Outcomes of Sequential CD19-Directed Therapies in Relapsed and Refractory Large B Cell Lymphoma

Multiple CD19-directed therapies are available for the treatment of relapsed and refractory (R/R) DLBCL, including CAR T cells, tafasitamab/lenalidomide (TL), and loncastuximab tesirine (lonca-T) (Sermer D., Blood Rev 2023). However, there are few data available on the efficacy of sequential CD19-directed therapies.

We performed a retrospective study evaluating all patients with R/R LBCL treated consecutively with TL at 11 institutions from 8/2020 to 8/2022, identifying 178 patients. In this study, we specifically evaluate outcomes in patients who received anti-CD19 therapy prior to or after TL. The primary outcome of interest was progression-free survival (PFS) in TL recipients who previously received CD19-directed CAR T therapy, with overall response rate (ORR), complete response rate (CRR), and overall survival (OS) also evaluated. Outcomes of lonca-T and CAR T after TL therapy were evaluated. Data on CD19 expression was assessed on biopsies after TL; this was determined locally using flow cytometry or immunohistochemistry per institutional protocols. In subgroup analyses, ORR and CRR were compared using Fisher’s exact test. PFS and OS were estimated using the Kaplan-Meier method, with differences tested using the log-rank test.

Of 178 patients who received TL, 52 had received prior anti-CD19 CAR T therapy, at a median of 7.4 months before TL (Table 1). Median PFS was lower in prior CAR T recipients (1.6 mo, 95% CI 1.1-2.5) vs no prior CAR T (2.1 mo, 95% CI 1.8-3.2), with hazard ratio 1.46 (p = 0.04; Figure 1). Best ORR was lower in patients with prior CAR T exposure (15% vs 33%, p = 0.02) though CRR was not significantly different (15% vs 18%, p = 1.0).

We specifically evaluated TL outcomes based on prior response to CAR T, given the previously identified association of refractory disease with poor TL outcomes (Qualls D et al., presented at ASH 2022). Of 19 patients who had progressive disease more than 6 months after CAR T, ORR and CRR to TL therapy were 31.6% (all responses were CRs); in 33 patients with refractory disease (less than CR or relapse within 6 months) after CAR T, ORR and CRR to TL were significantly lower, at 6.1% (p = 0.04). Median PFS after TL was shorter in CAR-refractory than CAR-relapsed disease, at 1.4 vs 3.5 months (HR 2.2, p = 0.02).

Of 88 patients who received therapy after TL, 20 (23%) received lonca-T and 14 (16%) received CAR T. Data on survival and initiation of new treatment after CAR T or lonca-T was available, but response and progression data after CAR T or lonca-T therapy is pending. These data allowed an estimate of OS and event-free survival (EFS), defined as survival without initiation of a new treatment after CAR T or lonca-T. With a median 3.9 months’ follow-up, median EFS after CAR T administration was 3.7 months (95% CI, 0.9 – 6.5), and median OS was 8.1 months (95% CI, 0.6 – 15.7). In patients who received lonca-T, with median 2.7 months’ follow-up from initiation, median EFS was 2.8 months (95% CI, 0.9 – 4.7), and median OS was 3.5 months (95% CI, 1.2 – 5.7). When comparing CAR T and lonca-T to polatuzumab vedotin- or chemotherapy-based therapies after TL, there were no significant differences in OS or EFS.

In patients who discontinued TL, 24 had a biopsy a median of 18 days after the last dose of tafasitamab. Of these, 13 (54%) were CD19-positive and 11 (46%) were CD19-negative. All samples obtained more than 21 days after tafasitamab (6/6) were CD19-positive, while 46% obtained within 21 days were CD19-positive. These time-dependent findings may reflect “epitope masking” by tafasitamab rather than CD19 loss, reflecting other recent reports (Fitzgerald K., Leuk Lym 2022; Duell J., Leuk Lym 2022).

In patients receiving TL after CAR T, responses and PFS were lower than in patients without prior CAR T therapy; however, with disease that was not refractory to prior CAR T, results were similar to patients who had not had prior CAR T. This may reflect that refractory disease, regardless of prior therapy, is associated with shorter PFS, though the possibility of CD19-mediated mechanisms of resistance remains. Modest EFS and OS were seen in patients receiving CAR T therapy or lonca-T after already receiving TL, though this may also reflect the high-risk disease characteristics of this cohort. Overall, in a high-risk, real-world cohort of TL-treated patients, these data suggest that some patients may benefit from subsequent CD19-directed therapies, but better therapeutic options are needed.