Primary sclerosing cholangitis
Primary sclerosing cholangitis (PSC) is a chronic, progressive cholestatic liver disease marked by biliary inflammation and fibrosis, with no effective medical therapy and frequent progression to cirrhosis and need for liver transplant. A landmark line of work from Keio University established that gut-derived Klebsiella pneumoniae from PSC patients disrupts the intestinal epithelial barrier, translocates to mesenteric lymph nodes, and drives a hepatic Th17 immune response that exacerbates hepatobiliary injury—making Kp a causal pathobiont rather than a bystander. Because this is a specific, culturable strain driving disease via a defined gut-liver axis, it is an unusually clean target for precision antibacterials. Lytic bacteriophages are well suited here: they can selectively deplete the PSC-associated Kp in the gut without the broad collateral dysbiosis that antibiotics cause, addressing the upstream microbial trigger rather than just downstream inflammation.
How phages act here
Mechanism
Phages target PSC-derived K. pneumoniae with strict strain specificity—the Ichikawa/Nakamoto cocktail of four lytic phages (KP13-2, KP13-16, KP13MC5-1, KP13MC5-2) was raised against a patient strain (Kp-P1) and, tellingly, failed to protect mice colonized with a different PSC Kp strain (Kp-P5), underscoring the need for strain-matched matching/diagnostics. To counter the rapid emergence of phage-resistant mutants seen with single phages, the team iteratively isolated escape mutants and added phages targeting them, extending suppression from ~6 hours to over 20 hours in vitro (a sustained-suppression cocktail design). Route mattered mechanistically: oral phage lowered fecal Kp burden, while intravenous phage reduced Kp that had already translocated to mesenteric lymph nodes—suggesting combined oral plus systemic delivery covers both the gut reservoir and the translocated pool. Critically, oral dosing depleted Kp without off-target dysbiosis of the surrounding microbiota, the central advantage over antibiotics.
Where it stands
Current evidence
Evidence is strong preclinical plus early-phase human safety/PK, but not yet efficacy-proven in PSC patients. The causal mechanism was established in humans and gnotobiotic/SPF mice (Nakamoto et al., Nat Microbiol 2019). The phage cocktail itself showed efficacy only in mouse models—lowering Kp and attenuating liver inflammation and disease severity in hepatobiliary injury-prone mice (Ichikawa, Nakamoto et al., Nat Commun 2023), a collaboration with the company BiomX. On the clinical side, BiomX advanced an orally delivered anti-Kp phage cocktail: BX002-A completed a Phase 1a randomized, placebo-controlled study in 18 healthy volunteers (NCT04737876, completed 2020/reported 2021), demonstrating safety, tolerability, and delivery of high-titer viable phage (~10^10 PFU) to the gut—reportedly the first demonstration of oral phage delivery to the human GI tract. BiomX subsequently consolidated its IBD and PSC efforts into a broader-host-range candidate (BX003). No randomized efficacy data in PSC patients have been reported to date.
Evidence confidence: medium
The data
Key studies & trials
- Ichikawa M, Nakamoto N, Kredo-Russo S, et al. Bacteriophage therapy against pathological Klebsiella pneumoniae ameliorates the course of primary sclerosing cholangitis. Nat Commun. 2023;14(1):3261. ↗
- Nakamoto N, Sasaki N, Aoki R, et al. Gut pathobionts underlie intestinal barrier dysfunction and liver T helper 17 cell immune response in primary sclerosing cholangitis. Nat Microbiol. 2019;4(3):492-503. ↗
- BiomX, Inc. A Phase 1, Randomized, Single-blind, Placebo-controlled Study to Evaluate the Safety, Tolerability, and Fecal Pharmacokinetics of Orally Administered BX002-A (anti-Klebsiella pneumoniae bacteriophage cocktail) in Healthy Adult Individuals. ClinicalTrials.gov identifier NCT04737876; completed 2020. ↗
- Liu C, Wang YL, Yang YY, et al. Novel approaches to intervene gut microbiota in the treatment of chronic liver diseases (review covering bacteriophage strategies against K. pneumoniae in PSC). FASEB J. 2021;35(10):e21871. ↗
Who is working on it
Programs & centers
The possibility
If strain-matched phage cocktails can durably suppress PSC-associated Klebsiella in patients, phage therapy could become the first treatment to act on the upstream cause of PSC rather than its downstream fibrosis—potentially slowing or halting a disease that today often ends in transplant. The natural next step is a companion-diagnostic model: stool-screen a patient for their resident Kp strain, then deploy (or rapidly assemble) a matched oral-plus-systemic phage cocktail, with sustained-suppression design and engineered or CRISPR-armed phages to outrun resistance. Beyond PSC, the same gut-liver-axis logic—neutralize a single translocating pathobiont without torching the microbiome—could generalize to autoimmune hepatitis, IBD, and other conditions where one culprit strain drives systemic inflammation.