“We know that relapsed diffuse large B-cell lymphoma has a particularly poor prognosis,” especially for patients who have undergone at least two therapies, Dr. Michael Dickinson, MBBS, of the University of Melbourne said in a presentation at the annual meeting of the American Society of Clinical Oncology.
Bispecific T cell–recruiting antibodies are emerging as a novel treatment option for B-cell cancers, said Dr. Dickinson.
Glofitamab is distinct among these therapies for its configuration that is bivalent for CD20 and monovalent for CD3, providing more potency than a 1:1 format, Dr. Dickinson explained in his presentation.
The study population included 154 adults aged 21-90 years with DLBCL who had received at least two prior treatments; all had received prior anti-CD20 Ab, and 149 had received anthracycline. The median age of the patients was 66 years, 65% were male, 75% had Ann Arbor stage III or IV disease, and 90% were refractory to any prior therapy.
The patients received intravenous glutamate-pyruvate transaminase, followed by an initial intravenous dose of glofitamab 7 days later. Glofitamab was given as step-up doses starting with 2.5 mg to a target of 30 mg.
The primary endpoint was complete response (CR) during initial treatment using Independent Review Committee (IRC) criteria, with overall response rate, duration of response, duration of complete response, progression-free survival, and overall survival as key secondary outcomes.
At a median of 12.6 months’ follow-up, the CR and overall response rates were 39.4% and 51.6%, respectively.
“Responses were achieved early; the median time to first complete response was 42 days,” Dr. Dickinson reported. Of the 38 patients with CR at the data cutoff point, 33 remained in complete remission (87%) based on IRC criteria. Complete response rates were consistent across prespecified subgroups, notably 42% of patients with no prior chimeric antigen receptor T-cell therapy and 70% and 34%, of those who were relapsed or refractory, respectively, to their last prior treatments.
The median duration of overall response was 18.4 months, and the median duration of complete response had not yet been estimated, Dr. Dickinson said. The median progression-free survival and overall survival rates were 4.9 months and 11.5 months, respectively, and the estimated 12-month overall survival was 49.8%.
“These are highly clinically significant results for this difficult to treat population,” Dr. Dickinson said in his presentation.
The most common adverse event was cytokine release syndrome (CRS), which occurred in 63% of patients. Of these, 3.9% were grade 3 or 4. Patients received corticosteroids (27.8%) or tocilizumab for management of CRS.
“As we have shown before, this is a first-course phenomenon, becoming far less frequent once step up dosing is complete,” Dr. Dickinson said in the presentation. “The median time to CRS is predictable, occurring around 10 hours after the IV infusion,” he said. Overall, 3.2% of the patients discontinued because of an adverse event.
A total of eight deaths occurred during the study; five of these were related to COVID-19 and the remaining three were in patients with manifest progression of disease.
Infections are to be expected in such a heavily treated population, and 14.9% of patients developed infections of grade 3 or higher, said Dr. Dickinson. Neutropenia of any grade occurred in 37.7%, febrile neutropenia in 2.6%. Neurological events occurred in 38.3% of patients; 3.2% were grade 3 or higher.
The study did not prospectively record immune effector cell–associated neurotoxicity syndrome, Dr. Dickinson said, but an estimate suggests a rate of 2.6%, and none of the events were considered to be related to glofitamab, he noted.
The researchers also looked at a supporting cohort of 35 patients with a median follow up of more than 2 years. In this group, the complete remission rate was 35% and the median duration of remission was 34.2 months. “Our six longest patients have been in remission for longer than 3 years,” Dr. Dickinson said.
The latest glofitamab data “reflect routine practice and an area of need for this disease,” said Dr. Dickinson.
“I think these results will prove to be very meaningful for our patients with large cell lymphoma, and this drug will prove to be an important treatment option,” he said.