CTX112, a Next-Generation Allogeneic CRISPR-Cas9 Engineered CD19 CAR T Cell with Novel Potency Edits: Data from Phase 1 Dose Escalation Study in Patients with Relapsed or Refractory B-Cell Malignancies
Authors: Ghobadi Armin , McGuirk Joseph P. , Shaughnessy Paul , Tam Constantine S. , Allen Melanie , Pan Chenyi , Li Ziliang , Stevens William N. , Weaver Annie , Cheah Chan Y. 
Published: December 2024

Introduction: CRISPR/Cas9 editing allows for advanced CAR T cell engineering, which could prevent common failure modes (e.g., exhaustion, lack of expansion) and potentially result in more efficacious therapies. CTX112 is a next-generation allogeneic CAR T cell therapy with 5 edits, including site-specific insertion of an anti-CD19 CAR transgene into the T-cell receptor (TCR) alpha constant (TRAC) locus using adeno-associated viral delivery, and targeted disruption of 4 genes: TRAC (to prevent graft versus host disease, GvHD), B2M (to remove major histocompatibility complex [MHC] class I expression), TGFBR2 (to overcome immunosuppressive signaling in the tumor microenvironment), and ZC3H12A (also known as Regnase-1, to increase cell expansion and functional persistence). This editing strategy was chosen based on a large scale phenotypic CRISPR screen to identify novel potency edits, and further informed by our first-generation CTX110 data. CTX110, which contains only the TRAC and B2M disruptions, produced durable remissions in patients with large B-cell lymphoma (LBCL) without long-lived CAR T cell persistence.

Methods: NCT05643742 is a phase 1/2, open-label, multicenter study evaluating the safety and efficacy of CTX112 in subjects with relapsed or refractory (r/r) B-cell malignancies. Eligible disease subtypes include LBCL, follicular lymphoma (FL) grade 1-3a, marginal zone lymphoma (MZL), mantle cell lymphoma (MCL), and chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Patients received standard lymphodepleting chemotherapy (LDC) with fludarabine 30 mg/m2 and cyclophosphamide 500 mg/m2 for 3 days followed by CTX112 infusion. The Phase 1 primary endpoint was the incidence of dose limiting toxicities (DLTs), with secondary endpoints including overall and complete response rates (ORR/CRR) and pharmacokinetics (PK). Data are presented from 9 subjects (3 FL, 2 MZL, 4 LBCL) treated with CTX112 at doses ranging from 30 x 106 (Dose Level [DL] 1) to 300 x 106 (DL3) CAR+ T cells who were followed for &gt;3 months.

Results: The study population was enriched for patients with high-risk characteristics, including: 1) primary refractory disease or early relapse to first-line therapy (78%); 2) high tumor burden (SPD &gt; 4000 mm2, 56%); and 3) high disease prognostic index score (IPI, FLIPI, MZL-IPI ≥3) or elevated lactate dehydrogenase (67%). No DLTs or adverse events (AEs) of GvHD, hemophagocytic lymphohistiocytosis, or grade (Gr) ≥3 infections were observed. All Gr ≥3 cytopenias resolved within 30 days following CTX112 infusion. Cytokine release syndrome (CRS) Gr 1/2 was reported in 4/9 (44%) pts with no CRS Gr ≥3. Immune effector cell-associated neurotoxicity syndrome (ICANS) Gr 1 was reported in 2/9 pts (22%) with no Gr ≥2. When comparing CTX112 vs. CTX110 at DL3, the mean Cmax with CTX112 was 7-fold higher (26,235 vs. 3,773 copies/μg) with significantly higher levels detected at D14, leading to a 10-fold increase in mean AUC (133,701 vs.13,830 copies/μg*days). The ORR and CRR (Lugano 2014 criteria) were 6/9 (67%) and 4/9 (44%) respectively. 4 patients have achieved responses lasting for more than 6 months, including 1 patient treated at DL1 who remains in complete remission over a year after CTX112 infusion.

Conclusions: These data provide the first clinical evidence that disruptions in the genes encoding Regnase-1 and transforming growth factor beta receptor 2 can lead to increased expansion and functional persistence of CAR T cells. Compared with first-generation allogeneic CAR T therapies like CTX110, CTX112 results in better efficacy at lower doses, higher response rates, and improved PK. Across multiple Non-Hodgkin lymphoma subtypes, treatment with CTX112 resulted in clinically meaningful responses without requiring the increased intensity LDC used with other allogeneic CAR T cells. Dose optimization within disease-specific cohorts is ongoing. These data demonstrate that CTX112 has the potential to be a highly effective allogeneic CAR T cell therapy for B-cell malignancies.