Abstract
We have developed genetically modified second-generation probiotics for the localized delivery of known
mitigators to the GI tract in order to reduce damage and regenerate tissue after exposure to ionizing radiation.
Mitigating the effects of ionizing radiation exposure is critical for improving survival in the event of a radiological
or nuclear (RAD-NUC) incident, where exposure could lead to hematopoietic or gastrointestinal (GI) acute
radiation syndrome (ARS). While Neupogen and Neulasta have been granted label extensions by the FDA to
treat casualties of a RAD-NUC incident, these drugs do not prevent GI-ARS-related mortality. There currently
are no FDA-approved mitigators for GI-ARS. To address this critical need, we have engineered Lactobacillus
reuteri to produce therapeutic cytokines (IL-22 or INF-ß) and target these mitigators to the small intestines to
recover intestinal stem cells, regenerate the radiation-sensitive intestinal crypts, and dramatically improve
survival from 0–10% to 70–80% after exposure to GI-ARS-inducing radiation doses. This is a new strategy for
therapeutic drug delivery, using a probiotic can be administered orally, facilitating its use in the context
of a resource-limited mass casualty scenario. In addition to mitigating injury following a RAD-NUC incident,
this approach is also applicable to radioprotection of the intestine during abdominal radiotherapy. Symptoms of
GI toxicity affect 60–80% of the >300,000 patients that receive pelvic or abdominal radiation therapy per
year. This project is based on an entirely new concept that addresses the fundamental major limitations
associated with delivery of any potential radiation mitigator of GI syndrome, including (i) non-invasive
administration, (ii) targeted delivery of the therapeutic, (iii) maintained bioavailability of the therapeutic
at efficacious dose, (iv) trivially scalable to produce, and (v) no need for formulation. The goal of this
project is to develop an FDA-approved mitigator for radiation-induced GI injury. We propose critical studies to
characterize the maximum effective dose, establish the rate of clearance from the body, and address safety by
examining the effect of the drugs on the intestinal microbiome. In parallel, we will meet with the FDA to develop
a strategy for IND approval that will guide subsequent studies. Successful completion of this work will place
these probiotic drugs on a strong path towards eventual FDA approval.
