Epcoritamab monotherapy for Richter transformation (EPCORE CLL-1): findings from a single-arm, multicentre, open-label, phase 1b/2 trial

BACKGROUND: Richter transformation is one of the most challenging B-cell lymphomas to treat, particularly in patients with high-risk chronic lymphocytic leukaemia features or who have had previous therapy for chronic lymphocytic leukaemia. Median survival remains 6-12 months across various therapeutic approaches. We evaluated the safety and preliminary activity of epcoritamab monotherapy, a subcutaneous CD3×CD20 bispecific antibody, in patients with Richter transformation.

METHODS: This multicentre, open-label, phase 1b/2 trial was conducted at 24 centres in nine countries (Australia, Belgium, Denmark, Germany, Israel, Italy, Spain, The Netherlands, and USA). Eligible patients were aged 18 years or older and had histologically confirmed Richter transformation (diffuse large B-cell lymphoma [DLBCL]), an Eastern Cooperative Oncology Group performance status of 0-2, and up to two previous lines of Richter transformation-directed therapy. The trial includes dose-escalation and dose-expansion phases. The expansion groups evaluate epcoritamab monotherapy (group 2A), epcoritamab plus lenalidomide (group 2B), and epcoritamab plus the combination of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP; group 2C). The current report describes results from group 2A. Epcoritamab was administered subcutaneously in step-up doses followed by 48 mg every week for cycles 1-3, every 2 weeks for cycles 4-9, and every 4 weeks thereafter until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed overall response rate per Lugano 2014 criteria in the full analysis set (all patients who received ≥1 dose of epcoritamab). It was evaluated against a null hypothesis of 30% versus an alternative of 50%. Prespecified subgroup analyses by line of therapy for Richter transformation and TP53 aberration and/or del(17p) status were performed. Safety was assessed in all treated patients. This trial is ongoing and registered with ClinicalTrials.gov, NCT04623541.

FINDINGS: Between Oct 18, 2021, and March 21, 2025, we enrolled 42 patients with Richter transformation. The median age was 69 years (range 50-80); and 32 (76%) of 42 patients were male and ten (24%) were female. Race or ethnicity data were available for 40 patients (37 [88%] identified as White, two [5%] as Asian, and one [2%] as Black or African American; ethnicity was not reported for two patients). The median time from diagnosis of chronic lymphocytic leukaemia or small lymphocytic lymphoma to Richter transformation was 7·6 years (range 0-23·9). 21 (50%) of 42 patients received epcoritamab as first-line Richter transformation-directed therapy. At a median follow-up of 22·9 months (range 0·5-39·9), 20 of 42 patients had a response with an investigator-assessed overall response rate of 47·6% (95% CI 32·0-63·6), which did not meet the prespecified alternative hypothesis (50%). Overall response occurred in 12 of 21 patients in the first-line population (overall response rate 57·1%, 34·0-78·2), in eight of 21 patients in the second-line or later-line population (38·1%, 18·1-61·6), and in eight of 20 patients with TP53 aberration and/or del(17p) alteration at baseline (40%, 19·1-63·9). The most common grade 3-4 adverse events were neutropenia in 19 (45%) of 42 patients, anaemia in 16 (38%) patients, thrombocytopenia in 16 (38%) patients, infection in nine (21%) patients, pneumonia in four (10%) patients, and COVID-19 in two (5%) patients. Cytokine release syndrome occurred in 36 (86%) patients with three (7%) being grade 3, immune effector cell-associated neurotoxicity syndrome in five (12%; all grade 1-2) patients and clinical tumour lysis syndrome in two (5%; all grade 1-2) patients. Three fatal adverse events were reported, one each due to general physical health deterioration in the context of progressive disease, sepsis, and cerebrovascular accident; none were considered by the investigator to be related to study treatment.

INTERPRETATION: In patients with Richter transformation, epcoritamab monotherapy showed clinically meaningful antitumour activity, although the investigator-assessed overall response rate was below the alternative hypothesis of 50%, with a safety profile consistent with previous studies. These findings support further investigation of epcoritamab as a potential treatment option for patients with Richter transformation.

FUNDING: Genmab A/S and AbbVie.