CRISPR-Based Anti-CD19 CAR T-Cell Therapy Is Safe and Effective in Relapsed/Refractory NHL

The CRISPR-based nonviral PD-1 locus-specific integrated CD19-directed CAR T-cell therapy BRL-201 was associated with a manageable safety profile and elicited early indications of efficacy in patients with relapsed/refractory non-Hodgkin lymphoma (NHL), according to findings from a first-in-human phase 1 trial (NCT04213469), which were presented during the 2023 SITC Annual Meeting.¹

No dose-limiting toxicities (DLTs) were observed in any cohorts of patients who received an infusion of BRL-201 (n = 21); however, cytopenias were noted at all dose levels, though most instances were resolved without intervention.

Furthermore, at a data cutoff of May 17, 2023, and a median follow-up of 29.0 months (range, 21.5-36.2), all patients responded to BRL-201 infusion, 85.7% of whom achieved a complete response (CR) and 14.3% of whom achieved a partial response (PR). Among the patients who achieved and maintained a CR, 7 had ongoing responses at the data cutoff. Notably, the 3-month, 6-month, and 12-month overall response rates (ORRs) were 80.9%, 71.4%, and 57.1%, respectively.

“Unlike the current viral-based or transposon-based CAR T cells, in which the [CAR] integration occurs randomly and with various copy numbers, yielding a very heterogeneous CAR T population, in our approach, the CAR sequence was precisely integrated, in this case, at the PD-1 sites,” Biao Zheng, MD, PhD, said in a presentation of the data. “This approach can generate a very homogenous CAR T population and has shown great efficacy and safety profile in earlier and current ongoing clinical trials.” Zheng is a senior partner, as well as the chief executive officer of BRL Medicine, Inc., in Shanghai, China,

In a preliminary data readout of this phase 1 trial, the CAR sequence of BRL-201, when inserted at the PD-1 locus, was safe and effective when used as adoptive therapy in patients with relapsed/refractory aggressive B-cell NHL.² Responses were observed in all 8 patients enrolled, with 7 patients achieving a CR and 1 experiencing a PR.

This phase 1 trial enrolled patients with relapsed/refractory NHL, defined as disease that did not achieve a CR, disease that relapsed after achieving a CR following more than 2 cycles of chemotherapy, disease that relapsed within 12 months of autologous stem cell transplant (ASCT), or disease that did not achieve a CR after ASCT.1 Eligible patients were required to have disease with at least 50% biopsy-confirmed CD19-positive expression, an ECOG performance status (PS) of 0 to 2, and a life expectancy of more than 3 months.

The primary objectives of this trial were the evaluation of the safety and tolerability of BRL-201 through DLTs and adverse effects (AEs), as well as the determination of the recommended phase 2 dose (RP2D) of the agent. Secondary objectives included the evaluation of preliminary antitumor activity of BRL-201 through ORR, progression-free survival (PFS), and overall survival (OS).

Between May 3 and August 10, 2021, 30 patients were screened, 25 of whom were eligible to enroll in the trial. Of these patients, 21 received BRL-201 infusion following lymphodepleting chemotherapy. The dose-escalation portion enrolled 14 patients.

Following screening, patients underwent leukapheresis, after which BRL-201 manufacturing commenced. During the CAR T-cell therapy manufacturing, patients were permitted to receive optional bridging therapy. At the end of BRL-201 manufacturing, patient eligibility was reconfirmed, and eligible patients underwent lymphodepletion with fludarabine at 30 mg/m2 for 3 days and cyclophosphamide at 500 mg/m2 for 2 days. Between 2 and 5 days after lymphodepletion, patients received BRL-201 at 1 of 4 dose levels: 2 x 106 CAR+ T cells/kg (dose level A; n = 5), 4 x 106 CAR+ T cells/kg (dose level B; n = 3), 6 x 106 CAR+ T cells/kg (dose level C; n = 3), or (0.56-0.8) x 106 CAR+ T cells/kg (dose level D; n = 3). Disease assessment occurred on day 28, after which the RP2D was determined, and a dose-expansion portion of the trial was initiated in 7 patients at the optimal biological dose of 2 x 106 CAR+ T cells/kg. The posttreatment follow-up period was determined to be 3 to 24 months, and the long-term follow-up period was determined to be 24 months to 15 years.

In all treated patients, the median age was 50 years (range, 34-70), and 52% of patients were male. Overall, 81%, 10%, 5%, and 5% of patients had diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), precursor B-cell lymphoblastic lymphoma (B-LBL), and transformed follicular lymphoma (tFL), respectively. Furthermore, 81% of patients had worse than intermediate-risk disease, 19% of patients had intermediate-risk disease or better, and 19% of patients had disease with PD-L1 expression of at least 50%. ECOG PS was 0, 1, and 2 in 14%, 67%, and 19% of patients, respectively, and 10%, 24%, and 66% of patients had stage II, III, and IV disease, respectively. Thirty-three percent of patients received bridging therapy.

All patients who received BRL-201 infusion experienced any-grade neutropenia, thrombocytopenia, and leukopenia. Other common any-grade AEs were anemia (86%), hypocalcemia (76%), cytokine release syndrome (CRS; grade 1/2, 66.7%; grade ≥ 3, 0%), fever (62%), decreased lactate dehydrogenase (LDH; 47%), cough (33%), fatigue (33%), hypoproteinemia (29%), immune effector cell­–associated neurotoxicity syndrome (ICANS; grade 1/2, 19.0%; grade ≥ 3, 0%), hypogammaglobulinemia (5), headache (5%), dizziness (5%), chest pain (5%), diarrhea (5%), and nausea (5%). The most common grade 3 or higher AEs were neutropenia (81%), hypocalcemia (38%), anemia (29%), leukopenia (29%), thrombocytopenia (10%), hypoproteinemia (5%), and decreased LDH (5%). Moreover, 1 patient experienced a grade 2 enterocolitis infection caused by Candida albicans and pneumonitis jirovecii pneumonia 9 months post-infusion. This patient had prolonged B-cell aplasia and eventually died of consequent disseminated infection.

Most instances of CRS were cured with nonsteroidal anti-inflammatory drugs. One patient received tocilizumab for CRS. All instances of ICANS happened within the context. Neither ICANS nor CRS were associated with elevated IL-17A levels, with respective P values of .027 and .025. The 1 patient with primary central nervous system DLBCL enrolled in the trial experienced no neurotoxicity.

CAR T-cell levels peaked between days 9 and 28 with a median of 211.87 cells/μL. Among all patients who underwent BRL-201 infusion, CAR copy number, monitored via quantitative polymerase chain reaction, peaked between days 0 and 21, with a median of 61,243 copies/μg of DNA. B-cell aplasia was observable in patients for at least 12 months. The 6- and 12-month B-cell aplasia rates were 70% and 40%, respectively. Eight patients experienced B-cell reconstitution during CR or PR, 4 of whom subsequently relapsed. BRL-201 expansion and persistence, as measured by peak CAR T-cell number or CAR copy number, was not significantly correlated with dose level or AEs across patient subgroups.

When responses were stratified by dose level, at dose level A, 83.3% and 16.7% of patients achieved a CR and PR, respectively. At dose level B, 66.7% and 33.3% of patients achieved a CR and PR, respectively. At dose levels C and D, all patients achieved a CR. When responses were stratified by disease type, in patients with DLBCL, 82.4% and 17.6% achieved a CR and PR, respectively. All patients with MCL, B-LBL, and tFL achieved a CR.

Among the 21 treated patients, the median duration of response was 15.1 months (95% CI, 5.9-not applicable [NA]), and the median PFS was 20.8 months (95% CI, 8.2-NA). The estimated median OS was not reached, and the 12-month OS rate was 76.2% (95% CI, 60%-96.8%).

BRL-201 elicited an enduring CR in 3 of 4 patients with PD-L1 expression over 50%. All 3 patients maintained a CR at data cutoff.

“Currently, to further evaluate the BRL-201 antitumor activity at a lower dose range, a phase 1/2 clinical trial (NCT05741359) is ongoing with a large-scale and multicenter design,” Zheng concluded.

References

1. Zheng B, Hu Y, Zhang J, et al. High safety and efficacy of CRISPR-based non-viral PD1 locus specific integrated anti-CD19 CAR-T cells (BRL-201) in treating relapsed or refractory non-Hodgkin's lymphoma: first-in-human phase I study. Presented at: 2023 SITC Annual Meeting; November 1-5, 2023; San Diego, CA. Abstract 690.
2. Zhang J, Hu Y, Yang J, et al. Non-viral, specifically targeted CAR-T cells achieve high safety and efficacy in B-NHL. Nature. 2022;609(7926):369-374. doi:10.1038/s41586-022-05140-y