Bacteria engineered as living medicines

How far are engineered bacteria and other living therapeutics from approved treatments?

Engineered bacteria have reached small human trials. A wound-healing candidate was tested in 36 healthy volunteers. An engineered strain for phenylketonuria (PKU) lowered fasting blood phenylalanine by 40% in a 20-person open-label phase 2 study. The PKU candidate's pivotal study was discontinued in February 2024, and the sources reviewed report no result from it. None of the sources reviewed reports an approved engineered living therapeutic. The approved live microbial products for C. difficile come from human faecal microbiota, not from engineered strains.

AI illustration · Illustrative scene, not a photograph of the specific device or experiment.
WHERE WE AREEngineering prototypes

Getting closer. Prototypes exist, but not in real-world use.

Engineered bacteria have been given to people in phase 1 and phase 2 trials. One candidate reached a pivotal study, which the company discontinued in February 2024 before any result was reported. None of the sources reviewed reports an approved engineered living therapeutic. The approved live microbial products for C. difficile are made from human faecal microbiota, so they do not show that an engineered strain can be approved. Engineered strains have been tested in people only in small early studies, which fits the engineering prototype stage.

The tech tree

Everything recorded on Vrulum that this future needs, oldest foundations at the top and the goal at the bottom. Lines show what each step requires.

What it takes: Bacteria engineered as living medicines Unlocked Being researched Locked
  1. 2023Engineered living therapeuticsResearch and prototypes Being researched.
  1. 2016Regulatory guidance for early trials of live biotherapeutic productsDone Unlocked.
  2. 2021Phase 2 trial in difficult diabetic woundsIn progress Being researched.
  3. 2022Live microbial products approved for C. difficile recurrence (not engineered)Done Unlocked.
  4. 2023Phase 1 safety study of an engineered wound-healing bacteriumDone Unlocked.
  5. 2023Phase 2 study of an engineered bacterium in adults with PKUDone Unlocked.
  6. 2024Mouse studies of engineered bacteria for colorectal cancerDone Unlocked.
  7. 2024Pivotal study result for an engineered bacterium in PKUNot started Locked.
  1. GoalBacteria engineered as living medicinesGoalRequires: Engineered living therapeutics, Phase 1 safety study of an engineered wound-healing bacterium, Phase 2 study of an engineered bacterium in adults with PKU, Pivotal study result for an engineered bacterium in PKU, Phase 2 trial in difficult diabetic wounds, Live microbial products approved for C. difficile recurrence (not engineered), Regulatory guidance for early trials of live biotherapeutic products, Mouse studies of engineered bacteria for colorectal cancer. Locked.

The road so far

5 of 7 steps done, 1 in progress.

  1. Done · 25 May 2023Phase 1 safety study of an engineered wound-healing bacterium

    Öhnstedt and colleagues reported a randomised, double-blind, placebo-controlled phase 1 trial of ILP100-Topical, a genetically modified Limosilactobacillus reuteri that makes CXCL12 at the wound. The trial enrolled 36 healthy volunteers with 240 induced wounds. Its primary objective was safety, and the authors report the product was safe and well tolerated at all tested doses, with no systemic exposure detected. [1]

  2. Done · 28 Sept 2023Phase 2 study of an engineered bacterium in adults with PKU

    Vockley and colleagues reported an open-label, 14-day dose-escalation study (Synpheny-1) of SYNB1934, an engineered bacterial strain. Twenty people enrolled and 15 completed treatment. Fasting plasma phenylalanine fell by 40% (95% CI -52 to -24). Four participants discontinued because of adverse events. The authors report no serious adverse events or infections. The study was small and open-label. [2]

  3. Not started · 10 Feb 2024Pivotal study result for an engineered bacterium in PKU

    Synlogic was running Synpheny-3, a pivotal study of SYNB1934. In February 2024 the company announced it would discontinue the study. An internal review, ahead of an independent Data Monitoring Committee assessment, had found the trial unlikely to meet its primary endpoint. The company said the decision was not based on concerns about safety or tolerability. The sources reviewed report no result from the study, so this milestone has not been reached. [4]

  4. In progress · 23 Jun 2021Phase 2 trial in difficult diabetic wounds

    On 23 June 2021 Ilya's Pharma announced that Swedish regulators had approved a 26-week phase 2 study of ILP100 in difficult diabetic wounds. The announcement calls the product ILP100 gene therapy and does not say whether it is the same product as the phase 1 bacterium. It gives no start date. The sources reviewed do not confirm whether the study has started, finished or reported results. [5]

  5. Done · Dec 2022Live microbial products approved for C. difficile recurrence (not engineered)

    Healio reported on 1 December 2022 that Rebyota, a fecal microbiota product, had been approved to prevent C. difficile recurrence in adults after antibiotic treatment. The FDA approved Vowst for the same use on 26 April 2023. Vowst is taken by mouth as capsules and is the first oral product of this kind. Neither product is an engineered strain. These approvals show that a live microbial medicine can reach the market, but they do not show that an engineered strain can be approved. [7][6]

  6. Done · Jun 2016Regulatory guidance for early trials of live biotherapeutic products

    The FDA's Center for Biologics Evaluation and Research issued guidance in June 2016 on the chemistry, manufacturing and control information needed for early clinical trials of live biotherapeutic products. The guidance does not apply to live biotherapeutic products intended as gene therapy vectors, oncolytic bacteria or oncolytic viruses, so some engineered bacteria may fall outside it. [8]

  7. Done · 20 Jan 2024Mouse studies of engineered bacteria for colorectal cancer

    Zhou and colleagues reported engineered Escherichia coli Nissle 1917 strains with a gene switch that increased signal output 1.8 to 2.3 times in engineered biosensor tests. The strains reduced tumour growth by 47% to 52% in a mouse subcutaneous tumour model. Engineered bacteria were also found in the liver and spleen after intratumoral injection, not only in tumours. About 40% and about 30% of bacteria kept their plasmid in the mouse gut for the two configurations tested. These are preclinical results. [3]

Why it matters

A living medicine could make a drug close to where it is needed, rather than sending it round the whole body. The same feature makes the approach hard to control. Regulators and patients will need evidence that engineered bacteria stay where they should, keep their engineered function and work in people who are ill, not only in healthy volunteers or in mice.

What stands in the way

  • Containment: after intratumoral injection in mice, engineered bacteria were also found in the liver and spleen. Spread and clearance would need direct testing in people.
  • Genetic stability: in mice, about 40% and about 30% of bacteria kept their engineered plasmid in the gut for the two configurations tested, so some bacteria lose the control circuit.
  • Evidence of benefit: the only pivotal study reported in the sources was discontinued before a result. Human data so far come from small studies, with 36 healthy volunteers in the wound study and 20 adults in the PKU study.
  • Patient differences: the wound study used induced wounds in healthy volunteers, so its results may not carry over to chronic or diabetic wounds.
  • Manufacturing: a living product must keep a consistent strain identity, stability and potency from batch to batch. The sources reviewed do not show a commercial process for an engineered strain.

Signals to watch

  • Results from the phase 2 study of ILP100 in difficult diabetic wounds, which Swedish regulators approved in 2021 as announced by the company.
  • A new pivotal or phase 3 trial of an engineered living therapeutic, and its primary endpoint result.
  • Human studies that track where engineered strains go in the body and how long they persist.
  • Regulatory guidance that names engineered live biotherapeutics directly, or a first marketing application for one.
  • Engineered strains with built-in kill switches tested in people.

Sources

  1. peer reviewed paper
    Engineered bacteria to accelerate wound healing: an adaptive, randomised, double-blind, placebo-controlled, first-in-human phase 1 trial
    Emelie Öhnstedt, Evelina Vågesjö, Andreas Fasth et al.. Elsevier (eClinicalMedicine), 25 May 2023.
  2. peer reviewed paper
    Efficacy and safety of a synthetic biotic for treatment of phenylketonuria: a phase 2 clinical trial
    Jerry Vockley, Neal Sondheimer, Marja Puurunen et al.. Springer Nature (Nature Metabolism), 28 Sept 2023.
  3. peer reviewed paper
    Enhancing tumor-specific recognition of programmable synthetic bacterial consortium for precision therapy of colorectal cancer
    Tuoyu Zhou, Jingyuan Wu, Haibo Tang et al.. npj Biofilms and Microbiomes (Springer Nature), 20 Jan 2024.
  4. company announcement
    Synlogic announces decision to discontinue Synpheny-3 study of labafenogene marselecobac and provides corporate update
    Medthority (reproducing the Synlogic press release), 10 Feb 2024.
  5. company announcement
    Ilya's Pharma Receives Approval from Swedish Regulators to Initiate Phase II Clinical Study of ILP100 Gene Therapy to Treat Difficult Wound Patients with Diabetes
    Ilya's Pharma (via 59 North Communications), 23 Jun 2021.
  6. government report
    FDA Approves First Orally Administered Fecal Microbiota Product for the Prevention of Recurrence of Clostridioides difficile Infection
    U.S. Food and Drug Administration, 26 Apr 2023.
  7. news
    FDA approves fecal microbiota biotherapeutic for recurrent C difficile infection
    Healio, 1 Dec 2022.
  8. government report
    Early Clinical Trials With Live Biotherapeutic Products: Chemistry, Manufacturing, and Control Information
    U.S. Food and Drug Administration, Center for Biologics Evaluation and Research, Jun 2016.

Last reviewed 21 Oct 2026.