CD19 CAR T-Cell Therapy Shows Promising Activity in Richter Transformation

A new international multicenter study published in the Journal of Cellular and Molecular Medicine provides important real-world evidence on the use of CD19-targeted chimeric antigen receptor (CAR) T-cell therapy in patients with Richter transformation (RT), a rare and aggressive complication of chronic lymphocytic leukemia (CLL).¹ The research, conducted by the European Research Initiative on CLL (ERIC), suggests that while CAR T-cell therapy offers meaningful clinical benefit in this difficult-to-treat population, outcomes remain more modest compared with other B-cell lymphomas.

The retrospective analysis included 54 patients with RT who received anti-CD19 CAR T-cell therapy between June 2018 and January 2024 across 10 participating centers. The patient population reflected characteristics of high-risk disease, with 53% demonstrating an abnormal karyotype, 56% harboring a deletion of 17p (del(17p), 58% carrying TP53 mutations, and 70% showing an unmutated IGHV status. The median age at CAR T-cell infusion was 63 years, and 72% of patients had an Eastern Cooperative Oncology Group performance status of 0 to 1 prior to lymphodepletion. Prior therapy exposure was extensive, with 67% having received Bruton tyrosine kinase inhibitors (BTKi), 44% BCL2 inhibitors, and 36% having both before RT. Most patients (76%) received R-CHOP as first-line therapy.

The study's findings reveal an overall response rate of 65%, with a complete response (CR) of 46% at 1 month and 50% at 3 months post-infusion.The median progression-free survival (PFS) reached 8 months, while the median overall survival (OS) was 14.4 months. Particularly noteworthy is the stark difference in outcomes based on treatment response. Patients who achieved CR at 1 or 3 months post-CAR T-cell therapy demonstrated a median PFS of 31.6 months, compared with just 1.2 months for those with stable or progressive disease (P < .001). Similarly, median OS was not reached for CR versus 3.37 months for non-responders (P < .001).

The study population was treated with a mix of commercial and academic CAR T-cell products. Tisagenlecleucel was used in 37% of patients, followed by Sheba point-of-care product in 34%, ARI-0001 in 20%, axicabtagene ciloleucel in 7%, and lisocabtagene maraleucel in 2%. Response rates did not differ significantly between CART-cell products, suggesting consistent efficacy across platforms. However, multivariable Cox regression identified lack of early response (P = .001) and older age (P = .05) as independent predictors of mortality. Elevated LDH (P = .005), high ECOG PS (P < .001), development of ICANS (P = .046), and no response at 1 month (P = .02) also correlated with inferior survival. No association was observed between genetic alterations (del 17p, TP53 mutation, IGHV status) and response to treatment.

Safety data showed that cytokine release syndrome (CRS) of any grade occurred in 87% of patients, though only 21% experienced grade 3 to 4 events. Immune effector cell-associated neurotoxicity syndrome (ICANS) was observed in 22% of patients, with 42% of these cases classified as high-grade. Academic CAR T-cell products were associated with significantly higher rates of toxicities compared with commercial products, with 60% experiencing CRS, ICANS, or infections within the first 30 days, versus 40% for commercial products (P = .04). Overall, infections occurred in 41% of the entire patient population, with bacterial pathogens accounting for 68% of documented infectious episodes.

“AlloSCT remains a debated topic in the context of RT,” the authors note. In this multicenter analysis, only 7 of 54 patients (13%) underwent alloSCT after receiving anti-CD19 CAR T cells; 4 as consolidation during remission, and 3 for relapse or progression. The median PFS was 6.5 months for patients receiving alloSCT compared with 8 months for those who did not (P = .46). Among patients receiving alloSCT, 57% (4 of 7) died - 3 from transplant-related toxicities and 1 from progressive disease.

RT continues to pose significant therapeutic challenges, with conventional chemoimmunotherapy yielding CR rates ≤ 30% and median OS under 12 months.² The findings observed here support CAR T cells as a viable option in this refractory population. Importantly, depth and timing of response, particularly at 1 month, were the strongest predictor of durable benefit, suggesting this may be a key decision point in aiding further therapeutic planning.

"This study adds valuable insights into the efficacy and safety of anti-CD19 CAR T-cells in patients with RT," the authors report. Even though outcomes remain less favorable than those observed in de novo diffuse large B-cell lymphoma, investigators point out that "given the historically poor prognosis associated with RT, CAR T-cell therapy represents a meaningful and effective treatment option for this challenging disease."

References

1. Beyar-Katz O, Benjamini O, Delgado J, et al. CD19 CAR T-cell therapy in Richter transformation: A multicentre retrospective analysis by the European Research Initiative on Chronic Lymphocytic Leukaemia. J Cell Mol Med. 2025;29(20):e70841. doi:10.1111/jcmm.70841
2. Thompson PA, Siddiqi T. Treatment of Richter's syndrome. Hematology Am Soc Hematol Educ Program. 2022;2022(1):329-336. doi:10.1182/hematology.2022000345