Sellas Life Sciences recently reported results from its Phase I clinical trial showing that survival was improved in pleural mesothelioma patients due to its treatment. The trial looked at the treatment called galinpepimut-S (GPS), an immunotherapy vaccine. There were 10 patients in the study with relapsed or refractory mesothelioma. Nine of the patients received at least three doses of GPS. The third dose of the vaccine was given alongside a checkpoint inhibitor called nivolumab (Opdivo). Researchers found the treatment to be safe since the safety profile seemed to be the same as checkpoint inhibitors alone. They believe the survival benefits will continue to help the stop of progression of extremely aggressive cancers and will be an effective combination therapy.
Results from the study are very promising. All patients enrolled in the study had a median progression-free survival of 11.9 weeks without any increase in cancer growth. One third of patients had stable disease with a decrease in tumor size by 17 percent. The median age of patients was 69 years and 60 percent of patients were enrolled with a stage III or stage IV mesothelioma diagnosis. Participants in the study received pemetrexed-based chemotherapy. Their cancer either progressed after taking the treatment or was not responsive to the treatment.
An immune response was defined by the study as a measurable increase in multiple types of immune cells. Around 78 percent had an immune response. These patients had a median overall survival of two years and four months which is 19 months longer than those who never received an immune response. For patients who did not have an immune response, the median overall survival was nine months. The median overall survival for patients with an immune response to GPS was 27.8 months, which is three times longer. The median overall survival of patients who received GPS and Opdivo was 18 months or 70.3 weeks. People with relapsed or refractory mesothelioma typically have an overall survival of about 28 weeks when given standard therapy.
In June 2023, Sellas reported the positive Phase I results from GPS, which was found to improve survival in mesothelioma patients by two months in patients with stage IV disease. There are now two studies where GPS increases the survival benefit in those with active disease: patients with relapsed/refractory WT1 positive ovarian cancer and relapsed/refractory WT1 positive mesothelioma. All patients in the study experienced adverse events. There were seven with treatment related toxicities, while three cases required hospitalization. There were three patients with mild GPS-related toxicity.
