistic insight into therapeutics for alcohol-associated liver disease. (The work also informs broader liver-disease and gut-microbiome science of interest to NIDDK.) By coupling a precision therapeutic to a cytolysin biomarker, the project targets a high-mortality, therapy-poor indication with a strategy that is mechanistically specific, manufacturable, and clinically deployable. ## Innovation The innovation is **precision rather than breadth**: instead of suppressing the microbiome, we eliminate a single toxin-producing population with lytic phages. Three features distinguish the approach. - **Theranostic by design.** An oral phage cocktail is paired with a stool cytolysin qPCR companion test, enabling clinicians to screen and treat only the cytolysin-positive subset—a true treat-the-responder strategy that is, to our knowledge, novel for alcohol-associated liver disease. - **Resistance turned into an ally.** Fujiki et al. (*Microbiology Spectrum* 2025) showed that phage escape arises via IS256 events (disrupting *xylA*, mutating *epaR*, deleting *galE*) but at a steep fitness cost—reduced intestinal adherence and increased bile-salt sensitivity—so resistance tends to coincide with impaired gut colonization rather than treatment failure. We design cocktail composition and dosing to exploit this trade-off. - **A defined, locked, biomarker-paired product.** Rather than an ad hoc mixture, the program delivers a composition-locked cocktail with release specifications and a paired diagnostic, de-risking the path to a precision first-in-human trial. Should three phages prove insufficient against contemporary strains, we will broaden coverage through iterative re-composition and expanded isolation (Aim 1, Pitfalls); any engineering-based extension would be pursued only as a clearly delineated contingency, not a core dependency. ## Approach ### Aim 1 — Define and optimize cocktail coverage against contemporary cytolytic *E. faecalis* **Rationale.** Individual phages have narrow host ranges; durable, broadly active therapy requires a rationally composed cocktail. Duan et al. assembled a sewage-derived phage panel and used a multi-phage mix targeting cytolytic *E. faecalis*; Garcia Mendes et al. advanced a defined 3-phage oral cocktail covering the majority of tested cytolysin-positive strains. We update coverage against contemporary, diverse strains because cytolysin prevalence and clinical relevance may be cohort- and geography-dependent. **Design.** We will (1) assemble a panel of cytolytic and non-cytolytic *E. faecalis* clinical isolates spanning multiple geographies, confirming cytolysin genotype and phenotype for every strain; (2) isolate and expand lytic phages from sewage and curate a candidate library enriched for broad-host-range phages; (3) quantify host range by efficiency-of-plating and growth-suppression (OD-based) assays; (4) score candidate 3-phage combinations for coverage breadth and resistance suppression in time-kill co-culture; and (5) lock a lead composition. **Quantitative criteria / go–no-go.** Lock requires a 3-phage combination covering a prespecified majority threshold of the cytolytic panel by efficiency-of-plating and demonstrating reduced resistance emergence versus best single phage over a defined co-culture window. **[ILLUSTRATIVE]** thresholds (e.g., ≥70% panel coverage) will be finalized at submission. **Expected outcomes.** A coverage map for the strain panel and a justified, locked 3-phage cocktail predicted to cover most clinically relevant cytolytic strains while limiting escape. **Pitfalls & alternatives.** If three phages give insufficient breadth, we iterate composition from the broad-host-range subset or expand isolation; persistent coverage gaps would trigger the delineated engineering contingency (Innovation) in collaboration. **Rigor/authentication:** all strains and phages are sequence-verified, banked, and authenticated; cytolysin status is confirmed orthogonally (genotype + functional assay). ### Aim 2 — Establish efficacy and the phage–host–liver mechanism in humanized ethanol-fed mice **Rationale.** Duan et al. showed in humanized (fecal-transplanted), ethanol-fed mice that phage targeting of cytolytic *E. faecalis* abolished ethanol-induced liver disease; we reproduce and extend this with the optimized cocktail and add biodistribution and resistance read-outs. **Design.** Mice will be humanized with feces from confirmed cytolysin-positive donors, fed the chronic-plus-binge ethanol regimen, and randomized to oral optimized cocktail versus vehicle, with non-cytolytic-colonized and uncolonized comparators. **Primary endpoint:** intestinal cytolytic *E. faecalis* burden. **Secondary endpoints:** hepatic cytolysin; steatosis, hepatocyte death, ALT/AST, and inflammatory markers; phage biodistribution to serum, spleen, and liver; and characterization of the immune response (expected predominantly anti-inflammatory and tissue-restoring per prior work). We will track IS256-mediated resistant variants and test the predicted colonization/bile-salt fitness cost in vivo. **Statistical plan & rigor.** Group sizes are set by power analysis to a prespecified effect size on the primary endpoint **[ILLUSTRATIVE]**; analyses use mixed models with predefined comparisons. **Sex as a biological variable:** both sexes are enrolled and sex is included as a covariate, powered to detect sex-by-treatment interaction signals. Randomization, blinded histology scoring, prespecified endpoints, biological-replicate minimums, and confirmation of colonization before dosing are built in. **Expected outcomes.** Demonstration that the cocktail lowers intestinal cytolytic burden and hepatic cytolysin and attenuates injury, with resistance—when it arises—linked to impaired colonization rather than rebound disease. **Pitfalls & alternatives.** Variable engraftment is mitigated by pre-dosing colonization confirmation and stratified analysis. If resistant variants retain colonization, we adjust phage combination and dosing schedule. A go/no-go precedes Aim 3 scale-up: efficacy must meet the prespecified threshold on the primary endpoint. ### Aim 3 — Generate IND-enabling safety, CMC, and a companion cytolysin diagnostic **Rationale.** Additional safety testing and manufacturing scale-up remain prerequisites before first-in-human phage trials, and a companion biomarker is needed to enrich for likely responders. **Design.** We will (1) perform repeat-dose oral safety/toxicology of the locked cocktail in animals, including endotoxin and purity assessment; (2) define manufacturing, purification, and release specifications (identity, titer, sterility, endotoxin) toward clinical-grade material consistent with the clinical-grade cocktail described by Garcia Mendes et al.; and (3) develop and validate a stool cytolysin qPCR companion assay (analytical sensitivity/specificity, reproducibility, limit of detection) for ICU-compatible screening. **Expected outcomes.** A preclinical safety dossier, a draft CMC/release package, and a validated cytolysin qPCR—collectively supporting an FDA investigational-phage submission and a precision trial design. **Pitfalls & alternatives.** If a single fixed formulation is constrained by strain diversity, we will define a controlled, specification-bound multi-component strategy. **Scientific-premise risk:** cytolysin-positive prevalence and its prognostic weight may be cohort- and geography-dependent, and some populations may show lower incidence; this is precisely why the qPCR-based enrichment is integral rather than optional. Multi-site specimen screening will establish a feasible addressable population and directly test premise robustness. ## Timeline **[ILLUSTRATIVE]** Year 1: Aim 1 strain/phage library and host-range mapping; cocktail lock (go/no-go #1). Years 1–3: Aim 2 efficacy, biodistribution, and resistance studies (go/no-go #2 on efficacy). Years 2–4: Aim 3 safety/toxicology and CMC. Years 3–5: cytolysin qPCR validation, dossier assembly, and pre-IND/FDA engagement. ## Budget Justification (modular R01-style sketch) **[ILLUSTRATIVE]** Modular direct costs of **$250,000/year [ILLUSTRATIVE]** over **5 years [ILLUSTRATIVE]**. Personnel: PI (microbiome/hepatology), Co-I (phage biology), Co-I (GI/hepatology clinician), a postdoctoral fellow, a research technician, and a part-time regulatory/CMC consultant. Supplies: phage isolation/propagation, strain-panel acquisition, sequencing, histology, immunoassays, and qPCR development. Animal costs: humanized ethanol-fed mouse cohorts (Aim 2) and toxicology (Aim 3). Other: biostatistics, pre-IND consulting, and publication. Specific dollar allocations across categories are **[ILLUSTRATIVE]** and will be finalized at submission. ## Vertebrate Animals Animal work is proposed in Aims 2 and 3. Humanized, ethanol-fed mouse models will test efficacy, mechanism, phage biodistribution, and safety, consistent with the humanized-mouse paradigm established by Duan et al. and Garcia Mendes et al. **Justification:** no in vitro system reproduces the gut–liver translocation axis central to this mechanism. **Minimization:** power-based group sizes, both sexes, randomization, blinded endpoints, and shared controls reduce animal use. All procedures follow an IACUC-approved protocol with appropriate housing, anesthesia/analgesia where applicable, and humane endpoints. Estimated animal numbers are **[ILLUSTRATIVE]** pending final power calculations. ## Human Subjects / Clinical Trial No human efficacy trial is conducted within this R01; the work is IND-enabling. Aim 3 develops a stool cytolysin qPCR using de-identified or consented clinical specimens under IRB oversight. We will engage FDA regarding the investigational-phage regulatory pathway to inform a future first-in-human, biomarker-enriched trial in cytolysin-positive severe AH patients. Any subsequent clinical study will proceed under a separate IND and IRB approval with informed consent. Enrollment figures for future trials are **[ILLUSTRATIVE]**. ## Team & Environment - **Contact PI — [Name, Institution] [ILLUSTRATIVE]:** gut–liver axis and alcohol-associated liver disease. - **Co-Investigator — [Name, Institution] [ILLUSTRATIVE]:** bacteriophage genomics and isolation. - **Co-Investigator — [Name, Institution] [ILLUSTRATIVE]:** hepatology/clinical AH and ICU specimen access. - **Regulatory/CMC consultant — [Name] [ILLUSTRATIVE]:** phage manufacturing, release testing, and FDA/IND strategy. - **Biostatistician — [Name] [ILLUSTRATIVE].** - **Environment [ILLUSTRATIVE]:** an institution with BSL-appropriate phage facilities, a humanized-mouse/ethanol-feeding core, GMP-aware manufacturing partners, and a hepatology service—to be populated with real names and institutions at submission. ## References 1. Duan Y, Llorente C, Lang S, Brandl K, Chu H, Jiang L, et al. (incl. Fouts DE, Schnabl B). Bacteriophage targeting of gut bacterium attenuates alcoholic liver disease. *Nature.* 2019;575(7783):505–511. DOI: 10.1038/s41586-019-1742-x. https://pubmed.ncbi.nlm.nih.gov/31723265/ · https://www.nature.com/articles/s41586-019-1742-x 2. Garcia Mendes B, Duan Y, Schnabl B. Immune Response of an Oral *Enterococcus faecalis* Phage Cocktail in a Mouse Model of Ethanol-Induced Liver Disease. *Viruses.* 2022;14(3):490. https://pubmed.ncbi.nlm.nih.gov/35336897/ 3. Fujiki J, Nakamura T, Kreimeyer H, Llorente C, Fouts DE, Schnabl B. Insertion sequence-mediated phage resistance contributes to attenuated colonization of cytolytic *Enterococcus faecalis* variants in the gut. *Microbiology Spectrum.* 2025; doi:10.1128/spectrum.03303-24 (PMID: 40231830). https://pmc.ncbi.nlm.nih.gov/articles/PMC12054073/