Background: In R/R DLBCL/FL, T-cell engager therapy (TCET) using chimeric antigen receptor T-cell therapy (CART) or bispecific antibodies (BsAbs) are promising options. Patients (pts) with R/R disease post TCET experience dismal outcomes with overall survival (OS)< 5 months (mos). Lonca, an antibody drug conjugate (ADC) targeting CD19 (FDA approved for R/R DLBCL and beneficial in R/R FL) has been increasingly used post-TCET. RWDA of Lonca is limited, especially regarding: 1) impact of CD19 expression on activity, 2) adverse events (AEs) in non-clinical trial setting, and 3) impact of sequencing Lonca and TCET. Thus, we conducted a RWDA of Lonca efficacy and toxicity in R/R DLBCL and FL pre- and post-TCET.

Methods: We conducted a multicenter retrospective study of R/R DLBCL or FL pts ≥18 years who received Lonca from 2017 to 2025 at 10 US academic sites. Demographic, pathological, treatment, and AEs were collected. Efficacy outcomes included overall response rate (ORR), complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD). Progression-free survival (PFS) and OS were analyzed by Kaplan-Meier method. CD19 expression by immunohistochemistry (IHC) and/or flow cytometry (FC) prior to Lonca administration was correlated to outcomes.

Results: Among 120 pts (DLBCL n= 101, FL n=19), all but 2 pts received Lonca monotherapy. At a median follow-up of 6.1 mos, median PFS and OS were 2.6 mos and 6.7 mos, respectively for the entire cohort.

For DLBCL, median age was 66 years (18-89). Median prior lines of therapy (LOT) were 4 (1-11). ORR was 37.7% (CR: 17%, PR: 20.7%), SD: 6%, and PD: 56%. Median PFS was 2.1 mos, and median OS was 5.8 mos. For FL, median age was 62 years (28-88). Median prior LOT was 6 (2-8). ORR was 49.4% (CR: 28%, PR: 21.4%), SD: 14%, and PD: 35.7%. Median PFS was 6.7 mos, and median OS was 6.8 mos.

OS by best response (entire cohort) was 11.3 mos and 11.8 mos in those who had CR and PR, respectively, 10.6 mos in SD and 3.5 mos in those with PD. Lonca LOT (2nd-12th line) was not associated with improved OS (p=0.58). Bulky disease (>7.5 cm) was not associated with worse OS (p=0.07). PD to Lonca was associated with PD at 2nd line treatment (OR: 4.3; 95% CI: 1.7–10.9) and 3rd-line treatment (OR: 4.2; 95% CI: 1.5–11.5), elevated lactate dehydrogenase (OR: 1.9; 95% CI: 1.2–2.9), and each subsequent increase of extranodal sites >1 prior to Lonca (OR: 1.5; 95% CI: 1.04–2.1).

Among pts with available CD19 status prior to Lonca administration, 28 were FC-positive and 22 were IHC-positive. Of the CD19 FC-positive pts (n=23), 22% (5/23) achieved CR, 26% (6/23) had PR, 8% (2/23) had SD, and 43% (10/23) developed PD. Of the CD19 IHC-positive pts (n=20): 15% (3/20) achieved CR, 20% (4/20) had PR, 5% (1/20) had SD, and 60% (12/20) developed PD. Among all CD19-negative pts (n=7), two achieved CR, one had SD, and four with PD.

Any grade AE was seen in 84% of pts. Any grade ≥3 (G3) AE was seen in 62% of pts. Notable G3 AEs included: anemia (35%), lymphopenia (34%), neutropenia (21.6%), thrombocytopenia (20%), infection (17%), fatigue (9%), peripheral edema (5%), pleural effusion (4%), photosensitivity (2.5%), and pruritus (2.5%). Treatment discontinuation due to AEs occurred in 17% (n=21) of pts.

Fifty-five pts (50 DLBCL, 5 FL) received both Lonca and CD19 directed CART (Pre-Lonca n=54; Post-Lonca n=1). There was no significant difference in PFS or OS between pts who received CART and those who did not (PFS: 2.7 mos vs 3 mos; OS: 7.4 mos vs 5 mos). BsAb was used in 41 pts (34 DLBCL, 7 FL) (Pre-Lonca n=30; Post-Lonca n=11). No significant difference in PFS or OS was observed between pts who received BsAb pre- or post-Lonca. There was also no significant difference in PFS between pts who received a BsAb (2.2 mos) and those who did not (2.9 mos), nor in OS.Conclusion: In this large RWDA of Lonca, pts who achieved any form of clinical response experienced a significantly longer OS than previously reported for heavily pre-treated pts. Lonca was predominantly administered after TCET; however, there was no significant difference in efficacy between pts who received CART and BsAbs and those who did not. CD19 positivity and earlier utilization of Lonca did not appear to have an impact on response rates. Our findings support a role for Lonca in the treatment of R/R DLBCL pts not candidates for TCET. This RWDA highlights the need to further investigate the sequencing of Lonca in R/R DLBCL and FL.

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2025
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