Treatment of the gut microbiome to prevent complications associated with stem cell transplants

Blood cancers such as leukemia and lymphoma affect the blood, the bone marrow, or the lymphatic system. As a result, the formation and maturation of blood cells no longer function properly—too many immature or non-functional cells are produced, which weaken the body and make it more susceptible to infections. The disease is often recognized by symptoms such as fatigue, pale skin, fever, or swollen lymph nodes. One approach to treating blood cancers is to replace the diseased cells in the patient’s blood or immune system. This treatment is called a stem cell transplant. If the stem cells come from another person, it is referred to as an “allogeneic stem cell transplant.” Despite careful selection (“matching”) of the donor and recipient, serious complications can occur, including infections, graft-versus-host disease (GvHD), or relapses.

A healthy gut plays an important role in the immune system. Following a stem cell transplant—and due to the frequent need for antibiotics as part of treatment—the balance of the gut microbiota can be disrupted, which increases the risk of complications. Currently, probiotics or a high-fiber diet are often used to address a disrupted microbiome. However, treatment of the microbiome is not yet standard practice in stem cell transplants. The study drug MaaT033 contains a precisely formulated mixture of various gut bacteria in capsule form. These bacteria are derived from the stool of healthy individuals and are intended to restore the balance of the microbiome, thereby stabilizing the immune system. MaaT033 has not yet been approved; its use is limited exclusively to clinical trials.

The goal of this Phase 2b study is to investigate whether taking the drug MaaT033 after allogeneic stem cell transplantation can improve survival and reduce the rate of complications. To this end, patients are randomly assigned to two groups. In Group 1, they will receive the study drug MaaT033 three times a day in capsule form; in the control group, they will receive an identical-looking placebo with no active ingredient, also three times a day. The study is blinded, which means that neither the healthcare providers nor the patients know whether they are receiving the study drug or the placebo. In both groups, patients receive the capsules for 21 to 7 days before the allogeneic stem cell transplant and for up to 90 days after the stem cell transplant, starting from the time when white blood cell counts have recovered (approximately from day 18 onward). Follow-up as part of the study will continue for up to 12 months after the transplant.

Men and women aged 50 and older who are scheduled to undergo an allogeneic stem cell transplant are eligible to participate in the study. Certain types of allogeneic stem cell transplants—specifically those of particularly high or low intensity—may be excluded from participation.