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FDA Sends Warning on Covid-19 Food Therapy Trials

Gut microbes illustration

Gut microbes illustration (

8 Sept. 2021. The Food and Drug Administration released yesterday a warning letter sent in late August to a company conducting clinical trials of a food therapy for Covid-19 symptoms. FDA sent the letter to Kaleido Biosciences Inc. in Lexington, Massachusetts, after an inspection showed the company conducting trials of its microbiome Covid-19 therapy without first submitting an investigational new drug application, or IND, required for conducting trials of experimental drugs.

Kaleido Biosciences creates therapies for infectious, metabolic, and immune-related diseases, as well as cancer designed to act on the microbiome, microbial communities found naturally in the body, particularly in the gut. The microbiome is an emerging area of research and opportunity for therapies, including for diseases not usually associated with bacteria or the gut, including disorders linked to the immune system and neurological diseases.

Kaleido Bio develops its therapies with synthetic glycans, simple to complex carbohydrate compounds with many known interactions with microorganisms in the gut. The company says it maintains a library of more than 1,500 synthetic glycans designed to influence metabolic functions of gut microbes. From this library, Kaleido Bio develops treatment candidates it calls microbiome metabolic therapies, or MMTs designed to act on classes of gut microbes with enzymes to produce metabolites with therapeutic effects.

The company is testing its MMT-derived product code-named KB109 as a treatment for symptoms in patients with mild to moderate Covid-19 infections. Kaleido Bio says KB109 consists of metabolites called short chain fatty acids that are known to influence immune responses. The company cites data showing short chain fatty acids may mitigate inappropriate immune responses to Covid-19, thus helping avoid more serious complications. Science & Enterprise reported in March 2021 on Kaleido Bio’s release of results from a clinical study that show KB109 reduces health care use and recovery times in people with mild to moderate Covid-19 disease.

No nutritional requirements for treating Covid-19

The company contends its MMTs meet FDA’s requirements for “generally accepted as safe” substances applied to food additives, thus can often bypass IND requirements. In the 26 Aug. letter, David Burrow, who heads FDA’s scientific investigations office, notes however, that Kaleido Bio’s clinical trial protocols test for changes in factors used to measure drug efficacy, such as symptom scores, from before treatment to after, as well as quality of life, hospital admissions, and health care utilization. Another trial protocol calls for measuring changes in biomarkers and lab tests indicating physiological characteristics of the microbiome, resulting from KB109.

In addition, Burrow points out medical foods are intended for dietary management to meet nutritional requirements for treating a disease or condition. However, no nutritional requirements for treating Covid-19 are yet established, and the trials’ endpoints, or measurable objectives, clearly exceed any reasonable definition of dietary management. Moreover, says the letter, meeting the “generally accepted as safe” standard for food substances does not preclude also testing the product as a drug.

FDA says its inspection team sent Kaleido Bio its findings in advance of the letter, to which the company responded. The agency’s letter says the company’s response indicates Kaleido Bio is establishing a procedure to determine the need for an IND, in consultation with FDA, where products may be considered a medical diagnostic or treatment. FDA says it is still waiting for more details from the company to determine if that process is sufficient.

Science & Enterprise asked Kaleido Biosciences to comment on FDA’s warning letter, and will update this story with the company’s comments.

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