Subcutaneous Epcoritamab in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia: Preliminary Results from the Epcore CLL-1 Trial

Background: Small molecules such as Bruton tyrosine kinase (BTK) and B-cell lymphoma 2 (BCL2) inhibitors have transformed the management of chronic lymphocytic leukemia (CLL). However, such treatments are not curative, and patients (pts) with relapsed or refractory (R/R) CLL following multiple targeted treatments present an emergent challenge with very limited therapeutic options. In addition, success rates of autologous T-cell-based therapies in CLL have been disappointing. In vitro data in CLL cells suggest potentially high efficacy of bispecific T-cell engagers (Martens et al, J Immunother Cancer 2020), but clinical data are extremely limited.

Epcoritamab (GEN3013; DuoBody ^®-CD3×CD20) is a bispecific antibody that can induce potent activation and cytotoxic activity of CD4+ and CD8+ T cells to specifically eliminate CD20-expressing cells (van der Horst et al, Blood Cancer J 2021). In the first-in-human trial in R/R B-cell non-Hodgkin lymphoma (B-NHL; EPCORE NHL-1; NCT03625037), epcoritamab showed manageable safety and meaningful antitumor activity across a range of aggressive and indolent B-NHLs. The most common treatment-emergent adverse events (AEs) were pyrexia (69%), cytokine release syndrome (CRS; 59%), and injection-site reaction (47%); CRS events were all grade 1-2 and most occurred in cycle 1 (Clausen et al, J Clin Oncol 2021). However, as CLL is characterized by presence of (high numbers of) circulating tumor cells, acquired T-cell dysfunction, and variable expression of CD20, data obtained in B-NHL are difficult to extrapolate to CLL. Herein we present the first results from the dose-escalation part of a phase 1b/2 trial evaluating epcoritamab in pts with R/R CLL.

Methods: In this open-label, multicenter, phase 1b/2 trial, toxicity and efficacy of epcoritamab are investigated in adults with R/R CLL (EPCORE CLL-1; NCT04623541). Eligible pts previously received ≥2 lines of systemic antineoplastic therapy, including treatment with (or intolerance to) a BTK inhibitor. Epcoritamab is subcutaneously administered via 1-mL injections in 4-week cycles as follows: once weekly in cycles 1-3, every 2 weeks in cycles 4-9, and monthly in cycles ≥10 until progression or unacceptable toxicity. Step-up dosing during cycle 1 (ie, priming dose followed by an intermediate dose, then full doses) is used in combination with steroid prophylaxis to reduce the risk of CRS. In the dose-escalation part, pts with R/R CLL received epcoritamab at 2 full-dose levels (24 and 48 mg) according to a modified 3+3 design. Primary end points of the dose-escalation part included dose-limiting toxicities (DLTs) during the first 28-day treatment cycle and the incidence and severity of AEs, CRS, immune effector cell-associated neurotoxicity syndrome (ICANS), and tumor lysis syndrome (TLS).

Results: The first pt was enrolled on November 30, 2020. As of July 12, 2021, 7 pts with R/R CLL received epcoritamab subcutaneously administered at 2 full-dose levels: 24 mg (n=3) and 48 mg (n=4). Six pts completed the DLT evaluation period, and 5 pts had a full response assessment. Pts had received a median of 4 lines of prior therapy (range, 2-5). Six of 7 pts had poor-risk features of del(17p), TP53 mutations, or both. Three of 7 pts had bulky disease.

No DLTs occurred at 24 or 48 mg. The most common treatment-emergent AEs (>30%) were CRS (100%), fatigue (71%), injection-site reaction (43%), and nausea (43%). All pts experienced CRS in the first cycle, but no CRS events were higher than grade 2. No cases of ICANS were observed. TLS was not observed. Antileukemic activity has been observed at both dose levels, with partial responses in 3 of 5 pts. Updated clinical and pharmacokinetic data, including data for additional pts treated with epcoritamab, will be presented.

Conclusions: These data suggest that epcoritamab is well tolerated in pts with R/R CLL at dose levels up to 48 mg and has clinical activity in pts with high-risk features. The expansion part of this study in pts with R/R CLL and Richter syndrome will open later this year.