FDA slaps hold on Finch's C. diff med to get info on COVID-19 screening for donor-derived therapy

Finch Therapeutics' phase 3 trial for a Clostridioides difficile med has been placed on clinical hold by the FDA as the agency requests more information on how the biotech screens the donor-derived microbiome therapy for the virus that causes COVID-19.

That means Finch has paused enrollment in the late-stage trial, dubbed PRISM4, of CP101, the biotech said Tuesday after market close. Shares slipped 11.5% to $7.44 apiece as of 9:38 a.m. ET on Wednesday. 

The study began in November 2021 and is meant to serve as the second pivotal trial of the investigational med in patients with the gastrointestinal pathogen that can cause inflammation of the colon, diarrhea and sometimes death. 

The company received the regulator's letter Feb. 24 after communicating with the FDA in January. Finch's Tuesday news came the same day Pfizer said its C. difficile vaccine failed a phase 3 trial. 

RELATED: Pfizer fails phase 3 C. diff vaccine test but still spies possible path forward

At the heart of the FDA's request is an ongoing issue during the pandemic. When COVID-19 hit the U.S. in March 2020, the FDA warned donor-derived investigational microbiome therapies carried a risk of transmitting SARS-CoV-2 and additional safety precautions would be needed.

At that time, the FDA put a partial clinical hold on Finch's investigational new drug request for CP101 and its then-contract manufacturer, OpenBiome. The agency asked for SARS-CoV-2 testing protocols for microbiota material donated after Nov. 30, 2019. Finch continued dosing patients in its phase 2 open-label trial at that time because the CP101 lots were made from material donated prior to Dec. 1, 2019. 

OpenBiome's clinical hold was released in January 2021 after it instituted a direct testing method for the pandemic virus using a third-party vendor. Finch then acquired some manufacturing assets from OpenBiome in March 2021 and began the PRISM4 trial in November 2021 using the same testing method and vendor as OpenBiome.

But the FDA now wants to know how the samples are shipped to the vendor that conducts the test and is seeking info on how the biotech will handle inconclusive test results. 

RELATED: Finch Therapeutics' microbiome med quells stubborn C. difficile

The Somerville, Massachusetts, biotech said it will "expeditiously provide the requested information" so the clinical hold matter can be resolved "as soon as possible."

Finch is evaluating whether the agency's action will impact timing of the slated top-line data readout. The biotech expects to collect final data for the primary outcome measure of the trial in February 2023, according to PRISM4's registry in ClinicalTrials.gov. 

The orally administered drug cleared C. difficile in 74.5% of patients through Week 8 after a single delivery in Finch's phase 2 trial, named PRISM3. The drug notched statistical significance for the primary efficacy endpoint in that trial by showing a 33.8% relative risk reduction in the recurrence of C. difficile compared to placebo. 

Existing treatments for C. difficile include antibiotics, which don't treat the superbug's underlying disruption to the body's microbiome, so the pathogen can return.