Duration of response to loncastuximab tesirine in relapsed/refractory diffuse large B-cell lymphoma by demographic and clinical characteristics: Subgroup analyses from LOTIS 2.
Authors: Caimi Paolo , Ai Weiyun Z. , Alderuccio Juan Pablo , Ardeshna Kirit , Hamadani Mehdi , Hess Brian T. , Kahl Brad S. , Radford John A. , Solh Melhem M. , Stathis Anastasios , Zinzani Pier Luigi , Feingold Jay Marshall , Ungar David , Qin Yajuan , He Shui , Carlo-Stella Carmelo 
Published: June 2021

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Background: Outcomes for patients with refractory/relapsed diffuse large B-cell lymphoma (R/R DLBCL) are poor, particularly for those with high-risk clinical characteristics. There remains an unmet need for new treatment options for these patients. Loncastuximab tesirine (Lonca) is an antibody-drug conjugate comprising a humanized anti-CD19 antibody conjugated to a potent pyrrolobenzodiazepine dimer toxin. LOTIS 2 was a pivotal Phase 2 study that demonstrated substantial single-agent anti-cancer activity of Lonca in patients with R/R DLBCL. Efficacy and safety data were presented at ASH 2020 (Caimi et al, ASH 2020; abstract 1183). Here we present subgroup analyses of duration of response (DoR) to Lonca by demographic and clinical characteristics. Methods: Adult patients with R/R DLBCL who had received ≥2 prior therapies were enrolled in this Phase 2, multicenter, single-arm, open-label study of single-agent Lonca (150 µg/kg every 3 weeks for 2 doses, followed by 75 µg/kg thereafter for up to 1 year). The primary analysis has previously been reported, with a primary endpoint of overall response rate (ORR). Patients are being followed-up every 12 weeks for up to 3 years. DoR was a key secondary efficacy endpoint, defined as time from the first documentation of response (central review) to disease progression or death. We analyzed pre-specified demographic and clinical characteristic subgroups for DoR. Results: As of data cut-off (August 6, 2020), ORR in the total population (N = 145) was 48.3% (24.8% had complete response [CR] and 23.4% had partial response [PR]). Median DoR (mDoR) for the 70 responders was 12.58 months. mDoR for patients with CR and PR was 13.37 months and 5.68 months, respectively. Overall, subgroups with high-risk characteristics for poor prognosis had a DoR comparable to the whole study population. mDoR for patients with double-/triple-hit DLBCL was 13.37 months, with advanced stage disease was 12.58 months, and with transformed disease was 12.58 months. The mDoR for older patients was longer than for younger patients (≥75 years, 13.37 months; 65 to < 75 years, 12.58 months; < 65 years, 9.26 months). Patients with DLBCL refractory (defined as no response to therapy) to first-line, most recent line, and all prior lines of therapy had mDoRs of 9.63 months, 9.26 months, and 9.63 months, respectively. Conclusions: Durable responses were observed with the recommended Phase 2 dose regimen of Lonca in heavily pre-treated patients and those at high risk of poor prognosis, including older patients and those with double-/triple-hit, advanced stage, transformed, and primary refractory DLBCL. Updated DoR data will be presented at the meeting. Clinical trial information: NCT03589469.