The US Food and Drug Administration (FDA) has just awarded Breakthrough Therapy Designation to a drug (OMS721) being developed to treat thrombotic microangiopathy that has developed as a result of haematopoietic stem cell transplantation. The full story can be read here, at Business Wire.
Haematopoietic stem cell transplants (HSCT) are used to treat patients with a range of different diseases. These include cancers such as myeloid leukaemia (acute and chronic), Hodgkin lymphoma, neuroblastomas, and multiple myelomas, amongst others. The transplant is also given to patients with non-cancerous conditions, including thalassemia, sickle cell anaemia, and many autoimmune diseases.
An HSCT procedure involves taking stem cells that are able to produce blood cells from either the patient themselves or a donor and transplanting them into areas of the patient’s body where they are needed. The stem cells can come from bone marrow, blood, or an umbilical cord.
Although the transplant is successful for many patients and significantly improves their prognosis, the treatment, unfortunately, has a high risk of causing complications. The major side effects patients are at risk of include infection, veno-occlusive disease, graft-versus-host-disease, and the complication that the drug OMS721 is being developed to treat, thrombotic microangiopathy (TMA). TMA affects approximately 10-25% of patients that undergo HSCT procedures. It occurs when small blood vessels in organs are damaged and blood clots form in them. This can lead to fevers, kidney failure, neurological issues, and low platelet counts, amongst other effects.
The current treatment for patients who develop TMA following a stem cell transplant is to change the immunosuppressant medications the patient is taking. This isn’t always effective, but there are not currently any other treatment options. There is an important unmet patient need for improved treatment options, given the extremely high (around 90%) mortality rates for high-risk patients who have not responded to changing their immunosuppressant medicines.
However, the treatment being developed, OMS721, has demonstrated promising results. A Phase 2 trial of the drug in patients who had not responded to modifying their immunosuppressant treatments found that patients who took it had much higher rates of survival compared to those who didn’t. Over half the patients given the drug survived over 100 days, compared to 10% of those who didn’t. Furthermore, those taking the drug showed improved platelet counts and levels of hatoglobin. A Phase 3 trial is currently on going.
The success of the drug in trials has led to Omeros, the pharmaceutical company behind it, setting up a compassionate-use program that will allow certain patients in the US and Europe to access the drug before it is approved by government authorities. Professor Rambaldi, from the University of Milan, described treating a patient with OMS721 who responded exceptionally well to it. He reported that a patient was hospitalised with several complications, including graft-versus-host-disease, TMA, and neurological disability. Following treatment with the drug, he was cured of TMA and his neurological condition improved, allowing him to leave the hospital and return to part-time work. Although this is a single case where a patient reacted particularly well to the drug, it highlights the potential of the treatment to help patients.